'conventional' boiler. Basic timeswitch on h/w, wireless digistat on heating.

[anthony james]

Is there going to be any problem with this set up?

At the moment theres a basic two channel mechanical timeswitch in the kitchen and a wired 'stat on the first floor landing. The timer switches both water and heating on together but manual over-ride allows them to be operated independently. There are two motorised valves in the airing cupboard with the boiler.

I want to put a ACL Tempus2 7 day timeswitch in the airing cupboard to control hot water (i figure with a 7 day timer manual override will be rare) and use an ACL Wireless Digistat3i to control the heating. IME a 'stat is far more useful placed in your primary living space (ie the living room) than a draughty hallway with few rad's.

Are there any pitfalls I haven't thought of? The boiler is a Keston130. I figure it's going to take a bit of time to work out what's what in the boiler cupboard but all the new wiring will be in one place.

AJ

[Christian McArdle]

Firstly, use a 2 channel programmer and wire the new programmable stat through the CH side. There is almost no difference in price. You don't use the programmer for actual timing, but it is very useful as a central location to turn everything off and on without having to traipse round to the room stat. The CH side is usually set to 24H (or Off). It is particularly useful if you have multiple heating zones, or your room stat doesn't have a simple "Off" feature, as many don't.

Secondly, ensure that you have a cylinder thermostat. It sounds like you have an S plan system. If no cylinder stat is present, you need to insert it in series between the programmer "HW On" output and the hot water zone valve motor live (normally brown) wire.

Christian.

[Lurch]

Why use a programmable room stat if there is already a 2 channel programmer, surely a standard wireless stat will suffice.

The spur that turns off the heating could quite easily do that. And it is unlikely anyone will have to traipse round to find the room stat, surely it would be where you screwed it on the wall?

Which there aren't as there are only 2 valves, so that would be an S plan then.

SJW A.C.S. Ltd.

[Christian McArdle]

Several reasons. Basically, the advantages of using a programmable stat over a separate stat and programmer are:

1. Controls are in the living area rather than in a manky undersink cupboard or inaccessible airing cupboard. This enables manual override and programming to be easily achieved.
2. Rather than turning off completely, the stat can just turn down the temperature, to say, 12C, ensuring that the house doesn't get freezing overnight, or whilst you are out.
3. Complex control laws can be used that can predict the house's response to heat, enabling temperature overshoot to be controlled and enabling the device to predict how long before the required start period the heating needs to be on.

The spur will also turn off the hot water, which may not be desired. If you are fiddling around with the system whilst testing, you don't want to have to frequently disappear down the stairs to turn the thermostat on and off when the nearby programmer can do the same function for pennies more than a single channel.

Christian.

[Lurch]

I was actually going more for the two programmers in series, a programmable roomstat is a good idea in my opinion.

Fair enough, but if it's set up correctly you don't really need to alter the timing. Although it's all up to the individual.

You've lost me there, you can turn the temp up and down regardless of where the stat and programmer are.

O.k. then, I'll let you off with that one!

I personally only test my heating systems once and then thats it, it generally doesn't break down that often.

So in general then to the OP, yes, your way would work but there are other ways, a good programmable room stat would be my choice coupled with a single channel on the water, but it's a free country!

SJW A.C.S. Ltd.

[Christian McArdle]

Unfortunately, when setting the timer in January, you don't know that a couple of mates are coming over on July 14th until 2am. A handy nearby "boost" button could be useful here, rather than searching for a torch because in the low light you can't see the programmer in its cubbyhole and can't remember which button boosts the heating (and the manufacturer decided to scratch the legend in rather than using high contrast printing, but you don't read braille).

What I mean is that a programmable room stat doesn't turn off and on, it just changes temperature. My "off" temperature is 10C. My "on" temperature is 22C. If you had a separate programmer, the "off" temperature is -273C, as it just cuts the power totally, with no ability to just keep it ticking along for the benefit of your furniture and pipework.

