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Plumberpro
Plumberpro, Plumber
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Experience:  Heating and plumbing answers. 20 years experience
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Hi Andrew. My thermostat does not turn off my central heating

Resolved Question:

Hi Andrew. My thermostat does not turn off my central heating even if it reaches temperature
Submitted: 2 years ago.
Category: Plumbing
Expert:  Plumberpro replied 2 years ago.
Plumberpro :

Hi ,what type of room stat is it?

JACUSTOMER-da0edzm6- :

Potterton PRT2

Plumberpro :

Hi , do the led lights light up ?

JACUSTOMER-da0edzm6- :

yes, the green light stays on when it is heating up and the temperature reached light lights up, but it just carries on heating up

Plumberpro :

If you turn the temp all the way down does it still continue heating ?

JACUSTOMER-da0edzm6- :

yes

Plumberpro :

Ok . if you were to remove the front plate , does the heating stop?

JACUSTOMER-da0edzm6- :

the front plate of the thermostat?

Plumberpro :

Yes, just wanted to confirm that it is the room stat that is powering the boiler and nothing else. Would that be ok ?

JACUSTOMER-da0edzm6- :

I will try it, will it just pull off?

Plumberpro :

It may have a screw or two underneath or on top, if not then it will be clips

JACUSTOMER-da0edzm6- :

no problem, just unscrewing now

Plumberpro :

Ok m

JACUSTOMER-da0edzm6- :

front plate is off, just trying to work out how to tell if it has stopped heating as the radiators are red hot

Plumberpro :

You may have to leave it for 15 mins or so

JACUSTOMER-da0edzm6- :

no problem, if it helps....there is also a separate timer/controller next to boiler.....I am getting the new https://www.tado.com/gb/ thermostat.............just want to make sure it will work in existing wiring before it comes

Plumberpro :

Hi just checked the website . it looks really good . the site had the install instructions and it will work with your room stat wiring .

JACUSTOMER-da0edzm6- :

Hope so, just to try and get this one working for another two weeks :)

Plumberpro :

Well at least you can turn the boiler off manually , better a bit too hot than too cold ☺

JACUSTOMER-da0edzm6- :

no sign of the radiator next to me cooling down yet, still burning hot to the touch

Plumberpro :

Oh . is the boiler still running?

JACUSTOMER-da0edzm6- :

orange light is on and it is making its heating noise so I presume so

Plumberpro :

Has anything been changed recently ? Is it a Combi boiler or do you have a hot water tank?

JACUSTOMER-da0edzm6- :

Its a combi boiler.....not it has always been like this since we moved in 5 years ago........I only found out about it by chance when I tried leaving it on in the day at a set temperature and my heating bill was hundreds of punds lol

JACUSTOMER-da0edzm6- :

only just got round to trying to sort it out

Plumberpro :

I'm surprised that the heating is still on . do you have a timer or programmer?

JACUSTOMER-da0edzm6- :

yeah that is at the side of the boiler, an old thing

Plumberpro :

Is the heating still going?

JACUSTOMER-da0edzm6- :

yeah it is.........programmer is a randall 3020p

Plumberpro :

Oh no. Not a Randall

Plumberpro :

Is the room stat face plate still off?

JACUSTOMER-da0edzm6- :

yep

Plumberpro :

I have a feeling that the room stat may have been bypassed at some point . has the room stat never worked properly?

JACUSTOMER-da0edzm6- :

not since I have lived here

Plumberpro :

Can you switch the heating off with the randall

JACUSTOMER-da0edzm6- :

yep

Plumberpro :

I think that the room stat has been bypassed and the power is going from the Randall straight to the boiler

JACUSTOMER-da0edzm6- :

ok......so do you think I should replace the randall with the other tado part https://www.tado.com/gb/thermostat-setup#extensionKit so that it talks to the tado thermostat wirelessly rather than relying on the wire?

Plumberpro :

Yes , definitely.

JACUSTOMER-da0edzm6- :

so, in your opinion the Tado thermostat wont work if I wire it in due to bypass?

Plumberpro :

It won't work how it is at the moment , no

JACUSTOMER-da0edzm6- :

thanks very much for your help, at least now I know to buy the extension kit :)

Plumberpro :

It could if you can put back the wiring properly in the Randall wiring centre

JACUSTOMER-da0edzm6- :

how would I do that, is it simple?

JACUSTOMER-da0edzm6- :

I can wire wall plug sockets etc and build pc's so would give it a go?

