Catalytic Infrared Oven Panel Online Manual

Table of Contents


Operation and Instructional Manual

This brief manual has been prepared to provide general information required for the installation, operation, and maintenance Trinity’s infrared oven control panels.

For questions on the control panel contact:

10708 – 181 Street
Edmonton, Alberta, Canada
T5S 1K8

Tel: 1-780-489-3199
Toll Free: 1-888-480-3199
Facsimile: 1-780-487-6397
Email Us

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  1. High voltage (120 VAC, 208 VAC, 220 VAC, 480 VAC, 600 VAC) is used in portions of the oven.  DO NOT perform wiring modifications to the oven or controls while the oven is running.
  2. The oven controller is energized even if the oven is shut off. Consult the External Control Cabinet Wiring Diagram for specific details.  Disconnect all sources of power to the entire system at the breaker(s) before performing any modifications to the controller.  Trinity Electronics Systems Ltd.
    must be notified before any modifications are made to the oven components.
  3. Extreme caution should be used around the heater surfaces when the oven is operational.  The heater surfaces are extremely hot and can cause severe injury when touched.
  4. Any damage to the heater surfaces must be repaired immediately.  Damage to the surface can result in un-reacted fuel passing through the heater potentially creating a fire or explosion hazard.  Return all damaged heaters to the manufacturer for repair.

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Batch Timer

The batch timer is typically used in paint booth applications where a pre-set amount of heat is required. The oven runs in standby mode until the timer is started. The oven then runs at full heat mode until the timer period is completed. The oven then returns to standby mode. The operator starts the full heat cycle by momentarily pressing the Start Timer switch. The time is set with the Timer Up and Timer Down switch.

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Catalytic Heater
Catalytic heaters do not burn fuel with an open flame but instead use a compound called a catalyst to combine the incoming fuel gas with oxygen to produce infrared energy. A catalyst is a compound that accelerates the rate of a chemical reaction without being consumed by the reaction itself. The catalyst pads must be heated electrically to bring the catalyst to the critical temperature before fuel gas is released to the heaters.

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Control Panel
The control panel is a self-contained control system which controls the valves and contactors in an oven system. It can control up to 56 heaters in one to eight zones. It contains a combination of oven control boards, displays, switches, fuses, relays, contactors, temperature controllers, modulating valve controllers, and timers. There are two sizes of control panel the smaller one is 32″ H x 20″ W x 8″ D and the larger is 38″ H x 26″ W x 10″ D.

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Critical Temperature (or Reaction Temperature)
The minimum temperature required for the catalyst to chemically combine fuel and oxygen is the critical temperature. Below the critical temperature, there is no heat producing reaction. The control system must not permit gas to flow to the heaters if the catalyst is below the critical temperature or the potentially explosive fuel gas will escape into the atmosphere.

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Full Heat
Full Heat is the mode of operation where the oven runs at its fully rated temperature. The maximum heat output may be controlled by flow regulators or by using a Temperature Controller and a modulating gas valve.

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Modulating Valve
A modulating valve is an electrically operated valve that uses a signal (typically 0-20V DC) to control the amount of gas flowing through the valve. A temperature controller is used to provide a signal to a Modulating Valve Controller, which controls the flow of gas and thereby the temperature of the oven system. The modulating valves used in catalytic ovens have a low flow or standby output but have no off position. Therefore each modulating valve must be used in conjunction with a solenoid valve for full on-off control.

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Modulating Valve Controller
The Modulating Valve Controller or Signal Conditioner is a device which takes either a 4-20 milliamp signal or a voltage derived from a potentiometer and translates it into a pulse of varying width to control a modulating gas valve. A quad Modulating Valve Controller can drive up to four modulating gas valves from one to four temperature controllers.

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Motorized Valve
A motorized valve is an electrically operated valve used as a main gas valve in an oven system. The valve will open when voltage is applied to the motor (typically 120 VAC). The valve is either off or full on – there is no pressure or flow control.

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Solenoid Valve
A solenoid valve is an electrically operated valve. The valve will open when voltage is applied to the coil (typically 24 VAC or 120 VAC). The valve is either off or full on – there is no pressure or flow control. Combinations of these valves allow for control of single or multiple zones.

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Standby is the state in which the heater is burning the minimum amount of fuel required to keep the catalyst pad above the critical temperature. Therefore its heat output is much lower than the normal operating state. Standby is used to reduce fuel consumption when a full shutdown and the subsequent pre-heat cycle is not required or desired.

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Startup Timer
The timer will allow unattended startup and shutdown of the oven system. It can be programmed to start the oven at a different time each day of the week.

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Temperature Controller
The Temperature Controller is a device which controls the temperature of the oven system. There are currently two types of temperature control systems used; open and closed loop controllers. The closed loop temperature controller is a digital device which can be programmed for a wide range of temperatures. A temperature sensor, typically a thermocouple, provides feedback so that the controller can hold the oven at a relatively constant temperature. The temperature controllers used can be programmed to receive a wide range of sensors but K type thermocouples are most commonly used. The output signal is the industry standard 4-20 milliamp output. This output is fed to an amplifier called a Modulating Valve Controller which provides the drive for a modulating valve which will in turn modulate the gas flow in proportion to the control input.

The Percentage Temperature Controller is an open loop temperature controller that uses a rotary control or potentiometer with markings that range from about 30% to 100%. The operator can select a setting anywhere within that range. This output from the control is again fed to modulating valve controller which will provide the drive for a modulating valve which will in turn modulate the gas flow. Because there is no feedback from a temperature sensor to compensate for changes to the oven, this is called open loop control. This type of control is less expensive than a full digital controller and is used where there is little change to the oven conditions and temperature control is less critical.

