Might want to log this one for future use.

[Evans Electric]

Resiting consumer unit yesterday  ready for DNO  next week  to re-site incoming supply  .

 So we switch the new board on about 3.30   ...mark it up ... go to the van to fetch tester .....  customer says  everything  works except  CH boiler keeps shutting off   on hot water  & heating . 

Do the usual ,  try pressure  recharge ....make sure flue fan is working ...    flames a funny colour  so make phone call .   How can having the power off  for  5  hours affect a  CH boiler? :C

Fitter says he'll call in an hour  ...."Oh by the way  , is the polarity correct ? "      I look at my mate & we head for the new  board  , which now has a temporary  supply  from the old one ....  and yes   L & N   reversed .   Senior moment  from my mate  ....apparently polarity affects some sensors in that boiler   :C    

 

[Phoenix]

Its not the first time I've heard of this, so I think its perhaps a lot boilers that do this, rather than just one brand? might have to reasearch it.

Can remember being told about similar on a TT installation, boiler not working, gas fitter sent for, boiler not working because of reverse polarity, but the reversal not in boiler spur must be upstream , spark sent for... polarity correct at spur, oh and boiler is working again it seems, next day, boiler not working, gas fitter sent for, reverse polairty again.

The TT installation had a knackered RCD / VOELCB, and a 2 way ligthing circuit had a fault to earth on one of the strappers, when swicthes were set so that strapper was live, it was dragging the earth potential upto near live potential, so to all intents and purposes it looked like a polairty reversal (as you see nothing between L and E, 240v L-N, and 240 N-E)

 

[Evans Electric]

Blimey !!  Not exactly an obvious fault to say the least .  

 

[SLIPSHOD & SLAPDASH]

A few years back  it was a boiler  that told me there was reversed  polarity on a whole job . Boiler locked out when new meters were fitted. Cant remember all the details but previous sparks had reversed cables but taped correct colours  on  tails. When  the ends were  cut off and reconnected , what we thought was correct it was now reversed. Would have found if shortly after when testing was done.