Three Phase to Single Phase supply - should I downgrade?

Discussion in 'Electricians' Talk' started by Lerwam, Oct 29, 2013.

  1. Lerwam

    Lerwam New Member

    Please help!

    We have moved to a house with a three phase electric supply - although two don't have fuses in. We are extending the house so moving the electrical supply three metres to a new wall - I have two quotes from UK Power Networks. One to move the existing three phase supply (more expensive) and one to downgrade it to a single phase supply and move it (cheaper). Am I best to keep three phase or move to the single? Our house is going to be a large family house but we are not a small holding or farm. Although in the future who knows what we might do - we are in an acre plot but most of it is outside of the village envelope so we can't build permanent structures on it. We also plan to install solar so generate our own supply...... Thanks in advance!
  2. Sean_ork

    Sean_ork Screwfix Select

    what size array do you plan to install ? having 3ph might be handy of you are considering one of a decent size
  3. Lerwam

    Lerwam New Member

    I've just been told by a solar installer that it's not worth going over 4KwH (even though I'd read that a family home would use 5.5KwH and we are a family of six!)

    Why would a 3ph be helpful if we had a large array? I understood that 3ph basically means that I have potential to run a business on the amount of electricity coming into the house from the grid. But how does that help me if we just use for our family domestic use? Thanks!
  4. Sean_ork

    Sean_ork Screwfix Select

    3ph allows for a larger incoming capacity, and, in the case of micro generation, the ability to export more

    3ph has it's uses within a domestic environment for hobby machinery etc, and it's becoming more common in large homes that use heat pumps as their primary heat source

    your decision to use just a single phase will depend entirely on the design, use and the loading
  5. unphased

    unphased Screwfix Select

    Hi Lerwam

    Three phase supplies were often put in by the suppliers incase of future increase in demand. It would be highly unlikely that two or more phases would be needed in one house. It is your call as to whether you think you would make use of additional phases in the future. A standard supply for a domestic property is 100A single phase. If you cannot justify keeping the three-phase I would just have the single and down grade.
  6. Lectrician

    Lectrician Screwfix Select

    You quite often find the last house in a cul-de-sac has a three phase supply. The DNO used to take the end of the cable into the building, rather than jointing it outside to a single phase. A three phase head was fitted, but only a single phase used.

    The larger your array of panels, the more money you will earn in your fits payments, and the more you can feed back to the grid and earn in too. Large arrays are best suited to three phase inverters.

    If the cost difference is not huge, it would be best retained as three phase, but its really your call.
  7. sparky Si-Fi

    sparky Si-Fi Well-Known Member

    if the OP keeps the TP+N but only requires Single phase, would not the DNO charge him for that privilege, even though he is not using it?
  8. Sean_ork

    Sean_ork Screwfix Select

    yep, there'll be the standing charge
  9. sparky Si-Fi

    sparky Si-Fi Well-Known Member

    Something else for him to weigh up then?

    Be interesting to know what the charge(s) are??
  10. Lectrician

    Lectrician Screwfix Select

    Usually the same as single phase. There is not normally any additional standing charges for three phase these days.
  11. Caddy

    Caddy Member

    These days they tend to try and charge for everything and anything they can!!! :)
  12. Alexa1

    Alexa1 New Member

    Our three phase fuses were upgraded from 80 to 100 amps by eon only last week and they told us the standing charge for 3 phase supply and single phase is the same.
  13. Lectrician

    Lectrician Screwfix Select

    I have not seen a standing charge difference between them in a VERY long time. Probably 15yrs at least. Standing charges are fees passed on through the energy provider from the DNO and government tax levies.
  14. Sean_ork

    Sean_ork Screwfix Select

    we have 3 phase here and have a per meter standing charge (3 meters) - we have been offered a single meter and a reduction of the SC but the cost reduction is not worth the hassle as I have multiple export sources feeding them

    SSE is the DNO
  15. Lectrician

    Lectrician Screwfix Select

    Three meters would be "three meter points" and three mpans, so three standing charges. A single polyphase meter would give you one meter point, one mpan, and one standing charge.
  16. Plum Duff

    Plum Duff New Member

  17. sinewave

    sinewave Screwfix Select

    Concur (as usual) with Lec!

    Our Gaff has a three phase 100A supply and our charges are no different that my neighbor on a 100A single phase supply! (Scottish Power / Manweb)

    Upside is I have a potential 300A supply and I have a TPN board in my Garage for testing purposes etc for work related stuff.

    We also have an Air Source Heat Pump so one phase is used exclusively for that.

    Upgrading from SPN to TPN costs loads, if U already have it then keep it, might even help to sell the house one day to a future buyer! ;)

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