Lennox Hearth VIN - Manual (Page 20)

0 NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Millivolt Control Schematic
Thermopile
ON/OFF Rocker Switch,
Thermostat, or Remote
Thermostat
Piezo Igniter
Thermocouple
Pilot Gas Line
Sparker
Pilot Hood
Pilot Assembly
Gas Inlet
Pressure Taps
Terminal 3 Terminal 1 Terminal 
Thermostat Wire
Wire Size Maximum Length
1 Gage 100 Feet
14 Gage 64 Feet
16 Gage 40 Feet
18 Gage 5 Feet
0 Gage 16 Feet
Operating Options
“On-Off” Switch, Thermostat Or Remote Control
Your stove comes equipped with an “On/Off” rocker switch used to turn
the burner on and off while the pilot light is on. The switch is a round
rocker switch located behind the main control panel door.
A millivolt wall thermostat, or a remote control, can be used to supple-
ment the rocker switch. The gas valve is powered by millivolts generated
by the pilot assembly. This millivolt system is very sensitive to electrical
resistance, therefore, make sure all connections are tight, clean and free
from corrosion. Do not splice any millivolt wires. Consult the table below
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 stove (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. 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
thermostat or remote control to the lowest temperature when you wish
to use the rocker switch only, otherwise one may override the other.
Millivolt Control System
This stove operates on a millivolt control system. As such, no additional
power supply is needed for the stove to heat. The pilot assembly contains
a thermocouple that, when heated by the pilot flame, generates electricity
(millivolts- mV=1/1000 of a volt) which opens a valve allowing gas to
continue flowing to the pilot assembly. The pilot assembly also contains a
thermopile that, when heated by the pilot flame, generates electricity that
flows to terminal #1 (labeled TPTH) on the gas valve. When the electricity
is conducted from terminal #1 through the on/off switch, thermostat,
or receiver of the remote control to terminal #3 (labeled TH) on the gas
valve, the main burner will ignite.
CAUTION: Label all wires prior to disconnection when servicing controls. Wiring errors
can cause improper and dangerous operation. Verify proper operation after servicing.
Gas Valve
Wiring Terminals
Figure 34