Worcester Bosch RD537i Explosive Igntion

[tnarg999]

Worcester Bosch RD537i. Boiler about 4 years old, condensing combi. Gas Supply pipe 26mm copper.

Each morning when a hot tap is turned on there appears to be delayed ignition which is quite explosive when it happens. The next time a tap is turned on, itit ignites "normally". If there is a longer delay, say a few hours, the explosive ignition returns.

I'm a bit reluctant to call on British Gas to investigate (they installed it) as when we had our free service that came with the boiler, the guy said "There's not much to maintain and test on these new types of boiler"...

Is there anything I can check myself before calling an engineer? Could condensation be getting into the ignition electrode overnight?

Thanks

 

[kitch0978]

call them out straight away to look at the boiler...you could have a gas valve that is passing (leaking). or electrode problem or maybe something wrong with your gas meter/regulator... if your paying them to look after your boiler then thats wat they should do, get em to look at it asap

 

[nickso]

can never remember bg's stupid boiler naming system but if its the one im thinking of its likely to be the ignition electrode.

 

[Agile]

can never remember bg's stupid boiler naming system but if its the one im thinking of its likely to be the ignition electrode.

I thought that BG paid you to remember their boiler names and sing their corporate tune?

The manufacturers dont call it "explosive ignition" they say we must call it just "noisy ignition" which is far less frightening!

Nevertheless you should get it looked at as it can be disturbing!

Tony

 

[nickso]

can never remember bg's stupid boiler naming system but if its the one im thinking of its likely to be the ignition electrode.

I thought that BG paid you to remember their boiler names and sing their corporate tune?

eh? you know very well i have little love for my employers or their "corporate tune"

the naming system is plain nonsense. a collection of random numbers and letters is never easy to remember. especially when they have ripped off so many boiler designs and dont distinguish between those manufacturers in any way.

 

[Agile]

He who pays the piper calls the tune!

 

[gaspro1981]

26mm copper

 

[holty]

wouldnt be the first time the gas valve has let by on these.actually getting more common.well it is every time i come across one this age.

 

[nickso]

He who pays the piper calls the tune!

you must knock em dead at the speed dating.

 

[tnarg999]

26mm copper

ok - 28mm, big stuff. This was an upgrade when the boiler was fitted. The salesman said you need the extra diameter pipe to get the required "whoosh" - I now know what he meant.

holty Posted:
wouldnt be the first time the gas valve has let by on these.actually getting more common.well it is every time i come across one this age.

Would the gas valve letting by be more likely first thing in the morning? i.e. after a long while since the bolier last fired?

 

[kitch0978]

if the valve is passing it`s probably doing it all the time....its just that when you`ve not used the boiler for a while then the slight extra build up of gas in the burner/ combustion chamber is more evident when the boiler does fire up and you get the noisy ignition... you not called an engineer out yet to look at it?

 

[Agile]

ok - 28mm, big stuff.

This was an upgrade when the boiler was fitted. The salesman said you need the extra diameter pipe to get the required "whoosh" - I now know what he meant.

Would the gas valve letting by be more likely first thing in the morning? i.e. after a long while since the bolier last fired?

Most boilers over the basic 24 kW need at least 28 mm and many need an even larger gas supply pipe!

If its only happening in the morning then I would expect it to be as a result of delayed ignition. Most likely as a result of wrongly adjusted ignition electrodes or condensation within the boiler or a weak spark generator.

Rather than lighting immediately the gas is turned on, it lights a little later by which time unburnt gas mixture is filling the combustion chamber.

Tony

 

[tnarg999]

Just so people didn't think I had blown up with this one..., I took the cover off the boiler and removed the condensate trap. It was full of liquid and at the bottom a silvery goo substance a bit like sand... The Missus said that in the 2 time we had it serviced, that trap was not removed by the engineer - he put a probe in the flue and that was about it.

I am hoping that the goo stuff was either as a result of the original commissioning, or "normal". In any case, since emptying the trap, the explosiveness seems to have gone away. Coincidence?.. I don't know.

I am getting the electrode assembly replaced for good measure.

 

[Agile]

I expect the people above thought that after paying so much for BG to fit the boiler you would have continued with their free cover for a while and then paid for it when it ceased to be free.

On a service the condensate trap should be checked for dirt.

I have not heard much feedback about Worcester boilers after a few years and they have an alloy heat exchanger althought those usually deposit a white sticky stuff.

I cannot guess why yours seems to have clean metal bits, perhaps from installation or perhaps not.

The relatively few I see have a brownish sandy looking deposit.

Unless it was seriously blocked I dont see why it should have been interfering with the start up process. Perhaps others have an idea about this?

Little point in changing electrodes in my view although the gap could be checked by a competent person.

Tony

 

[nickso]

the "goo" is oxide form the H/E. not particularly worrisome.

the electrodes are well known for failure/wear. check them before you buy a set as they are almost £50 iirc. its only two screws and the whole lot comes out. my bet is they are mishapen and the detection probe will be corroded green.