help with hot tub

[LlamaPrince]

Hi,

i would like to install a hot tub at the bottom of the garden, but there is a few questions i need help with before i start ground works etc.

the hot tub will sit on decking i will build at the end of the garden,

the hot tub i ideally would like requires a 32 amp supply.

the Consumer unit in the house is 40 meters away, i wish to install a new consumer unit in a summer house next to where the hot tub will be, ideally i would like to run a light in here too and maybe one socket.

can i use 6mm swa? or do i need 10mm for the Volt drop? or should i look for a smaller rated hot tub, i.e a 13 amp one?

just need to know all this before i start to get prices of everything etc.

thanks

 

[Leesparkykent]

Hi,

i would like to install a hot tub at the bottom of the garden, but there is a few questions i need help with before i start ground works etc.

the hot tub will sit on decking i will build at the end of the garden,

the hot tub i ideally would like requires a 32 amp supply.

the Consumer unit in the house is 40 meters away, i wish to install a new consumer unit in a summer house next to where the hot tub will be, ideally i would like to run a light in here too and maybe one socket.

can i use 6mm swa? or do i need 10mm for the Volt drop? or should i look for a smaller rated hot tub, i.e a 13 amp one?

just need to know all this before i start to get prices of everything etc.

thanks

have you carried out any calculation? whats the Ib?

 

[telectrix]

at 32A over 40m, 6mm will give a VD of 10V. just about OK except for lighting.

 

[LlamaPrince]

is the max VD 5% and 3% for lighting? although lighting wont be running at 32 amp, i havnt worked as an electrician for years, will get someone else to wire it but i just want to know what cable to lay for them.

 

[Leesparkykent]

is the max VD 5% and 3% for lighting? although lighting wont be running at 32 amp, i havnt worked as an electrician for years, will get someone else to wire it but i just want to know what cable to lay for them.

10mm2 with a 40A OCPD with give you roughly 2.6% VD.

 

[SJD]

You should be able to calculate or look up the voltage drop from the BYB regs (or onsite guide), and if you want to route the supply to the summerhouse, and also feed a light and socket, then allow for these as well in the calculations (the allowable drop for lighting will likely require a larger cable size).

If you feel unable to make those calculations, then really you ought to consider getting someone in to do the work for you. Bearing in mind that this sounds like notifiable work under Part P of the building regs (which yes, nobody will check till either you sell the house, or there is some mishap).

 

[LlamaPrince]

so to be on the safe side 10mm i thought so, my regs book is lost somewhere otherwise id just look in the table there,


thanks for the help.

 

[telectrix]

thing is though.you got at least 8V to play with as the supply will rarely be below 238V and the nominal is 230V. also this 3% for lighting was specced long before LED lighting became popular. LED lights will tolerate a lower voltage with ease. tin hat time.

 

[Leesparkykent]

I would be installing 10mm

 

[SJD]

thing is though.you got at least 8V to play with as the supply will rarely be below 238V and the nominal is 230V. also this 3% for lighting was specced long before LED lighting became popular. LED lights will tolerate a lower voltage with ease. tin hat time.

I agree that LEDs might tolerate a lower voltage, but if the regs say 3%, would you - for example - complete an installation with a bigger drop (that includes lighting) - say 5% - and note the deviation on the certificate on this basis?

 

[bigspark17]

I would be installing 10mm

100% agree! I agree with what your saying about the LED lights but until the regs change we still have to design to 3% VD!

 

[Leesparkykent]

100% agree! I agree with what your saying about the LED lights but until the regs change we still have to design to 3% VD!

It wasn't me who said about LED lights lol I do get what Tel is saying though.

 

[telectrix]

all comes to bugger all when i have a valued customer who has a supply voltage of 210V at peak times, and SPEnergy say " tough, all we can do is put you a ne supply in for £15.000". kerrching!.

 

[Blademan_98]

I would like to point out (as a newly qualified test and inspection chap ) that you really should not lay any cable until you have discussed the project with a qualified sparks.
It is notifiable work and as a responsible person, I would urge you to do it properly.
Knowing the cable size is only part of the design, reference methods and earthing are equally important.
Cheers
B

 

[Barrie Patrick]

Also treat as a special location.