Weil-McLain EG-30 THRU -75, Control Supplement, Page: 20 / 24

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Part Number 550-110-032/0607
EG-30 thru 75 Series 4 and PEG-30 thru 65 Series 4
Figure 11
1. Checking thermocouple or thermopile open system (Figure 10):
a. Use an electronic multimeter, with leads fitted with alligator clips. Set meter
scale to DC Millivolts.
b. Unscrew thermocouple or thermopile fitting from gas valve.
c. Attach one meter lead to the end of the thermocouple or thermopile gas
valve fitting.
d. Attach other meter lead to thermocouple or thermopile lead (copper sur-
face).
e. Follow Lighting Instruction label on boiler (also found in Control Supple-
ment or User’s Information Manual) to light the pilot burner only, and hold
the pilot flame manually. (DO NOT light main burner.)
f. Check the reading on the multimeter. The reading should be around 8
millivolts for a thermocouple, or 00 millivolts for a thermopile.
g. If multimeter reading is significantly less than above and pilot flame is
appropriate, replace the thermocouple or thermopile.
. Checking thermopile and high limit control circuit closed system (Fig-
ure 11):
a. Use an electronic multimeter, with leads fitted with alligator clips. Set meter
scale to DC Millivolts.
b. Loosen the insulated terminal on the TOP thermopile lead wire enough to
allow clipping a multimeter alligator clip to the spade terminal.
c. Attach the other multimeter lead to the thermopile lead (copper surface).
Light the pilot burner per step 1 e, above.
d. Check the reading on the multimeter. The reading should be around 00
millivolts.
e. If reading is significantly less than 00 millivolts, check tightness of lead
wire assembly in gas valve. If the connections are secure and you have
checked the thermopile per step 1 above, replace the thermopile lead wire
assembly.
f. If reading on TOP thermopile lead wire is around 00 millivolts, move the
multimeter alligator clip to the BOTTOM thermopile lead wire terminal
and check multimeter reading.
g. If multimeter does not read around 00 millivolts, check wiring connections
and wire integrity to the high limit control.
h. Check voltage at each limit terminal to make sure limit is closed. Correct
pressure or temperature condition causing any limit to be open. Replace
limit if necessary.
Pilot does not stay lit —
Troubleshooting thermocouple or thermopile
and high limit control circuit
Figure 10
Troubleshooting
continued