Hot tub confusion

[Boomerrat]

Hi, just finished fitting my hot tub and need to run a 45m length or armoured cable from the garage to it. Next to the tub will be a summerhouse with a couple of sockets in it nothing heavy just a phone charger and stereo. The wiring it used to have when I bought the tub was 16mm outer / 4mm inner but I have been told 4-6mm will suffice as the tub states on top it is 16amp /230v, inside on the wiring diagram it shows a jumper setting of 20a-50a? Really confused as to whether the 16mm cable was purely overkill and 6mm will be fine and the other information on the wiring diagram?? Any help will be greatly appreciated.

 

[pc1966]

How is this cable being connected?

In England & Wales the Part P building regulations require notification of any new circuit, etc, and by far the cheapest and safest route is to get a local sparky involved to sort that out.

The outer diameter of the wire is largely immaterial, is it the cross-sectional area of the conductors (along with the conductor type) that is the main factor in the rating of a cable. In your case it appears to be 4mm^2 and, presumably, copper wire.

But beyond the simple question of current-carrying capacity, there are also the issues of voltage drop and fault impedance (that depend on cable type & length) to be factored in before deciding if a given solution is safe/acceptable practice, or not.

 

[Andy78]

As above this cable needs sizing properly through calculation and the load demands of the summerhouse use as well as the hot tub taking into consideration. Sizing the cable for earth fault loop impedance values and voltage drop will be more important than the load to be drawn in this case.

A competent electrician should be employed for this job from the start.

 

[Boomerrat]

Hi, i appreciate both replys, thank you.
I did speak to one explained it was 45mtr between garage and tub would only be for tub and low powered items stereo etc (max 2) I was just a little taken back by the 6mm wire for the job as a posed to the 16mm outer 4mm inner that came off it originally. I will have an electrician wire it all in just wanted to run the correct cable myself.

 

[pc1966]

Get a clear agreement with the electrician about exactly the cable to run in, and how it is done (depth of burial, sand packing around it, etc, as required). Usually they will be happy to sort out the rest as long as they know the cable is acceptable in both choice and installation method.

After all it is their name that is signing it off as safe!