Detroit Radiant Products Company HL3 Series - Manual (Page 17)

17
HL3 Series
Check to make sure gas pressure is within minimum and
maximum inputs, as indicated on the heater’s rating plate.
Is gas pressure OK?
Were the gas lines purged of air?
Is the heater properly
grounded? Is the heater’s
polarity correct?
With microampmeter, check DC
amperage at flame rod. Is it
greater than 1.0 microamps?
Check to make sure flame
sensor wire is OK and then
replace circuit.
Sensing rod is faulty or flame is weak.
Check to make sure heater is operating
at proper gas pressure as indicated on the
heater’s rating plate and then, if needed,
replace sensing rod.
Replace gas valve.
Yes
Correct problem.
Correct problem.
No
No
Yes Yes
No
Yes
Purge gas line.
No
4.0 Troubleshooting Guide
Is there 24V across the GROUND and HIGH
(HIGH to COM on heaters with optional
isolation relays) on the terminal strip located
on the outside of the control box?
Repair or replace faulty
wiring or thermostat. Replace relay.
No
If heater does not go into high fire mode:
Measure voltage across the red wire
on the VALVE and GROUND (red wire
on RELAY to GROUND on heaters with
isolation relays). Is it 24V?
Yes
No Yes
Replace gas valve.
NOTE: To confirm that the heater is not in high fire mode, check manifold pressure.
If manifold pressure is 3.3” to 3.5” for natural gas or 9” to 10” for propane, the light is faulty and should
be replaced.
When the heater is in low fire mode, manifold pressure is approximately 2.0” to 2.5” for natural gas or
5.0” to 6.5” for propane. If this is the case, the following troubleshooting steps should be followed: