American Water Heater GAS-FIRED COMMERCIAL WATER HEATER 用户手册

 

35

 

Start - Disconnect sensor 
leads from electronic control 
module and measure 
resistance of sensor(s) with 
ohmmeter 

Is resistance between 700 and 
30K ohms (see page 38)? 
YES

↓              NO→ 

Sensor(s) may be shortened 
or open. Check for loose, 
broken or shorted wires.  
Replace sensing bulb(s) if 
necessary. 

Sensors O.K.  Disconnect 
ECO leads and measure 
resistance with ohmmeter 

Is water temperature greater 
than 210°F (99°C) and ECO 
resistance less than 10 ohms 
(shorted)? 
YES

→              NO↓ 

Replace sensing bulb with 
ECO limit and check out 
balance of system. 

Disconnect potentiometer 
leads from electronic control 
module. Measure resistance 
of potentiometer with 
ohmmeter. 

Is resistance greater than 
4800 ohms at minimum 
temperature setting (checks 
for short)? 
YES

↓              NO→ 

Replace electronic  control 
module. Reconnect all leads 
and check out system 

Potentiometer O.K. 

 

Replace electronic  control 
module. Reconnect all leads 
and check out system 

 
 
 

If water temperature is too cold or heater does not come on, proceed as 
follows: 
 
Test or Condition: 

Start: Check voltage at 24-volt 
terminals of electronic control 
module of thermostat board. 

Is voltage between 21.5 and 
28.5 VAC? 
YES

↓              NO→ 

Check power supply, 
transformer.  Correct as 
necessary. 

Are main burners operating or 
is pilot trying to light 
(sparking)? 
YES

↓              NO→ 

Check for voltage at N.O. 
thermostat terminals (terminal 
to meter to ground). Is voltage 
between 21.5 and 28.5 VAC? 
YES

↓              NO→ 

Thermostat relay is not 
closing.  Check thermostat 
setting. Refer to thermostat 
troubleshooting below. 

If water temperature is too cold or heater does not come on, proceed as 
follows: