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J.C.E

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Been asked to make previsions for elec shower in a future outbuild in garden of house I am starting to rewire tomorrow.

The house itself will be heated by central heating- all lights led etc just 1x induction hob then a fan oven +MW. so no excessive load in the house.

Head is 100a SP in external meter box- and c/u in house is >3m so will need to fit a switch fuse isolator switch in the external meter box then 25mm 3c swa from box to c/u.

My question is for the outbuilding supply- theres no space in the meter box for a 2nd switch fuse isolator for the outbuilding so will have to come off of an upfront mcb in the house c/u. But if there wanting like a 9kw shower plus a handful of sockets/lights/heater down there- thats looking at 25/35mm 3core at a 35meter run- which i think is pretty excessive.

1)Has anyone ever fitting a shower at such a distance in for example an outbuilding
2)does the isolator for the house >3m swa tails need to be fused or can it just be a 100a dp main switch? (i think the answer to my question is yes as I can't rely on the dnos mains head fuse- but space looks tight and I know them wylex fused isolators are quite bulky!)
 
I'd fit an rcbo off the existing board, less faff and switchgear. Plus one point of isolation, for the cable size you need to design the final demand for the outbuilding and size from there.
 
Just a thought, can you not fit another surface meter box adjacent, split tails at origin, conduit between the 2 boxes and fit your switch fuse etc in box 2.?
 
I'd fit an rcbo off the existing board, less faff and switchgear. Plus one point of isolation, for the cable size you need to design the final demand for the outbuilding and size from there.

would do an upfront mcb (as will be running in swa) then have the rcd protection at the local c/u in the outbuild
 
Could you fit a small cu in the meter box and use BS88 fuse carriers mcb's instead? One to the house cu and one with the armoured glanded off?
 
for the switch fuse for the out building/shower. Is a builder involved with the job?

yes but shells all built now (his sparks broke his foot) so I got the job
(his crap temp supply- on the other side of meter box (see photo)

If I get rid of the old meter at the bottom and get the client to get a new small digital meter in place of the big dial meter I can probaly squeeze a 100a switch fuse iso in there and 25mm to c/u in house

then a upfront 50a mcb in the house c/u- and 16mm out to the outbuilding

electric shower in outbuilding IMG_0397.JPG - EletriciansForums.net
 
yes but shells all built now (his sparks broke his foot) so I got the job
(his crap temp supply- on the other side of meter box (see photo)

If I get rid of the old meter at the bottom and get the client to get a new small digital meter in place of the big dial meter I can probaly squeeze a 100a switch fuse iso in there and 25mm to c/u in house

then a upfront 50a mcb in the house c/u- and 16mm out to the outbuilding

View attachment 36914
would take the builder about half an hour to cut in a recessed box and cost about £30 to buy.with this you could house a switch fuse for the house and another for the outbuilding. In the existing you could install something like a rec 2 for a single point of isolation. Much better than having to run the SWA internal and also having the distribution circuit on a circuit breaker where you will struggle to achieve any discrimination... just my thoughts.
 
would take the builder about half an hour to cut in a recessed box and cost about £30 to buy.with this you could house a switch fuse for the house and another for the outbuilding. In the existing you could install something like a rec 2 for a single point of isolation. Much better than having to run the SWA internal and also having the distribution circuit on a circuit breaker where you will struggle to achieve any discrimination... just my thoughts.
like this idea lee thanks!
going to ask the builder to cut a 2nd meter box in and run 2x 32mm pipes between.

then fit a 100a rec switch after the meter- then into a henley (in the 1st meter box)

then 2 sets of 25mm tails through the pipes into the 2nd meter box

hopfully 2x of these will fit side by side:
Wylex 100A Domestic Switch Fuse Unit - http://www.screwflix..com/p/wylex-100a-domestic-switch-fuse-unit/5290J?kpid=5290J&gclid=CM6_4P3cytQCFc2d7QodAP0FJg&gclsrc=aw.ds&dclid=CJHY__3cytQCFWmnUQodOrQIRw

have a 63a isolator with 35meters of 16mm going to the future outbuilding
and a 80a isolator with 10meters of 16mm supply the house c/u
 
like this idea lee thanks!
going to ask the builder to cut a 2nd meter box in and run 2x 32mm pipes between.

then fit a 100a rec switch after the meter- then into a henley (in the 1st meter box)

then 2 sets of 25mm tails through the pipes into the 2nd meter box

hopfully 2x of these will fit side by side:
Wylex 100A Domestic Switch Fuse Unit - http://www.screwflix..com/p/wylex-100a-domestic-switch-fuse-unit/5290J?kpid=5290J&gclid=CM6_4P3cytQCFc2d7QodAP0FJg&gclsrc=aw.ds&dclid=CJHY__3cytQCFWmnUQodOrQIRw

have a 63a isolator with 35meters of 16mm going to the future outbuilding
and a 80a isolator with 10meters of 16mm supply the house c/u
sounds good to me.
 
Why is the off peak supply connected to the normal supply like that? Seems a waste of a cable!
 
Personally, I would consider not putting one of them 'instant' heat shower in the outbuilding.
Instead, have a look at one of the smaller unvented direct hot water tanks (Megaflo, etc) with an immersion heater. A 70litre or 125litre tank should be plenty big enough.
Your electrical current requirement for the shower then plummets to 3KW. Its also easy then to add other hot water items, like a wash-basin.
 
Why not use a smaller switchfuse like a KMF unit, if the meter gets changed for a digital one you might get two in the same meter box.


I'm curious as to what people would think about having only one distribution circuit which feeds both the house and the outbuilding?
 

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