3 Phase - again!

[tipu]

Hi Guys,

how easy is it to convert a single phase property into 3-phase? How do 3-phase electricity meters charge?

Am i correct in understanding that the wiring has to be done in such a way that the load on all three phases is roughly the same? What will happen if one of the phases is fully loaded while there is not any load on the other phase?


Thanks
Tipu

 

[Big_Spark]

Tipu, why would you want 3 phase in your home? It is not for DIY and you would need to seriously need it for the supply company to consider it, then you would get a HUGE bill for replacing your existing supply with a new 3 phase one.

 

[plugwash]

there are 2 types of 3 phase

3 phase with neutral and 3 phase without neutral

almsot all exectrical supplys to buildings are 3 phase with neutral so you can get away with uneven loading it just means less efficiancy and possiblly slight voltage increase on the underloaded phase however it is still considered bad practice to load unevenly if it can be avioded

small scale 3 phase (up to 125A iirc) is usually metered useing a special meter with 3 wheels which drive onto a common rod to the main display of the meter i have heared a 3 phase install is about 3 grand but i'm not sure exactly

larger scale 3 phase is metered useing current transformers

3 phase is normally terminated into a specific 3 phase board like this

here outgoing cuircuits can either be single phase or 3 phase depending on the mcbs fitted

most boards sold with isolators seem to come with 3 pole ones which really need a sperate 4 pole isolator upstream however with some brands you can buy a board with no isolator and buy 4 pole isolator kits to fit them

theese isolators are usually only availible in up to 125A though so beyond that a 200A direct connect kit is used with a seperate isolator

with 3 phase boards your rcd options are far more limited than with single phase CUs

you can use a 30ma rcd incomer but this means you can't put stuff like lights and alarms on non rcd

for single phase outgoing cuircuits you can fit 1 module rcbos for rcd protection
for 3 phase outgoing cuircuits that need rcd protection your only option seems to be a seperate rcd in an extention box like

here

 

[Stod]

You ask your local Distribution Network Operator for a three phase connection. They will charge you the full cost of doing this, but will give you a quotation first. You can find your local DNO from here.

You will have to provide a three phase main switch and take it from there.

You don't have to balabce the phases: that's what the neutral's for.

 

[breezer]

3 phase for a domestic does seem a bit much........................unless he has click me

 

[supersparks]

3 phase for a domestic does seem a bit much........................unless he has click me

actuly breezer...ya would be supprised at what someone had the other day......
one 3 phase line, AND kept the original single phase supply....

only a BL**D*y kiln!!!!!
and it was a massssssive house!

 

[breezer]

i take it he was into pottery?

 

[tipu]

FWL - It isn't for my home. It's for one of my businesses. It's come to the point where more than 100Amps will be drawn due to the number of appliances!

plugwash & Stod - thnx for the info.

There does seem to be all three phases coming in and being terminated in the building but only one is connected to a meter which supplies the property.

When you say isolators are available in 125A - i assume that means i can draw up to (not personally!!) 125A from each phase?

Breezer - i don't have one of them! Its all single phase appliances but just too many circuits being added.

If I did get someone onto to convert it would they be just replacing the existing CU and split the circuits between the 3 phases?

 

[Big_Spark]

FWL - It isn't for my home. It's for one of my businesses. It's come to the point where more than 100Amps will be drawn due to the number of appliances!

If it for a commercial operation, DIY is out of the question, IT IS ILLEGAL.

If you have a three phase head, then it is simply getting a contractor to install the necessary equipment for the Supply Company to upgrade you to a three phase meter. That should only cost a couple of hundred for them to do that.

However I cannot stress strongly enough that this is not a job for an amatuer, you will need to get a contractor to do this work.

 

[plugwash]

yes a 125A isolator is 125A each phase

you would need to get a sparky to replace the cu with a 3 phase distribution board and in doing so he would probablly have to do a full test and inspect on the system

it's probablly best to ask the sparky to deal with the rec so that the changeover can be made quickly some downtime is to be expected though

i would expect in your situation the 3 phase supply you get from the rec will be 100A though it may be 125A

 

[BR]

3 phase for a domestic does seem a bit much........................unless he has click me

That's only a Mickey mouse siren. The one on our fire station was replaced last year. "It broke" I brought it home and found it was only a faulty winding (although awkward to repair)

It's a 3-phase 305db motor driven siren
Fancy living beside me!

 

[Big_Spark]

Brian, is your surname Steptoe by any chance

 

[ban-all-sheds]

It's a 3-phase 305db motor driven siren

As long as you could be absolutely sure you'd never get a false trigger while you were in the house (somehow the word "nuisance" seems inadequate here), it'd make one hell of an effective burglar alarm sounder if placed inside.

 

[Big_Spark]

It would be illegal I suspect, unless you posted clear warning signs of the danger. This namby pamby state today would prosecute you for damaging the hearing of the burglar, then he would sue you because he got arrested as he could not hear the siren of the Police car responding to the alarm!!

Yes I am cynical

 

[breezer]

Br, havent got a picture have you?