State Industries GPX, GSX, GS6 manual Testing the Thermocouple and GAS Control VALVE/THERMOSTAT

Models: GPX GS6 GSX

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TESTING THE THERMOCOUPLE AND GAS CONTROL VALVE/THERMOSTAT

IMPORTANT: Before performing any test, check the area around the water heater for any source of a Flammable Vapor (i.e gasoline, paint thinners, etc.) If any sources are found do not proceed until they are removed.

Thermocouple Output Test

The following test will check the DC voltage generated by the thermocouple when the pilot light is lit.

1.Disconnect the thermocouple from the gas control valve/thermostat as shown in the adjacent figure.

2.Using a multimeter with alligator clips leads, attach the red lead to the body (copper part) of the thermocouple. Attach the black lead to the end (silver part) of the thermocouple. Reference the adjacent image for placement of the leads.

3.Follow the lighting instructions on the front of the water heater to light the pilot and watch the voltage readings on the multimeter. NOTE: You will have to hold the button down to keep the pilot lit for the duration of the test. After 45 seconds the meter

should read 20-30 millivolts DC or more.

Figure 20

 

IF . . .

 

. . . THEN

the multimeter voltage reads

check the positioning of the thermocouple tip to the pilot flame. If

at least 20-30 millivolts DC

 

necessary position the thermocouple to ensure the flame contacts the

 

 

thermocouple’s tip. Re-test the thermocouple, and if it fails replace the

 

 

thermocouple. (See p. 22)

 

 

 

the multimeter voltage reads

the thermocouple is working properly. Proceed to the gas control valve/

more than 20-30 millivolts DC

 

thermostat test.

Gas Control Valve/Thermostat Test

(Thermal Switch Models)

The following test will check the gas control valve/ thermostat’s ECO & TCO (Energy Cut Off & Thermal Cut Off). NOTE: This test applies to gas valves with wire leads that attach to the thermal switch on the manifold door.

1.Remove both wire leads from the TCO (thermal cut off switch) and jumper the two leads to complete the circuit. Once the test is complete, remove the jumper and reconnect the wire leads.

2.Follow the lighting instructions on the front of the water heater to light the pilot.

3.Release the knob and check to see if the pilot remains lit.

GAS CONTROL

 

KNOB

 

TCO

TCO

WIRE LEADS

WIRE LEADS

 

(JUMPERED)

 

TCO

 

SWITCH

Figure 21

IF . . .

 

. . . THEN

the pilot lights and remains lit

the TCO (thermal switch sensor) has tripped OR the TCO is not

 

 

working (OPEN). Reattach the wire leads and press the TCO reset

 

 

button. Relight the water heater. If the pilot will not remain lit, replace

 

 

the TCO. If the pilot does remain lit, the TCO was tripped-possibly

 

 

due to a lack of combustion air (see pp 13-16 & 18-19) OR because

 

 

of a Flammable Vapor event. Check around the water heater for any

 

 

source of flammable vapors (i.e. gasoline, paint thinner, etc.).

 

 

 

the pilot will not light or remain

replace the gas control valve/thermostat.

lit with the wire leads jumpered

 

(See p. 24)

 

 

 

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State Industries GPX, GSX, GS6 manual Testing the Thermocouple and GAS Control VALVE/THERMOSTAT, Thermal Switch Models