Split Phase to three phase ?

[KEVINDOE]

Hi Guys,

Just after some thoughts on changing a domestic property to three phase.
present supply is split phase with shared neutral, overhead, one phase dedicated to holiday cottage on 80 amp switch fuse submain to local c.u.
The second phase is dedicated to the house consumer units of wich there are two six way 3036 boards and four other garage type additions for showers and power circuits.
Taking into account doubling up on some fuses by others, there are 22 circuits in all.
The property is a large farm house {two knocked into one} and has four en-suites and a family bathroom all with elec showers { all 8.500kw }, total of six people living full time there.
The owner wants to install three phase washing machine and dryer and has asked the d.n.o. to look at the possibility of a three phase supply.
I have been asked to do the rest.
Have any of you done this before ,? any advice very much accepted and cherished !

Thanks Jem

 

[johnboy6083]

put one phase to holiday cottage, and load the three phases in the main house so that the overall installation is as balanced as possible, taking into account the holiday cottage.

 

[KEVINDOE]

Thanks john,
Im not sure they will go ahead when they relize how much the lay out will be , rcbos and such,

Jem

 

[johnboy6083]

hope you get the job mate

 

[Richard]

I may be wrong, bu coulnd't you use three 17th edition single phase boards as opposed to a single three phase board? I take what you mean about the outset of buying 22 rcbos!

 

[KEVINDOE]

Yeh, its well placed to work on, lots of room, keep me out of trouble for a day or so !

 

[KEVINDOE]

Hi Rich,

How would you wire the three phase washer and dryer ?

Or am I being thick ?

 

[Richard]

Sorry just re-read that. good point!

Maybe a small three phase board to feed those circuits?

I'm just trying to think of ways for you not to have to buy and wire 22 rcbo's!

 

[KEVINDOE]

Yes Rich , Me too !

Feed TP C.U. via henly blocks ?

 

[Guest123]

Best get them to sit down when the DNO come back with a price for installing 3 phase.

 

[KEVINDOE]

Yes Lenny,
and thats just the start !,
Am i right in thinking that they would just add another phase to th two existing ?,,

 

[roukel01]

We had a factory 3 phase supply upgraded 2 years ago, the work cost £25,000 for the upgrade, that was a 200 meter run, all ground works etc on the factory site had to be completed by others.

A campsite we work at wanted their supply upgrading, the transformer supplying the site was literally 15 meters from mains position, so it was a very straight forward swap. 2 years ago quote was £13,000 to install new transformer, this year it was just over £17,000

Obviously I have no idea where this farm house is or how close it is to a 3 phase supply, but I would imagine that if in the past it was a practcle option to upgrade to 3 phase, it might have already be done. Also, many villages around me simpoly do not have a 3 phase supply coming into the village and so on farms, 3 phase is not an option, and they are all running on split phase.

 

[KEVINDOE]

Supply is from a pole, about 15 meters away at the mo,
If its anything like that price, it wont happen.

Thanks rouke

 

[somersetsparks]

Is there 3-phase coming to the pole near house - I very much doubt it split phase can only be supplied from a split phase transformer (centre tapped) from 2 legs of 11kv 3phase, Gernerally they will not have bothered to bring the 3rd phase accross to the farm and sometimes it might be a couple miles away. This is the whole idea of split phase. You may be lucky but still they will try to rip the customers off due to the fact they dont have to compete with anyone.

 

[KEVINDOE]

Thanks for that post somerset,
There are also six other holiday cottages on the premisis with there own supply, there is a three phase header in the switch room and a three phase board feeding all six cotts, however there are only two phases connected ....your post would explain why this is ?

Jem

 

[somersetsparks]

Well without seeing what you have Jemmajones its hard to say. But it sounds about right, basically nobody but nobody makes any specialist split-phase gear so even the DNO will use a 3-phase cutout and only connect two-phases, they will also use use 3-phase concentric cable etc. The same goes for sparkys, there is no split-phase gear available now so the most common solution is to use 3-phase gear and blank off every L3 way in the DB.

The easiest way to check for splitphase is to look at your incoming 11KV supply like this :
http://upload.wikimedia.org/wikiped...Marchouse_Hill_-_geograph.org.uk_-_106798.jpg

Then i'm afraid you only have 2 of 3 phases present, how far away 3 phase is is anyones guess could be 500 yards, could be 3 miles or more.

If you have 3 11kv lines coming over you probably have 3 phase readuy to connect.

If it does happen, do the job properly and go the 3-phase DB route, you may have to get more RCBO's but balancing 3 single phase boards properly will be a living nightmare !

 

[KEVINDOE]

Thanks somerset,
advice welcomed

Jem

 

[IQ Electrical]

Yes, Somersetsparks is spot on, you will have a 460/230V 1-phase 3 wire system-if you check between 'lines' at the main switch etc. you'll probably have around 480 Volts.

 

[somersetsparks]

The question always is with split phase, is the switchgear adequate when it is only rated at 415v, like IQ electrical says you would normally get 480v between the two live conductors and 240 to neutral but some places get 500v generally because the transformaer is sat on a pole 10 yards away.

Although I'm sure it would be fine I wonder if the manufacturer would pay out on any warranty claims etc. ?

Just food for thought!

 

[Engineer54]

Just wondering how your going to wire-up a 3 phase washing machine if you intend installing 3 seperate CUs??

 

[IQ Electrical]

The question always is with split phase, is the switchgear adequate when it is only rated at 415v, like IQ electrical says you would normally get 480v between the two live conductors and 240 to neutral but some places get 500v generally because the transformaer is sat on a pole 10 yards away.

Although I'm sure it would be fine I wonder if the manufacturer would pay out on any warranty claims etc. ?

Just food for thought!

If the devices are rated at 415v then this rating is per pole so there shouldn't be a problem, enclosures are as stated by the manufacturer and the answer from Schneider was 'not covered if the voltage is exceeded'

I didn't push them on U and Uo ratings!

 

[KEVINDOE]

Hi Engineer,

I dont intend to, think wires got crossed along the way if you excuss the pun!,,

jem