Glow-worm Black Beauty 4 - Manual (Page 19)

19 221906B
Closed Circuit Voltage (millivolts)
DIAGNOSIS GRAPH FOR FIRE
THERMOCOUPLE CIRCUIT
Open Circuit Voltage (millivolts)
0 1 2 3 4 5 6 7 8 9 10 11
7
8
9
10
11
12
13
14
15
16
17
A B C
Diagram 9.2
Diagram 9.3
9.3 Thermocouple
To test a thermocouple, a meter with a range of 0 to 30mV is
required together with a thermocouple interrupter test unit.
Refer to Fault Finding diagram 9.2 and Diagnosis Graph diagram
9.3.
9 Fault Finding
5243
0065M
Disconnect appliance thermocouple from the gas tap. Check that all connections are
clean and in good condition. Fit test meter interrupter into the magnet unit. Fit appliance
thermocouple into the test meter interrupter.
NO
YES
Hold down control tap in ignition position. Ignite burner, allowing thermocouple to attain
operating temperature. Measure the OPEN CIRCUIT voltage.
Is voltage greater
than 15mV?
Faulty thermocouple.
Replace flue blockage
safety device.
Faulty thermocouple.
Replace flue blockage
safety device.
Note the open circuit reading then measure the CLOSED CIRCUIT voltage. Note this voltage.
Referring to the diagnosis graph, mark the open circuit voltage on the VERTICAL axis,
and the closed circuit voltage on the HORIZONTAL axis. Note the point where these
two values intersect on the graph.
THERMOCOUPLE
CIRCUIT IS
SATISFACTORY In which area of the
graph is the intersect
Faulty magnet unit in gas tap.
Replace gas tap
B A
C