Triple phase electric supply in a house

[ssmyther]

Hi all.

I am in the process of buying a house which currently has a triple phase electric supply. I don't know anything about them as have always had a standard single phase before.

Can anyone shed any light on pros and cons? Whether it is a good thing/bad thing? Whether it costs more in terms of having works done on the property? Can standard electricians work on them or is it a specialist area?

Many thanks for your help.

 

[AndyPRK]

What's it used for ?

Do u have storage heaters ? Is it a big house

 

[ssmyther]

It's a 4 bed bungalow which used to be part of a farm, but the house has been sold off separate to the farm. I think it has retained it's hard-core supply even though it is now just a 'normal' size house.

Any thoughts?

 

[Jackrae]

Could be useful if you want to buy some ex-factory workshop machinery.

Without a description of your house, this is conjecture : 3-phase could have been installed because of excessive demand due to a load of storage heaters being fitted many years ago (mine has for that reason). If that was the reason and you no longer have storage heaters there are measures you might want to consider.

If your house has been split loaded across the 3 phases this poses a potential risk to occupants as there could be 400/415 volts between appliances. If your domestic load is reasonable you might want to get your sparkie to look at reconfiguring your consumer units so's all domestic supplies come off a single phase.

Registered electricians should be aux-fait with 3-phase since all single phase
systems originate as 3-phase. If they are not then get another because they are obviously lacking in the basic skill required.

Metered units, cost is the same whether single or three phase installed

Edit ; previous post came in whilst I was writing this. Get sparkie to see whether house is 3-phase wired or not. If 3-phase then get him to look at sorting out consumer units so's they all come off a single phase. No need to get your supply company involved even if you have a 3-phase meter since it'll happily work (correctly) with only one phase being loaded.

 

[ssmyther]

Thank you for the reply.

The house has gas central heating so storage heaters are not a concern (maybe had them previously but the gas heating has been there for over 20 years)

I believe the house is wired off a single phase but three phase is coming in.

Wasn't sure if this is something that will cause problems down the line or whether it is a 'nothing' really?

 

[plugwash]

Advantages:
1: You can run three phase equipment, large motors (think car lift or similar) are much cheaper in three phase than single phase. In theory there are also advantages for DC power supplies but in practice I doubt you will ever see a three phase DC power supply in a domestic environment.
2: There is usually a maximum size of single phase supply an electricity sompany will supply. A three phase supply may under some circumstances also be cheaper to have installed for a given supply size because it may require less work on the network.
3: The higher effective voltage in a three-phase system means that for a given total load smaller cables can be used.


Disadvantages of three phase are
1: you have to think somewhat about balancing single phase loads across the phases to avoid overloading any one phase.
2: the highest voltage present in the system is higher, it used to be frowned upon to have multiple single phase loads on different phases close together for this reason. In practice though this is a very minor issue, the chance of two seperate appliances having total insulation/earthing failures simultaniously is negligable.
3: A three phase distribution board will be more expensive to install/replace than a single phase CU.
4: The standing charge may or may not be higher depending on your electricity supplier's policies.

A properly trained electrician should have no problem dealing with three phase systems. The "two week wonder" domestic installers may be another matter but I'm not sure you'd want to be using them anyway. All but the smallest commercial properties tend to have a three-phase supply so it isn't all that unusual from an electricans perspective. The cost of most jobs should not be significantly affected.

In general as long as the installtion appears to be in good condition I wouldn't worry too much about the fact it's three phase. If the property is in need of a rewire then it may add a bit to the cost but probablly not much in the grand scheme of things.

 

[flyingsparks]

Nothing to worry about. The only thing I'm not sure of, and someone here will probably clarify, is I expect there is a higher standing charge to have the three phase supply. If not tho, keep it and build yourself I nice workshop!

 

[westie101]

The standing charge is made by the supplier based on the metering. If there is no need for a three phase supply just get the metering changed to single phase and leave two phases unused.

A common arrangement in a lot of units

 

[ssmyther]

Does anyone know if the standing charge is different for triple phase, and whether you can still shop around on money comparison sites when it comes to finding utilities tariffs?

 

[RF Lighting]

I think the standing charge relates to the meter rather than the supply. If three phase is not required you can just have a single phase meter fitted and it'll be no different to a standard domestic supply.

 

[westie101]

In the old leccy board days a 3 phase standing charge for whole current metering used to be three times that of a single phase.
I've no idea of the present situation

 

[ssmyther]

Thanks for the advice everyone. I feel reassured that it isn't going to present a big issue. I was worried it might mean considerably bigger bills for running and repairs etc.

 

[deadshort]

Hi, if you have a 3 phase meter your standing charge is more than single phase, but as has been said, if you change to a single phase meter it's less expensive.

Regards,

DS

 

[JohnW2]

In the old leccy board days a 3 phase standing charge for whole current metering used to be three times that of a single phase. I've no idea of the present situation

With E.ON, I pay essentially the same standing charge for 3-phase as my neighbours do for single phase. In fact, until a recent tariff change, the standing charge was zero (instead replaced by a premium price for the first N units).

Kind Regards, John

 

[JohnW2]

Get sparkie to see whether house is 3-phase wired or not. If 3-phase then get him to look at sorting out consumer units so's they all come off a single phase. No need to get your supply company involved even if you have a 3-phase meter since it'll happily work (correctly) with only one phase being loaded.

That sounds a bit back-to-front. If the OP is going to retain the 3-phase supply, it would surely be better to try to balance the load across all three phases, rather than put it all on one phase?

Kind Regards, John