Thomas & Betts UDAP - Manual (Page 34)

Form RZ-NA I-UDA, P/N 195673 Rev 5, Page 34
Trial for Ignition
Call for Heat
Is there a
spark across gap at
ignitor?
Does gas
ignite?
Is there minimum
flame current at the
flame sensor?
Is there
minimum flame current
at the control
module?
Replace control
module.
Check connections to flame
sensor and/or moisture in the
burner assembly.
Is the flame
sensor corroded?
Clean flame
sensor.
Is the sensor
located in flame
correctly?
Replace flame
sesnsor.
Reposition
flame sensor.
Is gas
flowing?
Is the ignitor
position correct in the
gas flow?
Check gas pressure
and supply voltage.
If either are low,
correct and repeat
startup.
Reposition
spark ignitor.
Is there
24VAC at the gas
valve?
Is there 24VAC
from gas valve output on
control module to
chassis?
Check wiring and
connections to
gas valve.
Replace
ignition
control
module.
Replace gas
valve.
Is there
spark voltage at
control?
Check high
voltage wire
continuity.
Is there 24V P1-2
to power control?
Replace
control
module.
Check wiring
and/or 24VAC
transformer output.
YES NO
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NO
YES
NO
YES
NO
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YES
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40. Troubleshooting
37. Flame
Rollout
Switch -
Sizes 30-125
only
39. Vent or Vent/
Combustion
Air System
For location, see
FIGURE 18, page 31.
The cause of a flame rollout switch activating must be determined. Activation of
the manually reset flame rollout switch could be caused by one or more of the
following:
• Restricted combustion air inlet or exhaust outlet
in combination with a defective pressure switch
• Building exhaust
• Electrical power interruption during operation
If a flame rollout switch trips, inspect the burner/control compartment for signs of
excessive heat and burned wiring.
If the compartment appears normal, reset by depressing the red button on the
switch. 15 to 20 minutes are required for the switch to cool sufficiently for reset-
ting. A distinct click will be felt when the switch resets. Operate the furnace. If
the flame rollout switch trips again, determine and correct the cause before reset-
ting the switch.
If there is damage to the control compartment, repairs must be made before
resetting the switch.
If it is determined that the flame rollout switch needs replacing, use only the fac-
tory-authorized replacement part that is designed for that size of heater.
38. Disconnect
Switch -
UDAS only
• Restricted or plugged
heat exchanger
• Pressurization of the
heat exchanger
The disconnect switch is located in the sealed electrical box inside the con-
trol compartment with the toggle on the rear of the heater.
If it is determined that the disconnect switch needs replacing, use only the
factory-authorized replacement part that is designed for the heater. Always
replace electrical box cover.
Check the complete system at least once a year. Inspection should include all joints,
seams, concentric adapter box (UDAS), inlet air guard or inlet air cap (UDAS), and
the vent terminal cap. Clean openings. Replace any defective parts.
DSI Integrated Control Module
(Circuit Board) Trial
Troubleshooting
Flowchart