Troubleshooting - A.O. Smith HW 300 User Manual

Before any extensive troubleshooting, perform the following:
Ensure that:
• Voltage (120 vac) is supplied to the boiler.
• System control (tank temperature control, thermostat,
etc.) is calling for boiler operation (call for heat).
• Other contacts (switches) are closed (relay, low water
cutoff, flow switch, coil protector, pressure switch, etc.).
• Gas supply pressure is within the maximum and minimum
operating ranges listed on the boiler rating plate/label.
TABLE 3. CER-TEMP 80 RECOVERY SYSTEM CHECKOUT PROCEDURE
Use this checkout for Cer-Temp 80 Recovery Systems. (For hot water supply application only)
CHECKOUT SEQUENCE
Circulating pump and
Set tank temperature burner shut off.
control (thermostat)
20°F (10°C) below tank With thermal balancer,
water temperature. pump off delay of
approximately 2 minutes.
Set tank temperature
control (thermostat) Circulating pump and
20°F (10°C) above tank burner on.
water temperature.
Boiler outlet
temperature exceeds Circulating pump on.
210°F (100°C).
Set tank temperature
control (thermostat) System maintains desired
for desired water water temperature.
temperature.

TROUBLESHOOTING

SYSTEM OPERATION
CORRECT INCORRECT
Pump and burner remain
on.
Circulating pump on.
Burner on.
Circulating pump on.
Circulating pump and
burner off.
Burner on.
Circulating pump and
burner on.
• Voltage (24 vac) is supplied by transformer.
• Boiler is wired according to wiring diagram.
Note: Cross wiring the 24 volt circuit of the relay will short the
transformer.
• All wire terminals/connectors are firmly attached to
valves, modules, switches, limit controls, etc.
• For Propane (LP) models only check for possible lockout
condition of the ignition module.
CAUSE
Tank temperature control
(thermostat) defective.
System wiring is
incorrect.
Pump wired for
continuous operation.
Gas control valve stuck
or defective.
System wiring is
incorrect.
High limit control set too
low.
High limit control
differential too wide.
System wiring is
incorrect.
Coil protector switch has
activated.
Gas control valve or
wiring defective.
Power off or system
wiring is incorrect.
Tank temperature control
(thermostat) defective.
System wiring is
incorrect.
High limit control
defective, or set too high
(max. should be set at
200°F).
16
REMEDY
Replace.
Correct wiring.
Correct wiring.
Correct or replace
valve.
Correct wiring.
Replace. (If
problem proven to
be at this control by
applying jumper to
terminals.)
Correct wiring.
Remove control
cover, depress
reset button.
Check wiring.
Repair or replace
valve.
Check power supply
and wiring.
Replace.
Correct wiring.
Replace.