electric shower in outbuilding

[J.C.E]

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!)

 

[J.C.E]

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.screwfix.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

 

[Leesparkykent]

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.screwfix.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.

 

[freddo]

Why is the off peak supply connected to the normal supply like that? Seems a waste of a cable!

 

[Taylortwocities]

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.

 

[davesparks]

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?

 

[Toneyz]

What about a 80A 3 phase switch-fuse in another meter box next to one with meter/cut out or if you think that after diversity the demand will be no more than 50A from house consumer unit.

 

[davesparks]

What about a 80A 3 phase switch-fuse

I can kind of see where you're going with this, but I'm not sure you'll get one small enough to fit in a meter box sensibly.
Plus I don't like the idea of a metal switchfuse in a meter box which doesn't really provide much in the way of waterproofing

 

[Taylortwocities]

Where's the over current protection for that bit of white T&E cable. I can only see the service fuse..

 

[Toneyz]

I can kind of see where you're going with this, but I'm not sure you'll get one small enough to fit in a meter box sensibly.
Plus I don't like the idea of a metal switchfuse in a meter box which doesn't really provide much in the way of waterproofing

100A Eaton Glasgow (reduced fuse size) but all depends on if after diversity the outbuilding can come off house consumer unit on 50A mcb

 

[davesparks]

100A Eaton Glasgow (reduced fuse size) but all depends on if after diversity the outbuilding can come off house consumer unit on 50A mcb

In my xperience they go rusty rather quickly in damp environments like this.

I thought when you said TP switchfuse you were suggesting using the L1 fuse for the house and the L2 fuse for the outbuilding, I can't see why you'd want a TP one otherwise on a single phase supply.

 

[Toneyz]

In my xperience they go rusty rather quickly in damp environments like this.

I thought when you said TP switchfuse you were suggesting using the L1 fuse for the house and the L2 fuse for the outbuilding, I can't see why you'd want a TP one otherwise on a single phase supply.

TP and switched N and yes fuse for L1 and L2 I take the point of if in a damp environment .I think Legand do a IP enclosure with din rail and have DP switches and fuse holders could be an idea

 

[davesparks]

TP and switched N and yes fuse for L1 and L2 I take the point of if in a damp environment .I think Legand do a IP enclosure with din rail and have DP switches and fuse holders could be an idea

Personally I wouldn't be trying to reinvent the wheel, KMF switchfuses fit nicely in a meter box alongside the meter etc, so will be fine with two in an empty meter box.

 

[J.C.E]

the wylex amd 3 switch fuse isolators litterally just fit side by side!!!
enough room at the top to have a tails gland and make the swa off at the bottom

 

[davesparks]

the wylex amd 3 switch fuse isolators litterally just fit side by side!!!
enough room at the top to have a tails gland and make the swa off at the bottom

Again they are going to be painted metal which is not suitable for the environment of a meter cabinet, it will rust.

 

[Toneyz]

Again they are going to be painted metal which is not suitable for the environment of a meter cabinet, it will rust.

Sorry I thought that I replied to your concerns regarding rust I thought I posted back perhaps Legrand IP enclosure with main switch and fuses