Monessen Hearth DEB20 - Manual (Page 25)

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HIGH
LOW
26D3
317
THE
RMOS
TAT
SE
TTING
A. COMPLETE MILLI-VOLT SYSTEM CHECK
(“A” Reading - Thermostat contacts CLOSED - Control Knob “ON” - Main burner should turn ON)
a. If the reading is more than 175 milli-volts and the automatic valve still does not come on, replace the control.
b. If the closed circuit reading (“A” reading) is less than 175 milli-volts, determine cause for low reading, proceed to
Section B below.
B. Thermopile Output Reading Check
(“B” Reading - Thermostat contacts OPEN - Main burner OFF)
1. Check gas pressure to the unit. If gas pressure is within minimum and maximum on data plate, then check pilot
voltage, 500 milli-volts minimum. If the minimum milli-volt reading is not obtainable, replace pilot.
CONNECT
CHECK TO METER THERMOSTAT METER
TEST TEST LEADS TO CONTACTS READING
TERMINALS SHOULD BE
A COMPLETE TP/TH and TH CLOSED MINIMUM
SYSTEM 175
B THERMOPILE TP and TP/TH OPEN MINIMUM
OUTPUT 500
CHECKING SYSTEM OPERATION
The milli-volt system and individual com-
ponents may be checked with a milli-volt
meter having a 0-1000 mV range. Conduct
each check shown in chart below by con-
nection meter test leads to terminals as
indicated.
ELECTRICAL WIRING (MILLI-VOLT)
OPERATION OF THERMOSTAT SENSOR
1. Follow millivolt lighting instructions on lighting plate attached to unit or in homeowner’s manual.
2. With control knob in the “ON” position make sure the ON/OFF switch is in the “OFF” position. See Figure 24.
3. The unit is now being controlled by the thermostat sensor. The sensor will now cycle the burners on and off. You can adjust
how often the unit cycles by turning the control knob on the sensor.
Figure 24 - Control Knob in “ON” Position and ON/OFF Switch in “OFF” Position
Control
Knob
T-Stat
Sensor
ON/OFF
Switch