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Variable Frequency Drive (VFD)
A Variable Frequency Drive (VFD) is used in conjunction with a blower motor to provide variable air flow. It is inserted into the circuit between the fuses for the motor and the motor itself. A VFD will often appear with recirculation blowers in cure ovens, but could be used anywhere a blower motor is required. Control of airflow is usually accomplished with a keypad interface or up/down buttons.

Note: output wiring from the VFD to any motor it controls must be contained in a dedicated conduit to ensure electromagnetic isolation.

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An oven zone is a group of heaters which act together. They receive gas from a common valve and have electric preheat elements that are switched on at the same time. Zones allow various portions of an oven to generate more or less heat than others. This accommodates different heat requirements of the various sizes and materials of the objects which are cured or heated in an oven. Zones may also be used to heat objects in stages to reduce thermal shock. Zones can be either true zones with full control or thermal zones which share common electric control but have separate temperature controllers and modulating valves. Thermal zones are less expensive to implement than true zones.

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Energy Required

Electrical Requirements

Catalytic heaters require electric elements to pre-heat the catalyst before gas may be applied. This cycle varies but can take up to 45 minutes per heater. The preheat current requirements and the power supply required by the entire system are described in the customized manual supplied with each oven.

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Fuel/Gas Requirements

The main gas pressure must be regulated by the user, to not exceed the maximum inlet pressure capacity to the systems mainline regulator.

The mainline pressure regulator must also be adjusted to supply enough fuel to the system to allow for pressure drops along the lines, each heater should receive approximately 7 inches w.c. (1.73 kPa) for natural gas or 11 inches w.c. (2.27 kPa) for propane.

The inlet pressure to the heaters must not exceed the above mentioned pressure. Above this pressure the gas may pass through the heater un-reacted, creating a safety hazard. The minimum inlet pressure to the heaters is 2 inches w.c. (0.49 kPa) for natural gas or 3 inches w.c. (0.74 kPa) for propane. Below this, sufficient fuel to support the catalytic reaction will not be present and the heater will begin to cool, which will shut down the entire system.

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Control Panel Description

Master Control Strip

The Master Control Strip (MCS) has six large indicator LEDs (Light Emitting Diode) that are located at the bottom of the panel. They indicate the status of the oven system. The Power lamp is lit when power is switched on. To start the oven, the master Power switch must be ON and the Startup Timer (if there is one) must be on.

The Full Heat lamp is lit when the system is applying full heat to the oven. If the oven is in the preheat cycle, this lamp may be lit if the Full Heat/Standby switch is set to Full Heat but there will be no gas flow until the preheat cycle is complete. Once the preheat cycle has been completed and the system enters operate mode, this lamp indicates the status of the oven. During the batch timer cycle, this lamp will be also be lit.

The remaining lamps indicate alarm conditions: Gas Fault, Air Fault, and Conveyor Stopped. The lamps indicate the status of those normally closed inputs. When those external switches open to indicate a problem exists, the lamp is lit and this signal is passed on to the oven controller CPU cards, which take the appropriate action.

The last lamp, Alarm, is an output from the oven controller (CPU) boards which lights when the oven controller responds to an error condition. When this lamp is lit, a problem has occurred which has required the controller to shut down at least one zone of the oven system. Specific information regarding the type of alarm condition that has occurred is covered in the second type of displays, which are described below. The only method of clearing these types of errors is to turn the Power switch to the affected zone(s) off, and restart the affected zone(s).

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Display Card

The Display Card (DC), relates specific alarm and status information for one zone. The LEDs on the display card are divided into two categories: the larger 12 LEDs provide status and alarm information and the smaller 28 LEDs provide low temperature information. During normal operation, the three larger LEDs in the left most column represent the operating conditions of a zone: Preheat, Gas On and Standby. The Preheat LED, which is labeled as Preht, is lit when the Preheat contactor is closed and power is flowing to the electric elements. The Gas On LED shows that the main gas valve and the zone gas valve for the particular zone are energized. The Standby LED, which is labeled as Stdby, shows that the oven is in Standby or low heat mode. The fourth LED in the column is unused at this time. When alarm conditions are encountered, alarm LEDs are lit to indicate the nature of the problem. As the heaters cool down below the critical temperature, their corresponding Low Temperature LEDs will light. The four Alarm LEDs on the display card and the Alarm LED on Master Control Strip both remain lit to indicate that an alarm condition has caused some zones to be shut down. Specific causes and remedies for these alarm conditions are covered in the “Alarm Faults” section.

The Low Temperature LEDs are labeled with the zone number and a letter which corresponds to each heater. A designation of 1A means that the heater is in zone 1 and heater is Heater A which is normally near the entrance of the oven. A designation of 3J would indicate a heater in zone 3 and heater J etcetera. Only those LEDs that are labeled represent heaters. The remaining LEDs are used for larger installations.

The Low Temperature LEDs glow red when a heater is cold and turn off when the heater reaches critical temperature. If the oven has been off for several hours and one LED does not glow when the oven is started, it indicates that there is a problem with the corresponding thermocouple. Alternately if all but one heater turn off during a normal preheat cycle, this indicates a heater which is not coming up to temperature or a bad thermocouple.

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Omron Digital Temperature Controller

The temperature controller option will provide either one controller for each zone or one controller for the entire oven. The controller uses a digital PID (Proportional, Integral, Differential) algorithm. The controller monitors a thermocouple wired to the face of one heater. The temperature of the thermocouple is neither air temperature in the oven nor part temperature but it does provide suitable feedback to hold the oven temperature stable. Part temperature is only available by using infrared thermometer or thermal sensors fastened to the part.

