At great expense!

If you want a proper TPN installation, you will need to speak to your local electrical supply authority.

The alternative is to use either a rotary convertor or a 230-415 invertor.

What are you looking at powering?

Typically in the UK, you don't. It's not impossible but – unless you can show you're going to buy a lot of electricity over several years – the cost is usually prohibitive. It's because the cost of wiring up is usually recovered over several years of big bills, and, because domestic users rarely consume enough power to make that economic, they get walloped with the full up front cost. As a single-phase house might be some distance from a 3-phase source, you might find yourself paying for trenches and poles as well as a the cabling. The second problem is one of safety. You don't want single phase domestic equipment running on different phases in close proximity. Also, most electricians wouldn't touch it.

These days there are many inexpensive electronic boxes t hat convert ordinary 240V single-phase into 3-phase specifically to drive 3-phase machines like lathes. VFDs start at about £60 for 2.5HP on ebay. Would one or several of those solve your requirement? Even largish workshops use them rather than plumb in real 3-phase.

Dave

Errr, that wasn't my experience.

I simply rang the local electricity board and they said they'd send a man out to do a survey. I asked where the nearest 3-phase was, as if it's half a mile away you pay for the whole length so no point getting a quote. But no, they said they'd send a man anyway. Turns out the nearest 3-phase is buried the other side of the road. They quoted £2500 to supply the 3-phase. I understand from a friend in the house building industry that about £1000 of that is for digging up the road. If a utility digs up the road they have to repair the work FOC if needed, for up to a year after the work is done. So given the sub-sub-contractors they employ they whack the price up. No questions were asked about usage or anything else. I just confirmed that the 3-phase meter wouldn't have a wobbly if only one phase was being used. I also checked that I would pay the domestic standing charge and pence per unit.

Having 3-phase makes life easy. All the control gear works and I can run two speed motors without any issues, including on the fly switching. The horizontal mill has a 4/5hp Dahlander motor and that's no problem either on proper 3-phase.

Andrew

I've put three phase into two properties. The last one was in the late 80's. The three phase supply runs up the road and is 6ft – 7ft below ground level. It runs just inside my property line. I was able to dig a trench across my lawn and under the drive and then tunnel under the garage/house foundations. I dug a 6ft x 6ft x 7ft down to the three phase cable to expose it. I was doing this in mid October, digging by floodlight every night after I got home from work. Had lots of funny comments from people when they realised there was someone down the hole digging. All they saw was heap of soil flying out of a hole.Laid a heavy plastic duct (supplied by the Electricity Board) and then fed the three phase cable through it. Ran it up wall to Meter Location and put up my own Distribution Board. Ran a Single Phase to my house Distribution Board. The Electricity Board turned up, terminated cable at Meter, I put the tails into my Distribution Board and they then cut open the three phase cable and soldered the new cable to the main feeder. All done with it live. IIRC it cost me around £500. The previous one was at my Dad's house for our lathes and milling machines, I did all the same work and it cost even less.

A friend of mine has just had the same thing done but he had to have a JCB a the nearest 3-phase was in a field about 100 yards away. Cost him a little more.

Colin

Shame I don't need three phase as its six feet from the house and runs along the gardens of all the houses in our Crescent, My builder found it when his digger brought up a busted gas main to my house whilst doing some work for me, don't break a gas pipe it costs £800 to join to ends back together

Martin P

You could buy quite a few vfds for 2000 squids.

The quote stated I would need to dig the trench on my property and install ducting. I couldn't get any sense out of the electricity board about exactly what I needed to do, so I ignored it. The digging team dug down to the cable on the road verge, dug a 4ft long trench my side of the road, another 4ft trench on my drive and a hole by the garage to get to the J pipe. They then moled between the holes and trenches to fit the cable. No ducting was used.

Andrew

Just a comment.

Utilities usually keep the phase loads reasonably balanced by connecting three houses with each one wired in sequence to each of the three phases.

Probably, they would not not be too happy to put in a 3 phase supply and then have one phase more heavily loaded that the others.

Howard

Hi Howard, I live in a residential street and when western power connected my three phase supply no mention was made of any concern to balance loads between ajoining residences.

Regards,

Gareth

Yes, it's a complete and total non-issue. A good example of overthinking.

The house is one on phase already ie the definition of unbalanced. Any additional true, 3-phase loads could only improve the balance. But in the scheme of things, averaged out over thousands of houses, it's of no consequence whatsoever what happens in one installation.

Murray

I thought long and hard before installing the 3-phase. This was done 15+ years ago when VFDs were more expensive than they are now. One also needs to take into account that my machine tools have large motors, up to 5hp, which makes the VFDs more expensive, and some also require 415V to function properly. I estimated that VFDs were going to cost me a significant proportion of the cost of 3-phase. Another factor was that the existing single phase installation was 60A with a wind yer own fuses consumer unit. The survey before I bought the bungalow pointed this out and recommended it should be changed.

Even if I could change motors a VFD wouldn't allow me to use the machines properly, particularly those with multi-speed, specialised or multiple motors. And I would also need to fudge the control gear. I suspect some machines would be very difficult to convert, such as the power guillotine. It would probably be possible to fudge the electromagnetic clutch so that it worked, but I'd rather be making parts.

To summarise, almost all my machine tools are inherently 3-phase and I want to use them, and all their facilities, to the maximum. In addition VFDs were going to be costly and it was sensible to update in the incoming supply anyway. So although it was expensive I don't regret doing it in any way. With the old supply if I was using the hob and oven I might have tripped the system simply by having a shower!

Andrew