oh it's question time Gary we've had a question in from Andrew an electrician in Cambridge who's been having
a spot of bother with the bell transformers in a doorbell installation okay so we're talking about
where the transformer is built within the consumer unit and the problem being where we've got band one
and band two voltages present yeah and i think it's mainly the cabling that's caused the problem
there i mean here's the typical installation we've got yeah obviously the bell transformer in there
and obviously these days a lot of people haven't either changed them or go back to installations
because people are fitting smart doorbells a bit like this netatmo one that we fitted on our smart
home takeover absolutely and you've got obviously that extra low voltage is 0 to 50 volts ac
and then we've got our band 2 which is called low voltage which is 51 to 1000 volts ac and there's
an issue where the two come together gordon yeah so what is that issue gary well you don't want the
voltage from effectively the band 2 appearing in the band 1 because the insulation around the bam
1 conductors is not as a higher value as those at band two okay so what's the solution we've
got here gary well there's a couple of solutions should we cut to those let's have a look yeah so
this is the problem that andrew was facing on site you can see that uh bell wire twisting
its way around all of the other uh cables in the consumer unit gary yeah and we've obviously got
the two different voltages that we've discussed as well and that becomes an issue doesn't it because
we don't want the voltage from the mains cables to appear in that one that's actually eight volts
so what's one possible solution yeah one possible solution is to over sleeve it in a material that
is rated at the same value of rating as the mains voltage in there so in other words the band two
value of voltage within the consumer unit that is very difficult to put on because the belt wire is
incredibly uh supple one would suggest yeah they don't seem to supply thick belt wire anymore
so we we over sheath it so the insulating material around the conductors was only rated up to 50
volts ac so now by adding that on we get the higher value of voltage uh insulation around it
yep straight forward yeah so you're putting that back through the hole there obviously we don't
know what's happening behind the scenes there that bell wire could be twisting its way around
all those cables behind the scene but at least there's an additional sheath on top of those yeah
and when we put the cover on the top of the bell transformer you'll see that you'll see none of the
well eight volts that it's rated at isn't it the transformer itself on the outgoing side
so we'll see it there you just see the eight volts on it now we faced this problem on the uh our
smart home takeover we fit the smart doorbell there and that has uh they've used security
alarm wire for the for the bell circuit and again that's only rated to 50 volts so that's something
we'll look to correct yeah when we return to that installation change the board so that that already
looks tidier we've rooted it better and obviously obviously this is one of my favorite ways of doing
it is just use mains rated value cable so in other words i've used one mil twin and cpc here
yeah twin earth if you're listening from the real world yeah i'll do that okay that looks
good gary i think you might struggle at the other end there where you bring that into the
chime itself because there those terminals tend to be very small and sort of the cable entries
yeah well it was tough sensible solutions there gary i've got a third one for you okay
gone in you do your third one don't put the bell transformer in the consumer unit okay yeah so be
perhaps nearer to the actual uh bell chime itself or built within it yeah you can get built-in ones
yeah i've got a question for you then okay let's presume that amendment 2 of the 18th edition
warren regulation comes in as it's uh proposed to be done okay and that was proposing that we'd have
an afd on final circuits up to including 32 amps so wouldn't that mean that an afd would have to be
on your final circuit then uh yeah it would do if it was a dedicated circuit then yes it would and
obviously we did one in here we had that debate didn't we is it a bit overkill to put putting the
fdd right next to the transformer there's probably a i don't know three inches of wire between them
to arc fault protect again so yeah it's a good point so what would my solution be there i would
be uh just putting the bell on the lightning circle absolutely and also we left the gap didn't
we this this uh bell transformer here isn't made by wilex so there's another question for everyone
he'll probably pose another question won't it can you introduce a transformer not specified or
from the manufacturer itself into that consumer unit type test and all that sort of stuff comes
into play yeah right yeah because obviously the problem we see in a lot of installations is the
existing bell transformer needs to be changed when you put a smart doorbell in depending upon
the manufacturer of the smart doorbell we didn't luckily but when we go back to site as well we've
got that problem with the cabling because someone wired the circuit in security wire which is only
rated at 50 volts so perhaps you'll tune back in when we do that board change on that project again
we think we've answered andrew's question so two solutions that i came up with but obviously the
oversleeving at the voltage band of band two okay or to wire it in thermoplastic pvc cables that's
fine your solution was to take it and put it obviously remote to the board and we then threw up
another scenario also we've thrown up the scenario about the actual transformer itself so we always
like these questions and if you're an expert on it please leave those comments and questions below
and help other people out in the chat we also are interested in your thoughts on this is there
another way have we come up with a fourth solution to the problem we didn't think about if you have
put that in the comments below and it will help everyone within our community we'll try and get
back to you as well well yes as many as we can we will but if you have another regulations related
question gary would be delighted to answer it absolutely i will pass it on to joe no problem