Crossed wires

[russellsmiler]

Posting here as I believe this belongs in this forum not electrics but possibly in combustion chamber forum.
Some time ago my stepdaughter bought a house that had seen the previous owners do all sorts of weird and wonderful things both to plumbing, phones, cctv, and electrics.. I had the job of making some sense of it and promptly ripped out 90% of phone extensions, disabled the unnecessary cctv, tidied up some electric flex extension leads that were behind units, and at my stepdaughters request replaced the socket and switch faceplates for some nicer nickel finish ones, on changing the fused spur to the boiler I changed the terminals like for like, but remember that it appeared that the live and neutrals did not correspond, but sort of assumed that this was how it was and this is how I will wire it!! everything worked perfectly afterwards, however nearly 2 years later the boiler as been playing up and some sensors have had to be replaced (not entirely sure what) but the problem she as been told is that the terminals at the fuse where wired wrong way round??? I am not an electrician (but a decent DIYer) so as said i copied like for like from previous wiring, but surely if live and neutral where wrong it would of tripped circuit... or am i missing something??

 

[terryplumb]

What exactly did you do ?

 

[Gasguru]

Always measure L-N, L-E & N-E to confirm correct polarity.
I've been to many homes over the years with reversed polarity on the meter tails at the consumer unit (even some with new fake inspection reports).
Many boilers will refuse to recognise the burner igniting...and that's when the problem arises.

 

[russellsmiler]

hi terry
I basically removed the fused spur faceplate on the boiler cupboard wall... removed terminals, but as said the terminals appeared incorrect.. blue to brown...brown to blue.... but as this was just a like for like I sort of assumed that because the house seemed to have lots of anomalies that I was better to keep it like for like as the boiler (combi boiler) had been working fine.

 

[terryplumb]

That would reverse the polarity to the boiler. It's debatable as to whether or not that would cause sensors to fail two years later ,I doubt it.
But it could cause other problems ,which would result in boiler failure at the time, not two years later .

 

[briwire]

Do you mean blue switched through to brown, and brown switched through to blue?
If you have a multimeter, at the boiler, the brown wire should be in L terminal and should read around 230v to earth. The blue wire should be in the N terminal and read very close to 0 volts to earth. If that is so, everything is correct. Try that first.

 

[ianmcd]

some boilers are polarity sensitive, some are not, if you had the polarity wrong and the boiler was sensitive to it, the boiler would have failed immediatley, it wouldnt run for 2 years then fail, has she had a smart meter installed ?

 

[stem]

I wonder if something has been lost in translation here as the story has now been passed on 4 times.

With some heating systems there are often many live connections to the various items of equipment (programmer / thermostat(s) / boiler / motorised valve(s) / pump) with just one common neutral shared by all. And here's the problem, most cables only have one brown (live) wire inside, so the neutral and earth wires are often used as live wires despite the colour of their insulation indicating otherwise. Could that be what was being referred to?

Also, some boilers have their internal connections with terminals that include a fuse, so could that be the "fuse" being referred to, and it's actually the wires at the boiler end that were transposed?