2 supplies

[russellsmiler]

Hope this makes sense to readers
we have a communal unit that is wired from 2 seperate supplies, each supply to this unit will have terminals in the same connector block, and then a single cable into the distribution box in the unit .
Questions asked here.
if both supplies are live would the unit draw equeal power from each supply??
or is it possible to switch of alternatively and choose which supply powers the unit without the need to alter wiring or remove cable from mains connector block.

For clarity I have not mentioned earthing or cable sizes or distances, am only looking at being able to run a unit from alternative supplys or determine if equal power would be used from both supplies regarding sketch.

 

[Lectrician]

You MUST use a changeover switch at the unit. Earthing would be best segregated, forming a TT. You cannot use both supplies concurrently.

 

[bernardgreen]

What you are proposing is extremely hazardous.

Where do the two supplies come from ?

If they are from separate meters then there is a 1 in 3 chance you will be shorting out two phases, 440 volts into a dead short will make a very big bang

 

[russellsmiler]

This is were i am confused as to why this is not possible bernard, supplies come from next door to each other semi detached houses, which in turn each house is supplied by a 25mm L and N supply bolted onto the same cable on external overhead to house (they then go through seperate meters etc) but could it be explained why two supplies re-terminating creates bangs?

 

[JohnW2]

This is were i am confused as to why this is not possible bernard, supplies come from next door to each other semi detached houses, which in turn each house is supplied by a 25mm L and N supply bolted onto the same cable on external overhead to house (they then go through seperate meters etc) but could it be explained why two supplies re-terminating creates bangs?

If, as you seem to be suggesting, the two supplies are on the same phase, then there will be no bang, but a common situation is for adjacent properties to be on different phases - hence about a 400V difference between them (hence the big bang).

However, even if the supplies are on the same phase, there are still many reasons why you should not do as you have suggested. Why do you want to do it?

Kind Regards, John

 

[Lectrician]

If on the same phases, no bang, but you would end up feeding each other's houses! Not just the unit. If you turned your power off, some poor electrician could be killed, similarly if a meter operator, or the DNO carried out work inside or outside your home.

Accept it. Can't be done.

 

[russellsmiler]

thank John
Yes they are on same phase.
why we look to do it this way is part neighbourly dispute, the sketch is just for clarity. basically the unit is lit and socketed from my supply but is a split unit with seperate curcuits but the need for some circuits to be communal whils occupied. if it was wired this way and it was as my 1st query equal power would be drawn from each supply then when both in residence the unit would have shared cost, if i was away i could simply turn of my supply and neighbour would have power through his meter and vice versa. I know we could introduce a sub meter and share cost, but as said its part neighbourly dispute and are looking at this option.
can you tell me the reasons that this is NOT possible.

Thanks
Rus

 

[russellsmiler]

i will accept it cannot be done , but just investigating,

 

[JohnW2]

why we look to do it this way is part neighbourly dispute, the sketch is just for clarity. basically the unit is lit and socketed from my supply but is a split unit with seperate curcuits but the need for some circuits to be communal whils occupied. if it was wired this way and it was as my 1st query equal power would be drawn from each supply then when both in residence the unit would have shared cost,

Quite apart from all the problems and dangers, even if you did it there would be no guarantee that the current would be shared equally between the two supplies (depends upon many factors) - one or other could end up paying for most of it!

I know we could introduce a sub meter and share cost...

If there is no other way in which you can resolve the issue, that would be the way to do it. What is this 'communal unit' and does it really use enough electricity to make this an issue?

can you tell me the reasons that this is NOT possible.

There are all sorts of reasons. Quite apart from electrical details, if your electricity supplier found out about it they would be extremely unhappy and would be within their rights to disconnect the electricity supply from both properties. In practical terms, one of the dangers is that parts of the electrical installation of one property could be live even if the occupier (or their electrician) thought it was all switched off, and someone working on the 'communal unit' might not realise that it was still live after one of the supplies had been switched off. Another risk, perhaps closer to your heart, is that the connection between supplies could mean that, under some circumstances, you ended up paying for some of your neighbour's 'private' electricity usage.

However, most of the problems/dangers are electrical ones, and, has been said, you just can't do it!

Kind Regards, John

 

[russellsmiler]

Thanks John
I can see the issues clearly regarding this and need a total rethink.
This unit does not comprise of much, however as said i am running it from my supply, when having not spent much time at the house my electricity bill was quite substantial, this is due to my neighbour being an avid welder, with a suspision he runs extension leads back to house to do washing when i am away.
we are in disagreement and as anyone in a similar situation with neighbour would testify all common sense goes out of the window.

 

[JohnW2]

This unit does not comprise of much, however as said i am running it from my supply, when having not spent much time at the house my electricity bill was quite substantial, this is due to my neighbour being an avid welder, with a suspision he runs extension leads back to house to do washing when i am away.

If this 'unit' (whatever it may be) does not require much current, you could supply it via a low-rating fuse within your property, which would largely thwart any attempts to draw large currents from your supply via an extension leads.

we are in disagreement and as anyone in a similar situation with neighbour would testify all common sense goes out of the window.

Many of us are very familiar with the issue of 'disputes with neighbours'!

Kind Regards, John

 

[Lectrician]

If the electric comes from your house, Its yours. Turn it off. Shared unit or not, you're not obliged to supply it, surely?

 

[Iggifer]

Aside from all the dangers involved, all your neighbour would have to do is turn off his main switch in his CU, and hey presto, he's got a free 50A backfed supply that you're paying for

 

[333rocky333]

How about a coin meter, then he can sort of pay as he goes, you should also feed the meter for your use, then use the money to put towards the bill

 

[magicmushroom666]

Feeding the supply to your neighbours property sounds pretty unusual, and not exactly a good idea, Surely it would make sense for you to disconnect any cables leaving your side of the unit and let them sort out their own supply from their property?
To achieve the 'shared' thing you was proposing, the neighbour would have to run a supply from his house to his part of the unit anyway, so then there would be no need for them to be connected together.
If you just need light in a common entrance maybe put in a window!