3 phase for a house?

scoffcruddle

Well-Known Member
I’m on with pricing up armoured cable to feed a barn I plan to convert in the future,if I use 2 core armoured (185mm2) it’s going to cost £28k in cable whereas if I used 4 core (95mm2) it would cost £26k in cable,I’m thinking 3 phase would be better because you’d wire say the kitchen to one phase and the other phases to upstairs and downstairs including showers on each etc

Never seen houses wired 3 phase before and as I’m paying for my own transformer at the pole It’s going to come off the high voltage wires in 3 phase anyway.
 
I know you are farming on a big scale but is just purely for your house and a future barn ? ... not including the main farm ?
Whats your total load and distance ?
 
I think three phase is good for charging cars . As far as I know we have a phase off a three phase transformer for a house . The yard certainly borrows a phase. Weird things happen when a phase gets dropped. We had lights in the yard but not the house.
Witchcraft I tell you.
 
Three phase be great to have alright. Brothers house is 3 phase. Why such large cable though. Google suggests capacity of 500+ amps. Isnt a standard connection 100 amp. Whats the run length? Is non-armoured in a duct any cheaper? Would it be cheaper to bring the transformer closer to the barn?
Would the network operator not provide transformer?

Sorry for all the questions but that cable sounds massive for a future domentic connection
 
The barn is 740m from the nearest supply,I bought 54 acres next door to get electric.

There’s only Hv on the land so I have to pay for the transformer anyway,this will be 3 ph because they won’t do a single ph supply off Hv,the transformer connection to a cubicle (sited 15m from the pole,minimum distance allowed)to house the meter will cost circa £15/16k,it will all be tax deductible while it’s an agricultural barn.

My thinking is houses don’t use as much energy as they did,better insulation,led lights etc,it will be a 5 bed large house so not small but if you heat your water using oil or a gas combi boiler there’s only the cooker and a couple of electric showers using the main power.
 
You seam to have your figures well done anyway, cable size is bang on to keep voltage drop below 5% at full load. It's a no brainer really to get your 3ph supply when it's been offered for the same cost as a single phase supply, any reason you haven't factored an earth cable into your pricing ?
Is the main incomer entering the barn or house ?
 
Price you own transformers each end of your cable to barn, higher voltage can use smaller cable, step up and step the voltage down, keep to 900v then you dont have the safety gumph that main lines have might be alot cheaper
in terms of phases, run kitchen on 1 phase, utlity with freezer, washmachine tumber dryer etc on another and rest of house on last phase, tho this does complicate the wiring a little but very possible

also, look into solar as you now will have 3ph to export on
 
If I get you right, you're getting a meter at the cubicle shed and then going 740m to the barn. If that is the best way of getting power to the barn then 3 phase would be the way forward. as has been suggested it would allow for 3phase car charger or 3 phase air to water heating/geothermal heating it gives a lot of options down the line .
 
Swalec wanted my ol man to have 3ph in his house to run the air source heat pump
In the end he found a pump with soft start
 
You seam to have your figures well done anyway, cable size is bang on to keep voltage drop below 5% at full load. It's a no brainer really to get your 3ph supply when it's been offered for the same cost as a single phase supply, any reason you haven't factored an earth cable into your pricing ?
Is the main incomer entering the barn or house ?
I was going to use the armour as the earth,I’ll price an earth cable.

It’s currently a barn standing on it’s own in a field I’m hoping to get planning to convert it into a house,if this doesn’t happen I’ll convert it into rural office space.

Price you own transformers each end of your cable to barn, higher voltage can use smaller cable, step up and step the voltage down, keep to 900v then you dont have the safety gumph that main lines have might be alot cheaper
in terms of phases, run kitchen on 1 phase, utlity with freezer, washmachine tumber dryer etc on another and rest of house on last phase, tho this does complicate the wiring a little but very possible

also, look into solar as you now will have 3ph to export on
I don’t think the electric company would let you have a high voltage supply to allow your own transformer either end.
If I get you right, you're getting a meter at the cubicle shed and then going 740m to the barn. If that is the best way of getting power to the barn then 3 phase would be the way forward. as has been suggested it would allow for 3phase car charger or 3 phase air to water heating/geothermal heating it gives a lot of options down the line .
Yes spot on,cheapest way is let the electric company do the minimum allowed by law,I already have a electric supply to a cubicle so does my brother and uncle,with the advent of smart meters you don’t even need to read the meters now.
Was a guy called here repairing a puncture, years ago,i think he was czech. He asked me what phase electric to run parlour. He couldnt get over we only had single as most houses in area he was from had 3phase
I know a 60point rotary that runs on single phase,they start the vac pumps in sequence.
 
I was going to use the armour as the earth,I’ll price an earth cable.

It’s currently a barn standing on it’s own in a field I’m hoping to get planning to convert it into a house,if this doesn’t happen I’ll convert it into rural office space.


