A
G-TRAC2
IOM-25
40 of 42
Mar 99 R7
form. Combustion that is set at maximum efficiency will produce excess moisture. Often it is desirable to have 1% to 2%
higher excess oxygen readings then those normally listed to assist in keeping the flue gases drier. Also note that extended
chimneys can contribute to condensation problems
(especially if they are not insulated or at least double walled)
. Water in
the heat exchanger can lead to premature failure due to thermal stress or freezing. Another source of excess condensation
is when a unit designed with capacity to heat 100% outside air is operating with very little outside air, therefore operating
at a low fire or cycling. This allows the cool flue gases from low fire to cool and condense in the chimney.
Burner Pulsing, Backfiring, Exploding, Noisy
An improper air/fuel mixture usually causes this condition. Do not attempt to do any combustion analysis until the inlet fuel
pressure has been checked with the unit operating at high fire.
(This should include other loads on the same gas system
being on.)
If the inlet pressure falls too low then the velocity of the air over the flame will be too great and tear the flame. If
the burner is designed and set up for proper fuel pressure and it does not have it, it will react exactly like a burner with too
much combustion air. If the inlet fuel pressure is correct at high fire then the combustion set up should be checked.
If an explosion occurs after the fire has been off and is in the process of being re-lit, it is likely due to a leaking gas valve. It is
recommended that both the main and pilot valve be replaced if you cannot prove the source of a leak.
Fire without Combustion Fan
If there is a flame operating in the burner section without the combustion fan in operation, check to see if there is power
across the G-TRAC2 terminal 3 and neutral. Record the result. Next check to see if there is power on G-TRAC2 terminals 2
and neutral. Record the result. Next, check to see if there is power to G-TRAC2 terminals T1 and T2. Record the result.
If there is no power to any of the above terminals and if all wiring is as per the original diagram, there should not be any
power to the pilot or main gas blocking valve. Very gently turn off the manual valve for the pilot gas. Check to see if the
flame has gone out. If it has then the pilot solenoid is likely leaking. If the flame is still on gently turn off the main firing
valve. If this stops the flame then the main valve has been leaking. At this time turn off the line valve to the unit and repair
the problem.
Heat Locked On – G-TRAC2 Slave to C-TRAC
Change G-TRAC to model 2.2
Set C-TRAC cooling deadband pot 3 to 4 degrees higher than normal.
Set C-TRAC heat envelope pot to position 1.5.
Heat may stay on due to G-TRAC2 integral timing if the G-TRAC2 heat switch is left on when the C-TRAC switches to
mechanical cooling. Stage 1 mechanical cooling call should turn power off to G-TRAC2 terminal “HS” by opening relay
contacts.
Prepurge Light Stays at “Damper Moving” Status
If the pre-purge light indicates that it is in the “Damper Moving” status for an extended period of time, and the damper
motors appear to have reached the end of their stroke, the problem is often the resistance value from the feedback pot in
the damper operator. Pushing the actuator linkage often moves it enough to correct the problem. Refer to Section XXII for
a diagram and description of this pot and its settings. Just tweaking this pot a few ohms will resolve the problem if it is
repetitive.
Replacing a G-TRAC2 in the Field
If the G-TRAC2 air operator, combustion air damper, main burner modulating valve or its operator is changed, the
combustion should be re-checked for correct set up. After the change is complete, operator travel and combustion should
be checked for proof of repetitive operation at least three times before acceptance. To just check it once is not acceptable.
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