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Central heating not coming on but still getting hot water?

(47 Posts)
PerspectiveUrgentlyRequired Sat 01-Sep-12 23:37:29

I thought it was a bit chillier today so decided to put the heating on for the 1st time in months. Nothing. Checked the hot water - still running in both the bathroom and kitchen. None of the radiators have got a bit of heat in them at all. Can't tell if it's the control switch, the radiators or the boiler. The only thing that made the boiler make it's usual 'groan' when starting up was to press the eco button off then on again, but still no heat in the radiators. The boiler is a worcester, and has a small green light flashing above the override button. Can't find anything in the manual that tells me what that means, if anything. The light could have been flashing before this happened, I've just never noticed it before.

Any ideas? It's due a service soon, now I'm worried it's going to cost me a fortune 'cos something is broke.

SoupDragon Sat 01-Sep-12 23:42:01

I think that if you get hot water but no heating it's usually a problem with something like a diverter switch/valve.

Other non-technical things - is the wall thermostat up high enough to trigger the heating? Or the thermostats on the radiators themselves?

SoupDragon Sat 01-Sep-12 23:42:54

I found my heating didn't come on because a child had been twiddling the wall thermostat and it never got cold enough in the house to trigger it. Despite it being freezing.

PerspectiveUrgentlyRequired Sat 01-Sep-12 23:51:40

Ooh, technical jargon! No idea about the diverter switch/valve. Is that visible? Where would that be? I've not touched the thermostats on the radiators, and DD wouldn't think to touch them either. The wall thermostat might be the problem, thinking about it, as it never triggers the heating even when it's cold either. I have to switch it on over 25 degrees to get the heating on at all usually. That's been a problem for ages, and the timer hasn't worked on it in a couple of years. It's maybe just packed in through not being used I suppose. Is it expensive to get the control switch replaced? Or the diverter/valve thingy?

kittycat68 Sun 02-Sep-12 08:15:32

most likely the diverter switch, but could be the central heating pump you need to get an engineer out to have a look, diverter switch replacement should be around £50-£75 depending on the engineers rates!! pump will be a little bit more up to £100. if you need it serviced get it done at the same time and save some money!

CumberdickBendybatch Sun 02-Sep-12 08:45:12

Likely the thermostat. Hopefully anyway, easier to replace!

kittycat68 Sun 02-Sep-12 08:50:35

if the worcester boiler has a flashing green light the fault is with the boiler does it have enough pressure in it what is it reading op.

seb1 Sun 02-Sep-12 08:53:13

Probably your 3 way switch may just be sticky after been off for the summer. You will find the switch (box like thing probably) near your hot water tank.

seb1 Sun 02-Sep-12 08:55:42

Try changing your timer to put your hot water on constant and see if your heating will come on then.

kittycat68 Sun 02-Sep-12 09:14:39

op can u tell us the model of the boiler , is it a combination boiler?

Imlostwithoutahope Sun 02-Sep-12 09:46:58

Our worchester is the same, it stopped working in April. We get to water but no heating. Our boiler is about twenty yrs old so we know we prob need a new one as the parts are getting rare. Of course when this happened in April we were going to through the summer get a quote for a new boiler or a quote to attempt to fix it before autumn when the rush started. Of course here we are in sept still in the same position with no quotes!

PerspectiveUrgentlyRequired Sun 02-Sep-12 11:23:46

Thanks for the replies. It's a worcerster combi boiler - think it's a greenstar 24i junior? The pressure indicator is sitting at 1, just in the green bit, so that's low isn't it? Is it worth switching the boiler off, then on again? Or maybe try the re-set? I'm wary of touching anything as I don't really know what I'm doing! The timer hasn't worked for ages, so can't really use that. I just switch it on or off when heating is needed normally. Service is due on the 13th, I'm sure we can last 'til then without heating as I've kept a couple of plug in radiators from before we had the central heating, just in case something like this happened. I'm just glad we still have hot water - I'd be buggered without that.

