Odd MCB issue

un5byh7sqpd2x0

Morning,

Noticed an odd issue with my MCBs last night - two of them which are beside each other on the board look to be linked somehow: upstairs sockets & downstairs sockets. If both or either one is up, then both circuits are live and the only way to kill them is to switch down both MCBs. Any ideas what could be the issue?

kramer1

Sounds like it might be a ring main split across 2 mcb s by mistake, what is the rating of the mcb s?

2011

Agreed.
One way or another the MCBs are connected in parallel.

un5byh7sqpd2x0

kramer1 wrote: »

Sounds like it might be a ring main split across 2 mcb s by mistake, what is the rating of the mcb s?

MCBs are 10A. Is this a safety issue? If they’re in parallel is the circuit now a 20A one or somewhere in between?

kramer1

Emilee Uninterested Pilot wrote: »

MCBs are 10A. Is this a safety issue? If they’re in parallel is the circuit now a 20A one or somewhere in between?

This all sounds really wrong, I'd get a sparks out to find out what's going on.

Maewyn Succat

Emilee Uninterested Pilot wrote: »

MCBs are 10A. Is this a safety issue? If they’re in parallel is the circuit now a 20A one or somewhere in between?

No it'll still be a 10 amp circuit. As said your best bet is to get an electrician to have a look at it because something is not right.

BigVanVador

Emilee Uninterested Pilot wrote: »

Morning,

Noticed an odd issue with my MCBs last night - two of them which are beside each other on the board look to be linked somehow: upstairs sockets & downstairs sockets. If both or either one is up, then both circuits are live and the only way to kill them is to switch down both MCBs. Any ideas what could be the issue?

Yeah I agree with Kramer. Its a ring circuit that was split probably by accident when the board was replaced more than likely just needs a 20a mcb to be whacked in and the two circuits joined.

kramer1

How many sockets on the affected circuit?

2011

The OP has highlighted more than one wiring issue. I would expect that a half descent electrician will uncover quite a few more. I would get this looked at sooner rather than later.

punisher5112

Sockets should be on a 20amp and lights on a 10amp.

un5byh7sqpd2x0

Sorry, my bad. They’re light circuits not sockets... 22 bulbs on downstairs circuit and 15 or so upstairs.

The board wasn’t replaced, it was wired this way day one. The house is pretty new so only discovered this issue this week

punisher5112

Are they tripping out?

I Am The Law

It's what is known as an Erroneous Connection, current rules (ET101) require a test to be done on new installations and give detail on how to carry it out.

Get your SafeElectric spark to sort it for you.

Xertz

This is way beyond DIY issue legally. You need to call in a professional.

Bruthal

Maewyn Succat wrote: »

No it'll still be a 10 amp circuit. As said your best bet is to get an electrician to have a look at it because something is not right.

Its likely it would require well over 20 amps to trip one 10a mcb if 2 in parallel. Then the second one would quickly follow.

un5byh7sqpd2x0

Xertz wrote: »

This is way beyond DIY issue legally. You need to call in a professional.

I've no intention of trying to fix it myself, there's a sparks coming tomorrow to sort it out. I just wanted to know how dangerous this was and how much of an arse kicking I should be giving the original electrician.

2011

Emilee Uninterested Pilot wrote: »

I've no intention of trying to fix it myself, there's a sparks coming tomorrow to sort it out.

That’s good news. It would be prudent to get him to check the entire installation.

adrian92

To answer the OP

As others have said the load side of the MCBs have been looped.

Remove both MCBs
Replace with one with,I think, 20 amp rating

adrian92

adrian92 wrote: »

To answer the OP

As others have said the load side of the MCBs have been looped.

Remove both MCBs
Replace with one with,I think, 20 amp rating

Attached

brightspark

Emilee Uninterested Pilot wrote:

Sorry, my bad. They’re light circuits not sockets... 22 bulbs on downstairs circuit and 15 or so upstairs.

adrian92 wrote:

To answer the OP

adrian92 wrote:

As others have said the load side of the MCBs have been looped.

adrian92 wrote:

Remove both MCBs Replace with one with,I think, 20 amp rating

Did you miss the post where they said it was a lighting circuit?

DublinDilbert

brightspark wrote: »

Did you miss the post where they said it was a lighting circuit?

If it's a lighting circuit the circuits are probably joined at a light switch or two switches are joined.

brightspark

DublinDilbert wrote: »

If it's a lighting circuit the circuits are probably joined at a light switch or two switches are joined.

I'd agree, but that isn't a reason to put them all on a single 20A MCB.

adrian92

brightspark wrote: »

Did you miss the post where they said it was a lighting circuit?

Yes, I missed that lighting circuits involved.

The OP originally stated power outlets only (later said lighting circuits involved)

Given that, I would be reluctant to give any advice .
Seems to me a need for an electrician required here.

2011

2011 wrote: »

That’s good news. It would be prudent to get him to check the entire installation.

They’d be leaving themselves open to getting fleeced then. If they’re not tripping then I’d be inclined to leave them.

Bruthal

brightspark wrote: »

I'd agree, but that isn't a reason to put them all on a single 20A MCB.

Its likely he was pointing out a possible cause, not this single 20A as a solution.

Bruthal

ReginaldSmythV wrote: »

They’d be leaving themselves open to getting fleeced then. If they’re not tripping then I’d be inclined to leave them.

Recommending leaving 2 lighting mcbs incorrectly connected in parallel is poor imo.

And with that level of electrical install, checking the rest of the installation is definitely good advice.

2011

ReginaldSmythV wrote: »

They’d be leaving themselves open to getting fleeced then. If they’re not tripping then I’d be inclined to leave them.

The idea of the MCB is to protect the connected cable from an over current condition. The way these MCBs have been connected means that they cannot provide adequate protection. Leaving circuits without proper protection is inadvisable as is concluding that the circuits are heathy just because incorrectly installed protective devices have not tripped.

The cost of making an electrical installation safe is generally very small when compared to the value of the property. Don’t be “penny wise and pound stupid”.

brightspark

Depending on the age of the house, if no other work was done since it was originally installed then the proper tests were not carried out for the certification.

TheBully

It’s just a lighting circuit lads, remove the loop on the load side. Problem solved

TheBully

brightspark wrote: »

Depending on the age of the house, if no other work was done since it was originally installed then the proper tests were not carried out for the certification.

What test? It was an oversight at best

kramer1

TheBully wrote: »

What test? It was an oversight at best

Erroneous test,but it might not been around at the time, and visual inspection if there's 1.5s going into a 20a breaker