New supply from transformer mast for 9 separate metres property connections?

[Richard Knight]

Hello,


We purchased a plot of land a while ago and we are trying to establish how we can actually connect into the mains transformer mast which is available on site.


Originally we had 3 options. There was a Scottish power owned cable that we could tap into this would cost £4500.00 to link to just our plot as it would be over 150m distance. Or each plot owner could take their own supply from the mast and have a single 100amp connection which would be metered and then extended using the private cable laid which links it to our plot £1200.00.


Or all the plot owners could chip in together on a communal solution - distribution fuse board?


Scottish power have said that if everyone does one of the first two options then there wouldn't be enough capacity on the transformer mast to supply everyone... So we have asked them to price for the distribution fuse board.


This is what they are pricing for:


We shall install and connect a 400v low voltage three phase cable from the LV pole, install a 9 way DFB, install 9 x 2m x 25mm LSOH cables from DFB to new cut outs, reconnect and energise the existing meter to one of the new cutouts. Our works will include 22m of service cable. All excavation, backfill and reinstatement will be carried out by the customer.


When I spoke to them on the phone they told be that this will give 9 x 60 amp connections (all separately metered) 100 amp cable head into the DFB, the DFB is protected by an 80 amp fuse and then each cutout of the DFB is protected by a 60 amp fuse...


I want to check that that means that all 9 properties can draw of 60 amps at the same time?


They have priced £4500.00 inc VAT for the works, seems quite a lot but I guess these things do cost allot! £458.00 of work is non contestable but the rest could be done by an approved company of a list they gave us... Do people think it's a fair price or should I try and get some further quotes?


Any advice is greatly appreciated!

 

[snowhead]

The chances of all the properties trying to draw 60amps at the same time is about the same chance of winning 1st prize on the Lottery.

Scottish Power are in the distribution business, they'll know that what they are providing will do the job. If it doesn't they'll have to upgrade it at their own expense.

The worst load case would be 3 x 60amp from 1 x 80 amp fuse.

£4.5k is cheap for 9 properties, it can cost £15 to £20k for a single new remote connection

 

[Marvo]

The price sounds good even by my local African standards, I'd accept before they change their minds.

A 60A connection per dwelling should be more than adequate and if they're offering 9 connections then they'll have done the diversity calculations and they'll be happy they can provide sufficient power.

 

[Engineer54]

Is your plot the most central for all 9 DNO supplies to be taken from and what sort of distance is it from the existing DNO supply?? What sort of distances are we talking about from this central panel, (let's call it a Ryefield panel) to the other plots??

 

[Knobhead]

The Ryefield (DFB) board to be protected by an 80A fuse. So that three plots on each phase fused at 60A. Not much by way of discrimination.

What do you think?

 

[Richard Knight]

Is your plot the most central for all 9 DNO supplies to be taken from and what sort of distance is it from the existing DNO supply?? What sort of distances are we talking about from this central panel, (let's call it a Ryefield panel) to the other plots??

The transformer mast is about 4m from the communal metre hut which will house the DFB.

Our plot is the furthest away from the DFB Arround 150m to the consumer box point int the house.

I can upload a site plan showing locations, would that help?

i just want to feel comfortable with the proposed solution, as it's all been very stressfull!

Thanks for the help everyone!

 

[snowhead]

There's one vital bit of information missing.

Are the properties all 5 bedrooms with plans to have swimming pools, saunas etc?

Has anyone done the calcs and costing for the 150mtr cable to your house, the cost of that is going to far exceed the DNO costs for that house.

 

[Richard Knight]

There's one vital bit of information missing.

Are the properties all 5 bedrooms with plans to have swimming pools, saunas etc?

Has anyone done the calcs and costing for the 150mtr cable to your house, the cost of that is going to far exceed the DNO costs for that house.

Hi Snowhead,

Our property is 3 bedrooms and two bathrooms. Low energy everything! Heating is LPG. 60 amps should be plenty considering the planning restrictions. They are Holliday chalets in woodland setting.

Our assumption is that we will run a 25mm 3 core armoured cable from the DFB, roughly 150 metres. I believe this will accommodate 60 amps, this will of course be designed and installed by an electrical engineer we have in mind.

 

[D Skelton]

Our assumption is that we will run a 25mm 3 core armoured cable from the DFB, roughly 150 metres. I believe this will accommodate 60 amps, this will of course be designed and installed by an electrical engineer we have in mind.

