Gas engineer's ??

[the-wizard]

anyone working in the gas game?, Ive got a problem with a back boiler and looking for pointers!.

[rob warrington]

im a heating engineer whats your prob buddy.

[Jezzy]

anyone working in the gas game?, Ive got a problem with a back boiler and looking for pointers!.

Eat less beans.

[mradz]

im a heating engineer whats your prob buddy.

me two

[the-wizard]

Soz for the late reply guys had to nip out!, now ive stopped laughing i can detail the prob!!, its a potterton homewarmer 45/55 type back boiler, Electronic pilot lights fine,then click clunk the gas valve opens! which SHOULD be a steady supply to the burner, then after a minute or so goes to the main full flow. But mine mostly goes straight to the main flow of gas first which in turn is to much to quick and that has a blow back effect hence lighting the mainburner feed pipe. Is this a gas valve problem or some problem electronic or circuit board wise, it seems to give the main flow first most times rarely starting in the correctly many thanks.

[rob warrington]

sounds to me to be a either a faulty gas valve or the ignition pressure is wrong. as you describe when the boiler lights the gas valve opens and should allow about 3mbar to the burner ( soft light function) this stops explosive ignition once lit the 2nd stage solenoid opens giving full gas to the burner. so either the gas valve is faulty or you will just need to check the ignition pressures ( well get a gas safe dude to do this ) i have also had this happen when the pilot injector was blocked thus making pilot flame very small this also will the boiler light with a bang. you say also you think the main burner feed pipe is lighting. ive had this loads of time. potterton now recommend dropping the ignition pressure from 3mbar to 2mbar, hope this helps

[the-wizard]

You got it down to a T, Its not soft lighting!, the pilot is OK size wise, so as you say it could be the gas valve playing up!, More often than not it goes straight to the full flow(2nd stage ignition) without lighting on the soft light first, So what happens is there's too much gas to quick and the pilot lights it, but the force of this catches on the the main supply acting like a bunsen burner!, I'm grateful for the info, its giving me some insight to arrange someone to have a look, I don't know anyone personally but need to get some one with back boiler experience, what sort of money are we looking at for a replacement gas valve ?. many thanks.

[rob warrington]

sequence of operation is like this. demand from clock heating/hot water on then pilot solenoid opens allowing pilot flame to light, once the pcb is happy there is an ignition source (ie the pilot) the first stage solenoid opens allowing small amount of gas to the main burner seconds later the 2nd stage solenoid opens allowing main gas to burner. then the boiler will just switch on and off depending how high/low the boiler stat is. So if the pilot lights and the 2nd stage solenoid opens too fast too much gas is being supplied at once hence explosive ignition, this can also lead to the burner injector lighting back. like i said yesterday though it may be a faulty gas valve but could just be the ignition pressure on the gas valve set too high. trouble is some plumbrs/heating engineers wont bother trying to set it up and just tell you the gas valve is faulty. obviously without seeing the boiler im guessing its the gas valve from what you've said, cant think what else it could be, need anymore info let me know.

[rob warrington]

also forgot to ask if its been serviced, can also get this prob if the gauze around the burner injector is blocked with dust or lint etc. may be Worth having it strip serviced and cleaned out if its not been done in a while,

[the-wizard]

It does start normally sometimes but not very often, it goes straight to high flow gas first not even attempting the soft start! Many thanks, As i said sounds like you have it to a T, just need someone local now that knows back boilers and dont go round the houses trying to bump the cost up!,