Temperature Controller Display

Large red 4-Digit Display – temperature measured in the oven

Smaller green 4-Digit Display – temperature set point

Small square LEDs – See the Omron E5CK instruction manual

The keypad has 4 keys:

A/M Key
selects automatic or manual mode
(a circular arrow) moves between levels and modes
moves down through levels or parameter list
UP Key
moves up through levels or parameter list

Programming an Omron Temperature Controller

The digital temperature controllers should arrive programmed for K-type thermocouples but the parameters can be changed in the field.

– Set Point

The UP and DOWN keys change the set point. Holding the arrow keys increments or decrements the display at a rate of one degree per second. After 10 degrees the display will change at a rate of 10 degrees per second. Pressing the keys repeatedly allows the display to increment by single digits. No other keys are required to program the set point. It should be noted that the process temperature readings will be representative of the oven temperature but not the objects in the oven. Use the readings as a guide only.

With the exception of the set point, all parameters are set within the “Menu” mode. To enter the Menu mode, hold the DISPLAY key down for at least one second. The display shows a message that looks something like “nEnu.” (The messages are not exactly alphabetical because the seven segment displays don’t have diagonal segments). The arrow keys will then select between three levels (level 0,1 or 2) and the three modes (set, expansion and option). Pressing the UP key will move upwards through the modes but when the top of the list is reached, the UP key won’t move any further – use the down key to move down.

Example – Selecting the Input Sensor

Most caltalytic ovens use a K type thermocouple placed on the face of a heater for feedback. This can be selected by as follows:

  1. Press and hold the DISPLAY key for 1 sec. to enter the Menu mode (nEnu)
  2. Press the UP key 3 times to display Setup mode (Set on green display)
  3. Press and hold the DISPLAY key for 1 sec to enter Setup mode
  4. The first entry in the list is “input type” (in-t on red display)
  5. Press the UP key to select input type 3 (K2 is K type T/C, 0 to 900 deg. F)
    (the input types show up as a number on the green display)
  6. Press and hold the DISPLAY key for 1 second to go back to Setup mode
  7. Press the DOWN key 3 times to return to level 0
    (Lu-0 on the green display)
  8. Press and hold the DISPLAY key for 1 sec. to leave the Menu mode and return to normal temperature display.

– PID Parameters

The simplest way to optimize the temperature controller response is to run the Auto Tune option. Auto tune is the first entry on Level 1. The AT indicator on the front panel will blink while the system is in auto tune.

Percentage Temperature Control

Oven controllers can also use open loop temperature control which does not monitor the oven temperature. The temperature is set with a potentiometer or dial. The operator manually sets the dial to select temperature. These potentiometers adjust gas flow between approximately 30% (scale 1 – corresponding to standby status) and 100% (scale 10 – corresponding to full heat status), which roughly corresponds to percentage of total BTU output of the heater.

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An oven control system may contain no timers, a Startup timer, a Batch timer or both timers. The two timers perform two separate tasks and must not be confused. The Startup timer is used to automatically start and stop the oven system. It is programmed to turn on the oven system and complete the preheat cycle before product needs to be cured. It is often programmed to start the oven an hour before the start of the morning shift. At the end of the working day, the Startup timer may be programmed to shut down the oven system. The Batch timer is manually started to turn the oven system to Full Heat for a preset batch time. After the batch time is completed, the oven returns to standby mode.

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Start-up Timer

The Start-up timer has a three position switch labeled “auto”, “on” and “off”. This switch allows for either manual or automatic control of the timer’s relay output. In the “on” position, the contacts are closed; in the “off” position, the contacts open; and “auto” position the contacts under the control of the timer’s program. The timer’s output contacts have been wired as a control signal input to the CPU(s) via the MCS. When the contacts are closed, the CPU(s) will operate normally, obeying the startup and operating procedures. When the contacts are opened the CPU(s) will not operate; the Power lamp will be on, but the LED displays will not work and the oven system will not operate. A brief description detailing the basic set up of the timer has been included for your convenience. For complete programming information, see the Omron Model H5S Weekly Time Switch Instruction Manual.

Setting the Time

Turn the OUT switch on the front panel to ‘OFF’ to disable the timer outputs. Set the Mode switch to ‘RUN’. Begin by programming the correct time and day of the week. The initial display will have a clock symbol flashing, and will display the current time as dashed lines. Press the ‘SHIFT’ key to select the correct day of the week. Then press the ‘SET’ key to accept the day. Press the ‘h’ key to set the current hour of the day. Press the ‘m’ key to set the current minute. Then press the ‘WRITE’ key to finish setting the correct time. The internal clock begins keeping real time immediately after pressing the ‘WRITE’ key.

Programming the Operate Times

Begin by setting the OUTPUT switch to ‘TIMER’ and the MODE switch to ‘P1′. You will see the display flashing the up-arrow symbol, indicating you are setting the ON time. Use the ‘SHIFT’ and ‘SET’ keys to set the day, ‘h’, and ‘m’ keys to set the hour and minute for program #1. Press ‘WRITE’ to save the on time and day. Then use the ‘h’, ‘m’ and ‘WRITE keys to set the off time. To begin operation, switch the ‘OUT’ switch on the front panel to ‘AUTO’. If you encounter any problems, or wish to set more complex operations, please refer to the Omron Model H5S Weekly Time Switch Instruction Manual.

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Batch Timer

The batch timer is used to apply a set amount of heat to objects inside the oven. The oven begins in standby mode at relatively low temperature until the Start Timer switch is pressed. The oven then begins a batch cycle, applying full heat to the objects inside the oven (in accordance with the programming of the zone temperature controller). The Full Heat lamp will light and the time remaining in the batch cycle will be displayed on the two digit LED batch timer display. Once the batch timer completes its cycle, the timer display will return to its preset value, the Full Heat lamp will turn off, and the oven will return to standby mode awaiting another batch cycle.

