Room stat and being green

[John]

Well, actually, rather than being green and thinking of the environment, it's my pocket I'm thinking about.

In an effort to cut our gas bill I'm trying to get the family used to having our programmer/room stat set at 20C instead of previous years where it's been normal to have it at around 22-23C. The condensing combi boiler is up in the loft and the guy who installed the system (which was already in when we bought the house last year) installed the room stat in the living room.

A sort of an unintended side-effect of the desire to cut our bills is that the living room seems to reach the required temperature of 20C quite easily and the stat then shuts off the boiler, resulting in the rest of the house being cold - or at least colder than son in his bedroom doing his homework, daughter in her bedroom, and anyone wanting a shower, would like it to be.

The programmer/roomstat thingy is wireless so I can move it with minimal disruption but the living room rad has no valves, which I know is the correct way of doing things. I would think that the hallway would be a better location for the stat but that rad has a TRV fitted. Am I alright in just opening this TRV and telling everyone in the house that it must remain permanently and fully open? I know it's a "bodge" and really, if I want to move the stat I should drain the system, take the TRV off the hallway rad, and install it on the living room rad, but that's such a lot of messing and I'd rather wait until the system has to be drained for whatever reason and do it all then.

TIA

[Mike Clarke]

Yes.

It's not a bodge. What happens in a few months time if you decide that the wireless stat would have been better in a different room instead of the hallway? Just leave the TRV fully open, it'll be fine. If you're concerned that somebody might turn it down then just remove the head from the top of the TRV.

OTOH getting an extra TRV and fitting it to the living room radiator might be worth doing when you get the chance.

[John]

Ah, brilliant. Thanks Mike.

[brass monkey]

That's what i'm currently doing, trying to find the best place for the stat. Also, being a tightarse, i'm closing off bedroom rads in the daytime and loung rads at night. I miss the direct heat from a gas fire in the lounge so I can see me buying one. The hall is no good for my stat, as you say, it warms up easily so everywhere else is cold. My stat moves to the lounge in daytime and to moms bedroom at night. You can't win, when mom gets up before us she goes to the cold lounge. I must quit being a tightarse.

[Lobster]

Mike Clarke wrote:

Mike Clarke wrote:

Well good luck with that...

Hah! Like there's any risk of that happening...

David Sorry, just a cynical 'family man'... ;-)

[Dave Liquorice]

That's a big drop to do in one go, you'll get complaints. B-))

Drop it by 0.5C every 2 or 3 weeks and they might not notice as they'll get used to it.

Is the system balanced and the radiators properly sized for the rooms they are in? With both of those correct the house should heat up evenly, but if there are lot of people in the living room all chucking out heat that room will stay warm as the rest of the house cools. So shifting the stat to the hall might be a good idea, simply remove the head from the TRV in there.

[John Rumm]

Just unscrew the thermostatic head from the valve body (no water will escape - its just taking the knob off in effect). That will leave it like a manual valve that is permanently open.

[Andrew Gabriel]

I suspect the living room is the right location -- it's just that its radiator is relatively too big. You can shrink it by draping something over it to reduce the heat it gives off.

[<me9]

I have TRVs on all my radiators. The lounge/diner and the front bedroom (where the thermostats are) have the heads replaced by the decorating cap, left loose enough to give full flow, but enable the radiator to be turned off fully if part draining the system.

[YAPH]

It should have lockshield valves on the rad(s) - just that they shouldn't have control knobs you can operate by hand. instead they'll either have blank plastic covers over a shaft with flats on it you can turn with a small spanner, wrench or the knob of an equivalent adjustable valve, or some have a brass hexagonal head cap which unscrews to reveal an Allen-head adjuster for the valve. Either way if you close one of these all the way then back it open a fraction you should find a point where the radiator heats up fully, but a bit slower, giving the other rads in the house a chance to heat up fully. You should also have TRVs on most if not all of the other rads if you're serious about being 'green'.

