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What size armoured cable?

I have recently built a garden lounge/bathroom building, which has its own supply and board taken off the main board in the house. We were going to have a sauna inside this building, so the armoured cable in to it is up to spec. I now wish to have the sauna outside (barrel type sauna), so will need to run a new armoured cable from the board inside to the point outside at which the sauna will stand. The sauna itself has a rating of 8kw. What size armoured cable will be required?

Kind regards,


2 Answers from MyBuilder Electricians

Best Answer


Not too sure what the last poster was thinking about, "NO volt drop" is actually impossible.

The method needed to do your external installation depends heavily on your existing earthing system. You also need to take into account the length of run, the route taken and the final position of the sauna. All of these things help determine the cable size.

Unless your sauna is right next to your consumer unit, and the cable is exposed to teh air through its length then 6mm is fine. If noty then 10mm is required.

As this is outside, it is a legal requirement that the work is done by a registered contractor. Do yourself a favour and make sure such a potentially dangerous appliance is connected properly, taking into account the existing system conditions.


Answered 22nd Feb 2015

hi, 6mm2 3 core swa would be sufficient as long as there is NO volt drop. you must have this on a RCD protected circuit.


Answered 14th Feb 2015

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