Question and Problem solving all in one :)

[stephen1974]

I see you guys like problems, and I have a question about a setup i've just seen.

Small CU with 4 breakers in it. 6a 16a 16a 32a (with the main breaker only rated for 63a)

As far as I can tell they power the following

1 lone plug socket.

1 fluorescent in one room

6 fluorescents in a second room

12 spotlights in the same room as the 6 flourescents

They are wired up as follows.

A 16amp and 32 amp breaker are not in use.

Cable for the plug socket goes in to one of the 16 amps.

There are 6 other cables coming in to the CU of which;

3 lives go in to the 6amp

4 nuetrals go to the nuetral bar

1 nuetral is connected to two lives via a choc block

1 nuetral is connected to a single live via a choc block

None of the cables are sleeved so im taking them on face value.

Question is, what the hells going on

We recently had a problem with the 6 fluorescents tripping the breaker when turned on. Someone came along, looked at it, got them working. Now the spots are tripping the breaker instead. I'm assuming the saw this CU and either didnt bother to say anything, or everything in there is perfectly ok and im wrong in thinking its a nasty mess.

 

[johninlondon1]

You need an electrician http://www.talk.electricianforum.co.uk/directory-uk-qualified-electricians-electrical-contractors-find-your-local-electrician/2370-find-your-local-electrician-here-list-uk-qualified-electricians.html Sounds like a bodge job, they have probably connected the fluorescents and downlighters on the same 6 amp breaker, this is exceeding the rated capacity of the circuit breaker and probably that is why it is tripping.

 

[stephen1974]

we have an in house electrician. The one who already looked at it.

 

[Doc Hudson]

1 neutral is connected to two lives via a choc block

1 nuetral is connected to a single live via a choc block

None of the cables are sleeved so im taking them on face value.

Question is, what the hells going on

Before anyone else comments I will just remind all students that Neutral IS a live conductor. So when you describe Live to Neutral you imply Line to Neutral or a Red to Black conductor or Brown to Blue. I assume you do not have a genuine Line to Neutral dead short or the fuses would blow. You need to identify exactly what each conductor is doing. Never take anything on face value until you have proved yourself exactly what each conductor is doing. It sounds like a typical DIY or builders job. It needs a proper competent person to come and identify and test everything out. As from the facts you have described the in house electrician is out of his depth

Doc H.

---------- Post Auto-Merged at 12:15 ---------- Previous post was made at 12:12 ----------

I assume what you call a Main 63a breaker is actually an RCD? and the other "breakers" are MCB's. the term breaker used on its own is not a formal recogniised term in BS7671.

Doc H.

 

[stephen1974]

Yes, 63 is the RCD.

Tracing the wiring they have some crazy system going on. To get to the lights which are just a couple of metres from the CU there is about 40 metres of wiring going in and out of several junction boxes. It will be quicker just to re-wire it than to try and figure it out.

Talking to the staff the in house electrican actually worked on a different problem last time so maybe he has not seen this yet.

 

[kerching]

Just because you think a wire does a specific job because it is a certain colour , it does not mean that you are correct in your assumption!

Live connected to neutral = bang ; end of. [unless there is an interposing load]...... :coat

 

[NozSpark]

Could be that they have brought the switch wires back to the CU,,,, maybe?

 

[ProDave]

Could be that they have brought the switch wires back to the CU,,,, maybe?

That's what it sounds like to me.

Unusual, but I can' see anything actually wrong with doing that, apart from the lack of sleeving on the cables.

 

[kme]

Concur with the Nozzer & ProD.

That sounds like switch wiring at the CU.

Very simple to determine; and even easier to resolve ( as long as the MCBs aren`t obsolete!