O Potterson CF 20/35, Installation And Servicing Instrucnions

Page: 29 / 43

COMMISSIONING - Page 17
FIG. 16. GAS CONTROL VALVE
FIG. 17. PILOT BURNER
Pilot Burner
The pilot burner pressure is non-
adjustable. The pilot flame should heat the thermocouple so that the pilot safet
y device is "held in" but must not cause the thermocouple toglow bright red.
FI
G. 17 illustrates the approximate size of a correct flame. The E.M.F. generate
d by the thermocouple should be of the order of 20-30 mV open circuit, 10-
14mV closed circuit. Due to the voltage drop in the overheat thermostat circuit
there should be 6.5-
8.5 mV closed circuit at the connection to the gas control valve. Drop outshoul
d occur between 1-3 mV closed circuit.
Boiler Thermostat