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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Wiring for Hot Tub https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1088322222 Message started by Jerry on Jun 27^th, 2004, 8:43am

Title: Wiring for Hot Tub
Post by Jerry on Jun 27^th, 2004, 8:43am

I'm about to have a hot tub delivered and installed in the garden. ?Before it arrives I have to provide a supply from a 32 Amp breaker through and RCD with a 4 metre SWA tail at the instalation point. ?The run from the consumer point to the location for the hot tub is about 20 metres and, with a 3 kW heater and four pumps, the start-up load of the unit will probably use a fair proportion of the 32Amp rating.

Having done most of my own house wiring and electrical instalation over the last 20 years, the thought of doing the work myself doesn't phase me. ?However, I have never installed an RCD or used SWA cable before. ?I did consider asking an electrician, but gave up because I couldn't get sensible or timely responses.

I currently have a Wylex Consumer Unit which includes a spare 30Amp breaker, but no RCD. However, it's obsolete, so I can't get an RCD / RCBO to fit it. I will use the existing 30Amp breaker for the supply.

My proposal is to run 6mm twin and earth from the consumer unit to a point just inside the garage where I will locate the RCD, then I will run 6mm three core SWA from the RCD for the remaining 10 metres to the hot tub. ?My questions are, is the cabling the correct size?, do I need to earth the steel wire covering of the cable as well as use one of the 3 cores as an earth back to the consumer unit earth? ?If so, should the steel wire covering be earthed to a separate earth stake (someone suggested this, but I can't see the need)? ?Do I need a special box for the RCD in order to accommodate the gland of SWA cable? ?Finally, I have a Proteus 32A, 30mA RCBO which has a black fly lead, the instructions aren't very clear - guidance on how this should be wired would be helpful. ?I assume that it goes to a point where it will connect with the neutral Line with the live Line going to the bus bar?

All advice will be gratefully received.

Note: You may be wondering why I have an RCBO. It's because I didn't know it was different to an RCD until I got home and read the instructions by which time CEF was shut!

Jerry

Title: Re: Wiring for Hot Tub
Post by rabbit_rabbit on Jun 27^th, 2004, 9:00am

Blimey Jerry you dont live over in Ash do you? What you describe is EXACTLY what I was doing last Thursday. My clkinet wanted a new CU prior to the tub circuit being installed and did both the same day.

Within the CU I fitted a 32 amp RCBO (30mA) on the non-RCD side of split CU. Frommthere 6.00 mm csa t/e through wall to IP junction box. From there 6.00 mm csa SWA with 4 mtr tail left near edge of tub area ready to be connected up. DO leave enough swa to get all way round tub if tub is not delivered yet.

I used 3-core swa earthed armouring and no stake.

Errr.. Proteus is sort of not good quality. Still. Most RCBO's for installation within DIN CU usually have two flying leads. One is of larger csa than the other and is to be connected to neutral bar (make sure its the right N bar). The smaller csa cable is to be connected to earth bar. Phase (live) comes in on underside (like MCB) and phase and neutral come out (to your 6.00 csa t/e) of top of RCBO and are usually or should be marked L and N.

By the way, some of the tub supplies desire an external isolator switch and for one reason only, so their service engineers can service the tub in the event that no-one is at home. My client was not impressed with that comment!

RR

Title: Re: Wiring for Hot Tub
Post by Jerry on Jun 27^th, 2004, 9:56am

Thanks. Coincidently, I used to live in Ash Vale (23 years ago). I now live in the Midlands - pity you don't, I get you to do the job!

I assume that I wire the SWA steel wire and the core wire (used for earth) to the same earth terminal in the CU.

I can't use the RCBO in the CU as the CU is 19 years old and I can't get parts to fit (it has no RCD). City Electrical Factors sold me a small CU to fit it in. I could use this as the junction for the 6mm T&E and the SWA with the RCBO as an extra breaker. However, as I already have a spare 30Amp breaker in the existing CU, it may be more sensible for me to exchange the RCBO for a simple RCD in its own box. What do you think?

Jerry

Title: Re: Wiring for Hot Tub
Post by Lectrician on Jun 27^th, 2004, 10:40am

An rcd in its own din rail box i would say, preferable a metal one so that you can gland the armour directly to that (although metal ones are harder to come by).

Title: Re: Wiring for Hot Tub
Post by Lectrician on Jun 27^th, 2004, 10:40am

Steel armours earthed to the same point as the yellow core, onto the earth in the 6mm T+E

Title: Re: Wiring for Hot Tub
Post by rabbit_rabbit on Jun 27^th, 2004, 12:29pm

My dear old pal Lectrician has answered well and agre with all he says.

By the way, Tubs do come under special swimming pool locations so NO control switches etc. with 2 meters of the tub. For example, if you want to install one of thsoe rotary isolation switches eventhoigh they may be IP66 or better it must NOT be installed within 2 meters of tub.

Any further queries ask away.

RR

Title: Re: Wiring for Hot Tub
Post by Jerry on Jun 27^th, 2004, 12:58pm

Thanks chaps. I know where to come with any future queries. Never thought I'd get answers this quick.

Jerry

Title: Re: Wiring for Hot Tub
Post by rabbit_rabbit on Jun 27^th, 2004, 3:13pm

Tiz a pleasure Jerry. Hope to see you again one day!

RR

Title: Re: Wiring for Hot Tub
Post by Jerry on Jun 27^th, 2004, 7:04pm

A final thought. On looking through supplier catalogues on line, I note that there is a shortage of 32Amp 30mA RCDs. I assume that it's OK to use a 40Amp 30mA version as the overload issue will be covered by the mini breaker in the CU?

Jerry

Title: Re: Wiring for Hot Tub
Post by Owen on Jun 27^th, 2004, 7:13pm

Yes

Thats just the maximum load of the RCD. Anything over will fry it - Well, unless the MCB protects it. Which it should do: The MCB will trip long before the RCD overloads.

RCDs only check Live and Neutral imbalences, not current ammounts.

Title: Re: Wiring for Hot Tub
Post by plugwash on Jun 27^th, 2004, 9:38pm

yup

higher current rated rcds are more expensive to make
however haveing a wider stock range also increases expenses

so the manufactureres set up thier ranges to find the best comprimise between theese issues

Title: Re: Wiring for Hot Tub
Post by Jerry on Jun 27^th, 2004, 9:48pm

Thanks once again all.

Jerry