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Central Heating programmer swap.

I'm in the process of rendering my CH/HW system more efficient. I've installed TRV's, double lagged the hot water cylinder (which is thermostat controlled) , and changed the old mechanical room thermostat for a more accurate digital model. My present programmer is a simple timer that switches both CH and HW on and off at the same time. I would like to replace this with a programmer that will switch CH and HW separately.

The problem is the mass of wires (many the same colour!) that presently terminate at the programmer. I only have a simple 'users guide' for the programmer (which is about 25 years old now) and that gives no information at all about the wiring.

Any simple way to determine which wires do what, and where they should go in any replacement programmer that I might buy?

Uno-Hoo!

Reply to
Uno-Hoo!
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Adam

Reply to
ARWadsworth

Thanks Adam - that's really helpful in relation to wiring up any new programmer that I might buy. The problem I have is knowing which of the wires that are presently wired into my existing programmer come from where!!

Kev

Reply to
Uno-Hoo!

Which system do you have or want to achieve?

Adam

Reply to
ARWadsworth

I worked for Potterton Boilers about 20 years ago and I can assure you that the circuit diagrams haven't changed in that time. You will probably have two independent switches for CH and HW (I know they switch at the same time but electrically the outputs are more or less independent). What you have to do is to try and trace where each wire goes to. How many valves do you have? Do you have one 3 way valve which diverts the flow from CH to HW or to both? Or do you have two two port valves which allow flow to CH and HW? Once you know the answers to these questions you may have a stab at establishing which system shown in the link is the one that you have.

What I might do from there is to isolate the mains to the system (very important as it can feed through thermostats in odd directions as I found to my cost once). Then make a careful note of which wire goes to which termnal in your controller. You can use tags or bits of masking tape to stick onto the wires which you can write the terminal number onto. Then you can go about unhooking the wires and tracing them through to thermostats and valves etc. Of course if you already know which are the switched outlets for CH and HW on your controller then you can just wire in your new controller in the same manner.

Reply to
Malc

"ARWadsworth" wrote in message news:IQdUg.28209$ snipped-for-privacy@text.news.blueyonder.co.uk...

I have a 'normal' gas powered wet central heating system with a hot water cylinder heated by an internal coil fed from the CH boiler. Both circuits are controlled by valves which are, in turn, controlled by thermostats - roomstat for the CH and tankstat for the HW. In addition I have put TRVs on all radiators but for the one in the hall (where the roomstat is located). My present programmer is an ACL. It has a mechanical clock and the off/on times are operated by pegs which you can remove or place wherever you want. It has a switch which can alternate between 'Timed', 'Off' or 'Continuous'. I cannot, however, programme the CH and HW separately. Both are either on or off (in the summer, of course, I can switch the digital roomstat off and then have the HW coming on twice a day - but when the heating is on - so is the HW). I want to swap the ACL timer for a digital programmer that will control the CH and HW separately. My major problem, as referred to above, is that there are numerous wires coming into the existing timer. Some will be from the roomstat, some will be from the tankstat, and some will be going out to the stat controlled valves and to the boiler itself. Because I do not have a wiring diagram for the existing timer I have no idea which wires are coming from where - nor where they are going to! The contacts are numbered but I presume that there is no 'standard' across manufacturers for numbering?

Uno-Hoo!

Reply to
Uno-Hoo!

Thanks for that Malc - very helpful. I have two separate valves, one for the CH and one for the HW. I can see that there is really no alternative but to laboriously track each wire and see what happens when it is disconnected!

Kev

Reply to
Uno-Hoo!

There should be some switched lives. YOu can determin this with a multimeter they will be the contacts that go live when the old timer is in the 'on' position. When they are live there should also be a live at your room stat. At the old timer disconect each switched live in turn till the room stat no longer has a live then you know which is the CH switched live and if there are only 2 switched lives at the old timer you also know the HW switched live is the other one. There will also be a permanent live neutral and earth. Hopefully thats all the wires you have.

Reply to
marvelus

Without seeing how many wires you have it is tricky, but basically there should only be live, neutral, earth and then two outputs to the thermostats. The valves are not wired directly to the programmer (or should not be) they should be in their own connection blocks else where.

You could try the danfoss radall web site as their programmers come with a guide that shows many older makes of programmers by many different manufacturers and what all the connections are for. You should be able to download an install guide for one of them

It may be you have a very nonstandard setup and you will have to remove links in turn to see what powers up and what does not power up in turn.

A photo would help and I find it very odd that you can turn the heating off with the room stat but not the hot water with the tank stat as you say they both have valves. It looks like Mr Bodgit did the work before you moved in.

Good luck

Adam.

Reply to
ARWadsworth

Thanks for that - although I clearly have caused some confusion. I can indeed turn the HW off using the tankstat but what I want to be able to do during the winter is have the CH on from around 0600 to around 2200, but have the HW on from around 0600 to 1100 and then again from around 1600 to

2200. At the moment I cannot do this because the timer switches both together.

I could, of course, keep popping up to the airing cupboard to turn the stat either up or down but that's hardly practical!

During the summer I do have the HW switching as described above - but that is only because the CH is turned off at the roomstat.

I will do as you suggest, however, to determine which wires go where.

Having just looked at the connecting board I can tell you that there are five connections in use = 1,2,4,6, and 7

1 = two red wires plus a short red link to No. 4

2 = two black wires

4 = the red link from No. 1 plus a short yellow link wire to No. 6

6 = the other end of the yellow link from No. 4 only.

7 = a single red.

Does that help?

Uno-Hoo!

Reply to
Uno-Hoo!

I've just responded to Adam and listed the wires terminating at the timer. They are:

Five connections in use = 1,2,4,6, and 7

1 = two red wires plus a short red link to No. 4 2 = two black wires 4 = the red link from No. 1 plus a short yellow link wire to No. 6 6 = the other end of the yellow link from No. 4 only. 7 = a single red.

I'll set to at the weekend and carry out the diagnostic as you suggest. I do have a multi-meter so that's not a problem.

Uno-Hoo!

Reply to
Uno-Hoo!

1 Live 2 Neutral 7 Feed to both thermostats (It must go to a jucntion box and split into 2)

It loooks like you need to partially rewire the central heating as you are a wire short.

Adam

Reply to
ARWadsworth

OK, thanks again for that. What should the missing wire do - or are you referring to the fact that I have only one wire going out to this junction box (wherever that may be!!!)

Uno-Hoo!

Reply to
Uno-Hoo!

Follow the wiring diagram for the S plan

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The programmer needs two switched live wires. One for the heating and one for the water. The single red wire (pin 7) is your only switched live in the setup you have.

Hopefully (I am sure that you can follow the diagram with no problem) then it is just a matter of getting an extra cable from the programmer to the junction box (it is probably near the motorised valves).

The link wires are meaningless as they are all linked to permanent live

HTH

Adam

Reply to
ARWadsworth

Many thanks for all of that Adam - your help has been most appreciated!

Kev

Reply to
Uno-Hoo!

You might be lucky. Looking at the number of wires you have at the programmer (3 reds and 2 blacks excluding link wires) then it may be that a twin and earth cable was used for the 3rd red and there may be a black wire lurking behing the programmer that you can use. This is only a small chance but have a look

Adam

Reply to
ARWadsworth

The only wires I can find not connected into the board are two earth wires that are twisted together inside a plastic wall-plug!!!

Kev

Reply to
Uno-Hoo!

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