Conservatory heating - how to 'zone' extended CH radiator?

[Army]

Hi all,

Just planning for conservatory self-build for which I'm sure there will be many questions over the following weeks!

After much googling of uk.d-i-y it seems that extending the CH pipework into the conservatory and plumbing into a decent finned double rad is the way to go. The conservatory rad needs to be controlled separately from the rest of the houses' CH as I may need heat in the conservatory during periods when the main house stat is not demanding heat and the boiler is therefore inactive.

Boiler is an ariston microgenus II31 combi. Control is by a battery powered 2 wire programmable stat. Zoning is beyond my current level of knowledge but I'm trying to plug that particular gap right now! I'm guessing that I need to introduce a 3-port mid position valve to the flow end of the CH and connect to it (a) the original house stat and (b) a new stat to be located in the conservatory. The resulting 4 peices of wire (and this is where it gets a bit beyond me) I'm guessing need to be connected to the valve in a configuration such that continuity across circuit (a) opens the valve to position a, circuit (b) opens to position b and (a and b) opens a+b. I think I'm correct in understanding that the valve will also act as a relay so that a single connection from the valve to the boiler can be used to tell the boiler that CH heat is being demanded.

I wonder if anyone could confirm (or not) that I'm barking up the right tree here. The bit I need further information on is the wiring. Does anyone have any good pointers to where I may learn about this?

Thanks

Mike

[Lurch]

On Fri, 30 Sep 2005 23:53:42 GMT, Army scrawled:

You guessed wrong! You want 2 2 port valves in the flow below the boiler, or before the first tee off, for the house and conservatory zones.

The wiring is much simplified doing it the correct way! The house stat controls the valve for the house heating, the conservatory stat controls the valve for the conservastory heating. The 2 sets of auxilary contacts control the boiler.

[dennis]

That's how mine works (except I have 5 2 port valves).

Wouldn't it work by just parallel wiring a new thermostat assuming the OP has TRVs on all the radiators?

[Lurch]

On Sat, 01 Oct 2005 07:09:49 GMT, "dennis@home" scrawled:

No, because the 2 stats will not do the job they are intended, in fact, I'm not really clear on exactly what you're suggesting but it won't won't work anyway.

[Set Square]

You *could* do it with a 3-port valve but, as others have said, you'd be better off with two 2-port valves.

Have a look at the 'plans' and their associated wiring diagrams in

of them exactly match your setup - but you should get some clues.

The Y-Plan is the one with the 3-port mid-position valve. It is intended to give independent control of HW and CH in a setup with stored hot water, rather than a combi. Note that the tank stat in the HW circuit has a changeover switch with 3 contacts rather than a simple on/off switch. If you use this setup to control two heating zones rather than HW + CH, it *will* work - but whichever heating zone is in place of HW *must* have a changeover thermostat.

The S-Plan (and S-Plan-Plus) are the ones which use 2-port valves. You can have as many zones as you like, with one valve per zone. The motor of each valve is controlled by a timer and stat for the appropriate zone or, even better, by a programmable stat. The secondary contacts on each valve - which close when the valve opens - are all connected in parallel and used to fire up the boiler and run the pump whenever one or more valves are open. The S-Plan shown in the Honeywell diagram (see URL above) shows a HW zone and a CH zone - but will work just as well for two heating zones.

[dennis]

If you have TRVs on all the radiators then all you need to know is if the conservatory needs heat. If it does you fire the boiler. You do this by putting a second stat in parallel with the room stat. In fact you could have several stats if the layout needs it.

I think its a bodge but TRVs are a bodge anyway.

[Set Square]

Yes, but don't forget that the room in the house where the original room stat is located *won't* (or *shouldn't* at any rate!) have a TRV on its radiator. Using your system, that rad will get hot when the boiler fires to heat the conservatory - even if the rest don't.

Also - unless the conservatory rad has a TRV - which will fight with its room stat if it *does* - the conservatory will get heated when the rest of the house is being heated, even if not required.

Positive zoning using motorised valve(s) would be far better - and would almost certainly be *required* if the setup needs to meet current building regs. Your solution is a recipe for heating *everything* whenever *anything* needs heating!

[dennis]

I did say TRV on all.

The TRV needs to be set slightly higher than the room stat.

I agree, zone valves with end switches is easy and how I have done mine. However it was designed properly not some bodge dreamed up by a committee like TRVs were.

No it will only heat if one of the stats calls for heat just like most systems with TRVs.

