4mm SWA or 2.5

[yellowvanman]

Customer has a number of outbuildings the furthest of which is 60m from sub main. Planning to run just 1 cable out to the buildings in a radial, in each outbuilding will be a double socket and a light (using a switched fuse). Unlikely anything of any significance will be used (in terms of power) - just the odd portable tool.

Tempted to run 2.5mm SWA (rat proof) on a 16A MCB. Considering 4mm is 50% more expensive. Any thoughts on this? In 2 minds!

 

[Octopus]

Offer the customer the choice and let them decide on the amount they want to pay!

Personally I'd recommend the 4mm being better if demand changes.

 

[i=p/u]

same boat myself, have to provide power to a shed for tumble dryer , washing machine and a light, was thinking 2.5 t&e from board to to attic, then 2.5mm high tuff out to shed as i only have 15m and is about 25m run....

on a 20A breaker

or just buy 4mm and have no joints, but my gargae is building up with scrap ends

 

[Rappid]

Just done a quick check, 4mm.

Voltage Drop Calculator

 

[i=p/u]

4mm then... i did plan to put small board out there but as jobs went on im at the end of spending and no more from client...

 

[KFH]

I always recommend bigger if the load is variable in any way, it always seems to increase and I have been caught by this a few times. The cost of installation is high especially if a trench needs digging and will cost even more if another cable has to be run in the future. The customer has to decide though.

 

[Rappid]

4mm then... i did plan to put small board out there but as jobs went on im at the end of spending and no more from client...

Sorry i=p/u I was very slow in responding to the OP which works out at 4mm, Your job should be ok on 2.5mm.

 

[Guitarist]

same boat myself, have to provide power to a shed for tumble dryer , washing machine and a light, was thinking 2.5 t&e from board to to attic, then 2.5mm high tuff out to shed as i only have 15m and is about 25m run....

on a 20A breaker

or just buy 4mm and have no joints, but my gargae is building up with scrap ends

If you are planning to supply a 2-way CU, then I'd just go in 2.5mm hi-tuff from the board. Your cpc will be the same size as your line, thus dispensing with a joint and the adiabatic equation. At just over a quid a metre, it's not going to break the bank. If you are expecting to run the td at the same time as the washing machine then I think your vd may be a problem.

 

[i=p/u]

works out at 7.8vd on guesstimate of 2kw each . then the lighting is over its 6.9v... 4mm seems the best on 20A breaker

 

[sedgy34]

I've got a job to price too 10 mm swa going up to shed 60 meter run 32amps

 

[Guitarist]

I always find it odd that you design your circuit vd based on expected load, yet someone could move in a year later and max out the sockets and add floodlights to the lighting circuit.

 

[i=p/u]

house could blow away too...

 

[Guitarist]

house could blow away too...

It could.... though unlikely, unless you have a big bad wolf with a lot of puff....

 

[i=p/u]

sorry for the ****ty reply, what wouuld you suggest guitarist,

i propose to come down the wall with swa in 25mm white pipe about 6inches below the block paving and up and under into shed... but would like to to of covered plumbers pipes aswell..... in the one trunking/separated .....

 

[Guitarist]

sorry for the ****ty reply, what wouuld you suggest guitarist,

i propose to come down the wall with swa in 25mm white pipe about 6inches below the block paving and up and under into shed... but would like to to of covered plumbers pipes aswell..... in the one trunking/separated .....

My comment was merely that we design our VD based on the expected load which could allow, say, a 2.5mm cable. Then someone hooks up a few heavy current devices a year down the line and suddenly the system is safe, but the calcs would be way out for VD, so you install 4mm. So, what is the answer? Design all garage supplies, expecting someone to plug in 2 large fan heaters every cold day, regardless of the fact that they may just want to charge their mobility scooter?
Anyway, back to your job.... I always try to take my swa through ducting of some sort (usually plastic water supply pipe). Why do you want to sort out the plumber's pipe? Would he be concerned about making your cable look nice?