[David Hansen]

On Mon, 10 Nov 2008 23:26:10 +0000 (GMT) someone who may be "Dave Liquorice" wrote this:-

The house should heat up evenly, provided solar gains are even. This can be nearly the case in some locations, but in others solar gains are an important factor.

[Dave Liquorice]

More important is the weather that day and it's not just gains but losses as well. So pick an overcast day that isn't particulary cold or windy to check the balance of the CH system.

[Kevin Poole]

Isn't that oversimplifying things to the point where it's misleading? Surely the purpose of balancing radiators is to ensure that the flow rate, and thus the average temperature of the radiator, is correct under steady state conditions - not some arbitrary transitional ones. "Correct" may mean "original design value", or it may be a modified value if the design was wrong.

If the original design called for rooms to be maintained at different temperatures, it is, of course, impossible to achieve if the outside temperature changes from the design value unless the master thermostat is in the room with the highest design temperature. For example, a system designed for 20C in the lounge and 15C in a hall with 0C outside will still need a quarter of the maximum output in the lounge when the outside is at 15C, but the hall will need none. So if the thermostat is in the hall, the trv in the lounge can open as far as it likes, but the boiler will still be resolutely off.

[YAPH]

Surely the aim is to get the rooms to correct (i.e. desired) temperatures. If it means the living room (with the 'stat in) taking longer to get up to temperature that may be better than having some rooms being too cold all the time.

Indeed.

On the other hand if there's an additional source of heat (e.g. open fire) in the lounge then if the stat's in the lounge the rest of the house will go cold when the fire's on. Sometimes you just can't win!

Basically the typical system is a crude approximation to an ideal system, so will end up as some sort of compromise. The question then is what sort of compromise is the least worst for the inhabitants.

[Edgar]

8>

[dennis]

No and you can get twin channel wireless stats just for that purpose. It will not save fuel of course as the heating will be on more often.

[Edgar]

Thank you. I'll consider those wireless thermostats, but I was thinking of using ordinary cheap wired ones - in this bungalow wiring isn't difficult and I think this is going to be a bit of an experiment.

I'm not trying to save fuel but to maintain all rooms at reasonable temperatures automatically (19C in sitting room, dining room and hall and 17C in bedrooms - which may turn out too low but seems a good starting point and satisfactory at present).

In fact I think it may save fuel too because when both main rooms are satisfied the boiler and pump will go right off instead of cycling and overheating the kitchen, hall and bathroom as at present.

It'll be interesting to see what happens in the main rooms, as the rads have TRVs. If I open them fully and rely on the room thermostat one room could overheat while the other is still trying to get there. So it seems I need to set the TRVs to switch off at a slightly higher temperature than the room 'stats to limit the rise.

Zoning the bungalow might be a better solution but that would mean lifting floor boards and disruptive things like that and it's just not going to happen at present.

Edgar

[David Hansen]

On Thu, 13 Nov 2008 14:44:03 +0000 someone who may be Edgar wrote this:-

There would presumably be relatively little disruption in fitting a motorised valve near each radiator, controlled by a thermostat in that room. If the auxiliary contact on either valve, or both of them, is calling for heat that activates the system. These two rooms are then controlled and the other rooms will be offered heat whenever one or both of these rooms is being heated.

[Mike Clarke]

Another option to consider might be the Honewell CM-zone system . It's a combination of a CM67z wireless programmer and HR80 TRV's with radio transmitters. I've no experience of it, we did think about it as an option a while ago and eliminated for various reasons including cost but it is quite an ingenious system.

[Edgar]

Thanks David.

I didn't think I could get acceptable looking cheap motorised valves small enough to fit within the existing pipework constraints (pipes come straight up from under the floor into the rad valves). I should have thought of this before we had new carpets.

I'd need four because the sitting room has three radiators. So cost is also a factor.

Edgar