Replacing Potterton ep3002 programmer with Nest

[jonathan baldwin]

Hi folks. I have recently moved house. I was informed by the previous owner that the CH had to be left switched on permanently on the ep3002 and was only controllable by the thermostat. Assuming as he had told me that the programmer was faulty, i invested in a Nest system but when i opened up the ep3002 it would appear that the wiring did not match the diagram on the inside of the casing. This has led me to a real challenge in working out what wires need to be transferred. I appreciate that i have my 3 core powering the ep3002 and that i will have a 4 core going to my thermostat, but i am getting lost with the others. Could someone with far more experience than me please help me by letting me know which wires i need to connect to what in the transfer of one controller to another. I am normally ok with deducing these kind of things but this one has me stumped and i dont want to go disconnecting things and running the risk of losing my way or compromising the new system. I have read about S-plan systems but not sure how to determine with the valves if mine is one or not and this changes the wiring plan to the Nest (Y system etc?)

...so some advice there would be useful too. My boiler is a Thermecon oil boiler and i have a megaflow cylinder installed upstairs. Hopefully the pics will assist.

Any advice greatly received - thank you in anticipation.

 

[jonathan baldwin]

Attached also are the Nest wiring diagrams for a generic installation and an S plan system if that helps...... thank you

 

[Echo the husky]

Connect the wires in A together in a separate connector block,
Wires in N connect to N
Wires in L connect to L
Wire link that is currently going from L to 5 needs to go from L to 2 then to 5
Wire in 3 goes to 6
wire in 4 goes to 3

Will basically get it going, you will need to find where the existing room stat is wired back to and disconnect the cable, fitting a wire link in its place. If the stat is wired back to the old programmer position you can connect the cable to t1 and t2 to send 12v power to the new stat.

 

[jonathan baldwin]

Echo - you are a star. Thank you for your help. Tomorrow morning my electrics await!
No prob with thermostat - cables run from it to the programmer and I inend to replace in the same location.
Really appreciate you help. I'll let you know how it goes.
Thanks again

 

[jonathan baldwin]

Hi Echo / other experts.....
Having followed the above instructions (thank you) i am up and running....

I have one issue however : i am presuming i have 2 valves at the cylinder as per the pic. When the NEST calls for CH - with the system cold, the pump starts and boiler kicks in but then stops as the auto valve that allows for circulation does not power over... i have switched this manually and all is well - but i have obviously missed something along the way as it should do this once power is delivered to it i am guessing?

Looking at the wires that arrive at the block upstairs, the red incoming connects to grey cables that then feed both valves....only thing i can think is that i have mixed up my red power feed cables? Currently the feed is from the 4 core from connector 3 on the programmer....with yellow connected to brown in a separate connector and blue connected to 6.

Can't think of why the valve didnt just waddle on over to allow circulation of the CH.....

Any thoughts?

 

[jonathan baldwin]

.

 

[jonathan baldwin]

latest on upstairs wiring:

I have removed the 3 core that powered the wired thermostat.... which leaves the following collection

I can see that the brown to the motorised valve needs to be connected to something - and that i have a red left over that originally powered the thermostat.

Still trying to marry up what i need to get the valve working....but i must be close. Advice appreciated.....

 

[Echo the husky]

Join that single red wire to the single brown wire.

 

[jonathan baldwin]

Hi echo. After much deliberation and testing this is what I did last night and I am pleased to report that all is well - had both CH and HW behaving themselves overnight and this morning. Thank you for your advice and guidance. Really appreciated.

 

[jonathan baldwin]