Hot tub volt drop

[robd]

Hi All,

Been to look at a job with a hot tub 27A load, 30 metre run. Don't do much volt drop calculating but here's what I did, anyone disagree? Thinking 6 mm armoured so:

7.3x27x30/1000=5.91v

max permissible (5% of 230v) 11.5, 5.91 v well within that.

Talk about use it or lose it, took me a lot longer than it should! Thanks for any feedback.

 

[Farmelectrics]

very good whats the qustion though

 

[ImpededLoop]

Hi All,

Been to look at a job with a hot tub 27A load, 30 metre run. Don't do much volt drop calculating but here's what I did, anyone disagree? Thinking 6 mm armoured so:

7.3x27x30/1000=5.91v

max permissible (5% of 230v) 11.5, 5.91 v well within that.

Talk about use it or lose it, took me a lot longer than it should! Thanks for any feedback.

Looks good to me.

 

[robd]

very good whats the qustion though

Just wanted to make sure I was barking up the right tree as it were!

 

[Richard Burns]

IF you are thinking about volt drop then you could as an easy check look at the standard circuits in chapter seven of the OSG. For a radial circuit with a 32A breaker on 6mm² T&E cable your maximum length (as limited by volt drop) is 49m, therefore a 30m run would be OK.

However I generally think it is better to do it the way you have done so that you can be sure.

 

[robd]

Thanks Richard have an osg, never seen that

 

[HappyHippyDad]

Hi All,

Been to look at a job with a hot tub 27A load, 30 metre run. Don't do much volt drop calculating but here's what I did, anyone disagree? Thinking 6 mm armoured so:

7.3x27x30/1000=5.91v

max permissible (5% of 230v) 11.5, 5.91 v well within that.

Talk about use it or lose it, took me a lot longer than it should! Thanks for any feedback.

I would have thought 4mm SWA would be absolutely fine. Volt drop works out to 8.91V so still well within the limits, so as long as Zs is ok then that could save you a little cost.

 

[Richard Burns]

Thanks Richard have an osg, never seen that

Just a quick extract (from green OSG) to demonstrate (also shows max length as 33m for 4mm² T&E confirming Happyhippydad's proposal)
I have also added the notes that explains that Volt drop is the limiting factor where there is no other indication.

 

[robd]

Thank you both for your thoughts very helpful, will stick with 6mm rather than go to the limit