Cata-Dyne™ Infrared Oven

Operation and Instructional Manual - Thermocouples

Cata-Dyne™ infrared 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.

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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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.

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.

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.

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.

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