LAARS U.H.E. - Service Manual - Manual (Page 9)

U.H.E Service Manual Page 9
Lockout conditions:
The system will go into lock out mode for the following reasons:
Blocked vent pressure switch contacts open:
Check for obstruction in exhaust pipe and vent terminal.
Check for blocked condensate trap or drain line. In cold climates, make sure drain is not frozen.
No ignition after 3 attempts:
a) Check inlet and outlet gas pressures (pressure taps located on top of gas valve).
b) Igniter resistance too high (lower resistance preferred < 150 ohms).
c) Misadjusted veturi screw (should be 6.5 turns out from bottom).
d) Flame sense microamp not present (1.0 microamps minimum, should be 5 microamps or more). If burner lit,
check flame rod for deposits.
e) Check burner tube condition. Refer to section UHE-III for Burner Tube Inspection and Replacement.
Ignition Module Specifications
- Ignition & heating functions in response to thermostat.
- Hot surface ignition using a microprocessor to control timing, flame sensing using flame rectification & ignition
retries.
- Monitoring of system pressure switches and limit switches.
- Control of gas valve, inducer motor, and hot surface igniter element based on thermostat demand and status of
safety inputs.
- Diagnostic indicators to provide information on power to control and control status.
- Non-interchangeable polarized plug-in connectors for all interconnections.
Control Functions:
- Thermostat call for heat.
- Blocked vent pressure switch
(normally closed)
- Flame sensing.
- Low voltage supply.
- Line voltage supply.
Control Inputs: Control Outputs:
Lockout Conditions
- Inducer motor
- Hot surface igniter
- Gas valve
- Status indicator LEDs
Power - Green
Purge - Red
Igniter - Red
Valve - Red
Flame - Red
IGNITION MODULE
WIRING DIAGRAM
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