Socket MCB Keeps Tripping

[Adam_151]

John is right, there is more to the issue than the PC power supply tripping it out, 16A isn't enough for a whole house (the french restrict to either 6 or 8 sockets on each breaker)

A B32 will have similar magnetic tripping properties to a C16

Just for some background info, MCBs trip by two mechanisms, a thermal overload one, for example connecting 25A of load to a 16A breaker, this is exactly the same in a B16, C16, and D16, the second one is a magnetic part thats used for short circuits and earth faults that are low impedance and cause many amps to flow B is somewhere between 3 and 5 times the rating, C between 5 and 10 and D 10 and 20.

The reason that you can't just swap them without testing, is you have to make sure that if a fault occurs (eg. live wire touches case) the fault to earth won't be less current than you need to operate the magnetic part of the device. Electricians have the equipment to measure EFLI (earth fault loop impedance)

Whole house on 16A is not good regardless of whether its B or C curve, however if it was just a circuit serving one socket by the PC, then a C curve breaker could be the answer (pending ELFI checks)

 

[leedrummond]

ok again thank you for your responce, some very helpful people on here, really appreciate this help

I can also confirm that it did trip when i ran another test, of

turning pc on, then going downstairs then turning the fridge on

so this is definately confirming some kind of overload, and not necesserraly the initial startup of my pc.

 

[mike++]

however if it was just a circuit serving one socket by the PC, then a C curve breaker could be the answer

Yes Adam!!

In my field, one MCB protects one device only. I should have said that before.

 

[leedrummond]

ahh i can deffinately confirm its not a problem with my pc, or any other pcs in the house, and must be simply down to overload

as its tripping when we have many electrical items on in the house, ie cd decks, mixer amp, etc

 

[Taylortwocities]

You could swap the B16 for a B20. That is ok for 2.5mm wired radial.
The extra may mean it will hold in without too much extra expense. Better to get checked out though - someone put a 16 in there for a reason.

 

[leedrummond]

ok i have a mate of mine coming over later this week to do some tests


ive just called around next doors to see what mcb they have on theirs, and they have a 32a mcb, and exactly same setup on their consumer board as us. same brand too

 

[leedrummond]

i have checked continuity of the circuit to proove it was a ring and it belled through, i havew ow rplaced the 16 mcb with a 32a mcb and its worknig perfectly now,

 

[Spark123]

Sorry if this sounds harsh but please call an electrician to test the circuit properly to establish that all the sockets are wired correctly on the ring. It may work but it may not be safe. We wouldn't like your house to burn down from an electrical overload.

 

[leedrummond]

Ohh right, erm what shall i ask when i phone up for quotes ?

 

[Spark123]

Tell them the truth like you told us!! It is probably a good idea to put the 16A MCB back in for now. Keep the 32A one handy so you can hand it to the electrician providing when it has been checked it is OK.

 

[Taylortwocities]

Just tell them what you have told us on here and that you think its OK but just need someone to check the continuity of the ring and that it is OK to use a 32A instead of the 16A.

That should do it. probably take an hour if everything checks out.

Edit: must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster, must type faster

 

[leedrummond]

cheers guys, ill give a few a call tommorow, surely the continuity s correct if it worked for me when i tested it ?

 

[GaryMo]

ohh interesting, this was mentions previously in the thread

can a C type be added onto my consumer board? ie 16a C type

The problem with C type MCB's is that the maximum earth loop impedance of the circuit will need to be much lower to comply compared to a B type MCB.

 

[GaryMo]

i have checked continuity of the circuit to proove it was a ring and it belled through, i havew ow rplaced the 16 mcb with a 32a mcb and its worknig perfectly now,

cheers guys, ill give a few a call tommorow, surely the continuity s correct if it worked for me when i tested it ?

Who's to say that you don't have an interconnect early in the ring with 2 legs running off - imagine a 'H' instead of a 'n'.
It's a little more complicated than a simple continuity test.

Assuming 2.5/1.5 T+E........

First perform a continuity test L-L (r1), N-N (rn) and E-E (r2) at the consumer unit, figures for L-L and N-N should be similar with figures for E-E being roughly 1.67 times higher.
You need to cross connect the live and earth conductors at your consumer unit then measure resistance between L and E at each socket. Figures should be very similar and roughly one quarter of the combined resistance of r1+r2, this is known as the R1+R2 value. You then need to cross connect the live and neutral conductors at the consumer unit and then measure resistance at every socket between L and N, again figures should be similar but a little lower than those you saw from the L to E test, around one quarter of the combined total of r1+rn.
This proves you have a healthy ring and that you have correct connection of conductors.

 

[Spark123]

A type C will not help with a prolonged overload as its thermal characteristic is the same as a type B. Its magnetic setting is higher which means it is less likely to trip with start up current surges. As has been pointed out the EFLI also needs to be lower for a C type. Not the best way forwards imo.