Programmer compatibility

[D Skelton]

Hi guys, I need some help with a small issue I have.

A friend of mine wishes to swap her existing Potterton EP2000 programmer for something with a larger and easier to read display. She is partially sighted and finds it nearly impossible to read what is displayed on the current programmer.

Now I will be the first to admit that central heating systems is something which I have absolutely zero experience with, never work with anyway and would normally never go near but as it's a small favour for a very good friend of mine, I was just wondering whether simply swapping a programmer over is as 'simple' as it seems. From what I gather the Potterton is a 2 channel 24 hour electronic programmer, so could I just swap it for another 2 channel 24 hour electronic programmer of a different make? for example this one; Digital Heating Programmer - 2 Channel - 7 Day or do I have to use the same make?

Any help appreciated guys, even if that help comes in the form of "get a spark who knows about heating systems to do it"

 

[HandySparks]

Yes, that one looks like it'll do the job. A programer swap shouldn't be difficult.

Edit: You may have to take a note of whether it's a fully pumped system or whether the heating of the hot water cylinder is by gravity only, without the pump running. All systems with a modern boiler will be fully pumped.

 

[D Skelton]

Thanks pal, I just wanted to check

 

[D Skelton]

You may have to take a note of whether it's a fully pumped system or whether the heating of the hot water cylinder is by gravity only, without the pump running. All systems with a modern boiler will be fully pumped.

Why? lol

 

[vjsmarwick]

Most programmers have micro switches on the rear to select what you want them to do eg. 12/24 hr 7day or 5+2 or pumped gravity also just watch the connections on the back plate some you can just use exciting back plate but some sneakily change the order of the connections so just watch.

 

[D Skelton]

Most programmers have micro switches on the rear to select what you want them to do eg. 12/24 hr 7day or 5+2 or pumped gravity also just watch the connections on the back plate some you can just use exciting back plate but some sneakily change the order of the connections so just watch.

Is there an easy way to find out if it's pumped or gravity?

 

[vjsmarwick]

If there is a pump on the pipe loop that feeds to the hot water cylinder then it's pumped but remember the pump could be on the return pipe so check the whole loop

 

[vjsmarwick]

Most systems in the last 10 years are fully pumped

 

[D Skelton]

Yeah this is a really ancient boiler so I'll have a full check. What are the procedures to follow if it is a pumped, or if it is a gravity fed system? Is it a simple case of just making sure that the programmer is set to the specific type of system or do I have to use another programmer type?

 

[vjsmarwick]

Yes should be straight forward check micro switches on bAck of programmer and also double check wiring is same for both programmers
Normally I think it's left to right L N hot water on hot water off heating on heating off but I would need to check that but you should only have 4 wires there L N HW on Heating on of there is wires in the hot water off then you have a mid position valve

 

[vjsmarwick]

1 is hot water off
2 is hot water on
3 heating off
4 heating on

 

[D Skelton]

Cheers buddy

 

[the oracle]

If you look at the components within the system you should be able to identify the type of system. Apart from a pump and a boiler, there will probably be a motorised valve or two on the pipework. Most systems these days are either 'Y Plan' (one three way mid position zone valve) or 'S Plan', (two two port valves, one on the hot water, one on the central heating). The programmer connections are fairly basic, there will be a line, a neutral and a cpc, those are the easy ones. On many systems you will then only have two other wires, one is the HW on (hot water) and the other is the HTG on (heating). If you have a wiring centre, these two conductors will go to separate terminals (often 6 and 4 respectively, but ONLY if standard wiring numbering has been followed!) They join there with the supplies to the cylinder stat and the room stat respectively. The sequence of control is fairly simple. The programmer calls for heat, and sends a 'supply' down to the stat, if the stat says it needs more heat, it acts as a switch and sends a supply via the wiring centre to the relevant valve, (brown wire) and the valve opens. Once open, a micro-switch on the valve closes, sending a supply back to the wiring centre, (orange wire) powering up the pump and boiler, and hey presto, we get heat. However, you may also have a HW off terminal and another wire at the programmer, and possibly just one 3 port valve. In this case (Y Plan) the HW off wire connects with the grey on the 3 port valve, at the wiring centre. There are, unfortunately, several other combinations, and plans (C plan, W Plan etc).
Have a look and follow it through, you can get wiring diagrams off the web from Honeywell's web-site. Good luck.

- - - Updated - - -

 

[vjsmarwick]

Potterton wiring from the left

N
L
HW off
Htg off
HW on
Htg on

The wiring for the programmer in your post from the left

Htg off
Htg on
HW off
HW on
N
L

As you can see you will have to change the back plate for the new programmer and move wires accordingly