Supply cable to a new dwelling

[rippa700]

I'm after a bit of guidance. I am building a holiday let on my proprty and already have a spare meter on my side of the main supply meter. From this meter to the new building is about 50m and I have burried plastic trunking for the main supply. I will have the consumer unit in the new building so my question is what size cable to run from my meter to the new consumer unit? I'm guessing 25mm2 T&E. Any comments much appreciated.
Thanks

 

[holmslaw]

..

 

[Chri5]

Impossible to advise, what are the electrical loadings?

Size of building ?

(number of rooms, bathrooms, kitchens)

Heating Gas or electric (if electric type and vol)

Water heating

SHower type

Cooking type

Lighting type and vol

Likely socket and circuits

etc.


PS 25mm TE

Cabling will need to be SWA

PPS Could you post a picture of the existing mains in service and the metering units you mentioned ?

 

[rippa700]

Hi Chri5
Thanks and sorry - should have been more specific...
4 bedroom holiday let. VERY well insulated
Electric immersion as back-up to solar hot water 6Kw max (2 x 3 Kw)
Usual A rated fridge
Electric oven and hob - nothing fancy
Eco-lighting throughout
Not many appliances - Kettle, TV and sockets in each room
Biomass heating

Q. Why SWA cable if inside a 50mm polypie duct?
I'll try and get a picture of the mains service. It arrives at the main import meter then serves 4 private meters and this new one would be the 5th - the meter is installed and had been used for a dairy but is not vacant.
Thanks
Ian

Impossible to advise, what are the electrical loadings?

Size of building ?

(number of rooms, bathrooms, kitchens)

Heating Gas or electric (if electric type and vol)

Water heating

SHower type

Cooking type

Lighting type and vol

Likely socket and circuits

etc.


PS 25mm TE

Cabling will need to be SWA

PPS Could you post a picture of the existing mains in service and the metering units you mentioned ?

 

[Taylortwocities]

No washing machine, tumble dryer, dishwasher?

I wouldn't let it without at least two of those!

re

Q. Why SWA cable if inside a 50mm polypie duct?

A. Because polypipe does not give the mechanical protection needed for any buried PVC-type cables.

The cable will need its own mechanical protection, buried direct in the ground or in a service duct. For domestic/general installations that means SWA cable.

The loading is a critical factor. Volt drop over 50metres can be significant, even for 25mm² conductors.

PS, can you actually get 25mm 6242Y T&E?

 

[1john]

surely you cant, can you imagine trying to clip it.

 

[Taylortwocities]

2 inch nail through the middle, that should hold it

 

[rippa700]

No tumble dryer or washing machine - possibly a dishwasher which falls into 'usual appliances'. There is a laundry room nearby serviced by a different supply.

No washing machine, tumble dryer, dishwasher?

I wouldn't let it without at least two of those!

re

Q. Why SWA cable if inside a 50mm polypie duct?

A. Because polypipe does not give the mechanical protection needed for any buried PVC-type cables.

The cable will need its own mechanical protection, buried direct in the ground or in a service duct. For domestic/general installations that means SWA cable.

The loading is a critical factor. Volt drop over 50metres can be significant, even for 25mm² conductors.

PS, can you actually get 25mm 6242Y T&E?

 

[ban-all-sheds]

I am building a holiday let on my proprty

When you applied for Building Regulations approval what did you say would be the way you would comply with P1?

my question is what size cable to run from my meter to the new consumer unit?

The size that the competent electrician you are using determines is needed.

I'm guessing 25mm2 T&E.

Stop guessing about things you don't understand, and leave it to your electrician who does.

Any comments much appreciated.

Leave it to your electrician.

Thanks

NP. --> CLICK <--

 

[xr4x4]

Thanks

NP. --> CLICK <--

Only click on this if you want to thank the f-wit.

 

[electronicsuk]

Thanks

NP. --> CLICK <--

Only click on this if you want to thank the f-wit.

Maybe not approached in the most personal manner, but the information was all correct. rippa700, I admire your efforts to save a few quid, but if you think that it's OK to bury T+E over a 50m run in plastic duct, then you probably don't have the necessary knowledge to undertake this work.

It's good that you came here to ask the right way to approach the job rather than ploughing straight into it and making silly mistakes, but there's no way we can provide enough information here to allow you to safely install a new submain and distribution to serve an entire holiday let when your questions seem to suggest you may lack much of the basic underlying knowledge. While asking questions will get you so far, what about the questions you haven't asked? What about volt drop, earth loop impedance, earthing of the remote dwelling, inspection & testing?

You'd do far better to involve an electrician right now, and make arrangements with him that will allow you to do much of the legwork, while he can design the installation and make sure your work is compliant with BS7671.

 

[ajrobb]

What odds can I get that 25mm² SWA is going to be the minimum accepted between buildings with meter and CU?

I can't see the supply type. If it is TT, should the earth rod be local to the CU rather than local to the remote meter?

I don't imagine this is worth DIY.

 

[rippa700]

Thanks Electronicsuck - appreciate your response. I fully planned to get a sparky in to do the work. 2 reasons I asked - one is that I have other work going on (installing a 3-phase for a wind turbine) and while the trench is there through our concrete farmyard I wanted to put the cable in. I asked 2 electricians about it and got 2 answers worryingly different and both very sure. Thought I'd ask here to see what sort of response I'd get. The power distribution guys were here all day and advised 25mm SWA after a chat but don't worry - I would not DIY this for a holiday let - too big a risk on insurance if nothing else.
The bit about T&E was because I was told to put in the polypipe duct and assumed therefore that it would be T%E and the duct isn't really needed for armoured cable.
Thanks for the answers and I'll go back to plastering the straw bale walls - something I know more about.

Maybe not approached in the most personal manner, but the information was all correct. rippa700, I admire your efforts to save a few quid, but if you think that it's OK to bury T+E over a 50m run in plastic duct, then you probably don't have the necessary knowledge to undertake this work.

It's good that you came here to ask the right way to approach the job rather than ploughing straight into it and making silly mistakes, but there's no way we can provide enough information here to allow you to safely install a new submain and distribution to serve an entire holiday let when your questions seem to suggest you may lack much of the basic underlying knowledge. While asking questions will get you so far, what about the questions you haven't asked? What about volt drop, earth loop impedance, earthing of the remote dwelling, inspection & testing?

You'd do far better to involve an electrician right now, and make arrangements with him that will allow you to do much of the legwork, while he can design the installation and make sure your work is compliant with BS7671.[/quote]

 

[electronicsuk]

The bit about T&E was because I was told to put in the polypipe duct and assumed therefore that it would be T%E and the duct isn't really needed for armoured cable.
Thanks for the answers and I'll go back to plastering the straw bale walls - something I know more about.

Maybe not necessary, but you and your electrician will be glad it's there, as it means you can backfill the trench now and worry about pulling the cable in when you're ready.

FWIW, you should easily be able to achieve 10kW with 25mmsq @ 50 metres, if not more. It may even just be within the allowable 3% volt drop with 16mmsq, although earthing arrangements at the supply origin may be the limiting factor.

 

[ajrobb]

At 1.8 mV/A/m voltage drop for 25mm² cable, you should be able to supply 76A over 50m within the 3% voltage drop for lighting. I may be ignorant, but I'm a bit worried that the circuits required for a 4 bedroom cottage are going to total much more than 76A.

• 32A cooker appliances
  32A downstairs sockets (100m² floor area)
  32A upstairs sockets
  16A immersion heater
  6A downstairs lights
  6A upstairs lights

124A total
intrigued