a 2/3 phase future?

[Steve]

does electricity cost more per unit on a 3-phase supply? I know it costs more to install, just wondered if it cost any more on the bills, as it is usually reserved for commercial rate customers. Is it freely available to domestic installs (if you ask, will you get it without a struggle?)

I was just wondering, because with the rate things are going, many new homes will be heated/cooled by electric heat pump air conditioning units soon, and obviously 3-phase units are easier to get hold of by big housing companies etc. Also, big power showers may turn 3-phase soon so they can be more powerful (20A across 3 phase = 60A so a 13.8KW shower ), and with part p2 (prediction), only qualified lectricians will be able to service them/replace them (being 3-phase, its not a DIY job)

As an alternative, is 2-phase available in this country? i mean, is it possible to tap off 2 phases to each house rather than 1 or 3? Do 2-phase air conditioners exist? I think the american system of 2-phase and neutral is good, with 240V washing machines and air con units, though im sure this has its downsides that the experts on here will tell us about!

Just hypothesising for the future of UK household electrics. feel free to comment!

 

[plugwash]

you would have to pay for installation of 3 phase which is likely to run to over a grand at the cheapest (ie if you have a 3 phase main down your street) there may also be a higher standing charge but i don't see why the price per unit would be affected.

there are at least 3 different systems with two live conductors. true 2 phase is very rare nowadays. most american homes get split phase (single phase with center tap) which gives cable saving advantages but no real advantages for motor design etc.

two phases from 3 phase is also possible though i don't know of any motors designed for this it stands to reason that they could be made more efficiant than single phase motors if carefully designed due to the ability to create a rotating magnetic field easilly from them.

 

[mapj1]

Unless you use megawatts, you'll find the standing charges higher too.

As an aside, and a personal hobby horse, you might think energy consumption is going to rise, but before you get carried away with the idea this is a limitless trend, type 'peak oil' into google, and read around. Obviously ignore the more sensationalist offerings, and stick to the respectable reporting, but none the less a problem looms in any world where more oil has been burnt than discovered, per year, by a slowly but steadily increasing margin, since about 1980. ( and any one retiring now has lived through the burning of about half of all the world's oil. )

Then as another aside realise that without cheap fuel or slave labour, then endless economic expansion ceases to be possible. (it needs things to be cheaper to make or do tommorrow than they were today, or your investment never pays off.)

You might find that you might be better investing your money in thicker insulation, reflective foils or more appropriate clothing for the weather.
The DTI asked these chaps to look into it and they came up with this
http://www.eci.ox.ac.uk/pdfdownload/energy/40house/chapter09.pdf and the rest of the report on nearby web pages but I suspect the required rates of house demolition and reconstruction will never be met, and we will be left what the authors call fuel poor.

Note the 2KW expected amount of heating required for a whole year 2050 house....

 

[mapj1]

something we May see more of, if it gets really tight for power is this sort of thing,
http://www.dynamicdemand.co.uk/grid.htm#

the idea being that loads can automatically be added or lost to the grid if the frequency changes indicating over or underload problems at the power station. This would save an awful lot of load dumping resistors, and allow generating plant and transformers to be more closely sized to the likely load.
I suspect the only reason it is not done much at the moment is there is no economic benefit to fitting one from the customers perspective.
Unlike these objects
http://www.savawatt.com/productdetails.asp?id=2
which are essentially a load sensing circuit plus triac that reduces the motor dissipation when the load is light. For freezers in shopping centres etc this sort of device is a serious saving on the electricity bill, and the motors last longer as they are running cooler.
no use for resistive loads though..

 

[Stoday]

You have to pay the connection cost of a three phase supply, but there are no ongoing costs for kWh. There may be extra standing charges.

Every DNO publishes its connection charge methodology, with the costs of typical connections. For example, here is EDF's connection methodology for eastern england:
http://www.edfenergy.com/attachments/epnmethodchargesconnection010405.pdf
On page 33 you will find typical costs for a 100amp single and 100amp three phase connection, £900 and £1000 respectively.

Energy costs are the same for single and three phase, but Use of System costs may vary. They are also published, for example:
http://www.edfenergy.com/attachments/chargesforusenetworksepnelecdistsyst010505revised.pdf
Page 9 shows the domestic standing charge (3.95p/day single phase, 4.87 three).

Normally you won't see the Use of System charge in your bill because the energy supplier will wrap it up with the energy charges to give one price.

 

[Lectrician]

On our estate, the houses have cutouts back-to-back (all TN-S which is nice). There is one underground service which rises to the cutout, and short length of split concentric comes back out the bottom of the cutout, through the wall to next doors. (pre-fuse on the first cutout).

The last house in every street or cul-de-sac has a 3 phase head - rather than pot-ending the service cable, or jointing to a smaller SP service.

I know one chap who has used this to his advantage, and has used the 3 phase in his garage. He reckons that charge is the same. (maybe it is for domestic) I cant be sure.

 

[ban-all-sheds]

Did he tell the supplier that he'd started using the other 2 phases?