At what sort of load would an electricity supplier want to provide a 3 phase supply? (How big a house?)
Is it normally possible for a domestic consumer to have a 3 phase supply?
Would a 3 phase meter installed for a commercial supply also be suitable for a domestic single tariff supply?
Most suppliers will do it at a price. They supply the meter. What do you want to run on 3 phase? There are other solutions for intermittent motor loads up to 10HP (converters) and intermittent or more continuous motor loads up to 4ish HP (inverters)
Also consider that your supplier is not likely to offer such a range of competitive tariffs with 3 phase leccy and possibly none with Dual fuel. Someone will be along soon to prove me wrong (or not?)
I don't think there's any minimum, but there may be an extra standing charge. Nowadays, there's probably a whopping great installation charge, although it used to be free back when it was done by your supplier and they were going to earn more money from you.
For a small load, it may be cheaper to generate your own 3-phase from a single phase supply.
There is a maximum singe-phase supply - generally if you need more than 100A, you will be required to move to a 3-phase supply.
Yes, providing the local network has it to hand.
Smaller ones, yes. I doubt they would use a large one with current transformers, as it probably isn't accurate with smalld omestic loads.
My questions relates to a house which has been used as offices and was fitted with a 3 phase supply. There are three floors each with a fuse box. I presume each box is connected to a different phase.
The house is now to be used as domestic premises and I am wondering what to do with this three phase supply. The house could be described as a large semi with say 5-6 bedrooms.
I have been in contact with the electricity supplier, but yet to get much response from them. The present commercial tariff is unbelievably complex - 37 line items. I presume they estimated the usage of each computer.
In article , Andrew Gabriel writes
The added complication is that you may end up with a commercial supply number which will limit the flexibility in choice if supply providers.
I'd get it taken out otherwise it will cost you more in both standing charges and lack of tariff flexibility. About the only advantage for retaining 3 phase (assuming you don't want to run big machines, would be for a big heat pump.
Simply joining the three floors together in a Henley block and then a single phase meter will do what you need with minimal work so the costs should not be too great.
One possible trap might be they will want you to bring the whole installation upto latest regs and count it as a new install
Adam W will possibly be along soon and be able to advise as a professional spark.
Indeed yes. I am trying to get it reclassified!
Get it converted to a single phase domestic supply, unless you have some particular need for a three phase supply. You will probably want to rewire the property anyway, but there is no reason why, as an interim measure, the different fuse boxes cannot all be connected to the same phase.
Colin Bignell
I have three phase in my barn / workshop with it's own 3 phase meter. As it is not commercial I pay the same standing charge and cost per unit as my (single phase) house supply. I also pay the lower 5% VAT rate on it. I certainly wouldn't want three phase taken out if I were you. Though I would use a single phase thoughout the house and retain the incoming three phase head and meter for possible later use running one phase to your consumer unit. It's an asset not a liability.
AWEM
When mine went in, initially they set it up as commercial with (then)
17.5%VAT - it only took a 'phone call to get it put correctly as domestic. If you need evidence, presumable you have change of use planning permission from offices to domestic so you have the 'bit of paper'. And my supply is 160 amps per phase with current transformers to measure it!AWEM
The alternative is to have a single phase meter on/for each floor (assuming they will be separate households.) Then you will get three separate bills. BUT you will be paying the premium price on the first part of each bill/acount.
Ditto. As this is a diy forum I would have thought 3 phase would be strongly endorsed as giving you ability to use all sorts of useful machinery. I am with EON and single or 3 phase makes no difference to domestic tariffs available, standing charge or cost of electricity.
Notionally, only if there was a need for a three phase supply. That would b e a significant load (over about 20 kW, give or take) that was likely to be used for prolonged periods, or if there was three phase rotating equipment . Think swimming pool heater, circulating pump.
Yes, and despite what the gainsayers are telling you, at no extra cost JUST because it's three phase.
I have a 3 phase supply in my garage, single phase supply in the house. The garage supply feeds a single phase installation in the garage, 3 phase for my swimming pool. Winter months the pool is completely isolated, and there is minimal consumption in the garage.
The unit consumption for the two meters is aggregated. I pay one set of sta nding charges, day units and night units.
Yes. in simple terms the spec to which the meters are constructed require t hem to be accurate no matter how the load is distributed.
I was offered it when they upgraded my transformer. In reality 100 amps per phase is about the limit. That's 23kW or so on a angle phase, not sure how the sums come out on 3 phase tho.
I'd guess the installation cost is in the 2-20k area.
Some rural places on single phases maybe even more
My house had a 3 phase supply installed originally, probably not when the hosue was built (1911) but later. I base this on the fact there was still some surface wiring to light switches when we moved in. We only use a single phase. Our phase was changed a few years ago since the phase we were on had an intermittent fault.
3 ase supples weer installed originally so that the supply co could balance the load between phases.
Root 3VIcosphi:-)
My farmhouse is supplied with 3 phase but the loads are spread between domestic and various outlying barns.
The tariff is no different to that for single phase.
My parents house - a small two bedroom one built in the '30s, had two phases incoming. Perhaps to allow electric central heating?
Easier to work out that on a balanced 3ph the sum of any two currents equals the other, so measuring current in one leg times rms voltage between phases is power.
The 100Amp limit giving 72kW was a supply metering issue for our yard so it worked out cheaper to have two 72kW supplies rather than move from whole current metering and peak power monitoring.
AJH
The supply cables won't be removed, so 3 phase could easily be restored should the need arise. As 3 phase is not expected in a domestic property, it is quite possible for a careless use of extension leads or later rewiring to introduce 415v where most people would expect 230v. It is safer to change to single phase unless you really have a need for 3 phase.
Colin Bignell
Well the 6 bedroom, 2 kitchens, 4 lounges, 8 ensuites, 3 toilets, 2 hallways, 2 landing, 1 study new build that I have just wired up has a 100A single phase supply!
I have worked in houses that used to be shops and the 3 phase supply was just left there and two of the fuses were removed and just a single phase was used. I pretty much did what you have suggested regarding the henley blocks.
I am also pretty sure that you will not have to bring the installation up to the current regs to get the meter swapped.
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