OK, our central heating is not working, the c/h thermostat clicks which indicates that the system is "on" because when it is "off" the c/h thermostat is inactive, also when the thermostat on the hot water tank is turned up the boiler springs into life.
So the boiler is working OK and generates hot water, there is power to the c/h thermostat which clicks normally as it is turned up and down however turning it up does not fire up the boiler and warm the radiators.
We have a service contract and they have been called though cannot come until tomorrow, thankfully it is a little milder than it has been though rather chilly all the same.
Any ideas?
Thanks.
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There'll be two demand valves serving the hot water system and the CH. The CH valve might be stuck. They are both probably next to your hot water tank. You should be able to manually push the stuck valve over to the open position. It'll most probably be a little box about the size of a fag packet with a lever on it. Just follow the pipework from both to establish which one is feeding the CH and which is serving the HW tank.
If still unsure, run off some hot water with the boiler off. Switch the boiler back on and get someone to watch the valves. If both move it's not that ! If only one moves the other one is the culprit.
Good luck !
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>>There'll be two demand valves serving the hot water system and the CH.
Maybe or else a three way valve.
>>You should be able to manually push the stuck valve over to the open position.
Honeywell is probably the most common valve installed.
A example is at the bottom of :-
www.hvaccontrolparts.com/honeywell.html
The little lever can be seen at the bottom side of the box.
The lever is surprisingly stiff to move but do it slowly.
The valve is powered into the open position and spring loaded to shut.
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Check the pump is working - if you use a screwdriver as a stethoscope you should be able to hear it.
Check the valve controlling the water to the radiator is open (are the pipes hot?)
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I thought pump when I started reading it but he says the boiler does not fire for CH but does for water.
Is the timer/programmer setup okay? Someone hasn't accidentally switched it to water only? I'm sure you checked that. Maybe the timer is not working properly and it not turning on the CH but it firing the boiler for water.
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Mr D'Bout has it spot on. I would 99% say that the motor in the CH zone valve has gone TU. Depending on access, it is a half hour job to replace and a new motor which is easily obtained costs about £12.
As he said, you can open the valve manually by gently pushing the lever over into the retaining slot. This will open the valve and should operate the microswitch which will complete the circuit and call for heat and fire up the boiler.
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Thanks Humph, henry k, Tigger, rtj, MrT,
It's a three way valve and it appears that it was stuck, manually actuating it generated heat in the rads and then turning up the tank stat caused it to switch itself to hot water. The c/h stat now triggers the boiler etc. All seems to be working though I will let the engineer have a look tomorrow.
I changed one of these myself (two way IIRC) at another house about 15 years ago though we have a contract so they can sort it.
BTW the valve is Drayton.
www.screwfix.com/prods/40818/Plumbing/Radiator-Valves/Drayton-Mid-Position-Valve-Actuator?cm_mmc=GoogleBase-_-Datafeed-_-Plumbing-_-Drayton%20Mid-Position%20Valve%20Actuator
Thanks again.
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In our last house we had a separate (i.e. additional) two way valve which controlled heating for upstairs. It had its own timer. It packed up and so no heating upstairs.
When I eventually found it, removing the motor and manually opening the valve meant upstairs heating came on with downstairs and made the valve redundant.
Now finding the valve which was in the middle of the floor of one bedroom took some time!
Cheddar, you're lucky this played up when it had gone a bit milder.
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Save starting a new thread.
We have an old type manual room thermostat. The circular wheel type that clicks on and off. Can we change this one for one to the newer LED display type with the current wiring or does the newer type need extra wiring to work?
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old manual stat is most likely just a switch contact closure - two wires and an earth needed.
newer powered things (not just a switch) need three wires and earth.
A quick google provides the following in no particular order:
www.diyfaq.org.uk/plumbing/controls/controls.html
www.heatmisershop.co.uk/products/Room-Thermostat-%252d-Heatmiser-DT.html
www.diydoctor.org.uk/projects/thermostats.htm
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>> old manual stat is most likely just a switch contact closure - two wires and
>> an earth needed.
>>
>> newer powered things (not just a switch) need three wires and earth.
>>
Some manual stats are powered so three wires and earth.
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Yes you can
The Drayton Digistat will fit as required just using your existing wiring.
I have the previous model (the digistat1)
www.gasapplianceguide.co.uk/drayton_digistat_programmers.htm
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I put in one of these at the beginning of the winter - working well. Runs on a couple of batteries so only needs the two wires. You'll find the wiring diagram on the Honeywell site (I had to register I think).
www.plumbnation.co.uk/site/honeywell-cmt907-7-day-programmerable-room-thermostat/
It has a couple of nice features - you can tell it you're off on holiday, and to reduce the temperature for a set number of days (you choose the temp), and you can tell it you're temporarily at home (when it uses the Sunday programme for the days you're around).
