Advice on replacing CH controls

[Jonathan Whitehead]

Currently I have a Danfoss 103E5 programmer and an external roomstat which controls a boiler used purely for CH which I would like to replace with a programmable room thermostat.

The problem is I'm a bit unsure about how to wire the programmable room stat in to control the boiler. The current set up is:

pwr supply in | | L N | | Fused isolation switch | | L N | | Programmer | | L N | | Room Stat | | L N | | Boiler & Pump

but reading wiring guides for various programmable room stats they seem to suggest that you only use the live for switching and make safe the earth and neutral but I don't see how that is going to work in this set up given that I need a live and neutral feed going to the boiler and pump.

My programmable room stat of choice is this one

it can be sunk into the wall and not have a big box on the wall and looking at the wiring diagram in the manual on page 17 where it shows you need to connect the live supply in to the A1 connector would it be correct to also link the neutral going in to the neutral going out to the boiler and pump thus making the required circuit?

TIA,

Jonathan

[Set Square]

Yes, the N-in and N-out need to be connected to each other - but *not* to any of the stat contacts. If using new cable, you would cut only the live wire - and loop the neutral round the side or back. If the neutral wire has already been cut, you'll need to re-join it with an insulated crimp.

[Jonathan Whitehead]

So why can't I put both neutrals in the same connector on the stat for the neutral going in?

It seems to me this is what is being done with the live. i.e. the live goes in and you also put in a link wire from the live in connector to the A1 connector.

Jonathan

[Richard Conway]

I think Set Square failed to follow the link you gave. Most programmable stats tend to be battery operated and therefore only have two contacts, live and switched live. As yours appears to be a fancy swanky one with a backlit display it evidently does need a supply.

You are right in what you originally suggested in that the incoming L & N supply should go to the L & N terminal on the stat. The N going out to the boiler and pump should also go to the neutral terminal so that the neutral continues to the boiler and pump. A link should go from the L terminal to the A1 terminal to provide a permanent live there, and the L to the boiler and pump should connect to A2 providing a switched live for when the stat calls for heat.

[Set Square]

Sorry - you're right - I *didn't* follow the link, and assumed it was like other programmable stats.

So yes, you *can* loop the neutral in and out of the N terminal. And, as you say, you will need a link from L to A1.

[Jonathan Whitehead]

Thanks for the help.

Jonathan

[Richard Conway]

What ya thanking him for ;)