There are two spring loaded toggle switches used to control Batch Timer. The Timer Up/Timer Down switch is used to increment and decrement the two-digit display until the desired batch time is shown. The time will increment (or decrement) one count when the switch is depressed but it will advance on its own if the switch is held in either position. This auto–increment or auto–decrement function is useful when making large changes in the batch time. Batch time is adjustable from 1 minute to 99 minutes. A short time will be required for the thermal transition from Standby to Full Heat modes and this warm up time must be taken into account when programming the batch cycle time.

The batch cycle is started and terminated by pressing to the Start Timer/Cancel Timer switch. When the switch is moved to the Cancel position, the batch cycle is terminated, the oven goes to standby mode, and the batch time display is reset to its starting value.

Batch Timer Finished Relay

One of the relays on the oven controller board can be programmed to act as a Batch Finished alarm. The default setting will cause the relay to close for 5 seconds at the end of the batch cycle. The relay closure time can be factory programmed from 1 to 63 seconds or it can be set to remain closed until the Cancel Timer switch is depressed.

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Start-up Procedures

Cold Start

Ensure that the manual fuel gas valve is tuned on. Turn the circuit breaker on and set the Power On/Off switch to the ON position. This will turn on the Power LED and power up the internal electronics. If the oven has more than one zone, turn the zone power switches (located under the display card) to the Auto position. The Preheat LEDs (labeled Preht) for all powered zones will light indicating that the system is in the preheat mode. The preheat cycle time depends upon ambient temperature but should be 20 – 30 minutes.

When the last heater has reached critical temperature as indicated by the Low Temperature LEDs on the display card, the exhaust fan is turned on to purge the oven. The oven will continue to heat for an additional three minutes. The main gas valve and the zone solenoid valves are then energized. This stage is known as Post-heat. The Gas On and Preheat indicator LEDs will show that gas is flowing and the electric elements are energized. Fuel gas flows at the full rate for six minutes while the preheat elements are on. If a heater does not “catch” and a the temperature in a heater drops below the critical temperature, the Low Temperature LED is turned on, fuel flow is interrupted and the sequence goes to a two minute warm‑up delay to allow the electric elements to bring the catalyst back up to temperature. Note that the system is in post-heat mode and it will ignore the position of the Full Heat/Standby switch. Fuel flow during preheat is at the maximum rate to ensure that the entire surface of the catalyst pads reach operating temperature. After six minutes of operation without a heater dropping out, the electric preheat elements are turned off and the Preheat indicator LED for each zone is turned off.

If there is a brief temperature fault in a heater after preheat cycle is complete, the corresponding Low Temperature LED will turn on. If the fault is cleared within 10 seconds, the LED will turn off and the system will remain functioning. If the fault is not cleared within this time or if there are any other faults, the system will shut down. The Gas On LED will go out, the Alarm LEDs will illuminate indicating the specific problem, and the alarm relay will close. The system is locked out until the Power On/Off switch(es) for the affected zones are turned off and then back on.

The power switch will turn the oven off – no other action is required. This closes all valves and removes power from the heating elements. Operational parameters and settings will be retained in non-volatile memory (EEPROM).

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After Alarm Re-start

If the oven encounters a fault condition and enters alarm mode, the all valves and preheat power for the affected zone are turned off. The power switch for affected zones must be turned off to reset an alarm condition. If the fault is noticed and reset quickly, the heaters will still be above the critical temperature and a Hot Start will begin. If even one heater drops below critical, a full cold start cycle is initiated.

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Power Fail Re-start

The system will recover from a momentary power failure in the same way that it would if the power switch was turned off and then off again. The gas valves will turn off and a preheat cycle will begin. If all the heaters are above critical temperature when power is restored a short “Hot Start” cycle will begin (see below for a description of the Hot Start cycle). If one or more heaters drops below the critical temperature, the longer “Cold Start” cycle will begin.

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Hot Start

If the oven is turned off and then on again (to clear a fault) or the power momentarily interrupted, all the gas valves will close and the oven will re-start.. If all the heaters are above the critical temperature, a short “Hot Start” preheat cycle is initiated. The electric elements are turned on for three minutes. Next, the gas valves are opened and gas flows at the maximum rate (even if standby mode is selected) for six minutes with the preheat elements on to ensure that the heaters solidly reach operating temperature. After this Post Heat cycle is complete, the preheat elements are switched off and the system will follow the setting of the Full Heat/Standby switch.

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Defective Heater Or Thermocouples

If there are one or more defective heaters or thermocouples in a zone, the zone will be disabled (the zone gas valve will close) but the remaining zones will continue to operate. In the case of a single zone oven system, defective heaters or thermocouples will prevent the oven system from operating. One or more alarm LEDs will indicate the source of the fault. If this should occur repeatedly, contact the heater manufacturer for assistance.

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Trouble Shooting Guide

Common Problems and Solutions

The unit will not start after the Power switch is turned on, but the Power lamp does not come on.
There is no power to the system.
Check incoming power. If it is OK, remove incoming power for about one minute, then try again. If the system now works, use it but report the failure to Trinity Electronics Systems Ltd. at (780) 489-3199.
The unit will not start when the Power switch is turned on and the Power lamp is lit.
The power is supplied into the system, but the Zone Mode switches (Standby/Auto/Off) on all zones are off.
Check the Zone Mode switches on all zones and turn at least one on (Standby or Auto).
I’ve been waiting for about 20 minutes, and all of the Low Temperature LEDs are still lit.
It can actually take up to 45 minutes for the heaters to come up to preheat temperature.
Most, but not all, of the Low Temperature indicators are off and now the Alarm indicator lamps are lit indicating a Preheat Failure.
One or more preheat elements in that zone does not appear to be working.
Turn off the system (with the Power On/Off toggle switch) and feel the surface of the heaters. If the failed unit(s) appears to be cool to the touch, check to make sure that all incoming power phases are OK. All Low Temperature indicators lit at the end of the time-out period indicates a missing power phase. Have an electrician perform tests to ensure that the preheat element power is connected properly.
The unit still does not work when the power is supplied and all control operations are done correctly.
There may be a short from wire strands to other wires or to the Printed Circuit Board traces; or there may be damaged components resulting from incorrect usage; or from problems during delivery and/or installation.
Check any short wiring, especially in the bare portions such as terminal strips and wire connection. If the above does not help, contact Trinity Electronics Systems Ltd. at (780) 489-3199 for troubleshooting assistance.

