Wall Therm does work Potterton PRT2, control EP2001

[leckie]

Hi I cannot get my wall thermostat to work, it has never worked since I moved in and I thought I would try and fix it. The main cotrol unit is a Potterton ep2001, the wall thermostat is Potterton prt2. The light on the prt2 never swith on and it never starts the heating.

Does anybody have any ideas?


Thanks in advance.

 

[kevplumb]

check the wiring

 

[leckie]

Hi I have just removed the prt2 from the wall and there are no wires attached to it, which could explain why it doesn't work

There are four wires red, blue, yellow, earth

The PTR2 has a diagram inside showing what connections should go where, it says 2 com, 3 H, 4 TL, 5 N.

There is also a brown wire in the PRT2 connection 2 and 4.

Does anyone know where the wires go.

Thanks again.

 

[ricarbo]

If I was you, I would check with a mains detector tool, possibly one of those screwdrivers with a neon in it. Only one wire should be live and it should be the red one, but it might be one of the others. Anyway, having found the live wire, I'd turn off the mains at the spur controlling the system, and check that nothing is now live. If all ok, then I'd assume this:
the red wire is the live in,
the yellow wire goes to the boiler/pump as a start signal when the thermostat contacts close,
the blue wire comes from the house neutral.
The earth wire should connect to the metal backplate
Then I'd use a multimeter to find which two terminals are connecting when the thermostat is turned to 'hot'. You can probably see which these two are anyway. One of these is to connect to red, the other to yellow, but which?? the answer is found with the multimeter. One of the two terminals previously found will also connect to the neutral teminal via a resistor with a value of about 100k ohms to 500 kohms regardless of the temperature setting and this should be put to the yellow. The other only connects to the neutral via the resistor when the contacts close and this should be put to the red. The blue goes to the neutral terminal.
Or - ringup Potterton!!
Provided your isolating fused spur is actually connected properly (i.e. circuits all dead when the spur is off) and you have the right fuse in it (probably 3A). I don't think you can go too far wrong, but you know it's all a bit dodgy, because it's not connected. So you may well need some help from an electrician.
A further thought - You don't actually say if the heating is running or not. If it is, someone has bypassed the thermostat and you're going to have to remove that link first, might be hard to find - gets worse, doesn't it!

 

[leckie]

Hi Ricarbo,

Thanks for giving such a detailed reply I'll give it a go and let you know how I get on.

Re:You don't actually say if the heating is running or not. If it is, someone has bypassed the thermostat and you're going to have to remove that link first -

The heating is running if you switch it on from the ep2001 programmer. When I removed the wall therm the wiring was there just not connected to the box. However someone has conected the red wire and the yellow wire that comes from the wall could that be the link?

Re: gets worse, doesn't it! Yes it does!!

Thanks again

 

[ricarbo]

Yes indeedy. You're a lucky one to find that so easily! It does rather imply that the roomstat doesn't work properly though, as they presumably disconnected it for a reason. If it doesn't work, you might want to think about buying a 'programmable' one as the replacement, they are current 'best practice', but I can't deny they are a bit fiddly to use - most unpopular witth my missus.