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THERMOSTAT BULB PLACEMENT DETAIL
MILLIVOLT CHECK (FOR QUALIFIED SERVICE TECHNICIANS ONLY)
The millivolt valve is a thermopile self-powered combination gas control. Before checking the millivolt system, the following
operations should be performed and observations made:
1. A genuine Keating millivolt thermostat should be used for millivolt operation.
2. The thermostat leads and all wire connections should be cleaned and tightened to eliminate all unnecessary resistance.
3. If pilot will not remain lit when gas valve knob is released, check automatic pilot.
NOTE:
The millivolt system and individual components may be checked with a millivolt meter having a 1-1000MV range.
Conduct each check below by connecting meter test leads to terminals as indicated. All readings are closed circuit.
CHECK
TO TEST
A
MILLIVOLT SYSTEM CHECK
B
THERMOPILE OUTPUT
C
SYSTEM RESISTANCE CHECK
D
AUTOMATIC PILOT DROPOUT
A. BURNER COIL CHECK
("A" Reading. Thermostat contacts CLOSED - Gas Valve knob "ON". Main burner should come ON.)
1. If the reading is more than 100 millivolts and the automatic valve still does not come one, replace the valve.
2. If the closed circuit reading ("A" reading) is less than 100 millivolts, determine cause for low reading and proceed as follows:
CONNECT METER LEADS TO
TERMINALS
TP
TH
THTP
TP
THTP
TH
THTP
TH
12
THERMOSTAT
METER READING
CONTACTS
CLOSED
100mV OR MORE
OPEN
BETWEEN 325–700mV
CLOSED
MEASURE LESS THAN 80mV
OPEN
BETWEEN 120mV–30mV
SHOULD BE:
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