CH Operation

[Rob]

We're having problems trying to figure out how the CH works with a newly installed system - Vaillant combi, Vaillant room stat (in the lounge), and an Altech controller fitted next to the boiler:

controller was wired up to operate two of the 3 zones - brown sticker - bedrooms, and silver sticker - basement, dining room, kitchen and hall. This was custom wired by the installer - obviously, there's no water heating.

The third zone, lounge and bathroom, is controlled by the room stat. All rooms have radiator thermostats except the lounge.

Now, this is all well and good and probably very clever, but the radiators seem to have a will of their own. All zones are on constant with stat valves fully open. The lounge is fine, always has been, and temperature modulates in line with the room stat. But the other zones vary between no heat, and luke warm as if providing background. Then, occasionally, they'll belt out heat. The dining room and kitchen have been cold all day. The basement's fine, well, 17C - where me and the computer live.

Apart from ask the installer, which is not an option, any ideas please?

Thanks, Rob

[The Natural Philosopher]

on or more of...

1/. System full of air still 2/. System running completely unbalanced with lounge hogging all the flow. 3/. Something so idiotic it hasn't even occurred to me yet.

[Fredxx]

1 check if each motorised valve is operated when the relevant thermostat is demanding heat. 2 Each valve has a switch which closes when the valve is open/on. Check these are wired together in parallel and effectively be the room-stat switch in a conventional single room-stat system.

Personally I would have thrown away the programmer/controller, if that is what the Altec controller is, and used 3 programmable room-stats to give independent timings.

[gremlin_95]

+1, ideally you would have time and temperature control of each zone.

[ss]

This may come into it others will know for sure, but if the controller that switches it on and off is sited wrongly it could be registering a high temp at that location before the other rads heat up properly so switching off prematurely. So that room is nice and warm and the others havent had time to heat up.

[A.Lee]

More info needed. How many controlled valves have you got? I presume this is an 'S plan plus' where the valves have only an in and out, rather than a 3 way fitting? If so, then you should have 3 valves.

As has been said, a programmable stat for each of the zones would have been better, there is no need for a on/off programmer then (you can leave the heating turned on all the time, but it will only come on when the room stats call for heat).

TRVs are doing the controlling of the 2 zones, and that is not the best of ways to control the zone, and will use far more gas then if a room stat was used.

I dont know that programmer, but it looks to me like it is a 2 channel programmer, it can be used to control the heating only, but it is not efficient without the use of room stats for the 3 zones.

Where are you?

Alan.

[Rob]

I think two. I've put some more pics at:

I presume this is an 'S plan plus' where the valves have only an in and

Afraid I don't know. The system was installed by a family member, I gather. *Looks* very neat and impressive to me. Just can't get it to work!

I can only see two from the pics.

We might look into that.

Well, at the moment the kitchen and dining room are using no gas ;-)

Frankly, we would use one zone, TRVs and one stat that operates as an on/off.

Bakewell, Derbyshire.

Thanks for replies. May have to get a plumber in, or the original installer after all. I've pored over it and it doesn't make any sense. But as i say, the lounge is warm as toast, and we have intermittent heat to the basement and bathroom, so not exactly slumming it.

Rob

Rob

[A.Lee]

controlled, the other is on whenever the boiler heating is on.

They cannot be controlled properly without room stats for each of the 2 valves. Also, you really want another valve and stat fitting for the uncontrolled heating, as the boiler is going to be on all the time for that zone, with only the TRVs, I presume, controlling it.

It is a poor install, which could be a lot better, as you have little control over which zone is on/off, and temperature in those zones. This is costing you money, as, say like today, your heating is on full downstairs, but you dont really need the bedrooms to be toasty, as you'll be dwnstairs most of the day, so, you'd have the bedrooms set at

14 degrees, and the downstairs at around 20 degrees. With your current set-up,the boiler will be on keeping upstairs warm, which is a waste of gas. Even if the TRVs are turned off, the boiler will still fire up, and keep burning until the return water temperature reaches a set level, so you can see it is very inefficient.

He likes his earth bonding between the pipes doesnt he? There is no need for that, as both the water and gas pipes should be connected to earth anyway.

Alan.

[Rob]

Ah thanks, good to know how to describe it.

Noted, thanks.

That's a slightly odd thing. No TRVs, just the wireless wall mounted room stat in the lounge. And I don't want to go messing with the rad valves just in case I upset anything. So whenever the lounge gets up to temperature, the other room (bathroom, which does have a TRV set at max but seldom gets warm) goes off.

I'd like to have thought those two zones would be controlled by the TRVs. But even when set to on/constant the heat is entirely unpredictable.

We can switch the bedroom zones off until needed I suppose.

Even if the TRVs are turned off, the boiler will still fire up, and

Yes, I can see that. We'll get it given the once over and fit room stats.

Thanks for your help, Rob

[The Natural Philosopher]

then throttle the lounge rads back. So the bathroom is red hot before the stat kicks in.

Are all the motorised valve switches wired in parallel so that any one of them can 'call for heat?'

that's because the lounge system is controlling when the boiler is on I suspect.

[Dave Liquorice]

Fairly normal to bond across all the pipes as they leave the boiler. you don't know that there is electrical connection within the boiler. Mind you some of the heating plumbing turns to plastic after the valves. If there is copper elsewhere that might be floating...

I agree that the best improvement would be programmable stats for each zone each controlling the appropiate zone valve and the aux contacts from the valves controlling the boiler.

Gotchas:

Boiler may require pump run on after being told to switch off. If so there needs to be an automatic bypass valve across the boiler output to enable water to flow through the heat exchanger when all the zone valves are closed.

The radiator in the same room as the stat, for each zone, should not have a TRV. So that the radiator warms the room until the stat is satisfied, a TRV could shut the rad down before the stat is satisfied thus the boler stays running and the rest of the zone roasts. If those rads have TRVs at some point they will shutdown and then there is no circulation through the boiler but it's still on...

[Roger Mills]

It looks to me as if the wireless stat in the lounge is the *only* thing that's controlling when the boiler fires. Is the receiver for that

*inside* the boiler casing? [I notice that there's an indication of signal strength on the front of the boiler - presumably for the wireless stat?]

My guess is that, even though you've got some of the components of an S-Plan system, it isn't *actually* an S-Plan. I reckon that the two channel programmer simply opens the valves *without* the auxiliary switches in the valves being wired up to make the boiler fire. You'd have to check the wiring to be sure. If I'm right, the two 'controlled' zones will only get hot when the timer has opened their valves *and* the wireless stat in the lounge is calling for heat. So, if the lounge demand is satisfied, the other zones won't get hot whatever their timer is doing!

As others have said, in order to do a proper job you need a zone valve in each of the 3 zones, which each one being controlled by a programmable stat located in the respective zone, and with the auxiliary switches in the valves wired in parallel to create a boiler firing demand. You may possibly be able to use the existing wireless stat if it's programmable and not just a bare stat and if it can be made to control a zone valve rather than controlling the boiler directly.

It's a relatively simple job to convert it into a decent system, but whoever does it will need to have their wits about them when working out how it's currently wired in order to correct it. Insertion of a third zone valve will, of course, involve a partial drain down - unless you can easily isolate the pipe into which it is to be inserted. (I note that you have a fair few gate valves, so you may be able to do it without too much loss of water).

[The Natural Philosopher]

Not necessarily.

I have an unstatted zone upstairs with fan blown statted heaters everywhere and the bathroom rads on TRV's

It isn't the most efficient way to do it but I never found a decent place to put a (single) master stat!