What's your max demand? 25mm seems very small for 150m.

 

[Richard Knight]

I'm sure the electrical engineer would tell us if 25mm isn't suitable, I'm not sure on our max load at the moment. Say it was 60 amps... What would be suitable given the distance?

thanks!

 

[D Skelton]

I'm sure the electrical engineer would tell us if 25mm isn't suitable, I'm not sure on our max load at the moment. Say it was 60 amps... What would be suitable given the distance?

thanks!

If it was 60 amps, alot more than 25mm. To limit your VD to roughly 3V, you'd need 150mm conductors. To keep your VD below 3V you're looking at 185mm conductors.

 

[Richard Knight]

Christ sounds expensive. From initial discussion with the electrical engineer he intimated that 25mm would be suitable with a sensible house usage design. We will see I guess :/ . Funny thing is the land owner laid 10mm cable to connect all the properties, we naively didn't see this as a problem when we bought the plot! Lesson learned, hard lesson!

 

[Richard Burns]

To comply with the volt drop requirements at 150m then you would need to be limited to 25A to use 25mm² SWA.
It may be that the electrician designed this with an anticipated diversity for each property to that the expected (average) current would be 25A or less.
The 10mm would have been installed only considering current carrying capacity not voltage drop.

 

[snowhead]

Wrong forum, but have you got the costs for New Water supplies?

And Foul drainage connections or is it Biodigestor?

 

[D Skelton]

I still think 25mm is too small for 150m. I'd certainly consider checking the credentials of this so called 'engineer' as for a 25mm cable to be suitable, and to keep your VD down to roughly 3V your max demand would have to be under 10-11A, highly unlikely for a house.

 

[D Skelton]

To comply with the volt drop requirements at 150m then you would need to be limited to 25A to use 25mm² SWA.

This would allow for no VD at all on any of the final circuits RB

 

[Richard Knight]

Wrong forum, but have you got the costs for New Water supplies?

And Foul drainage connections or is it Biodigestor?

We paid £3000.00 to the development site owner, this was to lay down and connect us into the mains water supply and the electrical mast available on site.

Can of worms... The water supply had issues, there wasn't enough pressure to supply the lodge plots at peek demand times. This has been rectified for other plot owners using a large break tank and pumps... we didn't buy into the system. The development owner wanted another £1200.00 for this. So we have decided to have our own holding tank in the property.

We bought the plot with SEPA consulted and agreed systems...

The system we are going for is a domestic sewage treatment plant, this removes 95% of bacteria where as a septic tank removes just 10% (if I remember correctly those figures are accurate)

All plots have passed percolation tests, apart from ours - the day ours was done the area got record rainfall so was't a fair test. The development owner has paid for all test for other plots... but he is refusing to pay for our re-test. Looks like that will be another £1200.00 for a SEPA consultant to test it and design the system.

Self-building is bloody expensive and stressful! But also very exciting, I hope it's worth it in the end!

 

[Engineer54]

All of which is WHY i asked about the distances involved questions above!! ...lol!!

The other question that should be asked, is how are you (OP) intending to run these supply cables to each plot?? Without knowing the layout, the distances may well need to be in excess of what your planning. Eg, are these cable routes following paths/road or as the crow fly's, crossing the other plots underground?? If the latter, you may need to go deeper than the recommended 600mm (60cm) and be run in heavy duty ducting....

 

[Richard Knight]

Here is the cable calculation for 10mm cable at 150m - he intimated it would give 25 amps at 5% VD.

The above doesn't make much sense to me.

 

[Richard Knight]

All of which is WHY i asked about the distances involved questions above!! ...lol!!

The other question that should be asked, is how are you (OP) intending to run these supply cables to each plot?? Without knowing the layout, the distances may well need to be in excess of what your planning. Eg, are these cable routes following paths/road or as the crow fly's, crossing the other plots underground?? If the latter, you may need to go deeper than the recommended 600mm (60cm) and be run in heavy duty ducting....

I'm not laying any cable for anyone else... just our own plot.

There is a 10mm cable laid in at the moment, which isn't of any use to us - maybe a temporary supply for plugging in tools - that would be useful and save on petrol with the generator! Max load would be 25 amps as suggested by the engineer and calculations above.

Not crossing any plots, following the road. It has been measured countless times. 115m to the edge of the plot, then another 30m to the entry point in the dwelling.