24v at switched side of room stat (230v) possible backfeed ?

[weep]

lol, yeah yeah, been wiring boilers like this for years

 

[davesparks]

And I've been wiring boilers for years too, but what does that prove? It only proves that the way we learned to wire boilers is out of date, it doesn't prove anything about our competence or knowledge.

 

[weep]

i know what your saying but in all honesty, nearly every spark i know wires them this way and very very rarely do we get any issues. still doesnt solve the problem at hand, will check boiler terminals with switched live on Lr disconnected (safely of course ) tommorow.

 

[Pondy]

Think Marvo hit the nail on the head in post two

 

[davesparks]

i know what your saying but in all honesty, nearly every spark i know wires them this way and very very rarely do we get any issues. still doesnt solve the problem at hand, will check boiler terminals with switched live on Lr disconnected (safely of course ) tommorow.

If lots of people do something wrong then it must automatically become correct?

Everybody I know wires them according to the boiler manufacturers instructions, there are a few manufacturers who specify that they be wired this way.
The point is to ensure that if the boiler is switched off or a fault takes the internal fuse out then the whole system goes off. As you have wired it at the moment the Lr would remain live and so be feeding a live into the boiler despite the fuse having blown.

It's perfectly logical and sensible if you take a second to think about it, and I'm sure they have a good reason for doing it.

 

[davesparks]

Think Marvo hit the nail on the head in post two

Then how do you explain the boiler constantly firing?

24V on the Lr terminal is something I have encountered before, but can't put my finger on exactly what the symptoms were at the moment but think it was prone to firing without a demand signal.

 

[Gazzdid]

The point is to ensure that if the boiler is switched off or a fault takes the internal fuse out then the whole system goes off. As you have wired it at the moment the Lr would remain live and so be feeding a live into the boiler despite the fuse having blown.

It's perfectly logical and sensible if you take a second to think about it, and I'm sure they have a good reason for doing it.

Most of the time theres a reason why a manufacturer specifies something, even if we cant see it. Ive done it myself, thought 'what a load of rubbish' then when ive had it explained thought 'ahhh i see!'
Above is a perfect example.

Just because 'it works' or 'ive been doing it for x years' doesnt mean were doing it right does it?
Its a bit like the 'ive been driving 50 years and never had an accident' syndrome

As far as im concerned, every days a school day ;-D

 

[weep]

mistake soz

 

[weep]

If lots of people do something wrong then it must automatically become correct?

Of course not and i aint getting into any arguments about it.

Everybody I know wires them according to the boiler manufacturers instructions, there are a few manufacturers who specify that they be wired this way.
The point is to ensure that if the boiler is switched off or a fault takes the internal fuse out then the whole system goes off. As you have wired it at the moment the Lr would remain live and so be feeding a live into the boiler despite the fuse having blown.

It's perfectly logical and sensible if you take a second to think about it, and I'm sure they have a good reason for doing it.

yes i know its logical and all that but sorry that wasnt what i was asking for.

Anyways got things working again, the only way i can explain it is mutual inductance on the 3 core cable between the boiler spur and the programmer (sounds crazy i know but had an old hand look at it as well and he was stumped). separated switched lives at programmer (made safe) and removed the black switched live from Lr and made safe. energised the circuit and got a reading of 24/57v on the black between the boiler spur and programmer (both ends).
Replaced said 3core cable with 2 twins and hey presto down to 6/12v ish, certainly low enough to allow the boiler to be satisfied.
could this be poor quality cable insulation, surely not ?

 

[weep]

Most of the time theres a reason why a manufacturer specifies something, even if we cant see it. Ive done it myself, thought 'what a load of rubbish' then when ive had it explained thought 'ahhh i see!'
Above is a perfect example.

Just because 'it works' or 'ive been doing it for x years' doesnt mean were doing it right does it?
Its a bit like the 'ive been driving 50 years and never had an accident' syndrome

As far as im concerned, every days a school day ;-D

Totally agree

 

[Gazzdid]

Glad you got it sorted pal, these are the types of faults that can have you banging your head against the wall!! :-D

 

[Doomed]

If lots of people do something wrong then it must automatically become correct?

Everybody I know wires them according to the boiler manufacturers instructions, there are a few manufacturers who specify that they be wired this way.
The point is to ensure that if the boiler is switched off or a fault takes the internal fuse out then the whole system goes off. As you have wired it at the moment the Lr would remain live and so be feeding a live into the boiler despite the fuse having blown.

It's perfectly logical and sensible if you take a second to think about it, and I'm sure they have a good reason for doing it.

And this is what bugs me about the new valiant range - there is no longer a live feed to take from the boiler to the stat - i phoned their tech line and they said take the feed from the mains block.

 

[davesparks]

What's wrong with that then?

 

[Doomed]

still covered by the isolator fuse I know, but with the old design if you turned off the boiler (on the front panel) or the internal fuse blew the stat would also lose supply - just seemed safer, their tech department said use the 12v line if you want that, but the plumbers I get subcontracted to always give me a basic cheap mains stat.

 

[davesparks]

I know, but if the manufacturers don't deem it necessary for their boilers then don't worry about it.