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From: firstname.lastname@example.org - Find messages by this author
Date: 14 Jun 2005 02:03:22 -0700
Local: Tues,Jun 14 2005 10:03 am
Subject: Potterton Boiler not firing up
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I need some advice on a Potterton Boiler.
It's an old ground standing unit and has worked fine since its
installation 26 years ago but is now not firing up. The power supply to
the control unit seems ok and there are no loose wires, the pilot light
is ok and I've had a look for a fuse but can't see one. I'm
therefore guessing it can only be one of two components within the
The first is the thermostat but this looks ok to me. It's only a
simple device and again there are no loose wires.
The second is the main unit (not sure of it's proper name) that
controls the gas flow. This is a sealed unit that again looks ok to me
with no obvious problems.
I'm not an expert on boilers but am a reasonably competent DIYer but
I don't know where to go from here. Any advice would be much
I am also no expert but had a similar boiler some years ago with a similar
problem. It was caused by the thermo couple. This is a long copper wire
with a thicker tube on the end. The thick end sits in the pilot flame and
the other end screws into the control unit. The thick bit detects whether
the pilot is alight and shuts off the gas to the burners if it thinks the
pilot is out. It gradually gets burnt away until the sensor is no longer in
the flame. I found it cheap and easy to replace.
(If you can't laugh at life, it ain't worth living!)
Do the pump and other peripherals start on the timer signal? If the answer
is yes to that question, then the main gas valve has indeed gone belly up in
the water as you say. This is normally caused by a flap mechanism inside
the valve, which has become weak and doesn't hold in when asked to do so by
the burner unit thermostat. More likely that on its last closing signalled
by the thermostat it hasn't opened up again.
It's best to swap all the thermocouplings and the valve if you want a repair
that is going to last for a good few years again. Just swapping one
component may mean something else in the very near future will go, and you
spend more time and money on this all over again. So it's best to swap all
these parts at the same time for a good, and proper, repair job.
If you can take the valve and couplings to a supplier so they can be matched
properly, then you should have no problems getting the parts. With the age
of your boiler, just going by numbered parts may get you something that just
isn't right for your system. So remove the valve and the couplings and take
them with you.
Remember to make notes, and take pictures if you can, to keep the job simple
when you come to put everything back where they belong. Make a note on how
tight everything is, and also which sequence you removed all the parts.
Turn the gas off at the mains valve beside the meter, and not just at the
service cock beside the boiler. Turn all the electrical supplies off at the
consumer unit fuse (MCB) if it is convenient to do so, and if not, then pull
all the fuses out from the spur units to the boiler and timer systems.
Good luck with it.
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