Alternative to the Potterton PRT2 Room stat

[ELily]

Hi all

Have been reading about the problems some have been having with the PRT2 room thermostat and sadly, I too have a tale to tell.

It keeps switching on and off several times a second and I hear the constant click click at warm room temperature but while thermostat is set really low!

I have tried to swap it for a Tower (cheap basic manual) stat but it has blown the fuse each time - I had to go away and check that I had wired it right in between. So I figure the Tower one is faulty too.

My question is this:-

Do I just replace the PRT2 with another or should I try another unit/brand instead?

I am tired of having no control over my heat and am turning the whole thing off, which at this time of year, is not ideal.

Please help. Thank you.

Ps I am so glad I found this forum!

 

[electronicsuk]

It seems very unlikely that you would have purchased a second faulty thermostat. How have you wired the new one? If you're popping fuses then it seems likely that your old PRT2 required a neutral, and somehow, with your new wiring, you have created a short circuit between this and a live conductor.

Your "cheap basic" thermostat may not require a neutral (although I haven't seen the instructions, so no guarantees there) although may have NO, NC and common contacts, so perhaps you've made the mistake of connecting neutral to one of these unnecessarily.

Can you give us a bit more to go on? Instructions? Pictures?

 

[ELily]

Thanks for the reply.

Well, the PRT2 is the same as mentioned by a few others on this forum, 3 wires, yellow, red and blue and a brown which is separated out in a loop (?earth).

The new tower is just labelled 1, 2, 3 and of course, came with no instructions what so ever! It was only by stumbling across this website and figuring out what each was for that I thought I would try it since at the most, I popped a fuse.

I have left the things behind as I work away from home and it was a Saturday night project to get the thing working and I am not back till Friday night.

I think I did find instruction for the Tower one on net but it did not give me much more to go on. As far as the difference goes, the PRT2 has an LED for when temperature is below or reached (red and green), the Tower one does not and that is about as far as it goes.

I can't recall where I found the wiring instructions for the Tower one, it literally is just a dial, 3A and 10C - 30C I think.

Sorry I can't recall much more than that and next w/e I could take pics and upload them if none of the above helps.

Thanks for any help!

 

[electronicsuk]

If the old stat had LEDs then it's likely you do have a neutral at the stat, and this would seem to fit with the fact that you've been able to pop a fuse/breaker through miswiring.

Really you could do with a multimeter to check out the contacts on the stat as well as working out which cables at the stat are live, live return and neutral. I would have expected the blue wire to be neutral, but there's certainly no guarantee when it comes to this sort of thing, as many installers choose to follow their own (often nonsensical) wiring schemes.

If, for whatever reason, you can't stretch far enough to buy a meter then you could try turning off the power, isolating the blue wire in a plastic terminal block, and connecting yellow and red to the terminals on the stat. Without the instructions I have no idea which two terminals on the new Tower thermostat you should be using, I've never installed this brand.

You also speak of a brown wire. Are you sure it isn't just the bare copper CPC? If so, it should be covered with a suitable length of green/yellow sleeving and either terminated at the stat if there is an earth terminal, otherwise put it into a separate plastic terminal block.

 

[ELily]

Thanks for that. I will try and dig out the wiring diagram for the Tower stat off the net in a couple of days as won't get back online till then. I am thinking that some other stats are only 2 wire, this may be the same. With having 4 wires coming out the wall, I do wonder what to do with the other 2!

What is a CPC?

The brown looks like it is separated off like you said (terminated at the stat) and will probably need a block on it when the old back comes out.

I can't stretch to a meter as I will never have need to use one again - as much as I hate to say it, I want a bloke to do it all for me! (but not if I can do it myself! Am no good at the helpless female act).

Will paste up the diagram in a few days and then hopefully have a bash come the w/e and once I have purchased some blocks. How do they come, individual or packs and how much for how many approx please & easiest place to buy??

Thanking you kindly!

 

[ELily]

Hi

I think I have made some sense of this with your and another dudes help.

You are right that the blue needs blocking off. It just uses the yellow and red, switch and live is it?

I have not yet tried this as no time this w/e past, job on my list...

I am going to pick up the blocks when I can and hopefully have the new stat on this w/e coming with a bit of luck.

The only problem will be to fit it to cover the hole in the wall! A bit of plastering will also be on the cards!

Thanks for your help and I will let you know if all goes well (like I hope it will). I should also mention that I found a wiring diagram on the inside cover of the Tower stat and if I had seen that before, it should have made more sense. Well, nevermind - it explains why I thought it odd that there was no instructions in the pack! Doh!

Thanks for the advice.

 

[electronicsuk]

You are right that the blue needs blocking off. It just uses the yellow and red, switch and live is it?

You're correct, as long as the old thermostat was wired using a fairly standard colour code.

 

[ELily]

Hey there

Thanks for your help. Finally a week later, managed to get the new stat wired - go me!

Yellow and red only, no blue required so blocked off.

Stat is working lovely all day. Took a whole of 3 mins to wire and half an hour to plaster the holes from the last one and get it mounted on the wall. A degree or so off level but hey, I can live with it for the sake of a working stat!

Thanks for your help on this. Much appreciated.

Tata!