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Alarm Faults

An alarm occurs when the CPU card detects operation outside of normal limits. Faults generated by the CPU are temperature related problems. Faults may also be detected from external inputs such as gas pressure switches, air flow switches, or conveyor stoppage switches. Any faults or alarm conditions will light the large ALARM LED at the bottom right of the control panel. In addition, the small Alarm LEDs on the display card(s) and the large LED on MCS will provide information on the specific problem and zone number.

If an external fault is recognized, a large LED on the display cards will light, the Alarm LED lamp on the master control strip will light and the corresponding external switch failure will be indicated by the master control strip LED. This will be a gas pressure failure, air flow failure, or conveyor stoppage.

If an internal fault is detected, large Alarm LEDs on the appropriate display card will light and specify the nature of the problem. These alarm LEDs are marked as “Alarm 1”, “Alarm 2”, “Alarm 3” and “Alarm 4”. These LEDs may be read using the following table to ascertain the specific failure.

Alarm 1 Alarm 2 Alarm 3 Alarm 4 Description
Off Off Off Off External Fault (Check MCS)
On Off Off Off Preheat Fail
Off On Off Off Post-heat Fail
Off Off On Off Operate Fail
On On Off Off Gas Pressure Fatal Fault
On Off On Off Air Flow Fatal Fault
Off On On Off Conveyor Stopped Fatal Fault
On On On Off Multiplexer or Thermocouple Fail
Off Off Off On Reserved
On Off Off On Reserved
Off On Off On Reserved
Off Off On On Reserved
On On Off On Reserved
On Off On On Reserved
Off On On On Reserved
On On On On EEPROM Error

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Types of Alarm Conditions

External Fault:
An External fault has occurred and continues to occur for some time, until the system times out and the oven shuts down.
External Faults are the easiest faults to diagnose because there is an indicator for each external fault. The indicator LED will show which input caused the fault. If the external fault clears quickly enough, the system will recover and carry on. If the fault extends past the critical time for each input the fault is fatal and the power switch must be turned off to reset the panel. The reaction times are:

  • Gas Pressure Switch: 8 seconds –> shutdown
  • Air Flow Switch: 30 seconds –> shutdown
  • Conveyor Stopped: 30 seconds –> standby

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Preheat Fail:
One or more heaters failed to reach operating temperature within the 60 minute period allowed. The problem heater(s) are indicated on the Low Temperature LED bank for the particular zone.
This could be a power or a thermocouple problem. The easiest way to find out is to turn the affected zone ON/OFF switch “OFF”, then back “ON”. This resets the alarm and starts the preheat cycle from the beginning. If the system is now able to start normally there may a problem with the thermocouple. If this is a recent problem involving a system that has been working flawlessly for a long period of time, check the incoming voltage, preheat element voltage, and preheat element current. Contact Trinity Electronics Systems at (780) 489-3199 for assistance. If this is a new installation, there may be a problem with the thermocouple transmitter board. See the section titled “Thermocouples” for details.

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Postheat Fail:
One or more heaters keep cooling off during the ten minute “gas plus preheat” cycle. The incoming fuel may be producing a cooling effect on the catalyst pads keeping them from reaching the critical temperature. When this occurs, gas is shut off and a two minute preheat using elements only is started. Then gas is turned on in conjunction with the elements for another ten minutes. This is allowed to happen up to four times without causing an alarm. The fifth time that it happens, this fault is reported and the affected zones are shut down.
The problem may be caused by a faulty thermocouple, contaminated fuel, or the fuel gas may be too cold. Contact the heater manufacturer  for assistance with this problem.

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Gas Pressure Fail:
Either the low pressure switch or the high pressure switch in the gas line is indicating a problem with the gas pressure.
This could be either a low pressure or a high pressure problem. Check the incoming gas pressure before it enters the appliance regulator. If the gas pressure is below 7.0 inches w.c. (1.73 kPa) for natural gas or 11.0 inches w.c. (2.72 kPa) for propane, check in incoming gas line for closed valves or for other problems. To check if the problem is due to high gas pressure, check the gauge on the gas line after it leaves the appliance regulator. If the pressure at this point in the gas line is above 7.0 inches w.c. (1.73 kPa) for natural gas or 11.0 inches w.c. (2.72 kPa) for propane, the regulator may require adjustment or may need replacement. Contact the heater manufacturer for assistance. If there are still problems, replace the wiring at the master control strip to the pressure switches with a jumper wire. If the lamp now goes out, there is a problem with the wiring to the switches or with the switches themselves.

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Operate Fail:
One or more thermocouples dropped below critical temperature while the system was in operate mode (no longer in preheat). This can take two different diagnostic paths, depending on whether the system was in Standby or in Full Heat Mode. To determine this, check if the Full Heat/Standby switches are in the Full Heat position or in the Standby position.
This depends upon the mode the oven system is currently in. First check the Full Heat/Standby switches. If the master Full Heat/ Standby switch is set to Standby, all zones are set to standby mode. If the master switch is set to Full Heat, check the zone Full Heat/Standby switches.

