Boiler wiring problem

Hi,
I'm having problem with a potterton boiler and stat. The boiler is firing up
when the timer is in Off position. With stat clicked on. A customer brought a stat to replace a broken 1 and i fitted it. This is when the problem started. I fitted a Sunvic 4101. When i fitted it the 3amp in the spur blew. I replaced it and changed wiring and all was ok apart from the problem stated. So i found which stat it should be and replaced it for that one and the same thing is going on. The stat is a T6360 1036B.

Standard Y plan- might help

The data sheet show 4 terminals plus earth the 4th terminal should not be used with heating.

Also to reduce the differential between between on and off it needs a neutral connecting to terminal 2. Unlike many switches swapping input 1 and output 3 will mess things up and nullify the neutral connection.

So it must be wired.
Line in 1
Line out 3
And works better if neutral is connected to 2

Rather an expensive antiquated thermostat I would always replace with one of the electronic types. Although they have batteries in there is no need for neutral and the differential is reduced from 1.5 degrees to 0.5 degrees so well worth changing a battery every couple of years.

Also very little extra and they can have timer combined which means instead of just on/off you can set different temperatures for different times of day which also means frost stat becomes redundant.

Chri5 said:

Standard Y plan- might help

Click to expand...

Yes, but is it Y plan? Presuming you have now wired the wired the stat correctly, you still appear to have a 'rogue' live connection to the boiler. Check the stat does make/break the circuit - if '3' remains live when you turn the stat down you have that side connected to a live contact. Go to www.honeywelluk.com and they have all the plans there.

Rather an expensive antiquated thermostat I would always replace with one of the electronic types. Although they have batteries in there is no need for neutral and the differential is reduced from 1.5 degrees to 0.5 degrees so well worth changing a battery every couple of years.

Also very little extra and they can have timer combined which means instead of just on/off you can set different temperatures for different times of day which also means frost stat becomes redundant.[/quote]

Hope you don't mind the side post - Eric - I have tended to use the T6360B just from habit/reliabilty and familiarity. I generally favour Honeywell controls, digital, RF etc, as I have found them straighforward both for installation and end user. I have tried some Salus products but don't like them.Do you have any favourites?

ltheb said:

Chri5 said:

Standard Y plan- might help

Click to expand...

Yes, but is it Y plan? Presuming you have now wired the wired the stat correctly, you still appear to have a 'rogue' live connection to the boiler. Check the stat does make/break the circuit - if '3' remains live when you turn the stat down you have that side connected to a live contact. Go to www.honeywelluk.com and they have all the plans there.

Click to expand...

When stat is turned down it breaks contact and boiler will go off.
But this is happening when the timer is switched off. By the look of it the timer is getting bypassed. Could it be a short in the timer causing this to happen ?

I was only taking a stab at help- so no, I have no idea what plan type is being used.

Just thought I'd throw a standard one in

I'd do a full review of the wiring centre, make sure you are happy with the wiring and it's end points. If the wiring checks out for the system used then it has to be the programmer unit / timer.

Most timer makers give very easy access to the pin outs and termination designations- so google the model and check from there.

Or 'borrow' a new one from a supplier, try it and if it sorts the problem job done.