56
Code
Fault
Diagnosis Step
Remedy
HF
Flame Present
with Gas Valve
not Energized
1. ICB is defective
Using the sight glass, check to see if the fl ame is present in the
unit. If not, replace ICB. If fl ame is present, move to next step.
Without disconnecting the valve from the wiring harness, use
a voltmeter to determine if 24 VAC is present at the gas valve
connections. If so, replace ICB. If not, move to step 3.
2. Gas Valve is defective
Replace Gas Valve
LO
Water pressure
switch fault
1. Verify that the pump is
running.
This is a normal display when the pump is off. Turn pump on.
LO code should clear. If LO does not clear, proceed to step 2.
2. Verify that water fl ow
is adequate
Verify that water fl ow rate to heater is above minimum
required (25 GPM for TR250 and 30 GPM for TR400). If OK,
proceed to step 3
3. Check for faulty wiring
or connection.
Inspect water pressure switch wiring. Ensure wire harness
terminals are securely fastened to spade terminals on water
pressure switch. If OK, procced to step 4.
4.Verify state of water
pressure switch contacts.
Remove wire leads from water pressure switch and measure
continuity across water pressure switch with the pump
running. If open, proceed to step 5. If closed, LO code is not
caused by water pressure switch fault. Reconnect wire leads to
water pressure switch.
5. Ensure that low pump
pressure does not exist.
Clean fi lter or clear blockages. Check position of valves in
plumbing system. If OK proceed to step 6.
6. Check for correct water
pressure switch setting.
Adjust water pressure switch setting as shown on page 35 of
Installation Manual (only if heater is above or below water
level). If LO does not clear, proceed to step 7.
7. Water pressure switch
is defective
Replace water pressure switch.
Vent pressure
switch fault
(applies only
if indoor
installation)
1. Check for faulty wiring
or connection.
Inspect vent pressure switch wiring. Ensure wire harness
terminals are securely fastened to spade terminals on vent
pressure switch. If OK, proceed to step 2.
2. Verify state of vent
pressure contacts.
Remove wire leads from vent pressure switch and jumper leads.
Operate heater. Measure continuity across vent pressure switch.
If closed, LO code is not caused by vent pressure switch fault. If
open, proceed to step 3. Remove jumper from wire leads and
reconnect wire leads to vent pressure switch.
3. Check for restricted or
blocked fl ue.
Ensure that fl ue is not blocked or restricted. See indoor vent
sizing requirements in installation manual. If OK, proceed to
step 4.
4. Vent pressure switch is
defective.
Replace vent pressure switch.
Temperature
limit switch
fault
1. Check for faulty wiring
or connection.
Inspect temperature limit switch wiring. Ensure wire
harness teminals are securely fastened to spade terminals on
temperature limit switches. If OK, proceed to step 2.
Figure 28:
TROUBLESHOOTING