18
Millivolt Control System
This insert operates on a millivolt control system. As such, no addition
power supply is needed for the insert to operate. The pilot assembly
contains a
Thermopile
, that when heated by the pilot flame, generates
electricity (millivolts, mV=1/1000 of a volt) that travels to terminal #1.
From this terminal it travels through a black wire to the
Vent Safety
Snap Switch.
If this switch overheats through a flue blockage or vent
pipe disconnection it will open, stop the flow of mV and shut the insert
off. This switch will automatically reset (close), when it is cooled down
to normal operating temperature. During normal operation, it is closed
allowing the mV to flow back to the valve, which opens so gas can flow
through.
To check for proper operation, use a multimeter and perform the system
checks shown in
Table 4
(and refer to
Figure 19
).
Thermostat Wire
Wire Size
Maximum Length
12 Gage
100 Feet
14 Gage
64 Feet
16 Gage
40 Feet
18 Gage
25 Feet
20 Gage
16 Feet
Table 3
Do not splice any millivolt wires. Refer to Table 3 to determine the
proper gage of wire for the thermostat or wall switch connections.
This table refers to the total length of the wire (out to the switch and
back). The thermostat must be a millivolt type. A 24-volt furnace
thermostat will not work. Never hook up household current, 120
Volts, to the millivolt system. It is not recommended to hook up
any more than two switches to the insert (for example a rocker
switch and a wall thermostat). Additional switches may affect
the system resistance and increase the chance of the burner not
igniting. Follow the instructions included with the thermostat or
remote control for wiring.
Millivolt and System Checks
Check
Test
To
Test
Connect
Meter
Leads to
Terminals
Thermostat
Connects
Meter Read-
ing
Should Be
A
Complete
System
2 & 3
Closed
100 MV
or More
B
Thermopile
Output
1 & 2
Open
Greater Than
325 MV
C
System
Resistance
1 & 3
Closed
80 Ohms
Table 4
The thermostat, remote control and rocker switch will turn the burner
on and off independently. Be sure to set the rocker switch to the “OFF”
position when using the thermostat or remote control and set the ther-
mostat or remote control to the lowest temperature when you wish to
use the rocker switch only, otherwise one may override the other. If a
remote thermostat is to be used with the insert, do not place the receiver
under the firebox.
Figure 18 - Millivolt Pilot
Thermopile
Igniter
Gas Pilot Hood
3/8” to
1/2”
Pilot Adjustment
All pilots are burned and checked at the factory prior to shipment.
(Note: If upon initial insert installation the pilot flame flickers or will
not remain lit, most likely the pilot is fine but there is air in the gas
line or the gas pressure is too low).
Pilot adjustment is not normally
required, but should it be necessary, it should be done only by a qualified
service technician. The pilot adjustment screw is located to the left of
the ON/OFF/PILOT control knob. With a flat bladed screwdriver, remove
the pilot adjusting cover to access the pilot adjusting screw. Adjust pilot
screw to the properly sized flame as shown in
Figure 18
. The flames
should completely surround the thermopile and extend across the main
burner ports. Be careful not to back the adjusting screw out of its threads.
Replace the cover and check for gas leaks.
Summary of Contents for FIRESTAR MERIT GC3
Page 27: ...27 NOTES...
