LAARS Mini-Therm JVi - Install and Operating Manual - Manual (Page 19)

LAARS Heating Systems
Page 18
3B. Electrical Troubleshooting
1. Remove the control box cover on the front of the
boiler.
2. Verify that 115 volts is reaching the boiler by
testing across the black wire and the white wire
on the transformer.
3. Verify 24 volts transformer output by placing the
meter leads on the yellow and red wires. If
24 volts is not evident, replace the transformer.
Perform the following series of tests with one
meter lead attached to the yellow wire on the
transformer.
4. Place the second lead on the “W” connection on
the terminal board. Turn the wall thermostat high
enough to call for heat. If the meter fails to
register 24 volts, the thermostat or its circuit may
be defective.
5. Make sure the thermostat is set high enough to
call for heat. Place second lead on the “A”
connection on the terminal board. If voltage is
evident, skip to step 6.
If no voltage, test the circuit between the red
wire on the transformer and terminal 4 on the pump
relay; from terminal 6 on the pump relay and the “A”
connection on the terminal board; and from the orange
wire terminal on the pump relay to the “W”
connection on the terminal board. If no output is
found, the connections or the pump relay could be
defective.
6. Place the second lead on the purple wire terminal
on the hi-limit switch. If no voltage across the
switch, check for defective hi-limit, open circuit
due to excessive water temperature, or a low
temperature setting.
7. Place the second lead on the blue wire terminal
on the fan proving switch. If voltage is present,
skip to step 8. If voltage isn’t present,
connections or the draft inducer/motor could be
defective.
8. Verify the voltage across the roll-out safety
switch.
9. If it is determined that there is voltage to the gas
valve, the pilot is lit and the pilot sensor is
properly positioned, and the thermostat is set
high enough to call for heat, the gas valve or the
pilot assembly may be defective.
Caution
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
WARNING
Follow local regulations with respect to installation of
carbon monoxide (CO) detectors and
manufacturer’s maintenance schedule of the boiler.