springcrocus
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I have been asked to provide an estimate to lay in the supply for a proposed hot tub in an existing customers back garden but they haven't yet chosen their new tub so manufacturers requirements are not available. I asked them, "How long is a piece of string" but the answer was, "Just give us a ballpark figure". Great. They also want to festoon the garden with a load of lighting.
Source is TNC-S with 100A fuse (someone's already pinched the seal) and current max demand about 50A. Hot tub is most likely going to be class II and will be filled by hand-held hosepipe so no bonding requirements that I can see and the tub will probably be a 6-8 person size.
I'm thinking split the tails into Henleys /ISCOs, 60A switch fuse, then 10mm SWA to IP65 CU (no shed to put it in) with two ways, out again with 10mm SWA to rotary isolator. The total run is about 25 metres and my best guess for the hot tub load is about 32A.
Now, three choices. If the hot tub goes onto wooden decking, I could use the TNC-S earthing with no real problems. If it goes on the ground, TT might be better but because there is no bonding required I could also use the TNC-S earthing supplemented by a rod near to the hot tub if I can get the resistance down low enough.
I would be grateful for anyones thoughts on this. I don't want to over-engineer this and lose the customers confidence because it's too expensive, nor do I want to underprice and end up way out of pocket.
Source is TNC-S with 100A fuse (someone's already pinched the seal) and current max demand about 50A. Hot tub is most likely going to be class II and will be filled by hand-held hosepipe so no bonding requirements that I can see and the tub will probably be a 6-8 person size.
I'm thinking split the tails into Henleys /ISCOs, 60A switch fuse, then 10mm SWA to IP65 CU (no shed to put it in) with two ways, out again with 10mm SWA to rotary isolator. The total run is about 25 metres and my best guess for the hot tub load is about 32A.
Now, three choices. If the hot tub goes onto wooden decking, I could use the TNC-S earthing with no real problems. If it goes on the ground, TT might be better but because there is no bonding required I could also use the TNC-S earthing supplemented by a rod near to the hot tub if I can get the resistance down low enough.
I would be grateful for anyones thoughts on this. I don't want to over-engineer this and lose the customers confidence because it's too expensive, nor do I want to underprice and end up way out of pocket.