3 phase

Likewise unbalanced loads weren't raised when I installed 3-phase, except by me to check the meter would cope. Unbalanced loads within one property aren't important. The average over a large number of houses is what matters. I probably cause more imbalance overall using the single phase shower (45A) than anything else.

I suspect that power factor is more of a concern to the utilities.

Andrew

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

Umm,

Does seem to be quite a bit of confusion with this. At the beginning I said '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.'

Andrew and others then describe situations in which connection to a nearby 3-phase source has been achieved for about £2000. (As Colin's £500 was in the 1980's, multiply by 3 to convert to today's money. I wonder if Clive's £15000 is a misprint for £1500?) Anyway, those who paid £2000 all descrive simple cases and I believe they were indeed 'walloped with the full up front cost'.

We're not all the same in what's considered 'prohibitive' - no way would it be worth my while spending £2000 on on a 3-phase installation!

But, and this is always the danger of arguing from a small sample, the positive experiences don't cover the situation where making the connection isn't easy. For example, I often drive past an isolated ex toll-house / second-hand car business. It's power comes from a pole-pig that's fed single-phase from overhead wires that disappear on poles across the fields. It's 5 or 6 miles from the nearest town. Likewise, when I lived in the big city, all the wiring was underground. Getting three-phase into my home might have involved digging a trench across a busy main road and private land to a substation about 300 yards away. In difficult cases you could be looking at tens of thousands, perhaps more.

Most if not all of the people on the forum are electrical small fry. How we use electricity as individuals is unlikely to concern the supplier in terms of power factor or phase balance or finance. Very different conversations are held if the customer is building a new housing estate, a factory, a large office block, an Aluminium smelting plant, or High Speed Two! Part of the fun with installing 3-phase in a home is having to sort out something a bit non-standard on a tight budget. A big outfit might have in-house expertise, or they might pay consultants to manage the project. You're on your own, which is a good way of saving money, but painful if you get it wrong. By all means ask for a quote, don't be surprised if it's serious money, and don't be surprised when your local sparky can't help and leaves you looking for a commercial electrician, who might not be keen to take on a small job. Keep eyes wide open for extra costs - if you physically can't do the on-premises work yourself, or don't understand the regulations, be prepared to pay full market rate for professional help.

I hope we've done a good job answering Michael's original question. The best case cost is £1500 to £2500 for connection, the internal installation work is extra, and we've identified some likely pitfalls.

Michael: if you do proceed, please let us know what happens and how much.

Dave

Edited By SillyOldDuffer on 21/10/2018 12:40:39

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

‘Horses for courses’. If I manage to move to a more rural location and there’s three phase on the property I’ll use it for the workshop but until then I happy using VFD inverters with single phase for my needs. I’m not a fan of rotary or static converters. I find the options available with VFD’s such as soft start, deceleration and dc braking for emergency stop function for example most useful. Another advantage is that youn can run the motors at 60Hz (as with my American surface grinder) to get the extra 20% increase in speed. Having said this I’ve being using inverter for increasing power efficiency as well as speed control on industrial equipment since the 80’s on three phase supplies as standard. At the end of the day it’s what your familiar and most comfortable with. 🤔👍

John

I had three phase fitted many years ago by the then Norweb local supplier. It is a long story but I was fortunate to have it done for free. One problem that I have found is that since the de-nationalisation of the supply industry it can be quite difficult to find a supplier who will support a three phase supply to a domestic property. Most of them now require meter readings via a website or app. However they only have a system for a single reading on the afore mentioned sites.

This leads to difficulties especially when contacting them over the phone. When you mention three meters they think your property is divided up into flats or that you have an ordinary meter, an off-peak meter, and can't count properly. Other problems can arise if one meter has a lower reading than the other ( normal on a mixed three phase / single phase supply) they then think you are doing something dodgy. It means for me that I am tied to one company who do seem to be able to cope. It also helps that I can work quite happily on three phase and fit my own wiring etc.

I have never had a problem running the domestic system alongside my three phase. Everything was done to sixteenth edition regs. originally and seventeenth edition later (not much difference in three phase) The main advantage of the three phase is the loading on a higher voltage is less than by using a VFC on a lower one. And it does depend on the number and types of machines you want to run. Some of my machines especially the specialist swiss types would be extremely difficult to convert or run on a VFC because of the integral multi pole motors used. Although I have fitted a three phase 415v Input inverter onto one of them for the speed control.

Three meters? I've only got one meter. My meter is 3-phase; one phase goes off to run the domestic consumer unit after the meter. So I only have one reading. Mind you I did have someone refuse to read the meter. The garage is quite crowded and he took a wrong turn. Having been corrected he muttered about only getting 50p per meter read and stormed out to go next door. Where, much to their amusement, he ranted about the idiot next door with machine tools and it shouldn't be allowed and the government should do something about it.

Andrew

A number of people have commented on the inability to use VFC/VSD on equipment with control gear or multiple motors. While it is true that there are difficulties using the variable speed capabilities due to the associated variation in voltage, there is no reason why a converter / drive cannot be left set on 50Hz 100% voltage to provide a 3 phase supply for such machines. You loose the advantage of variable speed but at least get the unit working. Some converters may need a small fixed load for stability but this could be 3 small lights or heater elements.

Robert G8RPI

Quite so, but it still wouldn't allow me to use the full facilities of my machine tools without significant additions or changes.

Andrew