A.O. Smith HW-420 User Manual

57

57

57

57

57

Use this checkout for Cer-Temp 80 Recovery Systems. (For hot water supply application only)

Set tank temperature

Circulating pump

Pump and burner

Tank temperature control

Replace.

control (thermostat)

and burner shut

remain on.

(thermostat) defective.

20°F (10°C) below

off.

tank water temperature

With thermal

System wiring is incorrect.

Correct wiring.

balancer, pump off
delay of approx-

Circulating pump

Pump wired for continuous

Correct wiring.

imately 2 minutes.

on.

operation.

Burner on.

Gas valve stuck or defective.

Correct or replace valve.

System wiring is incorrect.

Correct wiring.

Set tank temperature

Circulating pump

Circulating pump

High limit control set too

Replace. (If problem

control (thermostat)

and burner on.

on.

low.

proven to be at this

20°F (10°C) above

control by applying

tank water temperature.

High limit control differential

jumper to terminals.)

too wide.

System wiring is incorrect.

Correct wiring.

Coil protector switch has

Remove control cover,

activated.

depress reset button.

 Gas valve or wiring

Check wiring. Repair or

defective.

replace valve.

Circulating pump

Power off or system

Check power supply

and burner off.

wiring is incorrect.

and  wiring.

Tank temperature control

Replace.

(thermostat) defective.

Burner on.

System wiring is incorrect.

Correct wiring.

Boiler outlet

Circulating pump

Circulating pump

High limit control defective,

Replace.

temperature exceeds

on.

and burner on.

or set too high (max. should

210°F  (100°C).

be set at 200°F).

Set tank temperature

System maintains.

control (thermostat)

desired water

for desired water

temperature.

temperature.

Before any extensive trouble-shooting, perform the following:

Ensure That:

— Voltage (120 vac) is supplied to the appliance.

— System control (tank temperature control, thermostat, etc.) is calling

for appliance 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 appliance rating plate/label.

— Voltage (24 vac) is supplied by transformer.

— Appliance 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 LP models only check for possible lockout condition of the ignition

module.