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TROUBLESHOOTING
All the following steps are assuming the unit is not having flame failure problems. If the problem
you are trying to rectify is one that requires the flame relay needs to be reset, it is not likely the
109 is related. The only exception would be if the 109 relay contacts at the 109 terminals “8” and
“9” are intermittent. If you are having temperature control problems or not establishing power to
the flame relay because the 109 relay terminals are not closing, then the following is relevant.
In mot instances troubleshooting the 109 is a matter of determining if the problem is with the 109
or another component. It is usually best to determine this by breaking the system into component
sections. We recommend the following steps.
1. Ensure there is a proper 24 VAC power supply to the 109 at the “T and T” terminals.
2. Disconnect the temperature control device from the 109. After this is complete connect a
potentiometer to the 109 series 90 terminals. If possible use a 135-ohm or a 270-ohm pot. If
none of these are available you can use a slightly larger value pot or a series 90 modulating
control such as a T991A or T991E. The purpose of this is to prove the 109 and the
associated components connected downstream of it are working correctly. In most instances,
internal 109 failures will be revealed with this step.
Connections for the pot are as follows:
- Connect the pot centre tap to 109 terminal “2”.
- Connect the pot end terminals to the 109 terminals “4” and “W” respectively.
- Turning the pot one direction should create a call for heat and turning the pot the
other direction should stop the call for heat. It should be possible to modulate the
control in between these points to obtain any mid range firing position.
3. Assuming the above works properly, the 109 and the components located downstream
(relays, gas valves etc.) are all operating to satisfaction. If a problem returns when the
original temperature control device is connected, check the temperature control device for
faults. If the system still did not operate to satisfaction when operated as in step 2 above,
shut the unit off and go to step 4.
4. If the 109 did not modulate the gas valve properly, remove the pot from the 109 and connect
the pot to the modulating section of the gas valve. The centre tap of the pot will connect to
the “R” terminal of the modulating valve. Connect the other two pot terminals to the “W” and
“B” terminals of the modulating valve. When the unit is again fired and power is re-
established to the modulating valve, the modulating valve should now be able to be
modulated by the pot. Turning the pot up and down should cause the valve to open and shut.
NO FIRE
This test is to ensure the 109 relay terminals “8” and “9” are closing. Insure 24 VAC supply is to
the 109. Disconnect the discharge control wires and simulate a call for full heat by the following.
Jumper 109 terminals “2” and “4”, or set the test potentiometer (described at point 2 above) on
the 109 to the setting that reduces the resistance across the 109 terminals “2” and “4” to zero.
This should cause the 109 to go to a call for high fire and close the relay terminals “8” and “9” to
energize the heat relay. Note there are other relays in the heat circuit that must also be closed to
activate the flame relay. If the flame relay got proved pilot, then the burner should go to at least a
low fire setting when the flame relay activates the main valve. If the 109 did not close the relay
terminals “8” and “9”, replace the 109.
(54 paginas)
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