16amp ring final?

[ashm]

Hello and thanks to all that answer,

I have a split load board with a ring final on each side. I noticed, the other day, that the ring on the RCD side has a 16a mcb. I know this is not usually the case and so double checked that it was a ring and not two radials. It is definitely a ring wired in 2.5 T&E, feeding the upstairs sockets. The sockets are lightly loaded and so the MCB has never tripped. My initial thoughts were that a 16a mcb would be safer as it would trip earlier but than began to wonder if its operating close to its trip point would cause longer term issues?

Is there any reason a 16a MCB would be used? should it be changed for a 32a?

Thanks.

 

[333rocky333]

There may be spurs off of spurs (branches) resulting in someone downrating it to a 16 amp, may be best to leave alone

 

[JohnW2]

I have a split load board with a ring final on each side. I noticed, the other day, that the ring on the RCD side has a 16a mcb. I know this is not usually the case and so double checked that it was a ring and not two radials. It is definitely a ring wired in 2.5 T&E, feeding the upstairs sockets. The sockets are lightly loaded and so the MCB has never tripped. My initial thoughts were that a 16a mcb would be safer as it would trip earlier but than began to wonder if its operating close to its trip point would cause longer term issues? Is there any reason a 16a MCB would be used? should it be changed for a 32a?Thanks.

If all the required tests on the ring final were satisfactory, if it's all 2.5mm² T&E, if there are no unfused spurs from it feeding more than one socket and if the cable is in no place installed in such a manner that its current-carrying capacity is less than 20A, then there's no reason why it couldn't have a 32A MCB. the last of those 'ifs' might be the most difficult to be certain of'.

However, the thing to be aware of, and to be asking yourself, is why it currently has a 16A MCB - there could have been a reason (maybe a violation of one of thsoe above 'ifs').

Kind Regards, John.

 

[JohnW2]

There may be spurs off of spurs (branches) resulting in someone downrating it to a 16 amp, may be best to leave alone

Even then, a 20A MCB would presumably be OK, provided CCC was not below 20A anywhere.

Kind Regards, John.

 

[ashm]

Thanks,

I had considered that the circuit may have been de-rated and as the 16a MCB has caused no problems so far I'm happy not to have to confirm all the ifs!

My only concern is for the MCB operating near is trip value. Do they not detect over current based on heat? Could this cause early failure or am I looking to deep?

 

[RF Lighting]

No, there should be no problem

 

[ricicle]

How are you sure it is a ring final circuit ?

 

[ashm]

I isolated the supply, removed a double socket joined L and N for each leg and tested for continuity at the board if that makes sense.

 

[333rocky333]

You could have just done L to L , N to N and E to E continuity, at that socket, however neither way would prove that there were no branches from it if it was a ring

 

[ashm]

That would have been easier! thanks. It wasn't to prove branches, just confirming the 2 circuits were a ring.

I cannot prove the circuit hasn't been de-rated so am happy to leave the 16a MCB if the general consensus is it will not cause a problem.

 

[333rocky333]

unless you plug in electric heaters then your unlikely to exceed 16amp upstairs i would have thought,
good quality 16 amp mcb's shouldnt have a problem running near capacity anyway, what make are they do you know, they may be obsolete and 20 or 32 may not be an option anyway

 

[ashm]

They are Wylex - good quality?

 

[333rocky333]

They are Wylex - good quality?

apart from a problem batch recently, yes, one of the best

 

[ashm]

Thanks for the reply's, going to stick with the 16a and probably ponder the many possible reasons for the original de-rating!