[Set Square]

The problem is that it will heat *both* zones when *either* zone is calling for heat rather than just heating the desired zone. You might effect some damage limitation by having TRVs set higher that the room stats - but that's pretty hit and miss, and still an *almighty* bodge!

[dennis]

Like I said that's how TRV based systems work. The room stat has to be in the warmest room and switch the system on even if only that room wants heat. That's why I think they are cr@p. But if the system already works like that then its reasonable to extend it in a similar way.

The only real problem is if the room stat is set higher than the TRV. Then the pump will run continuously. Even that may not be too bad if the pipes are insulated.

[Set Square]

No it isn't!

The conservatory will get heated to its TRV setting even when *no* heating is required - as will the room in the house with the room stat - when *only* the conservatory is required to be heated.

The difference is that when you want to heat the house, you are presumed to want to heat the

*whole* house (without conservatory) - and the current TRV solution makes a reasonable job of that. As soon as you introduce another zone which requires *independent* control, the whole thing falls down unless you zone it properly.

Simply wiring two stats in parallel *WILL NOT* meet the OP's requirements.

[dennis]

Yes.

Why would anyone want to heat a whole house? Why would anyone not want to be able to walk into the conservatory in the midle of winter without waiting two hours for the heating to work? He might want it for frost prevention in which case heating the whole house would be fine.

Neither of us knows the answer to that question.

[Lurch]

On Sun, 02 Oct 2005 19:57:03 GMT, "dennis@home" scrawled:

If you stop being a pillock and read the OP you'll find that Mr. Squares statement is true, doing as you propose will not meet the OP's requirements.

[Set Square]

You may not - in which case you would install some sort of zoning - such as upstairs and downstairs, but the OP hasn't done that - so it's fair to assume that he's happy for the whole house (excluding the conservatory) to be heated as an entity.

Surely, that's the whole point of zoning! If you have independent control of the heating in the conservatory, you can have *just* that on - and use as much of the boiler's output as the conservatory radiator can absorb. Why should this take two hours? It can be on a timer, to be hot when required, anyway!

Then let me remind you of what the OP said in the initial post, namely:

"The conservatory rad needs to be controlled separately from the rest of the houses' CH as I may need heat in the conservatory during periods when the main house stat is not demanding heat and the boiler is therefore inactive."

He clearly therefore needs to be able to heat *just* the conservatory without heating *any* part of the house at the same time.

I rest my case!

[dennis]

No he actually states that the stat in the rest of the house will be off so he gets no heat from the boiler. Adding a second stat gets around this. The OP may well be happy to turn the stat and TRV on and off.

Shame as you didn't read what you quoted.

[Set Square]

That's precisely what I *did* do!

It's a shame that you're not big enough to accept that what you suggested is a damn silly idea - rather than continuing to try to defend the indefensible! I haven't noticed anyone else agreeing with you - not even Dr Drivel.

[dennis]

Then read it properly.

I wouldn't do it (my house has five zone valves including the conservatory each fed from a timer stat.). But it does allow the OP to get heat even if the room stat is off. This is what the OP said was his problem.

If he wants to do the job properly and fit zones then he can do so. If all he wants is an override for the room stat then what I said will work too. If he only wants to heat it for frost protection purposes then it is probably the easiest way and easiest is invariablly the correct way in my experience.

Most people don't care and are bored, just like me.

That would be evidence for me being correct then.

[fred]

In article , Army writes

In case you were in any doubt, the advice of Mr Square, supported by Mr Lurch is sound, the other is er, not :-).

[Set Square]

Indeed, in my post of 5:16pm on 1st October, I gave a reference to a Honeywell site showing various heating plans with their associated wiring diagrams, and explained that and S-Plan arrangement would be best - but also explained how a Y-Plan could be adapted to suit the OP's needs if he really wants to use a 3-port valve.

This information should be sufficient to enable any competent DIY-er to sort out the wiring.

[Set Square]

But there is no evidence that that is *all* he wants.

On the contrary, why would he mention *separate* control of the conservatory, and *zoning* and *motorised valves* if all he wanted to do was to over-ride the room stat? He clearly had something slightly more ambitious in mind! And, as I have said so many times that I am becoming blue in the face, what you suggested *won't* work in a satisfactory fashion.

Meanwhile, we've almost certainly succeeded in confusing the poor sod with all these red herrings about wiring stats in parallel. He hasn't been back, anyway!