What size cable for 32A hot tub?

[leegsi]

What size armored cable do I need to put a supply for a 32A hot tub to my decking.

We have a 32A feed going to the outside wall that we had terminated at an isolatior.

Now I need to run the armored cable to the bottom of the garden where the hot tub is going to go.

It about a 10 meter of cable run.


Thanks for any help.

 

[chivers67]

What power rating is the hot tub? 4mm should be ok has the circuit got RCD protection or does the hot tub come with it's own device?

 

[jj4091]

Only ever installed one hot tub & the manufacturers instructions demanded 4mm even though 2.5mm would have sufficed. What do your installation instructions say?

 

[leegsi]

Not bought the tub yet but want to make sure that I dont under rate the cable.

Most we are looking at say they need a 32A supply.

And yes its RCD protected at the fuse box.

 

[bernardgreen]

The current taken by a motor when it starts is several times the normal running current taken by the motor when the motor has reached full speed.

A cable that is adequate for normal running current will carry the starting current but the voltage drop due to the starting current may be enough to affect the way the motor starts.

Manufacturers will be aware of this and will recommend a size of cable that limits the voltage drop when motor(s) start,

 

[JohnW2]

Manufacturers will be aware of this and will recommend a size of cable that limits the voltage drop when motor(s) start,

If manufacturers were concerned about that, their recommendation for 'cable size' would obviously have to be dependent upon cable length.

In practice, I would suspect that they don't have such concerns - even during start-up, the current drawn by the (presumably quite small) pump motor (if there is one) will be a very small proportion of the total current draw of a hot tub, most of which relates to heating.

Kind Regards, John

 

[jj4091]

Manufacturers instructions are often wrong and there is no legal requirement to follow them anyway.

No but it would be an easy way to refuse to do warranty work the owner would probably not be in a position to argue with them. The extra costs of installing 4mm over 2.5mm are peanuts compared to how much a hot tub can cost

 

[Taylortwocities]

It was helpful and correct. If you have nothing useful to say, say nothing.

Look in the mirror, pal!

 

[EFLImpudence]

If it needs a 32A supply, then it needs 4mm² cable.

 

[leegsi]

If it needs a 32A supply, then it needs 4mm² cable.

Thats what I thought but didnt know if the distance would effect it.

Thanks for a simple reply lol

 

[EFLImpudence]

Thats what I thought but didnt know if the distance would effect it.

Well, it does if a long way, but 10m. - or 20m. won't affect it.

 

[JohnW2]

Thats what I thought but didnt know if the distance would effect it.

As has been said, if it needs a 32A supply, then it needs at least a 4mm² cable. However, you're right in that distance is also a factor (because of potential 'voltage drop' issues) - so if it were a very long run of cable, bigger cable than 4mm² might theoretically be needed.

As has been implied, if the circuit is protected by a 32A MCB in your CU, then the cable would have to be at least 4mm², no matter how short/long.

Kind Regards, John

 

[leegsi]

Thanks for all the help

4mm it is then.