Nest 3rd Gen to replace Potterton EP2002-Installation Advice

[stem]

The Nest L terminal does need connecting with links to both Nest terminals 2 and 5.

The EP2002 connections are as follows.



So it is just a matter of moving the relevant wires to the same terminals as the Nest, as you seem to have figured.



All wires connected to the N terminals at the EP2002 = Nest N (That includes the top left terminals if used as a neutral)

All wires connected to the L terminal at the EP2002L = Nest L
Then the Nest L terminal does need connecting with links to both terminals 2 and 5.

EP2002 1 'HW Off' = Nest (4) 'Hot Water Satisfied'
EP2002 3 'HW On' = Nest (6) 'Hot Water Call for Heat'
EP2002 4 'CH On' = Nest (3) 'Heating Call for Heat'


EP2002 terminals ABC&D are just there to assist with the installation they are not part of the EP2002, but if used, the wires in A need to be connected together in a separate terminal, The wires in B need to be connected together in a separate terminal. The wires in C need to be connected together in a separate terminal. And the wires in D need to be connected together in a separate terminal.

The only other issue would be if you have an existing room thermostat somewhere. Because the Nest carries out the functions of the room thermostat as well as the EP2002 programmer, the old wired thermostat needs to be decommissioned to prevent it overriding the Nest. It can't simply be disconnected as this would leave the heating wiring 'open circuit' and it will not operate. The thermostat can be decommissioned in three ways, in order of preference, they are.

1. Find the origin of the thermostat cable and disconnect it. Then link the terminals where the two switching wires came from together.

2. Remove the existing thermostat and replace it with a junction box, connect the two switching wires together and isolate the neutral (if there is one)

3. Leave the existing room thermostat in place and put both of the switching wires in the 'L' terminal (or set it to the highest setting and hope that no one moves it)

If you need any further assistance with this, post back details of your existing thermostat make / model and what wires are connected to which terminals.

 

[Scott O'Hara]

Thanks for the advice stem.I will see if that works for me and get back to you guys.

Thanks for the help again

 

[Yossi Dahan]

Can I just double check, before I do something daft - the Nest has warnings to not connect it to 240v systems, and yet isn't this one?

Edited: sorry - silly me - it is the thermostat that needs to be 12v

 

[Yossi Dahan]

Dear Stem,

I have installed the Nest Using the above said procedures. Central heating is working but Hotwater is not responding at all.
I have disconnected the old thermostat PRT100 and joined the wires together. Please see the attached picture.
To confirm I have conneted as following.

EP2002------------------NEST HEAT LINK(Bold)
N-------------------------N
L--------------------------L
1-------------------------4
3-------------------------6
4-------------------------3
5-------------------------5----------2---------------L

Please help
View attachment 111001

In my installation of Potterton there was nothing connected to '1'; I wired everything else and heating works well, but hot water setting do not appear to be influencing the boiler (although the schedule did work with the Potterton device); any thoughts?

 

[stem]

Terminal 1 (EP 'Hot water off') is only used by systems that have 3-port motorised valve fitted. So, if your system was working before without a wire to terminal 1, you won't need to add one.

If the water contained in your hot water cylinder is already hot, switching the hot water 'on' won't cause the boiler to fire until the water cools enough to operate the cylinder thermostat.

If the cylinder thermostat is calling for heat and the boiler's not operating, I would check the wires associated with the hot water terminals at the Nest Heat Link, [5, 6 and the link between 5 and L] they are quite fiddly and it is not uncommon to have a poor connection.