I don’t think the electric company would let you have a high voltage supply to allow your own transformer either end.

Yes spot on,cheapest way is let the electric company do the minimum allowed by law,I already have a electric supply to a cubicle so does my brother and uncle,with the advent of smart meters you don’t even need to read the meters now.

I know a 60point rotary that runs on single phase,they start the vac pumps in sequence.
Looks like you have it well enough thought out I would go with either a 5 core swa or run a earth with the swa the armour wouldn't be enough at that length and size I'd guess though that's from an Irish regs perspective we run tn-c-s mainly here
 
Looks like you have it well enough thought out I would go with either a 5 core swa or run a earth with the swa the armour wouldn't be enough at that length and size I'd guess though that's from an Irish regs perspective we run tn-c-s mainly here
Not allowed to use to use armour anymore but was fine for years (I might be better with some old colour cable😀)
I’ve just been told to use earthing rods at the barn end as that’s all they use at the connection end.
It’s another £9k for 5core over 4core,or £4K extra for a single earth cable.
Yes use to-c-s here,I don’t suppose over earthing would do any harm,the only time I’ve ever employed an electrician was when we split the farmhouse some 20 years ago,he said I’ll see you when I come back to earth your plumbing,I said you’ll do well I’m using plastic…..
 
I was going to use the armour as the earth,I’ll price an earth cable.

It’s currently a barn standing on it’s own in a field I’m hoping to get planning to convert it into a house,if this doesn’t happen I’ll convert it into rural office space.


I don’t think the electric company would let you have a high voltage supply to allow your own transformer either end.

Yes spot on,cheapest way is let the electric company do the minimum allowed by law,I already have a electric supply to a cubicle so does my brother and uncle,with the advent of smart meters you don’t even need to read the meters now.

I know a 60point rotary that runs on single phase,they start the vac pumps in sequence.

You can use transformers, just to 900v, 900v is still classed as low voltage, so get 3ph =400v .. step up to 900v and cable and step down again at barn to 400v

neighbour is doing similar here to take a cable 600metres
 
You can use transformers, just to 900v, 900v is still classed as low voltage, so get 3ph =400v .. step up to 900v and cable and step down again at barn to 400v

neighbour is doing similar here to take a cable 600metres
What sort of load was on his transformers, must have been enough to justify all the extra cost ? , For scoff he'd get away with reducing cable size to about 50 sq buy 2 x transformers and then take transformer losses x2 into account for their lifetime, remember a transformer consumes power just sitting there with no load and then multiply that x 2, the cost saving on cable wont be long disappearing.
Im not knocking it just curious as to how it worked out for him.
 
What sort of load was on his transformers, must have been enough to justify all the extra cost ? , For scoff he'd get away with reducing cable size to about 50 sq buy 2 x transformers and then take transformer losses x2 into account for their lifetime, remember a transformer consumes power just sitting there with no load and then multiply that x 2, the cost saving on cable wont be long disappearing.
Im not knocking it just curious as to how it worked out for him.
But the meter would be at the house, so any loss before that wouldn't be his problem.
 
You can use transformers, just to 900v, 900v is still classed as low voltage, so get 3ph =400v .. step up to 900v and cable and step down again at barn to 400v

neighbour is doing similar here to take a cable 600metres
Any idea where I could find a price/spec for a transformer?

Only downside I could see is I’d lose the ability to slice the cable half way along to power an electric gate,not the end of the world,I’m open to all suggestions.
 
But the meter would be at the house, so any loss before that wouldn't be his problem.
What Ricky is proposing would be customer side of metering, unless i picked it up wrong. you would be adding 2% per transformer when loaded.
Any idea where I could find a price/spec for a transformer?

Only downside I could see is I’d lose the ability to slice the cable half way along to power an electric gate,not the end of the world,I’m open to all suggestions.
Im not commenting anymore :blink::laugh:
 
So you are paying for the transformer but will the network operator own it? i.e. who maintains it, who replaces should it fail? Presume meter and isolator will be low voltage side of transformer (Just like normal connection) and you are responsible from there on. I would certainly try to get 3 phase connection/transformer as leaves options open for future.
 
So you are paying for the transformer but will the network operator own it? i.e. who maintains it, who replaces should it fail? Presume meter and isolator will be low voltage side of transformer (Just like normal connection) and you are responsible from there on. I would certainly try to get 3 phase connection/transformer as leaves options open for future.
Yes,I pay for the transformer (I never own it)within the connection price is an infrastructure charge etc,I’m responsible after the meter.
Even if I opt for a single phase supply I still have to pay for a 3 phase transformer,I do have plans for a building on the land so I’m going to have a separate 3 ph supply to it.
 
transformers are all customer side of the meters, thats why you gotta stay 900v max

ill ask more questions when i see him again and let you know
 
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