Replacing An Old Potterton Controller for a Drayton

[Mr_Ribble]

Hello

Hopefully a quick question. Moved into a house and one of the long list of issues is fixing the central heating. The issue is that the controller unit for our Potterton boiler is broken. Not sure of the exact model but its something like the EP2002 7 day unit. From what I'm aware I cant buy a new unit like for like, so I went for a Drayton LP722 model.

When I took the old unit away, I was presented with two wires (one 2 and one 3 core). I studied carefully how the old unit was wired in relation to the wiring diagram. But I wasn't confident of translating that across to the Drayton unit. Can anyone help me. I've included a picture of the wiring below. Its a standard open vented system with feeder and expansion tank in the loft. Hot water tank in one of the upstairs rooms, and boiler in the kitchen.

Many thanks
Ribble

 

[stem]

To do that we need to know what each of the terminals of the original programmer did (and there are lots of variants, not all programmers have identical connections, even those from the same manufacturer). There should be a diagram marked on it somewhere showing this information.

Then we need to know which of the wires in your photo went to each terminal. From that we can work out what each wire does and then tell you where to connect them at the Drayton.

There's no such thing as a standard system when it comes to wiring unfortunately, much depends upon the layout of the various components of your heating system in relation to each other and the personal preferences of the installer.

Also, with the previous installation, could you have the central heating 'on' on its own, without the hot water also being on at the same time?

 

[Mr_Ribble]

Stem - thanks for the swift reply. I have a picture of the current controller wired up and the diagram at home so I can post that up tonight.

Yes the old one was dual control https://www.plumbcenter.co.uk/product/potterton-ep2002-5-2-day-electronic-programmer/

 

[Mr_Ribble]

Ok - Posted a pic of the Potterton wiring diagram and a better pic of how the guy that installed it had wired it up.

 

[stem]

OK, thanks for the photo's you have all the information you need from those diagrams. So, it's just a matter of determining the function of each wire from its connection at the EP2002, and moving it to the terminal at the Drayton that has the same function, as follows:

Remove the link between the EP2002 L and terminal 5. The remaining red wire in terminal 5 is the Live = L at the Drayton
Black wire in N EP2002 = N at the Drayton
Red wire in 3 EP2002 (Hot water on) = Drayton terminal 3 (Hot water on)
Black wire in 4 EP2002 (Heating on) = Drayton terminal 4 (Heating on)

 

[Mr_Ribble]

Stem - many thanks for all your help on this. Changed it over last night and really easy to follow your instructions. For the first time since we bought the house, we woke up this morning with the heating on! Thanks again

 

[stem]

Well done. Glad to hear it's working and thanks for the update.