Boiler not firing up

[Bob141uk]

[e-mail] Jun 14, 10:03 am show options

Newsgroups: uk.d-i-y From: [e-mail] - 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 Reply | Reply to Author | Forward | Print | Individual Message | Show original | Remove | Report Abuse

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 boiler itself.

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 appreciated.

Thanks.

[Keith Willcocks]

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.

[BigWallop]

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 c*ck 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.