how to wire room thermostat?

bob123 · 28 Mar 2004

Just moved into my new house, and spent an age trying to suss out how the heating works.

I have a Worcester 240 combi boiler, age unknown. There is no wall thermostat anywhere, and none of the radiators have thermostat valves. This means the only method of controlling the temperature is via the dial on the front of the boiler (which I am told is used to set the temperature of the water as it leaves the boiler.)

This doesn't seem very efficient, or effective.

My long term plan is to upgrade the radiators, at which time it makes sense to fit thermostatic valves. In the mean time I would like to add a simple wall mounted room thermostat to help regulate the temperature throughout the house.

My problem is that I don't know where on the boiler to wire it into.

Any ideas?

Thanks in advance...

PS - Even if I raise the pressure manually it always settles back to 0.6 bar. I was advised this meant there was a problem, as it should never drop below 1. Is this true?

weargas · 28 Mar 2004

bob123 said:
I would like to add a simple wall mounted room thermostat to help regulate the temperature throughout the house.

i never have and probably never will understand how the heating for all of the rooms in a house could possibly be efficient if controlled by the heat from one room. if the room containing the thermostat heats up quickly it could shut down the ch and starve other rooms that require further heating. the opposite applies, if the room containing the thermostat heats up very slowly then the thermostat may never shut down. If the latter is the case then the boiler is being controlled by integral thermostat anyway.
my opinion is that the most efficient way to heat a house is with trvs and the boiler stat. you can stick part L up yer erse!!!!!!!!!

ChrisR · 29 Mar 2004

Well the theory of the no-TRV system is reliant on getting the calculations for the rad sizes right. Works fine. "open loop control system". As long as you don't leave any doors open!!
Wiring a 240 isn't hard, get a manual from worcester. It probably has a crude 24hr timer, so install a programmable thermostat and leave the boiler timer on 24 hrs. Can sell you one if you like, I have various new & used ones. 24 hr and/or 7 day control so you get the temp you want when you want it.

Bldg regs Part L say you should have trv's on at least the bedrooms. But 90% of the ones I find are wide open!. Can be handy in a bedroom where there's an airing cupd. Don't get cheap & nasty trv's they'll last no time at all.

bob123 · 29 Mar 2004

ChrisR - Thanks. Thats pretty much what I thought, altho I haven't had much joy getting anything out of Worcester.

weargas - You must have too much time on your hands, if you can spare some to waste everyone's time just spouting opinion.

In an ideal world we'd all have the ideal system. But it's not an ideal world, and I don't. Nor do I have the money to just do what's best. My post was clear in that I wanted an interim solution. Something that would HELP.

You're no better than the idiot at my gas supplier who tried to sell me a TRV installation. 'We estimate it could save you about £40 a year', he said. The cost - £400.

Stick to the real world, and try to be constructive.

Now I'm down off my soap box, this is a great site - keep up the good work.

ollski · 29 Mar 2004

bit harsh....I don't think weargas was getting at you bob just using your topic to raise a general point.
worcester aren't very good at dishing out old manuals but if you get the gc number off the data badge and give their techs a call on 08705266241 they should help.

weargas · 30 Mar 2004

Well, it was only an opinion.
Also, I didn't mean to waste anyone's time.
Nobody says you have to take any of the advice offered on this forum. I'm sure people have a different opinion to me.
Keeping to your original question, have you opened the control panel to see if there's a room thermostat wiring terminal?
Every combi boiler usually has one. I just can't bring to mind the inside of the 240 control panel.
Remember, whoever posts a reply is just trying to help.

COG · 30 Mar 2004

The terminals are marked on the controll board ? at present it will have a link in place of the room stat switch wires. Its 230v .

combiner · 31 Mar 2004

Sounds like you have a leak. The boiler should automatically disabled itself, if the pressure drops below 1 bar.
Sorry, I agree with Weargas. A room thermostat only monitors the temperature of air in its immediate vicinity. For such a device to switch off the entire central heating system is ridiculously illogical and inefficient.
I, personally, do not like TRVs. Standard radiator valves are reliable and give less trouble.

COG · 31 Mar 2004

Your boiler wont shut itself down if the pressure falls below 1 bar as it has no low water pressure switch or anything similar. Acording to the latest regs you should have a room stat (boiler interlock) and trv's fitted but at this stage its up to you as your boiler would have been fitted before the part L regs came out. If your pressure keeps falling to .6 bar then you do have a small leak and obviously one that only leaks above .6 of a bar so check out your rad valves and the outlet from the pressure relief pipe.You are correct about the dial on the boiler in that it controls the primary temp at the boiler between 52C and 84C.

weargas · 12 Apr 2004

please tell me someone "got" my subtle reply

oilman · 12 Apr 2004

How do you define efficiency with domestic centrasl heating anyway?

As people here have pointed out, most TRVs are left on full, because comprehending the complexities of the thermostat is beyond most peoples' capabilities.

The most efficient form of central heating is the jumper. If you have the whole house at say 60 F, you can just add or shed jumpers depending on your level of activity

weargas · 13 Apr 2004

oilman said:
The most efficient form of central heating is the jumper. If you have the whole house at say 60 F, you can just add or shed jumpers depending on your level of activity

if the jumpers were lined with plastic your sweat would cool and condense onto the plastic making them super efficient condensing jumpers! The EU may have something to say about the emissions though.

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how to wire room thermostat?

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