my pilot ignites but then goes out on rsf 820/20?

it works the same way as the oven in the kitchen
when you hold the button in it opens the gas valve
when the pilot is lit it sends a signal to the valve via a thermocouple witch keeps the valve open

near the pilot light there should be a probe that is being heated by the pilot light if this is not being heated by the pilot it will shut the valve off as soonas you release the button

if it is being heated it sounds like you may need a new thermocouple these are not expensive

eck hi
August 2008

Your thermocouple (Flame Probe) is at the end of its life.
Turn your boiler off and remove cover to gain access to the pilot assembly. Carefully remove the probe and its capiliary tube from the pilot and undo the nut on the other end securing it to the gas control unit. Take it to a plumbers supply outlet and get a matched replacement or a recommended 'universal fitting' .
Read the instructions carefully and follow them. Use your old thermocouple as a template to ensure a matched fit. Refix all covers and secure all joints before testing.

Cledlyn
August 2008