Installing 3 Phase supply to new 5/6 Bed house

[dmelec]

Been asked by a customer to quote for a 3 phase 100amp supply to his new build 5/6 bedroom house. His meter by the front gates 135-150m from house. Cable will be buried in ducts, i've done some working out myself (long time since i've had to do this). Using a 70 degree thermosetting cable its coming up at 50mm. Just wondered if anyone had a website or companies I could check by calculations just for my peace of mind.

Thanks

 

[Octopus]

Where is the DNO supply?

 

[Darkwood]

Been asked by a customer to quote for a 3 phase 100amp supply to his new build 5/6 bedroom house. His meter by the front gates 135-150m from house. Cable will be buried in ducts, i've done some working out myself (long time since i've had to do this). Using a 70 degree thermosetting cable its coming up at 50mm. Just wondered if anyone had a website or companies I could check by calculations just for my peace of mind.

Thanks

You have a website here you are writing on that can check your calc's, if you wouldn't mind posting up your calc's I'm sure members will be happy to confirm them or if needed, point out any errors.

 

[Simlec]

What are you protecting this SWA with? as 50mm by my reckoning is too small and whats your Ze?

 

[UKMeterman]

Ask the customer to get a quote for the DNO to provide a supply to the property itself based on the customer digging the trench for the DNO and also explain to the customer how your quote will be cheaper, the supply may perform better and less liablity on the customer.

 

[rich.250]

From experience, I would expect the cable to be in the range of 95-120mm at that load and distance.
Volt drop being the reasoning.
As it would be a sub main I would try to keep volt drop to 1% so you don't have to massively oversize your final circuits.

 

[dmelec]

I was going to install a

Hager - 100 Amp ​

TP & N Switch Fuse HRC. So will be protected by BS88 Fuses. The electricity board are install Incoming head in the next couple of weeks. They charge £55 per meter thats why client wants me to run sub main from front of property to house​

 

[davesparks]

I was going to install a

Hager - 100 Amp ​

TP & N Switch Fuse HRC. So will be protected by BS88 Fuses. The electricity board are install Incoming head in the next couple of weeks. They charge £55 per meter thats why client wants me to run sub main from front of property to house​

£55 per meter for a new supply? That's pretty damned cheap!

Or did you mean £55 per metre?

 

[Simlec]

I was going to install a

Hager - 100 Amp ​

TP & N Switch Fuse HRC. So will be protected by BS88 Fuses. The electricity board are install Incoming head in the next couple of weeks. They charge £55 per meter thats why client wants me to run sub main from front of property to house​

So as post #4 with a 100amp BS88.
£55 per meter not a bad price.

 

[Leesparkykent]

Is that £55 a meter digging their own trench?

 

[dmelec]

Is that £55 a meter digging their own trench?

No thats with client digging his own trench

 

[Leesparkykent]

No thats with client digging his own trench

You could probably save your customer a few grand installing it for them then. So you want to provide them 100A per phase at the house? Is a TNCS supply being installed? Knowing the Ze would be a great advantage to base your calculations on as 100A bs88 fuses aren't going to give much room to play with where earth fault loop impedance is concerned at that length.

 

[dmelec]

You could probably save your customer a few grand installing it for them then. So you want to provide them 100A per phase at the house? Is a TNCS supply being installed? Knowing the Ze would be a great advantage to base your calculations on as 100A bs88 fuses aren't going to give much room to play with where earth fault loop impedance is concerned at that length.

Thinking about it now, would only need 80amp per phase. The board will be installing a TN-C-S supply so can only assume that it will be 0.35 or below.

 

[dmelec]

Thinking about it now, would only need 80amp per phase. The board will be installing a TN-C-S supply so can only assume that it will be 0.35 or below.

Was planning on running a separate earth with SWA armoured cable.

 

[davesparks]

Was planning on running a separate earth with SWA armoured cable.

Why run a separate earth?

 

[dmelec]

Why run a separate earth?

Just easier to terminate

 

[Martin Kerr]

That's some house that needs 80a per phase?

 

[dmelec]

That's some house that needs 80a per phase?

Its a big 5/6 bed house, with a few outbuildings. 80 amps is probably a slight overkill haha

 

[davesparks]

Just easier to terminate

How is it easier to terminate?

Do you really think that laziness is a good basis for design over any technical or regulatory considerations?

 

[dmelec]

How is it easier to terminate?

Do you really think that laziness is a good basis for design over any technical or regulatory considerations?

Not sure how this wouldn't meet any technical standards as i would run a 4 core armoured with a sufficient separate earth?