The RTRM uses a communicating ignition module to pass commands, status and diagnostics back and forth.
Before the RTRM will command heating on, the following criteria must be met:
- Unit must be in Heat Mode
- Ignition Module must be online and communicating
- No other unit lockouts present on the unit
Is my unit in Heat Mode?
- For thermostat control units, 24 vac on W1 and/or W2 would be heat mode
- For dual fuel heat pump units, gas heat is requested on W2 or X2
- A unit with any cooling call with a heating call will not heat until the cooling call is removed
- For zone sensor controlled units, heat mode is driven by space temperature vs. space temperature setpoint. It may be necessary to raise the setpoint through the BAS or at the zone sensor to force heat mode.
- For units configured as VVDA (MZVAV), there is a 6 min time delay before the unit will begin to heat, this applies in test mode as well.
If not able to get the unit in heat, use Test Mode on the LTB to operate heat.
Does the IGN Module have power?
The IGN Module has a status LED that gives the status of the module. The placement of the LED1 varies based on the age of the ignition module and based on if it is installed in a Precedent or Voyager II (different boards).
Precedent 2 Stage Ignition Module (single stage similar):
Voyager II Ignition Module:
IGN LED1 will be solid green with no heat call or in a slow pulse (3/4 sec on, 1/4 sec off) for a heating call. LED1 will also blink codes (1/4 sec on, 1/4 sec off with a 2 sec pause at the end of the code) for diagnostics. See the link below for details on LED1 blink codes:
What are the gas heat fault codes for Precedent units?
What are the gas heat fault codes for Reliatel controlled Voyager II units?
If LED1 is out, this indicates that there is no power to the ignition module.
On Precedent units with ReliaTel controls, power comes from the backside of LTB1-5 (same LTB that the test mode terminals are on) to IGN P1-7:
On Voyager II units with ReliaTel controls, power comes directly from the RTRM J5-1 to IGN J1-7:
Note: Wire numbers will vary based on cabinet size and unit age, see unit wiring diagram for more details.
One Flash Diagnostic on LED1 (¼ sec on, 2 ¼ sec off)
No Communications
A 1 Flash diagnostic on the board is indicating that the ignition module has power but is not communicating to the RTRM. This indicates a problem with the communications between the RTRM J5 and ignition board P1 (12 pin connector). The RTRM will also have a 2 flash diagnostic on LED2 indicating that a diagnostic is present.
The communication voltage can be measured with a meter as the ignition board.
- J5-4 (+) to J5-3 (-) when connected to a good ignition module will read 9.6-10.7vdc pulsing approx every 15-20 sec.
- J5-4 (+) to J5-3 (-) when disconnected will read 10.5 to 11.2vdc pulsing approx every 15-20 sec.
Two Flash Diagnostic on LED1 (¼ sec on, ¼ sec off, 2 times w/ 2 sec pause)
Failure to sense flame
A 2 flash diagnostic indicates that either no flame was sensed on ignition or that the flame dropped out while running. Troubleshooting for this issue would be the same for any gas heat unit that uses a flame sensing rod or element for proving.
- Verify that the gas is on to the unit and the inlet/line pressure to the gas valve is between 4.5" - 14"
- Verify that gas valve opened and that manifold pressures are set correctly (see unit IOM for pressures)
- Note on Voyager II staged gas heat, the manifold pressure it negative, it should be set to -0.20" +/- 0.15"
- Verify that ignitor is working and that there is gas flow
- On Precedent units, verify that there is not an obstruction with the manifold gas spuds/orifices
- On Voyager II units, verify that the manifold pressure is negative and not positive
- Verify the flame sensor operation
Precedent flame sensor troubleshooting
Flame Sensor Testing on Staged Gas Heat
Voyager II Hot Surface Ignitor troubleshooting
Flame Signal Testing on Voyager II
Hot Surface Ignitor (HSI) Troubleshooting and Specifications
Three Flash Diagnostic on LED1 (¼ sec on, ¼ sec off, 3 times w/ 2 sec pause)
Pressure Switch failed to close or stay closed
A 3 flash diagnostic indicates that the the pressure switch did not close in the correct amount of time after the combustion fan was energized, opened while the unit was heating or is closed when the combustion fan is commanded off. Only Precedent units use a pressure switch, Voyager II does not require a pressure switch due to the use of a negative pressure gas valve.
Combustion Fan not running
The combustion fan on both Precedent and Voyager II unit with ReliaTel controls is a 2 stage 208-230/1ph capacitor start motor. On 460/575vac units, power for the combustion fan motor is supplied by a step down transformer.
On Precedent units, the ignition module takes one leg of power in on L2 and switches the L2 leg between Lo or Hi/Single to operate the fan at high or low speed. The other leg of power is applied directly to the motor (typically the black wire) and is hot at all times.
On Voyager II units, the ignition module takes on leg of power in on L1 and switches the L1 leg between HI/Single or LO to actuate the Combustion Fan Relay (CFR). This relay was only present on V2 starting around 2011 and on, it disconnects one leg of power from the fan motor when there it no call for heat and controls the is used as part of the speed control. The other leg of power is applied directly to the motor (typically the purple wire) and is hot at all times.
