Problem with Central Heating

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Hello Everyone,

Okay firstly sorry for such a long post.

I think we may have a problem with our central heating system.

We have recently had problems with our boiler where the pilot light would only light but rarely actually fire up, on the occasions it did fire up there would be a clicking/crackling/almost electrical arcing kind of noise come from the boiler. We have a cover plan (£15/month) with British Gas so called them out and their engineer (for £50 callout fee, not bad). He did two things (sods law that the boiler didnt make the noises when the engineer attended our house but I explained the noises and asked could it be the gas valve), he didn't know what the problem was so he did the following:

1) Lubricated and sprayed WD40 around the boiler fan
2) Replaced the PCB (circuit board) with new one he had in his van

He tested the boiler after doing this and again it didn't make the crackling/rapid clicking/electrical noises that it had made before so he left.

The next day I came home from work to my partner saying she felt light headed, dizzy and had headache, there was a distinct smell of gas in the kitchen and the boiler was on, again making the intermittent crackling/clicking/electrical noise so we phoned the gas emergency helpline 0800 111 999 and isolated the gas valve outside in the meter cabinet -this was at 6:50pm. Northern Gas Networks eventually turned up at 1:10am and made everything safe and thankfully their engineer witnessed the noise being made by the boiler, he mentioned it could be the selonoid on the gas valve so we called British Gas back and although they wanted another £50 callout (we told them where to go) they sent an engineer out on a recall the next day. Upon his inspection he agreed that it must be the gas valve and so went away to order the new part from Middlesbrough and the next day afternoon he returned with a new Honeywell gas valve (which incidentally makes a slight humming noise when the boiler is operating, you can hardly hear the humming to be fair and assume this is normal).

Since then everything seems okay, no gas smells or leaks, no clicking or dodgy electrical shorting noises from the boiler... however...

For some reason - and to be fair i think this has been happening before, possibly for the last 12 months or so... I think the boiler could be short cycling, whenever we turn the heating on via the room thermostat it gets up to temperature and then gets in a cycle of on for a few minutes then off for a few minutes and keeps repeating until we switch it off by turning the room stat below about 16deg... Thinking back I'm now not sure if this is whats worn out the old gas valve... on, off, on, off, on, off etc etc possibly thats what wore out the old valve turning on and off all the time so frequently?

For some reason the room thermostat doesn't click on when its at say 15/16deg even if we leave it at that and it gets cold, it only clicks on when we physically move or touch the dial to around 20deg (sometimes the dial can be slightly pushed inwards without turning and it starts the boiler), i have tested it and let the room get quite cold with windows open etc and it doesn't come on on its own but when we adjust the dial and force it above 20deg it comes on and then goes into the short cycling process repeating on, off, on, off every few minutes, its quite annoying and not sure if this is right.

Can anyone offer any advise please?

Our setup is as follows:-

Boiler - Ideal Classic Standard FF 230-280 (located in kitchen)
Boiler stat range is 1-6 - currently set at just below 5.
Programmable timer - Landis & Staefa RWB9 - both CH and HW are set to ON - we dont use the timer to be honest we just leave both the hot water and central heating set to ON position all the time.
Room Thermostat - Towerstat RS (located in lounge)
Cylinder stat - wrapped around hot water cylinder in upstairs airing cupboard, stat position approx 1/3 of way up from bottom, set at 63deg.
System is open vented
Pump is a Grundfos UPS 15-60 (3 speeds) set on 2.

Our house is a three storey two bedroom end terrace with approx 8 radiators.

Incidentally the LED doesn't seem to work on the room thermostat but i think this stopped working a long time ago. I have opened the stat up and there are only two red wires to terminals 1 and 3, live and switched live, no neutral although I thought this type of stat needed a neutral?

Sorry for such a long and laborious post, hoping someone can help or at least point me in the right direction. At the moment am thinking of spending £15 just to try out a new room thermostat but not sure if this will even work, just want to stop the short cycling of the boiler as it cant be doing any good and could possibly lead to frying the heat exchanger?

Dont really want the turn up the boiler stat or hot water culinder stat as don't want to cause scaling. Although to be fair i have tried a combination of both and it doesnt stop the short cycling, i have also tried the CH pump on all three speeds but its just the same.

Many thanks. Merry Christmas & Happy New Year.

Regards

Matt
 
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P.S. The house is approx 15 years old and i believe there could be sediment in the bottom of some of the rads and also in the hot water cylinder, when we used the immersion heater last week there was spluttering steam/hot water coming out of the bath hot tap along with bits of sediment etc.

