Triphasic electricity supply - does the supply to our boundary need to be upgraded?

[Daft Doctor]

Hi, have tried to get the answer to this from various sources, so thought the sparkys out there might just know.  We are having a house built.  The land was provided with a supply to the boundary via ERDF, a (monophasic) 12kVA supply was requested when it was done.  The builder has passed on the conclusions of a 'thermic study' of the house and a 15kVA supply has been recommended as part of these conclusions.  The builder has admitted that this thermic study doesn't take account of any heat which might be provided by a poele à bois, and admits that if we stuck with 12kVA it would only likely be a problem if everything was run to capacity, i.e in the depth of a very cold winter snap.

They have rightly said that if a 15kVA supply is provided, it would need to be triphasic, and have quoted around 1,000 euros for an upgraded board, additional wiring, etc.  What I am unsure of however is whether the supply currently provided to our boundary would also need to be structurally upgraded, i.e. incurring additional costs with ERDF?

If the answer is no, then 1,000 euros might be worth the absolute certainty of no trip-outs, but if there would be additional costs on top, I'd rather just manage with the 12 kVA originally planned and burn more logs on the woodburner.  Can anyone help or advise?  [:D] 

   

[nomoss]

I am sure ERDF costs will be incurred, the amount of which will depend on whether three phase is available at/near your property boundary, and the works necessary to connect a three phase supply to replace the existing single phase supply.

I think the only way you will get a definitive answer will be to make a demande de raccordement to ERDF, which can be done via their website https://connect-racco.erdfdistribution.fr/prac-internet/login/

 

 

[BJSLIV]

Wouldn't it be easier to install a délesteur?.

It forms a part of the distribution board.

When the system is overloaded it disconnects the lower priority circuits such as bedroom heaters, until the load reduces, hence avoiding the main trip cutting out.

[Hereford]

A délesteur is what we have and it works a treat. I would have posted earlier but could not remember the name!  It was suggested by the electrican who wired the house.

We have 12 electric radiators, an "all electric" house (no gas even for cooking), a dishwasher etc etc. and have a 12 Kva supply. EDF always seem to say that an all electric house needs a 15 supply but at least in our size of house you don't.  We only use our wood burning stove for fun on, say, a week-end in winter - our radiators are quite capable of heating the house.  We have cheap(er) electricity at night so normally run the dishwasher then and heat the water in the ballon.

We do still get the occasional trip cutting out but always in connection with thunderstorms never our fault.

Hope this helps.

H.

[mint]

Hereford, can you please read the PM which I am going to send you?

[suein56]

[quote user="BJSLIV"]Wouldn't it be easier to install a délesteur?. [/quote].

Totally agree. TBH I thought they were obligatory in all new installations today.

Although the final decision might depend on the size of your new property.

Certainly a positive and cheaper option to talk about with your electrician.

Don't forget that there is a built in extra amount available to you over-and-above your rated supply value. It is quoted as being 10% but I think it might be more than that. Let me explain via what happened to us.

When we had a problem - nothing wrong with the installation in the house, the problem was EDF was not supplying enough voltage - our electrician tried to get out 9KW supply to trip out by switching every heater to max (we have 8 in a well insulated house) last December. That didn't work so at the second attempt we had all the heaters going full blast, the chauffe-eau on forced 'on' and I had to boil water in the kettle all at the same time. That made the trip switch close with a bang. I believe we were well over 11KW in a supposedly 9KW supply.

Edit : Have sent you a pm.

Sue

[Théière]

On a new build the size of the supply may also have a bearing on the insulation level of the property, Passivhaus levels of insulation require very little additional heating. Use of ordinary electric radiators would again require a bigger supply than heat pumps.

Voltage optimisation units shouldn't be over looked either as they can save around 20% of your electricity bill.

[Hereford]

Sweet:  will reply to PM in  a minute!

 Edit:   Théière:  what is a "Voltage optimisation unit" please - anything that can cut consumption would be a help with pries going up. Can it be fitted o an existing system?

[Daft Doctor]

Thanks for all that.  Seems a délesteur may be the answer, makes a lot of sense.  they are approx 200 euros in Leroy Merlin for a good-un. 

Aside from that, I was scouring EDF's website regarding increasing the puissance of the raccordement.  It seemed to suggest that if you had 12kvA monophase already then you could have it increased to 18kvA monophase.  Not sure if that's true for very recent installations. 

[Théière]

Maybe, but maybe only if you increase the size of the incoming cable.  Insulation, insulation, insulation, that's where the savings are to be made.

[Daft Doctor]

Hi, by way of giving some information back to fellow forum users, I thought I would update you on this thread.

Regarding the supply to the boundary, I have been told by ERDF that all mains network supply is now triphase, so no upgrading was required to the boundary.  There was however a need to upgrade the inbound wiring from the coffret and the distribution board itself, but that was all.

On the subject of délésteurs, I was advised that the spec for our new house included one, but even they can only do so much.  If there is a large shortfall in available kW vs demand, the non-prioritised circuits constantly compete with each other for available power, so none works effectively.

After taking independant electrical advice we have opted for triphase as recommended.  Our house is being built to current BBC standards, so hopefully it will prove reasonably efficient.  [:D] 

[Wilko]

Like Hereford I'd like to know " Théière: what is a "Voltage optimisation unit"

Cheers

W

[BJSLIV]

Presumably something like

http://www.vphase.co.uk/How-It-Works

Sounds a bit like snake oil to me. But I suppose it all depends how much they cost.

[Théière]

Exactly like that BJSLIV. No not snake oil, and it's more to do with how much electricity you use than how much they cost, high consumers will save most, low consumers may only break even after a few years.  That will make a difference as OP is upgrading to 3 phase and a bigger incoming supply, mind you balancing the phases is probably more important for saving money, whereas I look for ways to reduce my electrical usage and have reduced the supply to our house from 12kw to 9kw through the use of energy saving pool pump, LED lighting and soon I hope some solar for hot water.