Installation of Garden Spa (Hot Tub)

[Johnv307]

I am installing a Garden Spa. Need a 35 amp supply (10mm Twin and Earth). My existing c/u is 100 amp split load with 25mm tails. The RCD is 63 amp 30ma trip. I already have sauna (6kw), cooker and immersion heater on the RCD. The Hot Tub will overload this. Only have domestic lighting and freezer not protected by RCD. Though about putting in a second c/u with 63 amp RCD and 40 amp mcb just for Hot Tub. This would mean putting 100 amp junction box in the tails. Other alternative is to uprate existing RCD. Any suggestions as to best way forward?

 

[ban-all-sheds]

Whichever way you go, note that you might need to use SWA not T/E - how is the cable to the spa being installed?

 

[Johnv307]

Proposing to lay it underground in a conduit and connect direct to the Spa.

I could use SWA to avoid using a conduit. I assume 10mm SWA is freely available. Any thoughts if a 2nd c/u is the better way forward to avoid a heavy load going through the existing c/u. I already have a DP isolator between the meter and the c/u so putting a 100 amp junction box in is not a problem.

 

[plugwash]

if you are using SWA (which you should for outside runs) then i would say use a small metal CU to give you somethign decently solid to gland the SWA to

something like
http://www.tlc-direct.co.uk/Products/CMM4slash80N.html

 

[Lectrician]

Cooker on the RCD?? Not usually required to be protected by an RCD.

I would propable go Plugs route, but also move the sauna across to the new 2way board. Takes 2 huge loads off of the other board.

 

[ban-all-sheds]

Proposing to lay it underground in a conduit and connect direct to the Spa.

Unless you can guarantee a watertight conduit run (which means metal, with welded joints), you shouldn't use T/E, as it's not designed for permanent immersion in water.

I could use SWA to avoid using a conduit.

Yup.

I assume 10mm SWA is freely available.

No - you have to pay for it.

 

[Johnv307]

OK I'm going 10mm SWA to the Spa with a second c/u which will take the Spa and the Sauna, unless anyone says otherwise.

 

[ban-all-sheds]

Sounds fine - as far as it goes. Use 3-core SWA, so you aren't reliant on the integrity of the armour earthing for the cpc (but do earth the armour as well).

Is the 2nd CU at the house, or out by the spa/sauna (if those 2 are adjacent)?

Also - I'm a little concerned about your "connect direct to the Spa" - what about local isolation?

You might like to read this about conecting up spas:

//www.diynot.com/forums/viewtopic.php?t=7884

 

[AdamW]

Assuming the spa isn't attached to the house, you will need to bury the SWA to a minimum depth. Not sure what it is myself, but it would certainly be deep enough that no-one hits it with a spade when digging the garden.

 

[plugwash]

450mm is reccomended by the regs for private land

i would say generally round this off to half a meter to be on the safe side

make sure nothing sharp can stick in the cbale by bedding it in sand if nessacery

finally you should put warning tape in about half way down the trench (where it won't get disturbed often but will wanr you in plenty of time before hitting the cable

 

[Johnv307]

C/u will be in the house by the incomming and main c/u. It will be about 4 mtrs to Spa and about the same to the Sauna. The 6mm to the Sauna is already run. All internal. The swa has to be run as does the build of the internal sauna. Thought about local isolation. Understand that this should be at least 2 meters away from the Spa and as the c/u is only 4 meters, although it is in the house was going to have the mcb and c/u as the isolation. For max safety I could put an external switch on the wall. Do you know of any waterproof switches/isolators which can take swa and are rated at 45 amp?

 

[ban-all-sheds]

Other makes are available - Klockner-Moeller are pretty good.