Full Heat: Not enough fuel is supplied to keep the heaters operating. How long after starting did it take for this fault to occur? If the fault happened shortly after the zone finished the preheat cycle, there is probably a gas pressure problem. Check to make sure that all the ball valves in the system (if any) are in the On position (handle in line with the pipes). Turn the zone On/Off switch “Off”, then back “On” again. Wait until the gas valve turns on (as part of the preheat cycle), and check the gas pressure gauge for that zone. It must read above 7.0 inches (1.73 kPa) for natural gas or 11.0 inches w.c. (2.72 kPa) for propane before it enters into the appliance regulator.

Standby: Same problem as with the Full Heat position above, using the same tests. It is also possible that the standby gas pressure is incorrect. After restarting the system (zone On/Off switch Off, then back On), wait for the system to reach the Gas On mode for that zone. Make sure that the zone is in standby (either the Master Standby switch is set or the zone Full Heat/Standby switch is in the Standby position), then observe the gas pressure gauge. It must read above 7.0 inches (1.73 kPa) for natural gas or 11.0 inches w.c. (2.72 kPa) for propane while the Preheat indicator is lit and 3.0 inches (0.74 kPa) pressure for natural gas or 4.0 inches w.c. (0.99 kPa) pressure for propane when the Preheat indicator turn off.

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Air Flow Fail:
The Air Flow switch indicates that blowers were called for and they did not function.
Check to see if any blowers are running. If they are running, this indicates a bad air flow switch or a wiring problem between the switch and the corresponding input on the Master Control Strip (MCS) located inside the control panel. Ensure this wiring has been completed correctly. If the blowers are not running, the problem could be related to the blower wiring. Check all the wiring associated with the blowers; the line voltage wiring, the output to the blowers, and the input from the CPU (or CPUD) boards inside the control panel. If blowers still do not work, check that the motors function without CPU (or CPUD) control, off line voltage directly. If the blowers do work independently, contact the oven manufacturer for assistance.

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Conveyor Stopped:
This indicates the conveyor has stopped.
At this time, the conveyor stoppage is not a fatal fault, and the oven will continue to operate independently of the conveyor’s state. The default action programmed into most ovens is to put the oven into standby 30 seconds after the conveyor input line is opened . This time can be changed through software. If the system indicates that the conveyor has stopped but the conveyor is running, check the wiring associated with the conveyor stopped switch. If the wiring is correct, check to see if the conveyor stopped switch has failed by removing the wires from the terminals, alternatively shorting the two wires together and pulling them apart. The conveyor stopped LED lamp on the Control Panel should turn off when the two wires are shorted together.

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Electrical Tests

WARNING! The following tests require opening the cover of the controller and must be performed by adequately trained personnel. Hazardous voltages are present which can cause serious injury or death.

Turn the Power switch to the Off position. You will see all display LEDs and lamps go off. Remember, any power connections to the controller are still live. CAUTION! High voltage (120 VAC, 208 VAC, 220 VAC, 315 VAC, 480 VAC, or 600 VAC) is present on circuit components such as relay boards, contactors, and temperature controllers. The only means to shut power off is at the circuit breaker. Consult the External Control Cabinet Wiring Diagram for specific details. Be certain all breakers are shut off before performing any tests or hook-ups!

Test power supply fuses by turning off sources of power at the breaker panel and using a continuity tester across the four fuses on the AC power (AP) card. This card is located at the top right hand corner of the back of the control panel. Also check the fuses on the dual relay (DR) cards, located on the inside of the lid. Turn power back on and use an AC voltage tester to check for 120/208 VAC at the input of the AP card and for 12/24 VAC at the output terminals of the AP card.

Remove the steel cover plate that covers the high voltage section and check the electric element fuses and the incoming power. The fuses may be tested and replaced by turning off incoming power at the breaker panel and using a continuity tester on each fuse. The incoming power is tested by turning the circuit breaker back on, then measuring the voltage on the input lugs of the contactors. 120, 208, 220, 315, 480 or 600 VAC should be present between the lugs. The disconnect switch will be turn on manually. Since the higher voltages are very dangerous, extreme caution must be employed when taking these measurements.

Next, turn the Power On/Off switch back on and measure the voltage at the output of the relay cards or contactors. On contactors, this is the three metal strips and lugs near the top of the contactor. The voltage measured at the inputs of the relay card or contactor should also be present across each of these outputs.

Finally, check the electric preheat element current using a clamp-on ammeter. This value should agree with the current requirement in the system specification.

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Thermocouple Usage

Catalytic oven systems can use up to three styles of thermocouples, all for different purposes. The first use is for temperature measurement of a zone. A thermocouple is used with each Digital Temperature Controller for proportional zone control. The other thermocouples are used for internal heater temperature sensing. This uses two different styles of thermocouple; one type for standard heaters, and the other type for Explosion-Proof (X-proof) heaters. The thermocouples are mounted inside each heater and are amplified by a Thermocouple Pre-Amplifier (pre-amp) or Thermocouple Transmitter mounted close to the heaters. The output of the pre-amp cards feed the Oven Control Card (CPU card). There are two styles of pre-amplifier cards: one used for standard heaters and containing 1, 2, 3, or 4 channels (for a like number of heaters), and a special dual pre-amplifier card for explosion-proof heaters.

