strange

[telectrix]

anyone come across this before. Building is combined offices and works canteen. think it was something else originally. Switch Room has 2 supplies 415 3phase and 230 3 phase. Yes, 230 3 phase. The 230 3 phase runs kitchen extractor fans. Now the unusual part. All the single phase 13A sockets are supplied by 2 phases of the 230v 3phase. i.e. there is 115v on the "live" and 115v on the "neutral", the earth seems to be taken taken from the star point. At some time past, each socket has been fitted on the incoming side with a20A D/P SWitch. I am reluctant to take on any work on this installation for obvious reasons. Your comments would be appreciated.

 

[malcolmsanford]

I can assume that your in the UK?

I work over in the Middle East and 3 phase 220v is quite normal. Also in Europe a lot of older installations have this as well mainly though it is 2 phase 220v

The only thing I can think off really that in a past life the building may have used a lot of 110volt equipment and the company asked the local DNO to supply a 115volt tapping off the tramsformer rather than installing a transformer themselves.

Have you asked the DNO why there is a 3 phase 220v supply? It is definately a seperate DNO supply, there isn't a transformer somewhere in the building supplying this.

Also at those sockets you don't have a neutral as such you have 2 phases the 2 phases give you the 220v that is why each socket as that double pole switch for isolation.

 

[telectrix]

yeah, i know that. the 230 3 phase is there also for the kitchen fans. it's a separate supply. can't see how it can comply with current regs without spending a fortune so i walked away, got enough headaches as it is.

 

[davelerave]

sounds more like a 230v split phase supply-haven't came across it

 

[Guest123]

It may be a 115-0-115 set up as Malcolm suggested, it may have been due to a requirement for a 110V supply. Due to the loading they may have supplied 2 "hots" and a CTE, rather than the usual 55-0-55 system for 110V gear.

 

[Guest123]

sounds more like a 230v split phase supply-haven't came across it

If it were 230V split phase then you would see 460V between phases, hence my 115-0-115 theory.

 

[telectrix]

nope. its 230 phase to phase. i said it was unusual esp. as there is a 415 supply present as well , so could have used one or more phases for sockets and lights

 

[malcolmsanford]

Well can understand your reluctance to work on the system if you don't feel confident enough to do so. I would think the majority of installations we come across don't comply to the Regs as they are now.

Could you not just advise the client of what you found put it in writing that in your IYO the systems needs to be brought up to current standards and that the 230v 3 phase supply is not suitable for the situation as it is now and advise them to contact the DNO. after all you never know when just a letter could get you the job of ripping all this out , which could be a nice little contract.

 

[davelerave]

If it were 230V split phase then you would see 460V between phases, hence my 115-0-115 theory.

i believe i'm correct ,115-0-115 is referred to as 230v split-phase

 

[Guest123]

I aint buying it but each to his own.

 

[telectrix]

could be, but its a multi-national company. 60 days credit is the norm. don't want to go there.

 

[davelerave]

I aint buying it but each to his own.

115/230V V, 3-wire may be a better description


http://www.fecservices.co.uk/Dynami...lectrical terms & your electricity supply.pdf
240-0-240 is referred to as 480 split single phase here


480 being the full phase voltage

 

[Knobhead]

Where is the building, is it an old colliery of quarry? 230V centre tapped was quite a common set up under M&Q regs.

 

[wattsup]

loads of 3-phase 110v stuff in power stations

 

[Knobhead]

Loads of 230V 3 phase in mines & quarries