Glowworm swift flow probs

14 Oct 2005
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United Kingdom
Boiler- Glowworm swift flow 75/80.

Problem appears to have started after removing radiators from wall to decorate.

With central heating turned off boiler appears to operate normal ie pilot light remains lit at all times and increases in size when turning on hot water at the taps. Sometimes however, especially if the shower has been running a noise could be heard through the radiators, as if they were filling.

WIth the CH on, the radiators all heat up as normal but after running the hot water, again especially the shower, the pilot light will be extinguished. This will occur approx 5 mins after the hot water has been turned off. The pilot can be re-lit almost immediately but will then keep going out until the CH is turned off.

The pressure gauge sits at about 0.6 bar when cold and was going to about 3 with the heating on, but is now sitting just under 2 bar.

Work carried out so far, by plumber, is to drain and refill system, bleed all radiators, replace the auto bleed ( this was seized) and replaced the pressure release valve ( this again was full of muck and continually leaking outside).

Thoughts from the plumber was that because the air bleed was seized that air was trapped in the boiler following removal of the rads by me. this in turn caused an abnormal increase in pressure with the heating on, hence the noise and knocking out the pilot. However there is no difference so I am asking you good people for any suggestions.

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sounds like it could be the over-heat stat you can test it by using multi meter or possibly scaled up heat exchanger get pumb back to check it out or call glow-worm.
I have checked the expansion vessel, no water so I pumped in some air and refilled the boiler. Started central heating, rads all warm, ran the shower for a time and switched off. Pilot light remained lit, after 5 mins it was still lit. It is fixed me thinks. Checked it after 1 hour and still working but I checked it after about 1 and 1/2 hours and find the pilot has gone out.

During the first hour of operation I kept an eye on the gauge. It started off cold at 0.7 bar. As the heating operated it gradually rose to a max of 2.7 bar. This appeared to coincede with the the rad stas operating wheras the heating cut out (pilot light remained lit) and the pressure dropped to just under 2 bar and remained there. I could hear the boier cutting back in as the room temp dropped.

As I said I thought at this point it was now fixed, only to find the light has gone out. INcidentally the pilot will relight immediately with the gas switch pushed in but will extinguish again as soon as the button is released and turned. This will keep happening for about 5-10 mins.
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I have now had the over heat switch checked. Athough it appeared ok it was changed. The thermocouple was checked as per the instructions and found ok. The heating was switched on, all the rads warmed and the gauge pressure gradually rose to approx 2.5 bar. Just after this the pilot light extinguised. IT can be relit immediately but goes out again when the control is released (SIT). After about 10 mins the pilot will remain lit. DHW only is fine but as soon as the heating is switche don the whole sage begins again. Things done so far by Plumber and myself.

Replace auto air vent ( seized)
Replace pressure releif switch ( leaking because of muck)
Expansion vessel checked by pressing valve, no water out and pumping up with cycle pump. This was difficult to do and could only manage a couple of pumps.
Boiler overheat switch replaced.
All parts cleaned.

The plumber reckons I should replace the boiler. I don't mind doing this if it is necessary but after paying out for all of the above I would hate to think that another couple of quid(so to speak) would cure the fault. ( see thread).

Any ideas, anyone please

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