Replacing old thermostat

[riksworld]

Hi everyone,

My old room thermostat has been acting up a little, so its time to replace it, im usually quite good at doing the odd bit of electrical work, but not 100% of this one, so I thought id post my question here.

On the old thermostat, which is a old metal type backing currently has a total 3 wires, the usual Live, Neutral and Earth, this i understand, on the new thermostat, a wireless type model, it has, for a 230V wiring diagram, which I assum this is correct because of the L,N, are 4 connections, SL off, L, SL on, N, the SL on is the load, I assume for the boiler to fire?, there is also a link wire from L to L IN, should this be removed or the L should be connected to the L IN

Can anyone please offer any advice on how this should be wired up.

Many thanks to anyone who replys

 

[Theorysparky]

whats the model number ?

 

[riksworld]

Many thanks for your quick reply

The Boilder is Alpha He33

The new thermal stat is a Horstmann HRFS1 Programmable Room Thermostat

The old one is a metal type affair, with earth on the plate, L and N

After reading the boiler manual, there is only a 2 wire output on there thermostat side

 

[Theorysparky]

This should explain how it is wired up

http://www.horstmann.co.uk/downloads/ElectronicDocuments/ThermoStats/RF%20Programmable%20Room%20Thermostat.pdf

where are you going to place the receiver near the boiler ???

 

[riksworld]

it will be placed nere the boiler, Ive just the link, but its the same leaflet Ive got, which doesnt match my old wiring

On the new one, there is a link wire located L In to L, does this need removing and does the SL (ON) need a connection?, as ive currently only got L,N,E on the old wiring from the old thermostat, just a little unsure

 

[Theorysparky]

you need to remove that link

you need a perm live to the reciever

two wires required from boiler live from boiler goes to the common,,,,,the SL on the receiver goes back to the boiler

hopefully it makes sense

 

[riksworld]

Think that makes safe

So basiclly, the live from my boiler, which is a switched live, according the boiler manual will goto SL (ON) and the neutral will go just to neurtal, would this be correct?

All I have have to do is find a feed for the permant Live in to feed the transmitter

Would this be correct.

 

[kme]

Probably not.

On some installs, the numpties used the earth wire for either the neutral exciter connection, or the switched live return. It doesn`t sound like they`ve done that with you, but best check the other end of the cable.

What I expect you have is a twin & earth, configured like this:

red: permanent live.

black: switched live

earth: earth (hopefully).

Check the other end of the cable, to verify this. I can only make educated guesses.

Leave the link in place. your main problem here is that your new thermostat wants 4 cores, and you only have three. Optimal solution is to replace the cable with a 4 core variant; which will provide your :

1. permanent live

2. switched live

3. permanent neutral

4. earth.

HTH

KME

 

[riksworld]

Thanks for your response

I have had a look at the other wiring end, and all it is a 2 core cable without an earth, looks like the earth on the old thermastat is linked elsewhere to another earth to provide this.

The cable from the boiler is a 2 core white flex, which goes into a box spliter, this then leads to another, normal grey 3 core cable, Live, Neautral, earth is not connected and cut

This then carries onto the thermastat via the grey 3 core cable, the earth is then linked via another earth which makes a loop im assuming, then the Live and Neautral are connected to a old mechanical thermastat.

On the boiler, it does state the Live wire is a switched live, so it would appear i only have 2 wires, when it looks like the new one requires more

Is there an alternate way of possibly wiring this in does anyone know?

 

[kme]

All that wiring needs a test on it, to verify the earth connection. Maybe the earth was taken elsewhere to "earth" something, without anyone being aware in wasn`t actually connected to anything.

Apart from anything else, the 2-core from the boiler needs replacing.

As you have a wireless stat, you can put the reciever next to the boiler, and connect the two with a piece of 4 core, heat resistant flex.

This will provide your permanent supply L & N; switched live and (hopefully) an earth that is connected to something, somewhere.

KME

 

[batty]

I honestly don't think you are compotent enough to do this job and its sounds that you need to modify your wiring which then means it will need notifying as it comes under the part p. I think it wil be safer to get an electrician to sort it out properly but welcome to the forum anyway.