You could always put a switch for the CH side. But then twin channel programmers are basically the same price as single channel ones, so it would be cheaper and neater just to use a twin channel programmer. OTOH, it isn't that important on a single zone heating system. On multiple zones, it is far more useful.

Christian.

[Christian McArdle]

It's just that I prefer not to cut the power completely when "off". I don't want it getting too cold (i.e. below 10C), even when I'm not there. My prog room stat is on the approximate equivalent of "twice" on weekdays, the middle of which can be filled in by pressing a single button, if required. I suppose some stats may have more complicated manual overrides.

Christian.

[Set Square]

Do you know something about the long range weather forecast with regard to a particularly cold spell in July?!

Most of us will have our heating switched off then!

[Christian McArdle]

D'oh!

Christian.

[Christian McArdle]

Alternatively, I thought the OP was in Tasmania...

Christian.

[Dave Plowman]

If your house normally drops from say 20C in the morning to 10C by the evening, I'd say you desperately need the insulation sorted.

[Christian McArdle]

Nah, it doesn't. In fact, despite lack of wall insulation, it doesn't drop that much during the day. However, during the night, it could well go below

10C. Wall insulation isn't practical. It has solid walls and original features that would get seriously disturbed. However, as it is a terraced house, the overall heat loss really isn't that bad in practical terms.

Christian.

[Dave Plowman]

Much the same as mine, then. But I'm not intererested too much in the nighttime temp as I'm in bed. ;-) Obviously, if it can't come up to temperature after the switch on time and I get up, then that's when I'd leave it on all night - controlled to the nighttime temp of the stat. But it's not many times a year.

[Anthony James]

Now you've lost me....there are other ways but you'd recommend a good programmable stat with a single channel on the water. Which is what i was described in my original post.

Aj

[Anthony James]

I've had one on a combi for the last 3 years so can confirm:

Generally the heating gets extra time if we stay up late. We're usually in the living room in that case. A minor point - if the controls stayed in the kitchen it would hardly be a problem, especially with 'boost' functions rather than just on/off.

or more importantly while you're on holiday. The ACL has 3 settings each day. By default it comes on in the morning and tries to get the house to 20C, lets it cool to 16 during the day, back to 21 in the evening and then down to 7 overnight (from what i remember). If you're ill or feeling the cold for some reason it's simple to turn it up a degree or two and it reverts to the normal settings at the next junction.

That's the plan. the claim is that it can save 10% of fuel bills and with a solid walled, single glazed house you need all the savings you can get!

[Anthony James]

Right. NOw you've lost me. Where can i find out what an 's' plan system is? Why do i need a cylinder stat if i dont have one at the moment?

[Christian McArdle]

I think he got confused who said what...

Whether to use a single or twin channel programmer is a minor point. The important thing is to check that you have a functioning cylinder stat. If not, it is very simple to add.

Christian.

[Lurch]

Which is exactly what I agreed with. In esscence my answer was- yes, that will work perfectly satisfactorily. The problem with ba simple question is it has many complex answers. A 2 channel programmer coupled with a programmable room stat would offer you more control and an increase in performance. If you are doing it the latter way just make sure that the settings are all at the optimum for your living situation and that you use a quality stat, some of the cheaper ones aren't as accurate on the temperature.

SJW A.C.S. Ltd.

[Lurch]

By the sounds of it there should be a cylinder stat, if there isn't one it would be required to modulate the hot water temp. If you don't have one at the mo you wont really see any benefits by having efficient heating controls if the rest of the system is innefficient. If you're thinking of entirely rewiring your heating system I would have thought you would be able to tell what sytem you have. If it is an S plan there should be the boiler flow coming into the airing cupboard, through the pump, then teeing into two valves. The outlet of the heating valve will go into the heating flow. The outlet of the water valve will go to the HW tank.

SJW A.C.S. Ltd.

[Anthony James]

in reply to both of you (I'm now at home):

There is a cylinder stat. I've been looking at ACL/Drayton (Invensys Climate Control) kit. It worked well in the past for me.