Another Potterton thread...

[Coliander]

I'm planning on updating our central heating system in the next few weeks and need some advice in regards to rewiring for the new central heating controller.
We currently have an ancient Potterton EP2000 unit controlling the central heating and I'm looking to replace it with a Honeywell T6R-HW.

Potterton Wiring / Potterton Wiring Diagram

Honeywell T6R-HW Wiring Diagram

My plan is to rewire the Neutral connection block, the Earth connection block and terminals A & C like-for-like into a Choc Box/Wiring Centre behind the old backplate. But I'm a little lost when it comes to migrating the controller wiring!

Can somebody help explain how to migrate the wiring from terminals 1,3,4 and 5 on the Potterton to terminals A, B, D and E on the Honeywell?

As best as I can tell, it would be:
Live feed to A with a link to D
Terminal 4 on Potterton migrated to terminal B on Honeywell
Terminal 3 on Potterton migrated to terminal E on Honeywell

But what do I do about terminals 5 and 1 on the Potterton unit? How would these be wired in relation to the Honeywell unit?

Thanks.

 

[stem]

You are 90% there. However, you have posted the S-Plan diagram of the Honeywell T6R. As you have wires gong to the EP terminal 1, that shows you actually have a Y-Plan (3-Port motorised valve) so you are looking at the wrong diagram. If you look at the Y-Plan version you will see the extra 'hot water off' connection to F.

As you have figured, A,B,C,D are just connections, so keep them as they are in separate terminals

N & L are straight forward, the wires migrate across respectively. The two L terminals at the Honeywell are joined together. [They provide two for your convenience]. You are also right in that the second L is used to link the Honeywell L to the two Honeywell common terminals A & D.

Then:

EP 1 is hot water off = Honeywell F
EP 3 is hot water on = Honeywell E
EP 4 is heating on = Honeywell B

The single wire in terminal 5 of the EP is just a link for the programmer to use, it's not needed anymore. [The links at the Honeywell I described earlier between L, A & D replace it.] I can't see another wire in 5, but if there is another one present it goes to L.

EDIT:
I forgot to mention that if there is an existing room thermostat, that will need to either be set to maximum, to prevent it overriding the Honeywell, or decommissioned properly which requires a small wiring modification. It can't just be disconnected. Post back if you need any more help with that.

 

[Coliander]

Fantastic, thank you! So just to clarify, I still need to create a manual live link from A to D?
I assume the simplest way bypassing the old room thermostat is just a case of removing the unit, closing the circuit into a constant 'on' position with a terminal block and blanking it off until the wiring can be physically removed?

 

[stem]

L, A and D need to be electrically connected by manually inserting links, and yes, you have the idea with the thermostat. If it was just disconnected that would leave the heating open circuit. If you do eventually remove the thermostat cable, the circuit will have still have to be closed at its origin.

 

[Coliander]

You're a life saver! Many thanks!