Sauna logistics

[Russanthonypowell]

Hope to bottom this out here
from the main consumer unit at home I have a 80 amp RCCB with a B40 mcb connected to this I have a 16mm SWA going to a barn approx 15m away inside the barn I have another CU with 3 circuits a B32 mcb for 8 sockets (rarely used) a B6 for lighting and a B40 from which a 10mm SWA powers a static caravan.
I am extending the barn and want to include potentially a 6 KW sauna heater and potentially run a 6 KW shower,
Main question is the 16mm from the barn to the house sized ok for my plans.
I may have to put a sketch of the configuration as i do not think I have described it well enough, basically I can upgrade everything in the barn mcbs etc,
the sauna I have provisioned 10mm TE cable and the shower 6mm TE (i may have to go for a lower KW shower.
Hope i can get some help here....

 

[ericmark]

16 mm² with a 40 amp overload seems OK to me, does not matter what loads are put in the cable if over 40 amp it will trip.

I would be more looking at distance and earth rods, I assume whole supply is TT, but I would want to look at the set-up to decide how many earth rods, and were, with a TT supply it is not really a DIY job.

 

[morqthana]

I am extending the barn and want to include potentially a 6 KW sauna heater and potentially run a 6 KW shower,

And potentially disappoint every user of that shower. (Mind you, shouldn't it be a 0kW one if it's to accompany a sauna? )

Seriously, put in a bigger one (10.8kW are easily found, and 12kW are available.) If necessary install a changeover switch so that the sauna heater and shower can't be used at the same time.

 

[ericmark]

And potentially disappoint every user of that shower.

I would have said that some years ago, however they were fitted here when I bought the house, and with the supplied rose, they seem adequate.

I look at the description 80A RCD - 40A MCB - 16 mm cable - CU - (32A MCB + 6A MCB + 40A MCB) the 40A feeds a caravan, so that feed can't be TN-C-S it is near impossible to work out if TN-S or TN-C-S so in real terms the supply needs to be TT.

A TT supply is good for supplying the sauna.

But all is off one 40 amp MCB, and for a caravan

Each socket-outlet shall be protected individually by an RCD

and

NOTE: In the UK the ESQCR prohibit the use of a TN-C-S system for the supply to a caravan or similar construction.

So it would seem that first 80 RCCB needs removing, and the RCD/RCBO's need fitting in the second consumer unit, and likely you will need more than 40 amps.

It would seem your OK to 60 amps, but the problem is the consumer unit, and can you get a 60 amp MCB, the old loadmaster went up to 70 amps, but most consumer units seem to stop at 45 amp.

You can get a larger moulded breaker, but the enclosures move into completely different range, and often the access has to be restricted to electricians due to being able to select tripping currents.

Then we also look at the supply, my home only has a 60 amp supply total, farms may has a split phase supply or three phase supply, but you are looking well beyond DIY.

I have two showers, never used together, two kitchens, so two cookers, two washing machines, so it does seem I do have a protential overload situation but my solar monitors the power used, and due to only being two of us, we never get near max load.

I would be looking at power showers from a hot water store, not instant electric. And also looking at current monitoring, so water only heated when the load is low, all can be done, but not really a DIY job.

I would want the caravan on a smaller MCB to the one supplying the whole CU, so if there is an overload, the MCB near to the caravan trips, not the main one in the house.

In other words it needs designing not everything forward and trust to the Lord.

 

[SUNRAY]

A lot of this depends on potential usage.
For a start having 2 B40 MCBs in line is incorrect. As already noted remove the RCD from the supply end and go RCBO - (Imagine the inconvenience of teh caravan tripping the RCD while someone is in the shower late at night when the household has gone to bed) - and upgrade the supply to a 50 or 63A, I'd suggest a double pole (A quick google will reveal a whole plethora of them), or downrate the caravan to 32A. However what size is your main fuse - No point in having a 63A MCB if your supply is only 30A - I've seen exactly this for a woodworking workshop!
Despite what others will postulate a 6KW shower will be fine, and further; a 6 or 7KW is fairly standard when installed as part of the sauna. Anyone being 'disappointed' by it has a serious 'their problem'. At home we have a 10.5KW and we never run it on high power.
Earthing arrangements for caravans are supposed to be TT (and not within touching distance of other earthed equipment) and the same is true for pools/hot tubs so I'd not be surprised if the same is true for a sauna in it's own cabin.

As has been pointed out this really needs a full design applied to it and with the certification required I'm doing something I rarely do...
I recommend getting several estimates and advice from electricians.