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Thermocouple Wiring – General Notes

  1. The thermocouple wires must NOT be in the same conduit with preheat or solenoid wiring as the thermocouple signals are very sensitive to electrical noise.
  2. If the thermocouple lead wires are not long enough to reach their terminals, they can be extended using ONLY thermocouple wire or thermocouple extension wire of the same type as the thermocouple (for example, don’t mix J-type & K-type wires). Use of any wire other than the same type thermocouple wire will result in serious errors.
  3. The thermocouple wires are polarity sensitive. Be sure to match wire colors when splicing wires together. For both J-type and K-type wires, the red wire is negative.
  4. The best way to splice thermocouple wires is with small wire nuts (Marrettes). This ensures that the thermocouple wire conductors are in direct contact with each other. Screw-type or crimp terminals can be used only if the thermocouple wires are tightly twisted together first.
  5. Although the thermocouple signals are very sensitive to noise and must not be run near solenoid or preheat wiring, the outputs from the thermocouple pre-amplifiers used for the heater thermocouples are under no such restriction. In other words, it is allowable and safe for the pre-amplifier OUTPUT wires to share the same conduit as solenoids and modulating valves. Under specific conditions and only with the written permission of Trinity Electronics Systems Ltd, it may also be possible to include preheat wiring up to 240 VAC in the same conduit as the solenoid and pre-amp output wires.
  6. The output wiring from the pre-amp card to the CPU card uses standard copper wire. Do not use thermocouple or extension wire!

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Temperature Controller Thermocouple Wiring

The zone temperature thermocouples are connected to the digital temperature controllers in the control cabinet using thermocouple extension wires of the same type as the thermocouple, either type K or type J. The end of the thermocouple wires close to heaters should be thermally protected. Be sure to program the temperature controller for the type of thermocouple used or erroneous temperature readings will occur.

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Standard Heater Thermocouple Wiring

The thermocouple pre-amps are supplied mounted to the cover of a standard 4 & 11/16ths inch square electrical box. Each card has components to handle from one to four heaters, depending upon the physical layout of the oven. The boxes should be mounted in an accessible location near the heaters they are to be connected to, ensuring that the maximum temperature at that location will not exceed 75°C. Each heater is connected to the input of the pre-amp card using K-type thermocouple or extension wire. Be sure to match the wire colors to the lettering on the pre-amp card (R=red, Y=yellow). It is standard practice to protect the thermocouple wires from the heater to the pre-amp box with 3/8 inch flexible conduit.

The output terminals from the pre-amp card connect to the CPU card with ordinary copper wire. The best wire to use is single pair 18 AWG jacketed twisted pair cable, although almost any wire will suffice. The output wiring may share the same conduit as solenoid and modulating valve wiring. Note that shielded wire is not required.

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Explosion-Proof Heater Dual-Thermocouple Wiring

Explosion proof (X-proof) heaters differ from standard heaters in that they use a special dual element thermocouple. The pre-amp card is specific to the X-proof heaters in two ways: the card is designed to be mounted in the same round X-proof junction box that houses the thermocouple, and the two channels on the dual pre-amp card are matched for accurate tracking. Redundant temperature readings ensure that the CPU card can shut the system down in the event of a wiring error, electronic failure, or thermocouple failure. The pre-amp card must be mounted in a location that does not exceed 75°C.

Explosion-proof heaters are typically used in two different situations: area heating in hazardous locations, or in an oven that contains hazardous fumes. All wiring from the heaters to the general purpose area must be explosion proof

Area heating: Heaters used for area heating usually have the pre-amp mounted directly to the rear of the heater since the heater is exposed to cool ambient air. There are also two solenoids usually mounted to the back of the heater. The standard preheat voltage for this type of heater is 208 VAC or 240 VAC. All wiring (preheat, solenoid, and pre-amp output) can share a single conduit. The usual wire is type THHN: 12 or 14 AWG for preheat, 14 or 16 AWG for solenoids, 18 AWG for pre-amp outputs.

Ovens: The ambient temperature inside the oven is usually too hot for the pre-amp, so it must be mounted outside of the oven in an X-proof box. Heaters in ovens require two conduit runs: preheat wiring must be separate from the thermocouple wiring. This also allows the use of preheat voltages higher than 240 VAC. The wire from the heater to the pre-amp card must be K type thermocouple or extension wire and should be fiberglass insulated. The wire from the pre-amp card to the CPU card is the usual twisted pair jacketed PVC. The preheat wiring depends upon the temperature at the rear of the heater but is usually type SEW or SEW2.

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Thermocouple Diagnostics

Most thermocouple problems are a result of wiring errors. To determine which thermocouple(s) are reporting problems, refer to the display card on the front of the control panel. Thermocouples corresponding to lights that are off immediately upon a cold start are questionable, as are those whose lights do not go off after the normal preheat cycle. Catastrophic failures are indicated by flashing lights and/or an alarm code of 7 (alarm LEDs 1, 2, 3 all lit) and are normally the easiest to troubleshoot.

To check the wiring connections to the Oven Control Card (CPU card) or to read the internal temperature of the heaters, you will need to make measurements at the four pin terminal blocks connecting to the heaters. These measurements may be performed using an analog or digital voltmeter.

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CPU Board Identification

Refer to drawings TC_MEAS1, 2, 3 or 4 accompanying this document. There are two types of CPU cards in use today: the older 2nd generation card and the current 3rd generation card. The 2nd generation CPU card has a board number of L147a0 or L147a1 and can be identified in that it has a tab-type voltage regulator fastened to a black heat sink with a square-head (Robertson) screw and has an 18 pin CPU chip. The 3rd generation CPU card has a board number of L147b0, L147b1, L147b2, L147b3 or L147b4; does NOT have a heat sink; and has a 28 pin CPU chip next to an 8 pin EEPROM chip. The CPU chip and EEPROM chip are the only socketed chips on the board.

The signal common point on the 2nd generation CPU board is the screw holding the voltage regulator to its heatsink. Hold the negative (black) lead of the meter to this point.

