12
V E N T - F R E E G A S H E A T E R S E R V I C E M A N U A L
Testing Control Valve and Thermocouple
The following procedure can be used to deter-
mine if the valve and thermocouple meet speci-
fication. This procedure requires a BASO milli-
volt tester. See Equipment, page 7.
PROCEDURE
1.
Connect the valve attachment to the con-
trol valve in place of the thermocouple.
2.
Plug the valve attachment connector into
the BASO millivolt tester as shown in
Figure 11. Set BASO to 0-500 Milliamps.
3.
Adjust the current to 80 ma (if using dry
cell batteries, set the current level by
adjusting the rotary volume knob).
4.
Turn control knob from the OFF position
to the PILOT position. Check to see if the
control valve holds in satisfactory.
5.
If the control valve does not hold in,
increase current levels by 10 ma and
repeat step 4. Repeat by 10 ma incre-
ments until the valve holds in. Note re-
sult.
6.
Gradually reduce
ma level until the con-
trol valve drops out. Note result.
Hold-in current specification: 230 ma maximum
Drop-out current specification: 80 ma minimum
If the control valve operates correctly during the
above test, it is likely that the problem is the
result of a bad thermocouple.
7.
Connect the thermocouple attachment
to the thermocouple as shown in Figure
12. Be sure the red clip is attached to the
outer (copper) thermocouple sheathing.
Set BASO to 0-500 Millivolts.
8.
Light the burner pilot and continue to hold
the control knob down to keep the control
valve open, or remove the thermocouple
and hold it over an open flame (a BIC
lighter can be used).
Thermocouple output specification: 20-28 mv
If the thermocouple millivolt output is below
specification, replace the thermocouple.
ADJUST
500
300
100
10
20
0
700
30
40
900
50
DC MILLIVOLT
0-50
MILLIVOLTS
MILLIAMPS
MILLIAMPS
0-500
GRH/OV 032
0-1000
MILLIVOLTS
BASO
Milivolt Tester
ADJUST
500
300
100
10
20
0
700
30
40
900
50
DC MILLIVOLTS
0-1000
MILLIVOLTS
MILLIAMPS
MILLIAMPS
0-500
GRH/OV 031
0-50
MILLIVOLTS
BASO
Milivolt Tester
Figure 12. Testing Thermocouple With BASO Milivolt Tester
Thermocouple
Attachment
Thermocouple
Attachment
Figure 11. Testing Control Valve With
BASO Milivolt Tester
Valve
Attachment
Control
Valve