Rads probably also need balancing and powerflushing. All rads are microbore piped (about 7 / 8mm? pipes coming out of wall).

Nothing has been changed on the system, all approx 15 year old now.
 
P.S. The house is approx 15 years old and i believe there could be sediment in the bottom of some of the rads and also in the hot water cylinder, when we used the immersion heater last week there was spluttering steam/hot water coming out of the bath hot tap along with bits of sediment etc.

Rads probably also need balancing and powerflushing. All rads are microbore piped (about 7 / 8mm? pipes coming out of wall).

Nothing has been changed on the system, all approx 15 year old now.



The Tower Stat is designed to have a neutral, Example 1 =live,
3 = switched live and 4 = neutral.

Your boiler is cycling more than likely because the radiators need balancing.
 
I'm no expert but I'm convinced you've got a switching fault on your thermostat.

Temporarily take it out of the equation by turning it up to max demand temperature, so that the heating pump is running constantly during the hours allocated by the timer. Then turn down the boiler temp to achieve a radiator temperature/room temperature you are happy with. Try a new thermostat ASAP!

(The radiator problem is beyond me)
 
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Thanks for the replies guys, will give it a go.

Anyone else any other suggestions?

Thanks,

Matt
 
I would turn the pump up to 3 for a starters, and the stat down to 4 and see how the temperature in the room goes.

You would need to check the header tank, to make sure it ok on 3 though.

You don't say anything about motorized valves.

Other than the room stat being dodgy, the boiler stat could be suspect, as well as other electrical bits, but first get the room stat sorted.
 
I would turn the pump up to 3 for a starters, and the stat down to 4 and see how the temperature in the room goes.

You would need to check the header tank, to make sure it ok on 3 though.

You don't say anything about motorized valves.

Other than the room stat being dodgy, the boiler stat could be suspect, as well as other electrical bits, but first get the room stat sorted.

Thanks for your reply.

We turned the pump down to 2 a few months ago (these problems were already ongoing then) due to it making a bit of a racket with the pipes, possibly a bit of air in the system? dont think pump likes that as water lubricates impellor.

I think there is a 3 port valve in the airing cupboard next to pump and hot water cylinder.

I will try get a new room stat tomorrow, got to be worth a £14 punt. Just need the two wire sort as only got a live and switched live on the existing stat.

Thanks for your help. Anyone else have any suggestions?

Note we also have an immersion timer device connected to the hot water cylinder, this is powered by a switched fused spur which is currently switched off so the immersion doesnt operate at all, could the switching off of this switch have done anything? As far as i know its only the immersion timer that operates from it unless the room stat is wired to the immersion timer/programmer? (The immersion timer/programmer is located next to the cylinder in the airing cupboard upstairs).

Regards

Matt
 
What you're suggesting now is a circulation problem which would make sense, dirty water, sludge etc, with maybe a semi blocked HX.
 
The heat exchanger is an integral component in a condensing boiler and is the source of its' extra efficiency. Unfortunately many manufacturers put very narrow water passageways in their heat exchangers, so the water circulating around your radiators etc tends to sludge up the boiler's heat exchanger and causes degradation in performance which eventually can only be rectified by powerflushing your system.

So it is sensible to regard modern condensing boilers as more sensitive to the quality of your system's circulating water than were their predecessors and maintain it accordingly, EG with periodic draining of the system to introduce an appropriate system cleaner. After the recommended cleaning period, drain the system a second time and refill with clean water and the correct dose of inhibitor.
 
'Doitall' is one of the most experienced on the forum so he does know what he's talking about.... :D

Condensing or not, all boilers have a HX, its where the heat from the combustion process is transferred into the water. If the HX is partially blocked with sludge the pump cannot dissipate the heated water quickly enough causing the boiler to short cycle.

Immersion needs looking at :!: Possible thermostat failure from the description, this fault has led to fatalities when the contents of the cold storage cistern have been heated by the cylinder and collapsed, showering the room below with boiling water :!:
 
Thanks guys for your time and replies.

Not got a replacement room stat yet but intend to get one, it seems to work intermittently.

I plan to have an heating engineer look at our central heating system early next year, Jan/Feb time and have it re-balanced, any air removed, and powerflushed - although I'm not sure how successful powerflushing is with microbore pipework to radiators?

In the meantime I will check out the header tank in the loft, what state should that be in? Should it have water in it? be full or part way up? (I believe it is the smaller of the two tanks as the other tank is for stored cold water).

I have set the boiler stat to about 4 and the Grundfos pump speed to 3 to see if that helps, I suppose time will tell.

Regards

Matt
 

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