JACUSTOMER-da0edzm6- :

if it is safe of course

Plumberpro :

But the Randall is quite old and may not have much life left in it .

JACUSTOMER-da0edzm6- :

could try it to last until the extension kit comes :) always ready to experiment lol

Plumberpro :

If the other part is expensive then you could definitely sort the wiring to just use the room stat. I would have a look at the wiring in the Randall .you may be able to work out what wires are going where

Plumberpro :

There should be live neutral earth . then heating out to the room stat ,then back to the boiler switched live.

JACUSTOMER-da0edzm6- :

ive took the front off, will tell you colours in order from right to left

Plumberpro :

Ok

JACUSTOMER-da0edzm6- :

1st - 3x blue wires

JACUSTOMER-da0edzm6- :

2nd - 1 x yellow

JACUSTOMER-da0edzm6- :

3rd - 1 xred

JACUSTOMER-da0edzm6- :

4th - 1x black

JACUSTOMER-da0edzm6- :

5th - nothing

JACUSTOMER-da0edzm6- :

6th 2 x brown

JACUSTOMER-da0edzm6- :

7th - nothing

JACUSTOMER-da0edzm6- :

8th - 3x green and yellow

JACUSTOMER-da0edzm6- :

that's the lot from left to right

Plumberpro :

Ok . you would have to check the room stat wires to work out what colour is going to the room stat and back out of the room stat

JACUSTOMER-da0edzm6- :

no probs, you probably already know but I just found a wiring diagram online if it is any use http://www.uk-plumbing.com/brochure/danfoss/3020Pdata.pdf

JACUSTOMER-da0edzm6- :

right, the thermostat one goes 1st - none

JACUSTOMER-da0edzm6- :

2nd - brown

JACUSTOMER-da0edzm6- :

3rd - red

JACUSTOMER-da0edzm6- :

4 - yellow

JACUSTOMER-da0edzm6- :

5 - blue

JACUSTOMER-da0edzm6- :

brown loops from 2nd to 4th

JACUSTOMER-da0edzm6- :

all from left to right

Plumberpro :

Ok , so the yellow is probably going into the room stat , then another from room stat into the boiler. You would have to check what colour is in the boiler switched live

JACUSTOMER-da0edzm6- :

no problem....how do I do that lol

JACUSTOMER-da0edzm6- :

and thanks for your help so far, been really useful

Plumberpro :

Erm, what boiler do you have?

JACUSTOMER-da0edzm6- :

vaillant turbomax..............and thanks for your help so far, its been really useful :)

Plumberpro :

Ok you would have to rake the case off and take off the wiring cover. But I think you could probably work it out looking at the room stat wiring. What colours have you got there?

Plumberpro :

Oh , have you already said that?lol

JACUSTOMER-da0edzm6- :

yeah :)

Plumberpro :

Ok . right think I have got it . yellow from Randall to room stat. Out from room stat to boiler switched live ,red. Your room stat stopped working so they linked live to the red bypassing the room stat and making the heating run continuously when Randall is on ☺.if you removed the link the heating would stop . but until you get the room stat , leave it there and just turn off at the Randall . so at your stat you have live brown , neutral blue, in( common or call) yellow and red out to boiler

Plumberpro :

Yeeehaaa

JACUSTOMER-da0edzm6- :

Sounds good, so how come the room stat stopped working even though the lights come on etc?

JACUSTOMER-da0edzm6- :

and what do I do when I get the new one?

JACUSTOMER-da0edzm6- :

I mean stopped working originally to make them put the link in?

Plumberpro :

It has power with the live and neutral , but has stopped switching

JACUSTOMER-da0edzm6- :

nice one, so what do I need to do when the new one comes to make it work properly......just wire the stat correctly?

JACUSTOMER-da0edzm6- :

and not alter anything at randall?

Plumberpro :

Yes , should be fairly easy , says it comes with full wiring instructions.

JACUSTOMER-da0edzm6- :

nice, so no need to change anything to remove the link?

JACUSTOMER-da0edzm6- :

when the new one comes I mean?

Plumberpro :

With the new one it only needs two wires . yellow to com and red to no. ( normally open ).

Plumberpro :

Plus remove the link

Plumberpro :

It will all make sense when you get the new one with the instructions , seriously .

JACUSTOMER-da0edzm6- :

great stuff, thanks for your help :)

Plumberpro :

Your welcome

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