We've moved into a house with a Glowworm Spacesaver 80B Mk 2 boiler which has two problems. Firstly, it's noisy, banging away like nobody's business, which I guess is kettling so I can hopefully fix that with various chemicals and a good flush. But of more immediate concern is that is sometimes trips the main RCD for the house, not an individual circuit breaker, but the one for the whole house, so I guess this is due to earth leakage. I don't think it's the CH/HW pumps (1 of each - strange setup), and when switching off sometimes I think the gas valves makes lots of rapid switching noises. Or could it be the timer? It seems to do it at no particular time, so not due to timer trying to switch on/off boiler for example.
The boiler seems to be fairly simple electrically with a transformer, a thermostat, a gas valve and very little else!
Any ideas? Or is it best to bin it and get a new boiler which I really don't want to do at this stage, though it's over 20 years old now.
Fair point, process of elimination. Only happens when the boiler is on, more so when the heating is on. I suppose it could be something else but as the boiler is on for 2 x 1 hr slots and it only occurs during these 1 hr slots, and having eliminated the pumps that leaves the boiler, which also generates a load of RF noise BTW... yet to determine if that's on firing up or switching off though.
Considering the age, I would dump it. Probably it needs a new thermostat, maybe a new gas valve after that, and .....
It's only 65% efficient, so by the time you've thrown good money after bad, you can have put in a new condensing boiler with 90% efficiency and be in a far better position.
and we're planning to extend over the garage, so we don't want to have to pay for it to be installed twice if you see what I mean. Would be nice to keep it going until we get the extension done.
I'd suggest starting with a cleaning session using Sentinel Ferroquest or X400 and allow it to "cook" for about a week if its kettling. If its REALLY bad then maybe an acid clean is more appropriate. Whether you keep the old boiler or replace it you will need a system clean anyway so it won't be wasted affort. If this sorts the banging then fine. Eds suggestion of the gel is ok but treats (well) symptoms rather than removing the cause.
The space saver as you say has very little in it to cause electrical problems. It does have a fairly low efficiency but not so bad that it screams out for instant replacement if its working. The gas valve is 24volt fed by the transformer so it will probably not be the source of an earth leak. The chattering is not likely to be due to a fault with the valve but something external. You are down to a limited range of possible earth leak points here, such as the transformer, the thermostat, the wiring loom, the suppressor if your boiler has one fitted. Have you got facilities to test for earth leakage on the wiring? Remember that using a megger is to be done with appropriate precautions (diconnection) for protection of electronic components such as found in programmers, timers, Y-plan heads etc. Also the use of two pumps suggests you may have a "pump plan" installation which has an electronic control board (box) associated. Again this may have a bearing on the rapid switching which you are hearing. Try taking a look at Grundfoss website for details of this unit.
The earth leak may be completely unrelated to the heating system anyway. I had a job a couple of years ago where I installed a replacement boiler to existing Y plan controls. Three weeks later (during heavy rain) I was called back as the house RCD tripped and by elimination, trying each MCB in turn, the householder had proved it was caused by one downstairs ring main which the boiler supply was fed from by an FCU. Of course the boiler was prime suspect but on investigation I found that disconnecting from the FCU did not remove the fault. To overcome the problem of no heat I rerouted the heating supply to a different ring main circuit (couldn't do it now with part P stupidity). I found there was rainwater running into the underfloor void, from the flooded yard via a low airbrick, which must have contained a Junction box, damaged cable or similar. The householder had recently relaid his lounge floor with a fine finish hardwood. I isolated and made safe the faulty ring and advised him to lift the floor, dry out the underfloor void and look for the junction box or any possible damaged cable with a view to carrying out a repair. I also gave him the name of a local electrical contractor to carry out the follow up work.
Unfortunately I don't have the facilities to test for earth leakage. Presumably I use a "megger" to test for that? Can they be bought cheaply? Regarding the two pumps, we have a strange setup: the boiler has two flows and two returns and you're supposed to just use one pair, however, when the boiler was plumbed in (about 20 years ago) they used both pairs, one pump per pair, and activate one pump for CH and the other for HW, or both for both CH and HW! I'm still fairly confident it's the boiler, the power *only* trips when the boiler is running. Initially I did think it was the CH pump but since turning off the CH, it still happens, just less often. No CH thermostat BTW, just the internal boiler one!
Is it possible to get a sort of multiple RCD that I wire the boiler into, and the pumps and each is monitored and rather than trips, displays a count? Would be very useful!
Yes and reasonably so but if you don't know how to use one correctly it may damage more than help.
You haven't mentioned the hot water pump being a candidate?
Possibly but I get the impression it might cost more for such a one time use device than it would cost to get someone in who can find and fix the problem. BTW where are you in the country?
That's me out then, I do have a degree in electronic engineering, but they don't teach this kind of stuff - maybe electrical engineering would have covered it.
I've been in touch with the pump manufacturers and they were insistent that the failure mode of the pumps would be different. And the fact that the problem occurs more when the CH is on would mean both pumps have problems... which occurring at the same time would be rather unusual.
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