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12425-10-1008 Page 11
CAUTION — Do not run wire behind flanges of Header Plate or
in any location where it might be damaged.
Millivolt wall thermostats are specially designed for use on self-
generating systems. They should never be used on line or low
voltage A.C. circuits.
Interior Wall — The thermostat should be installed on an inside
wall away from the furnace but in the same room.
It is important to use wire of a gauge proper for the length of the
wire:
RECOMMENDED WIRE GAUGES
Maximum Length Wire Gauge
1' to 10' 18
10' to 25' 16
25' to 35' 14
Proper operation depends on a good pilot flame. The flame must
cover the top of the thermopile. Cleaning of the pilot orifice and
burner may be required due to spiders.
System Check (Figure 7)
A millivolt meter is required to check the system. Millivolt readings
should be:
• Across the thermopile terminals, 400-450 millivolts with
thermostat OFF.
• Across the thermopile terminals, 150-250 millivolts with
thermostat ON.
• Across the thermostat wires at the valve, less than 30 millivolts
with thermostat ON.
• Across the thermostat wires at the thermostat, less than 5 millivolts
with thermostat ON. (Dirty pilot or low pressure will reduce
readings.)
Connect thermostat wires to gas valve as shown in Figure 7.
Figure 7
THERMOSTAT LOCATION (SG MODELS)