Electric shower in outbuilding 55m from consumer unit

[Tom Wallington]

Hi we've built a cabin in our garden and we're using it as a second home, because every now and then the house will flood and we have to move out! It's an old listed mill building and there is nothing we can do to fix or stop the problem other than to rebuild the house. So we want all the mod cons of the house in the cabin I estimate around 13000w max total with the 9000w electric shower, computer, TV, electric heaters. So I've bought a 63a mcb for the consumer unit in the house, a 55m swa 16mm 3 core, then a 6 way c/u for the cabin, the swa cabin end will be straight into the c/u however at the house end it needs a junction box on the wall outside to a twin and earth 16mm to the c/u inside, my problem is that I can find a 63a junction box there's 60a and below and the 100a ones don't look right as they don't seem to be 3 pole for earth, neutral and live. I don't really know what I'm doing, can someone look this over and tell me if I'm going about it the right way? Thanks

 

[Taylortwocities]

PICTURES please!

But, you do realise that everything you are talking about is notifiable to the local authority. Are you able to convince LABC that you have the required knowledge of BS7671 and the competence to design, install and test the whole thing?
Tom, you've already admitted

I don't really know what I'm doing,

You need to get a qualified, registered electrician on site to look over whet you have done, check it out and make it legal by signing it off as his own work. (good luck with that)..

 

[Silly Sausage]

however at the house end it needs a junction box on the wall outside to a twin and earth 16mm to the c/u inside, my problem is that I can find a 63a junction box

No it doesn't.

 

[telectrix]

here. 101A rating, and not too ugly.

https://www.screwfix.com/p/ip65-ada...mm/18734#product_additional_details_container

however, if you are connecting into T/E, will the cpc be large enough to comply, esp.as a bonding conductor? this is a job for an experienced electrician.

 

[Strima]

What design criteria have you used for your cable selection?

At that length you will struggle due to voltage drop especially as you have lighting to consider.

What's your existing earthing arrangements, Ze, PFC etc?

As you have a shower that means a water service, how is this supplied, type of pipe etc? Is there gas/oil or other services?

 

[Tom Wallington]

We're not going to be wiring it up ourselves, we'll be getting an electrician to do it, but I thought if I work it out first buy all the bits, then the electrician won't have to charge as much! We already have an outbuilding with power on a 32a, I'm just trying to copy that but uping the capacity to 63a is it possible? We'll be wanting to use it for guests as well so two showers could be used at once plus whatever else is on.

 

[Pete999]

Hi we've built a cabin in our garden and we're using it as a second home, because every now and then the house will flood and we have to move out! It's an old listed mill building and there is nothing we can do to fix or stop the problem other than to rebuild the house. So we want all the mod cons of the house in the cabin I estimate around 13000w max total with the 9000w electric shower, computer, TV, electric heaters. So I've bought a 63a mcb for the consumer unit in the house, a 55m swa 16mm 3 core, then a 6 way c/u for the cabin, the swa cabin end will be straight into the c/u however at the house end it needs a junction box on the wall outside to a twin and earth 16mm to the c/u inside, my problem is that I can find a 63a junction box there's 60a and below and the 100a ones don't look right as they don't seem to be 3 pole for earth, neutral and live. I don't really know what I'm doing, can someone look this over and tell me if I'm going about it the right way? Thanks

Tom, probably you won't like what I'm about to post, it's not meant to be having a go at you, but in my opinion, running s supply from a house that you mention is prone to flooding seems rather silly, personally I think you should spend your money more wisely and tackle the problem of the leak that causing your house to flood, can you explain how and why it floods? I see you have already built your "new house" if you are that intent of moving into this "new House" then I would have thought that the Local DNO would be a better option, of course all this is from afar and as we have no eyes on or pictures to view it's very difficult to advice.

 

[Andy78]

Same as you, I've not done any calculations, but I don't think the 16mm will be any good over that distance.

Stop everything you are doing and get a professional in to start at the beginning, the design stage.

 

[Tom Wallington]

here. 101A rating, and not too ugly.

https://www.screwfix.com/p/ip65-ada...mm/18734#product_additional_details_container

however, if you are connecting into T/E, will the cpc be large enough to comply, esp.as a bonding conductor? this is a job for an experienced electrician.

The spec on screwfix says it's rated to 57a is that not the spec?

 

[Spoon]

I'm presuming the mill flooding is a natural flood and not a water leak @Pete999 , but I could be wrong. This is why the OP has the extra building up (I'm guessing) at a higher level, 55 meters away.

OP: Please read @Taylortwocities post #2. You are doing work to a listed building that is notifiable to the local authority. This needs to be done by the book.
Get an electrician in to do the job. If you want to save money, have a word with the electrician about digging the trench for them.

 

[Taylortwocities]

OP: Please read @Taylortwocities post #2. You are doing work to a listed building that is notifiable to the local authority.

Not only that. There is a new circuit, house to outbuilding, a new consumer unit there and several new circuits in the outbuilding itself.
All notifiable work.
Not to mention all of the design, installation and testing requirements....

 

[Spoon]

OP: also just checked.... The below is true. Above the 3%

At that length you will struggle due to voltage drop especially as you have lighting to consider

 

[davesparks]

So we want all the mod cons of the house in the cabin I estimate around 13000w max total with the 9000w electric shower, computer, TV, electric heaters. So I've bought a 63a mcb for the consumer unit in the house, a 55m swa 16mm 3 core, then a 6 way c/u for the cabin, the swa cabin end will be straight into the c/u however at the house end it needs a junction box on the wall outside to a twin and earth 16mm to the c/u inside, my problem is that I can find a 63a junction box

Why an electric shower, why not an unvented hot water cylinder to provide for all of your hot water requirements? This will reduce the power consumption and improve the overall reliability of the installation.
16mm is too small for the load you are planning.
Feeding this via a 63A MCB is not a good plan, there are far better ways to design this installation.

 

[Pete999]

I'm presuming the mill flooding is a natural flood and not a water leak @Pete999 , but I could be wrong. This is why the OP has the extra building up (I'm guessing) at a higher level, 55 meters away.

OP: Please read @Taylortwocities post #2. You are doing work to a listed building that is notifiable to the local authority. This needs to be done by the book.
Get an electrician in to do the job. If you want to save money, have a word with the electrician about digging the trench for them.

You could be correct Spoon, maybe it's me being a skeptic, but without being rude or unkind to the OP, but without knowing the ins and outs, it seems like throwing good money after bad, sorry OP if I'm wrong, I just keep thing why take this route.

 

[telectrix]

The spec on screwfix says it's rated to 57a is that not the spec?

if you look at bottom of spec. it says 5 x 16mm terminals each rated 74A. don't know where the 101A comes into it.