Outdoor Electrics

winston1 · 2 Mar 2020

Personally I would not worry. It's been alright up to now. You are unlikely to use a heavy load in the shed (over 14 amps) while using the hot tub are you?

bernardgreen · 2 Mar 2020

winston1 said:
Yes, the cable can still carry 27 amps.

2.5 mm² can carry more that 27 amps before getting too warm.

What will be the voltage drop along the cable ?

How long is the cable ?

Use this calculator.

https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

5 kW ( 22 amps ) and 10 metre of cable would require 4 mm² if the voltage drop is to meet regulations.

DIYSOS2018 · 2 Mar 2020

The only thing permanently running in the shed is the fridge freezer, so arguably you’d have that and the hot tub running through one cable in tandem? Obviously the hot tub is on 24/7 though...

Appreciate you’ve said it’s not been an issue before but the hot tub has never been on since the shed got built...

Eccles · 2 Mar 2020

The important bit is to first assess what the possible maximum load might be in watts. E.g. Max load in the shed could be lawnmower 1500 watts plus electric drill 750 then my understanding is that a hot tub could use as much as 7500 watts although some use less. Add those numbers together and we could be talking about almost 10000 watts which according to official figures would require a 10 sq mm cable to be safe. Then you might ask what can a 2.5 sq mm cable safely carry and the answer is about 4800 watts although I personally would maximize at 4500 watts to be belt and braces safe. Sorry but I agee with others that your present set up is completely inadequate and you need to get a qualified sparky to fix up something decent - probably a covered cable directly connected to your consumer unit.

winston1 · 2 Mar 2020

It has already been stated the hot tub is 13a, around 3000w not 7500w. Unlikely lawn mower and drill would be used together and probably not at the same time as the hot tub (which would be cycling anyway once up to temperature).

10mm cable is often used to supply a whole house!

DIYSOS2018 · 2 Mar 2020

Great hearing everyone’s replies. Although some make me relaxed, some make me terrified!

terryplumb · 2 Mar 2020

As Winston and Bernard green have correctly said prior ,2.5 mm² cable is capable of carrying 27 Amps+ ,but that is the upper limit ,and dependant upon the installation method. As we have limited information on the length of your cable run , you said some of it is in conduit ,and we have no idea what ,if any ,insulation it passes through, I took the view that it would be prudent to consider the current carrying capacity to be somewhat less than 27 amps ,and advised you accordingly.
Regulations aside ,it really comes down to what loads you put onto the circuit / spur. As Winston quite rightly stated earlier ,if you only use the hot tub ,fridge and the odd drill etc ,you wouldn't overload the spur cable . I think you said there are 3 socket outlets ( doubles ?) So there is the possibility that several items could be in use simultaneously ,as long as you don't overdo it ( and start plugging in high current drawing items ) you can quite happily carry on as you have done.
You originally asked for recommendations ,upgrading and complying with regulations is one option. Leaving it be is also an option. The choice is entirely yours.

Eccles · 2 Mar 2020

The "choice" is not really "entirely yours". If I assume that you have a contract with an insurance company and they discover that your electrics are not in line with best practice, they could refuse to pay if you ever needed to make a claim.

DIYSOS2018 · 2 Mar 2020

Hi Terry

Thanks for this. Sorry I missed the distance point. The outdoor socket is about 4m from the socket it’s spurred off.

The spurred power to the shed, off the outdoor socket, is about 6m from the outdoor socket!

Based on that distance I assume nothing changes that dramatically

Thanks Eccles surely any insurance company can’t hold you liable for works you haven’t done therefore don’t know about?

Eccles · 2 Mar 2020

DIYSOS2018 said:
Thanks Eccles surely any insurance company can’t hold you liable for works you haven’t done therefore don’t know about?

I doubt that very much knowing what I know about insurance, why not ask them? Personally I don't use insurance because I know that they will do everything possible to avoid paying out.

ajohn · 2 Mar 2020

My understanding is that a 2.5mm spur can be extended to another socket but the source then needs to be via a 13a fused spur unit. There is a picture in either the site guide or the regs / both. If newly installed now it would be fitted with a spur unit that also conatains an RCD if there wasn't already one in the main CU that would trip.

Some have sockets fitted with a 2.5mm radial from the CU but that is protected with a 20amp MCB and needs the usual calculations to meet the regs. A 4mm radial may be used instead of a 2.5mm ring for the usual 32amp circuit rating.

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Outdoor Electrics

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