Installation Guide

55
55
Code Fault Diagnosis Step
Remedy
LO
Temperature limit
switch fault (cont’d)
2. Verify state of temperature limits’
contacts
Remove wire leads from limit switch and jumper leads. Operate heater. Measure
continity across limit switches. If closed, LO code is not caused by temperature limit
switch fault. If open, proceed to step 3. Remove jumper from leads and reconnect
leads to temperature limits.
3. Verify that water ow is adequate
Verify that water ow rate to heater is above the minimum required
(20 GPM for H150FD and H200FD, 25 GPM for H250FD and H300FD, 30 GPM for
H350FD and H400FD). If OK, proceed to step 4.
4. Temperature limit switch is
defective.
Replace temperature limit switch.
IF
Ignition Failure 1. Ensure gas supply shutoff valves
are open.
Ensure that main gas shutoff installed adjacent to heater is open. Ensure that knob on
gas valve inside unit is in ‘‘on’’ position. If OK, proceed to step 2.
2. Check for low gas supply
pressure
Ensure inlet gas supply pressure is between the minimum and maximum values
indicated on rating plate. If OK, proceed to step 3.
3. Check for faulty ame sense
wiring or connection.
Inspect ame sense wiring. Ensure wire harness terminals are securely fastened to
ame sense and to control module. If OK, proceed to step 4.
4. Check for faulty gas valve wiring
or connection
Inspect gas valve wiring. Ensure wire harness terminals are securely fastened to spade
terminals on gas valve. If OK, proceed to step 5.
5. Check for gas valve failure or gas
valve relay failure.
1. Measure voltage across gas valve during trial for igintion. If 24VAC is present and
gas valve does not open, gas valve is defective. Replace gas valve.
2. If 24VAC is not present, gas valve relay on control module is defective. Replace
control module.
6. Check for blockages in gas
orices and burners
Inspect gas orices for blockages which could prevent gas ow. Remove and inspect
burners for blockages.
AC
Blower vacuum
switch closed.
1. Check for defective blower on
relay or control module.
Disconnect Blower plug fron Control Module. With heater off, measure continuity
across pins 1 and 2 of receptacle on Control Module. If closed, control module relay is
defective. Replace control module. If OK, proceed to step 2.
2. Vacuum switch is defective.
Replace blower vacuum switch.
AO
Blower vacuum
switch open.
1. Check for faulty vacuum switch
tubing
Check tubing and replace if necessary. If OK, proceed to step 2.
2. Check for faulty vacuum switch
wiring or connection.
Inspect vacuum switch wiring. Ensure wire harness terminals are securely fastened to
spade terminals on vacuum switch. If OK, proceed to step 3.
3. Check for faulty blower wiring or
connection
Inspect blower wiring. Ensure plug on blower is securely fastened to control module.
If OK, proceed to step 4.
4. Check for defective vacuum
switch
Disconnect Blower plug from Control Module. Measure resistance across Blower
windings. Winding resistance across lead should be in the following range; Red-to-
White: 8 to 9 ohms. If measured values vary substantially from these values, Blower
is defective. Replace. If OK, proceed to step 5.
5. Check for defective blower relay.
Disconnect Blower plug from Control Module. Place heater in Pool or Spa Mode.
Lower set point temperature to generate call for heat. During pre-purge period,
measure for 120VAC across pins 1 and 2. If 120VAC is not present, control module
relay is defective. Replace control module. If OK, proceed to step 6
6. Vacuum switch is defective
Replace blower vacuum switch.
bO
Bypass Operation 1. Check to see if Control Module
is in Bypass Operation
This is normal display when heater is being controlled by a remote thermostat. No
service is required. If heater is not being controlled by remote thermostat, change
setting by using the MODE key to put the heater into STANDBY. Press and hold
the DOWN key and then press and hold the MODE key. Hold down both keys for 3
seconds until the indication ‘‘bO’’ is removed from the display.
Figure 32: TROUBLESHOOTING