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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> mcb https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1106342261 Message started by cupid on Jan 21^st, 2005, 9:17pm

Title: mcb
Post by cupid on Jan 21^st, 2005, 9:17pm

Today the niece & nephew came over to stay for the weekend :'( we have a cupboard under the stairs for elec/gas meters ect plus lots of bits &bobs for the kids, my nephew went to the cupboard to get some toys and said UNCLE that BUZZING noise in the cuboard sounds really cool :-/ , i found that it was coming from the mcbs turning each one of in turn i found that it stopped when turning upstairs lighs off ??? tuned it back on no buzzing WTF (all lighting is 6a type c mcbs)

many thanks
cupid

Title: Re: mcb
Post by bstyle on Jan 21^st, 2005, 9:51pm

I thought you were going to say that he pulled a vibrator out of the cupboard!! lol

Title: Re: mcb
Post by cupid on Jan 21^st, 2005, 10:01pm

na, wrong cupboard :o ;)

cupid

Title: Re: mcb
Post by L.Spark on Jan 21^st, 2005, 10:36pm

wrote on Jan 21^st, 2005, 9:17pm:

Heya Cupid

Sounds like a bit of a concern, buzzing noises are almost always loose connections with resulting arcing, this can cause burning inside the board, and in extreme cases result in a fire.

I would for now at least open up the board, do a quick visual inspection, check for any melted wires, any wires come loose etc

Best do this when the kids aren’t around, and if you feel like you can do it safely and properly.

If not it's calling in an electrician, but you may well find out it's something simple that you can fix, and if it is you just need isolate the entire board via the main switch, take off the cover, fix the problem, fix cover back on and turn main switch back on

Perhaps you could take a picture of the inside of the board for us?

Hope you resolve it, arcing can sometimes come and go, and I really wouldn’t forget about it just because you can't hear it buzzing at any one time.

Title: Re: mcb
Post by ChubbyPhaseWire on Jan 21^st, 2005, 10:48pm

mcb? :(

Title: Re: mcb
Post by JerryD on Jan 21^st, 2005, 10:51pm

just wondering why he's got type c's? type b is the norm isn't it?

Title: Re: mcb
Post by L.Spark on Jan 22^nd, 2005, 12:25am

Quote:

mcb?
:(

Yea could be faulty MCB

wrote on Jan 21^st, 2005, 10:51pm:

just wondering why he's got type c's? type b is the norm isn't it?

Actually Type-B's are not ideal for lighting because they trip when bulbs blow, this usually doesn’t happen with Type-C

Eventually Type-C for lighting will become the normal thing..

I've personally fitted several Type-C MCB's for lights on domestic installations, had no problems so far

Title: Re: mcb
Post by JerryD on Jan 22^nd, 2005, 7:01am

Do type c still comply with disconnection times in line with BS 7671?

Title: Re: mcb
Post by plugwash on Jan 22^nd, 2005, 9:31am

on a worst allowed case TN-S with a C6 and 1.0mm cable you are fine up to about 80 meters.

Title: Re: mcb
Post by L.Spark on Jan 22^nd, 2005, 1:30pm

PW has pointed out about Type-C there, nice one

Yes Type-C comply with disconnection times, so do type D, but it's not about disconnection times it's about impedance, if the impedance is right any breaker will disconnect

It's a case of a lower impedance to get type-c or d to trip, therefore you CANNOT really get away with a Type-C 32A breaker on a TN-S, as I've already found by doing some research with a Ze of around 0.7, your Type-C breaker won't trip

For lower Amp's such as 6A/10A it is easy enough to comply and for impedance to meet requirements

Title: Re: mcb
Post by cupid on Jan 23^rd, 2005, 5:24pm

Sorry to take so long in replying guys,kids have had me jumping through hoops all w/end (bless em >:() on the strenth of what L SPARK said i popped in to see a lecky friend of mine he agrees it is possable that it is a faulty mcb, he is going to check it out for me monday,
THANKS TO ALL who time to reply.

cupid