Older Voyager units did not utilize a CFR and had 2 hot legs at all times. The motor was started and the speeds were changed base on how power was applied to the black and orange wires. IF you have a combustion fan motor that will not turn off, see this article for troubleshooting → Voyager II Combustion Fan runs all the time
Combustion Fan Runs, but I'm getting a still getting a 3 blink code on the ignition module
If the combustion fan is coming on, but still not making the pressure switch, verify the following:
- pressure switch tube and pickup port on heat exchanger/combustion fan housing are clear of debris and moisture
- Verify the pressure switch has 24vac from one side of the Flame Rollout Switch from LTB1-3 at all times on.
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The 24vac for all the heat safeties are daisy chained to one side of each switch with the output of that switch going to it's respective input on the ignition module.
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- Using a manometer, tee into the pressure switch line to validate the pressure the switch is seeing. The switch trips at 0.15" wc +/- 0.07" wc
- The switch opens ~ 0" wc
- If pressures are not high enough to actuate the switch, verify that the exhaust flue is open and not obstructed and that the burner openings are also not obstructed
No call for heat, but I'm getting a still getting a 3 blink code on the ignition module
This fault can also be caused by a pressure switch that is closed when the combustion fan is not commanded on or jumped out.
Verify that the switch is wired for Normally Open operation, closes on pressure and that there are not jumpers present across the pressure switch terminals/wires. If testing shows the switch closed with the wires removed, replace the pressure switch.
Four Flash Diagnostic on LED1 (¼ sec on, ¼ sec off, 4 times w/ 2 sec pause)
High Limit switch protection device open
A 4 flash diagnostic indicates that one or both of the Thermal Cutout (TCO) switches are open during a call for heat. TCO lockouts are auto reset and will do not require a manual reset. When a TCO trips, it will keep the supply fan on, run the combustion fan at high speed.
On Precedent, TCO1 receives power from the common power side of the pressure switch. They are wired in series where TCO1 feeds 24vac to TCO2. Trouble shooting should always start by verifying that 24 vac is present on both sides of TCO1 then down to TCO2.
The 24vac path is shown below:
On Voyager II, TCO1 receives power from Control Terminal Block 2 (CTB2) which is powered by Transformer 3 (TNS3). They are wired in series where TCO1 feeds 24vac to TCO2. Trouble shooting should always start by verifying that 24 vac is present on both sides of TCO1 then down to TCO2.
TCO trips are typically caused by a low airflow situation or damaged TCO wiring/switch/mounting. TCO locations vary based on the unit size, but there are always 2. TCO1 will be located in the burner section and TCO2 will be installed in the side of the indoor fan housing or on the fan assembly mounting frame (6-10T Precedent w/ plenum fan)
Looking for TCO locations on 3-5T or belt driven fan → Coming Soon!
Looking for TCO locations on 6-10T Precedent w/ ReliaTel Controls → Where is TCO1 & TCO2 located on a Precedent 6 - 10 ton Legacy Precedent with the BC Plenum Motor?
Looking for TCO location on Voyager II → Coming Soon!
Airflow adjustments vary by unit type, but V2 and belt driven Precedent, adjustments are made at the motor sheave typically. On variable/multispeed Precedent only, fan speed is adjusted on RTOM potentiometer R136 "DA COOL/FAN SPEED"
Five Flash Diagnostic on LED1 (¼ sec on, ¼ sec off, 5 times w/ 2 sec pause)
Flame sensed and gas valve not energized, or flame sensed and no call for heat.
A 5 flash diagnostic indicates that the ignition module is sensing a flame without a call for heat. This could be a failing flame sensor or a gas valve that is not closing. When the ignition board is in a five flash, the combustion fan will be on at high speed.
Troubleshooting would include checking the signal from the flame sensor as shown in the troubleshooting for a 2 flash diagnostic shown above.
If the gas valve is not closing, immediately isolate/close the gas valve from the unit
If voltage is present remove the low voltage connection from the valve and check voltages again from the board, stray voltage from the board with no call requires ignition board replacement and locking the gas valve out until the board is replaced.
Verify wiring between the ignition board and gas valve.
If voltage is not present and the valve is staying open, lock out the gas until the valve is replaced.
Six Flash Diagnostic on LED1 (¼ sec on, ¼ sec off, 6 times w/ 2 sec pause)
Flame Rollout Switch open (Precedent Only)
A 6 flash diagnostic indicates that the temperature at the top of the heat exchanger has reached the trip limit and or there is an actual flame on the top of the burner (rollout).
The Flame Rollout (FR) receives power from LTB1-3. Trouble shooting should always start by verifying that 24 vac is present on both sides of FR.
The 24vac path is shown below:
Troubleshooting flame rollout includes:
- Check heat exchanger for cracks
- Check for dirty/stopped up heat exchanger (typically caused by improperly set gas pressure, set too high)
- Check gas pressures, see IOM for settings
- Check combustion fan operation and verify that it is running in both speeds and is staying on at all timesIf the combustion fan is shutting off and the heat is not shutting off in 5-9 seconds after the fan loses power, a functional check of the pressure switch is necessary
A tripped flame rollout requires a manual reset at the flame rollout switch.
If the switch, wiring, burner or any other part of the burner is compromised from a flame rollout, close and lockout the gas valve until repairs can be completed.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.