The signal common point on the 3rd generation CPU board is the left most (GND) terminal of the 3 pin connector at the top of the CPU card marked “GND RX TX” or “GND TX RX” (Rev a or Rev b card). Connect the negative (black) lead of the meter to this point.

The CPU card 4 wide screw terminal blocks connecting to the thermocouple pre-amps are different for X-proof systems and standard systems. The terminal blocks are mounted on the CPU card slightly differently and the pins have different functions.

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Terminal Identification

Standard Heater Terminal Connections

Each 4 pin terminal block connects to 2 heaters (refer to drawings TC_MEAS1, 2, 3 or 4). The top-most and bottom-most terminal on each block is the power supply to the pre-amps and should read from 14 VDC to 18 VDC. Of the two middle terminals, the lower is the lower number heater, the upper is the higher number heater. In other words, the signal terminals are the 2 middle terminals in each 4 wide terminal block and the heater number increases from the bottom up.

Explosion-Proof Heater Terminal Connections

The thermocouples used for X-proof heater temperature sensing are dual thermocouples in a single housing. This redundancy allows detection of problems which could not be detected using a single thermocouple; specifically pre-amp, wiring, and multiplexer faults. The control system reads both thermocouples and must see agreement within 6.25% or it will shut down the affected zone of the heating system.

Each 4 pin terminal block connects to a single heater (refer to drawings TC_MEAS1,2,3 or 4). The top-most terminal is GND. The next terminal is the power supply to the dual pre-amp card and should read from 14 VDC to 18 VDC. The two bottom-most terminals are the signal pins. The voltage at the signal pins should be within 5% of each other. The heater number increases from the bottom up.

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Voltmeter Tests

Ensure that the negative (black) lead of the meter is connected to signal common as described earlier (refer to drawings TC_MEAS1, 2, 3 or 4).

Begin by measuring the power supply voltage. A voltage less than 12 VDC indicates a possible power supply problem. A voltage near 0 usually indicates a short or other overload – confirm this by feeling (gently!) the gold colored discs near the edge of the CPU boards. A disc that is too hot to touch indicates an overload. Look for strands of wire touching where they should not be. Record the measured power supply voltage, you will need this reading for some of the tests following.

Measure each connected heater’s signal lead. A signal voltage reading of 0.75 VDC to 4.25 VDC on the signal terminal is normal. Refer to the table at the end of this document to determine the heater temperature.

A signal voltage near 0 VDC indicates a disconnected or defective thermocouple pre-amp. Measure the voltage across the two output terminals at the pre-amp card. A voltage reading of 0 VDC indicates a broken or disconnected wire. A voltage exactly equal to the measured power supply voltage indicates a defective pre-amp channel. A voltage between 5 VDC and the measured power supply voltage is normal.

A signal voltage reading above 4.75 VDC is also an alarm condition. If the signal voltage is exactly equal to the measured power supply voltage, look for a short on the two wires that connect that pre-amp channel to the CPU card. Try disconnecting one of the wires for that channel at the pre-amp board and see if the signal voltage drops to 0. If it does, the pre-amp is most likely defective. If not, there is a short in the pre-amp wires back to the CPU.

A signal voltage reading that is a couple of volts less than the measured power supply voltage most often indicates a disconnected or defective thermocouple. Try disconnecting the thermocouple from the pre-amp board and measuring its resistance. A resistance greater than 25 ohms indicates a defective thermocouple. Also try putting a jumper wire on the R-Y terminals of that pre-amp channel in place of the thermocouple. The signal voltage at the CPU card should now read between 0.75 VDC and 1.0 VDC.

The last problem is best diagnosed when starting the oven from a cold start. Measure the signal voltages on all the connected thermocouple channels every 20 seconds or so and observe the voltage change as the heaters warm up. A channel that shows a voltage DECREASE as the heaters warm up indicates that the thermocouple is wired to the pre-amp card backwards. If the wire colors match the letters on the card, replace the thermocouple in the heater. On rare occasions, the thermocouple manufacturer has been known to swap the lead wires inside the epoxy transition area at the rear of the thermocouple. This causes all manner of strange readings and can only really be detected from a cold start (while the back of the heater is at cold). A thermocouple that has its lead wires reversed inside the transition is not usable and must be replaced.

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Temperature Measurements

It is possible to read the approximate internal thermocouple temperature of each heater using nothing more than a simple multi-meter, either analog or digital. The thermocouple pre-amps convert the thermocouple signals into currents so that wire resistance doesn’t effect the value. The current is then turned into voltages by precision resistors on the CPU card. These voltages can be read right at the pre-amp terminal blocks on the CPU board as shown in the following table.

The internal thermocouples are placed at the rear of the catalyst pad inside the heater. Note that the internal temperature of the heater can be very different from the temperature at the face of the heater. The notes to the right of the voltages are based upon software versions CIS2b2c and CIS3a0X.

Temp (°C) Volts Notes: Software Versions CIS2b2c & CIS3a0X
100 1.29 Minimum preheat temperature with electric elements
125 1.41 Minimum operate temperature
150 1.54 Hot start threshold temperature
200 1.79
250 2.04
300 2.31
350 2.55 Max startup temp (begin preheat duty-cycle modulation)*
400 2.81
450 3.06
500 3.33
550 3.59
600 3.85
650 4.12
700 4.39


*Preheat duty-cycle modulation – This is a safety feature designed to limit the maximum temperature while the electric elements are powered. The controller will turn the preheat contactor on and off when the temperature exceeds 350 degrees Celcius. The ratio off “on time” to “off time” or duty cycle is varied to prevent over heating.

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If you have any further questions, or for further assistance, please contact:

Trinity Electronics Systems Ltd.  (1-888-480-3199)