Major supply Upgrade

[mindthegoat]

Hi
This is well outside of DIY, and may be outside the scope of this forum, if there is a better place to ask, please let me know.
I own a campsite and am looking into a major upgrade of the incoming supply, my question relates to pricing from National Grid. I was quoted 6 figures for a 500kVA supply, this would be our own transformer. work requires the addition of a 3 third phase along local supply poles (currently 2 phase into a split phase local transformer), a feed from the nearest pole to the site and supply and fit of a transformer.
We have recently asked for a different quote, half the power @ 240V. This involves the same 3rd phase added to poles and an upgrade of the local pole-mounted transformer. This has come in at considerably less. It occurs to me that the transformer is probably the same and the cabling for the second option may be more expensive. Trying to understand why such big price difference. I wondered if the DNO would prefer to get me to pay for to upgrade the local transformer, which is currently at max capacity, even though my requirements could leave the next transformer at maximum capacity.
I will go back and ask but wondered if anyone here had experience of dealing with DNOs for big upgrades?

 

[binky]

they are a bit of a mystery You can get a third party to quote for the work, with DNO doing final connections I believe. That should work out lower, but simole fact is it's expensive work. Pole transformers start at around £13k, form what little experience I've had with such things.

There is something else you could explore, fitting solar panels, or at least applying to fit solar. They don't like more than 30% backfeed on the transformers, now if any neighbours have solar already, or you fancy fitting some anyway, you are legally allowed to back feed 16A per phase. If the local transformer cannot cope with any additional solar backfeed, it's the DNOs legal obligation to upgrade the transformer free of charge to you. That migt save you the transformer cost, if not the additional cabling.

 

[ProDave]

How big is your camp site?

A normal touring caravan hookup is 16A max 230V so 3.6KVA allowing some diversity, caravan's rarely draw that much and indeed many sites have a lower supply limit, so lets say typical 2KVA max. Do you really have 250 pitches on your site?

 

[Sharpend]

I look after a residential site with 68 full time homes and the park has a supply of 79kva but only actually operates at 40-45kva.

More info on current site arrangements required me thinks? , have you actually used an electrician to assess your needs?

 

[mindthegoat]

Curŕent supply is around 40kVA which includes a large house and 30 touring pitches. For the new project we would like the option of electric heating and cooking. Also need to consider car chargers.
We are also looking into solar and batteries.
Interesting that your usage is quite so low, do you monitor peak loads?

 

[mindthegoat]

How big is your camp site?

A normal touring caravan hookup is 16A max 230V so 3.6KVA allowing some diversity, caravan's rarely draw that much and indeed many sites have a lower supply limit, so lets say typical 2KVA max. Do you really have 250 pitches on your site?

No, considerably fewer but this is for new development, 32A or even 64A per outlet, some car chargers and can't rule out a few hot tubs unfortunately.

 

[mindthegoat]

We are looking at solar and batteries but it seems we are limited to capacity based on our current incoming supply, I didn't realise it was as low as 16A. I don't think there is any other solar connected to the current transformer. The top end supply here would cover heating in the winter but we could use lpg for that.

 

[ProDave]

So you have asked for the "impossible" for a supply upgrade and got your 6 figure quote, which is a good way of saying "don't be silly we don't want to do that"

Now go back to the DNO and see what IS possible for a reasonable sum and see if you can work with what they offer?

Hot tubs, make them wood fired, more fun for the guests and no electricity. Just a few car charging points for you and your guests.

Are you looking to build an additional house as well?

 

[binky]

We are looking at solar and batteries but it seems we are limited to capacity based on our current incoming supply, I didn't realise it was as low as 16A. I don't think there is any other solar connected to the current transformer. The top end supply here would cover heating in the winter but we could use lpg for that.

back feed is liited to 16A unless DNO says you can have higher, but you can install a larger solar array with 16A export limitation. If you are ging to go down this rute, work on the basis of putting a large hole in your bill, rather then trying to effectively go 'off grid' it's a lot cheaper.

As for EVs, you don't have to install fast chargers, or you can put some of those in , but use software to limit charge rates . The ones I've installed that do this work on a first come first served basis, so first car plugged in gets a high rate of charge, later cars get a lower rate, but when first car has charged up, it then feeds a higher charge rate to the next car, etc etc. By doing this I limited the max charge to 50Amps to suit the supply I was connect to.

 

[mort2376]

The other option is to restrict the touring connections. I know of some places that limit to 6a or 10a per socket. This may make your total usage calculations lower. You may be able to apply some diversity factors to the touring connections but as your thinking long term and supplies for hot tubs and car charges you need to allow for these. Hot tubs are only high power use during initial warm up after that its like a hob, the thermostat comes on and off this means that only at very limited times are all the hot tubs likely to demand heat at the same time.

As has been stated above car chargers now can be smartly restricted to analyse your total demand and then control charging accordingly. You also need to look at how you will charge for charging.

I know that some manufacturers through CEF electrical wholesalers will supply chargers for cheaper rates and they look after the charging for use. Could be worth looking at to save some costs.

 

[mindthegoat]

back feed is liited to 16A unless DNO says you can have higher, but you can install a larger solar array with 16A export limitation. If you are ging to go down this rute, work on the basis of putting a large hole in your bill, rather then trying to effectively go 'off grid' it's a lot cheaper.

As for EVs, you don't have to install fast chargers, or you can put some of those in , but use software to limit charge rates . The ones I've installed that do this work on a first come first served basis, so first car plugged in gets a high rate of charge, later cars get a lower rate, but when first car has charged up, it then feeds a higher charge rate to the next car, etc etc. By doing this I limited the max charge to 50Amps to suit the supply I was connect to.

This is interesting, so there are control systems that can disconnect part of the solar array so that on bright days with low on site power usage, there would still only be 16A (or whatever the defined limit was) fed back to the transformer? I have had conversations with several 'experts' in solar generation and have not had this mentioned.

 

[binky]

It doesn't disconnect parts of the array, it limits export by limiting power output at the inverter. It's where batteries come in useful, or heating hot water to store energy that would otherwise be lost.