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Ah! internal battery for display.
Good solution.
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Cheers guys. Will take the plunge at the end of the month.
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Are Lass has had 3x new room thermostats replaced now in 12 years the contacts burn out & it's worth just checking this.
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radiators - when they are cold at the bottom and need to be bled . with the boiler in the loft - is there a correct order in which to start ?? and what can I do when opening the tap no air seems to come out, just a little stream of hot water but no improvement in coldness at the bottom - any suggestions cheers
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A radiator cold at the bottom with hot water out of the top when bleeding is most likely choked up with black sludge.
This is bad news, and involves serious flushing out..
I'm sure a plumber will be along when it gets light, and I hope he says I'm wrong.
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Not a plumber but recently been messing with heating so some experience.
Sounds most like sludge to me. You can get an additive which you leave in the system for a week or so to break down the sludge before you flush. You can hire power flushers from the usual suspects - it would take a good 5 hours to do a decent job and hire is around £70 - or pay a plumber a few hundred to do it for you. Alternatively you could take each offending radiator off and wash it through - also not a quick job, with some element of risk of sludge leakage onto carpets.
Once you've cleared the sludge you need to add an inhibitor to prevent build up (although in my case this seems to only slow the process down)
Could be balancing too maybe, but if it was once working and now it's not then that's not likely.
Examples:
Additive - tinyurl.com/65m966a
Power flushers - tinyurl.com/6cqsbev
Inhibitor - tinyurl.com/6cl7b34
I have problems with sludge build up and am planning to have one of these installed, which will hopefully make a difference - tinyurl.com/65bcuo8
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>>radiators - when they are cold at the bottom and need to be bled<<
Turn off valves each side of the rad, have large bowls, a bucket and old cloths @ the ready,
undo the valve connection to the rad on one side only, open the bleed screw and drain water into bowl, when bowl is full, tighten bleed screw to stop flow of water, then start again.
When you think all the water is out, do the same to the valve on the other side but leave a bowl under the valve you've just worked on!
When rad is completely drained, remove rad to the outside of dwelling & flush through from one side then t'other using hose.
Carry out smokies advice in the Spring/Summer.
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>>When rad is completely drained, remove rad to the outside of dwelling & flush through from one side then t'other using hose.
>>
I find that rads are never completely drained so beware of the remaining concentrated sludge finishing up on carpet / down the stairs etc.
IMO the most difficult part is the final removal / lifting of the radiators.
It is almost impossible to lift them staight up so the remaining sludge will pour out of the low end so be well ready to cope with that.
When the vast amount of sludge has been removed I plug the open ends of the radiator with kitchen roll and secure with packing tape. Only then will I move the radiator to the flushing site. I alway flush rads on the lawn to avoid the sludge staining anything.
Finally radiators even pressed steel ones are surprisingly heavy.
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I would second henry k and temp sealing the ends with tape etc before moving the rad.... that last bit of black sludgy water is evil for staining.
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>> I would second henry k and temp sealing the ends with tape etc before moving
>> the rad.... that last bit of black sludgy water is evil for staining.
Far too much effort. Just slip an (un blown up) balloon over the end of the radiator. Used that tip for years,
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Henry is absolutely right.
A trick (which I may have learnt here) is that once it is mostly drained, you loosen the nuts enough that you can lift the rad off the wall then swivel the rad over so that the top is leaning on the ground - then undo the nuts completely and carry the rad upside down. Still not infallible though.
Last edited by: smokie on Wed 12 Jan 11 at 09:59
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>>IMO the most difficult part is the final removal / lifting of the radiators.<<
Affirmative :( ... if its a big dude, then hire a power flusher to do it in situ.
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To add to Dog's advice,
>> When rad is completely drained, remove rad to the outside of dwelling
Carry it out of the dwelling upside down... Less drips.
EDIT: Beaten to it, by a few of you at that.
Last edited by: Dave_TD {P} on Wed 12 Jan 11 at 10:06
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We used to say about an open fire that by the time you'd cleaned the grate, taken out the ashes, humped in the coal and laid the fire, you were warm enough not to need it.
Seems central heating could be the same.
Just flick on the electric heater, sit back - and wait for the bill.
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>>Carry it out of the dwelling upside down... Less drips.
Having made sure you've closed the bleed screw first - I now know. ;>(
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>> Carry it out of the dwelling upside down... Less drips.
I made the mistake recently of carrying a radiator out of the house the right way up. Good job we're replacing the hall carpet soon. :-(
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Alanovic... were you able to claim on in surance ?
many thanks to all those who contributed, I think I'm gonna have a busy weekend !!
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Nah, no need. There's fabulous original parquet under the carpet, when the old carpet comes up after all the renovations, we're just leaving the parquet exposed.
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Central heating question? - Runfer D'Hills
