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DIAGRAM II
_- B300
THERUOCQIjPL(
THERMOSTAT
Thermostat wire disconnected from Terminal 1. Selector switch turned to
300 MV. Clip
cable plugged into
MV
jack. Red clip attached to Terminal 1. Black clip attached to
Terminal 2.
PROCEDURE No. II (See Diagram II)
Closed Circuit MV Test of Entire Circuit
Attach Millivoltmeter cable as shown.
Set thermostat to highest setting.
Turn plug valve knob to PILOT position, push down r&set button and Ight
pilot. Allow thermocouple to become fully heated, and note maximum reading.
AT THIS POINT, THE METER WILL INDICATE AN OPEN CIRCUIT
MV
READING
OF THE THERMOCOUPLE AS IN PROCEDURE IA.
Assuming the open circuit MV read-
ing
is within range, touch the dis-
OPEN CIRCUIT
CLOSED CIRCUIT
connected
thermostat wire to
its
MV READING
MV READING
terminal.
AT
THIS
POINT,
THE
METER WILL INDICATE A CLOSED
150
45
or less
CIRCUIT READING, AND SHOULD
145
43½ or less
BE
.3 OR LESS OF THE OPEN
140
42
or less
CIRCUIT READING AS TABULATED.
135
40½ or less
130
39
or less
If the closed circuit reading is
125
37½
or less
greater than indicated -
120
36
or less
Test the thermostat circuit under
115
341/2 or less
Procedure IV.
110
33
or less
Test the actuator under Procedure
105
31½ or less
IIIB.
100
30
or less
If both of these check out satis-
95
28½ or less
factorily, replacement of the
90
27
or less
thermocouple is indicated.
85
25½
or less
5.
With thermostat wire connected, turn plug valve knob to ON to light main
burner. UNDER OPERATING CONDITIONS THIS READING SHOULD REMAIN
FAIRLY CONSTANT. A considerable decrease in millivoltage would indicate
adverse conditions in the combustion chamber affecting the pilot flame. Check
suggestions listed under PILOT BURNER OUTAGE.
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