What are the Implications ....

[Martin Page]

Mains Electricity

What are the safety implications from taking the positive from one circuit and using the negative from a different circuit.

After some 30 years of this houses existence the Electric Gate takes it Positive from the Kitchen isolator and returns the Negative back to the Lights isolator through a daisy chain of external lights.

There is no actual problems with either the gate or the external lights, they all work fine.

I cant understand why its wired this way, other than I cant find the corresponding Negative since the existing Positive is the only wire sprouting from within the wall itself and the Negative is a cobbled together single spur wire from the light loop.

Do I have a major task to hand, or do I let sleeping dogs lie

[wollie]

there is no problem here as all the negatives are connected together on the consumer unite at source and it is just the live wire which is on the trip but for cookers and electric showers different.
the only issue could possibly be if the cables were different on the two circuits but unlikely someone with the knowledge to wire in this way would make a simple error like this.
out of interest is it UK or Spain as the technique is slightly different but same in principle.

hope this helps

[El Cid]

If it's worked OK for 30 years why change it now? I would let the sleeping dogs lie.

Sid

[northandsouth]

Theoretically you can but it depends on how the consumer unit is wired. Yes the old "bundle all the neutrals together" is still in existence in many homes but has been outmoded for over 14 years now, all breakers must be bi polar ie switching both live and neutral on all circuits.

Also it will depend on whether more than one RCD (diferencial) is being used in the unit, (again something that has increased over recent years) you cannot use a live from one dif circuit and a neutral from another dif circuit.

With electrical wiring just because something "works" doesn't necessarily mean it's correct and safe.

[flyeogh]

Martin I know you didn't ask about cost but hope our experience might be useful to you or someone

Our electrics over here in Cadiz were a bit of a mess. They dated from 1983 with a few mods here and there. They functioned ok.

But I think good electrics is very important so justified the upgrade in addition to safety concerns by having more sockets (+14) installed, light switches moved and new ones installed, TV aerial points renewed, and ceiling light fittings re-positioned.

Todate:

The new consumer unit now caters for over 20 circuits - the former 4. And it has lots of nice safety features.

When the wiring was inspected it went all over the place so new channelling was necessary almost everywhere. It took the builders 3 days (Up to 3 of them at times) and the sparky 2 days.

To put that in perspective it is a 4 bedroom 158 meter house and they did the down stairs (6 rooms) and prepared for the kitchen. So just over half of a full rewiring job.

Cost so far 1380 Euros including all material, labour, re plastering and rubbish removal.

When I saw the quotes I was fully prepared for the cost to rise but they stuck exactly to quotation even though we added an extra switch and socket.

When they do the three bedrooms, bathroom and landing up stairs, and complete the newly fitted kitchen it will be less than 2700 Euros.

For peace of mind I'm glad I spent that even without all the convenience mods.

Well hope that helps someone.

[Martin Page]

The house is in Spain

The Neutrals are not all bundled together each breaker has its own Neutral as well as a Positive.

Sleeping Dogs are definitely getting a lie-in me thinks

Thanks

[spanish_lad]

Martin,

the neutrals from each area / room will be connected together.

if you only have 4 or 5 breakers in the fuse box then they WILL be connected together. Only if you have a newer style box with 20+ breakers will they all be separated.

implications? in an older style box.. none. In a newer style box, as above - a new box is basically 2 or 3 "old" boxes all powered from the same source. So imagine that you have the live and neutral from the same breaker and you are working on a light fitting. you flick the breaker off, the rest of the house stays on, so that you can use power tools and a radio and make tea while you work.

now imagine that you have the live from one breaker.. and the neutral from another.... you flick it off. make a cup of tea. take out your power drill. put your hand on the fitting to unscrew it.. and BAMMM 230v up your arm, hot tea all over you. OUCH.

the problem is that the 230v is a circuit. you´ll get a belt from either side of it.