Thelobsterswife Sun 02-Sep-12 11:29:59

This happened to us. Got British Gas out, luckily under a service contract, and it turned out to be the battery in the wall thermostat. blush A new AA and we were rocking and rolling! Not sure if I have read this wrong but how can it be your boiler if your water is being heated?

kittycat68 Sun 02-Sep-12 12:54:19

presure is a bit low this could be it thier are two black taps towards the bottom of the boiler turn on one then the other your presure should be between 2 and 3. as soon as the gauge reaches this turn off one tap then the other. then try heating again

Northernlurkerisonholiday Sun 02-Sep-12 13:06:20

This happened to us when the three way valve went. It wasn't hugely expensive to fix, less than £100 I think.

peeriebear Sun 02-Sep-12 13:07:56

When this happened to me I was utterly baffled until I realised the kids had turned the wall thermostat down as far as it would go.

PerspectiveUrgentlyRequired Sun 02-Sep-12 13:12:21

Well, I've no idea. I'm clueless about how central heating works. Showing my complete ignorance really. smile

PerspectiveUrgentlyRequired Sun 02-Sep-12 13:13:42

Thanks kitty, I'll try that and see what happens. Previous reply was to thelobsterswife.

PigletJohn Sun 02-Sep-12 13:26:59

As you have a combi, you will not have a three-port valve. The groan is probably the diverter valve moving. So I will guess the controls are telling the system to heat the rads (so not faulty timer or stat). So it sounds like the water is not circulating round the rads, so I will guess the pump is seized as it has not been run for some months. It is a moving part so is capable of mechanical failure.

If the radiators and the rest of the system are older than the boiler, it might be due to old sediment which occurs as the steel radiators slowly corrode, especially in an older system which has/used to have an feed and expansion tank in the loft (your combi almost certainly will not have one now). If, when you have it mended, the mender takes the front off the pump and tells you you have a sediment problem, come back. BG would want to sell you a powerflush for some hundred pounds but this is not always necessay.

PigletJohn Sun 02-Sep-12 13:29:11


If it is giving hot water then it will not be a pressure problem.

You can try flicking the wall stat from hot to cold and back again a few times - it will probably click - this might get it started, but I reckon it needs mending.

PerspectiveUrgentlyRequired Sun 02-Sep-12 13:39:02

Thanks pigletjohn, that's very helpful. The whole system was put in at the same time about 4 or 5 years ago so all the same age. Will update once the service has been carried out.

PigletJohn Sun 02-Sep-12 15:45:10

you mention problems with the thermostat and the timer. It is worth changing to a Programmable Thermostat which incorporates its own timer. For example mine is set to (Monday to Friday) on at 7am to 20C; down at 9am to 18C; up at 5pm to 20C; down at 11pm to 15C, and weekends, on at 8am to 18C, up at 6pm to 20C, down at 12 midnight to 15C.and you can press a button for a temporary override up or down, without changing the regular setting.

This is also more economical, except that it is quite common for women to say "I'm cold" and turn the stat up at random intervals.

You can usually have about 5 different time/temperature combinations per day, to suit your lifestyle, and you can extend the timings by x hours if e.g. you are going out for the day, or having friends round for the evening; and you can set it, when you go on holiday, to tick over at, say, 12C for 13 days, then automatically revert to normal cycle the day you are due to come back.

It will fit into the wiring where your old stat is, and might cost in the region of £50 to £100. You no longer need a separate timer. Mine, you can set to "holiday" for 99 days so that the heating never comes on in summer (if you want)

kittycat68 Sun 02-Sep-12 19:39:49

if the prssure dont work its most likely to be the diverter valve as i said before failing that its the pump , its very unlikely to be the timer as you have a flashing light on the boiler. you will need an engineer to come out for those, i ahve a mobile timer that moves around the house with me and remotely talks to the boiler! so does not need to be wired in. you would need to speak to the engineer to see if your model could have one though. odds on its the diverter woresters are known for them!!!

marriednotdead Thu 06-Sep-12 14:46:51

I was watching this thread as my Worcester combi boiler was doing the same thing.

The 'gasman' came to do the annual service today and diagnosed a faulty thermostat. He unscrewed it and fiddled about with it <technical term> and all's fine now smile

PigletJohn Thu 06-Sep-12 14:51:34

thermostat on the wall or in the boiler?

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