Wiring up socket at bottom of garden

[Shaun matthews]

Hi
I want to put a socket about 40 metres down my garden , to run a lazy spa hot tub , I have bought 4mm armoured cable would this be sufficient and what mcb would be best a 20 or 32 amp

 

[telectrix]

first we need to know the rating of the tub. (kW). and does the tub come with a fitted plug?

 

[Shaun matthews]

first we need to know the rating of the tub. (kW). and does the tub come with a fitted plug?

Sorry yes its 2kW and comes with a 13amp plug fitted

 

[telectrix]

OK. working on 13A and 40m, your volt drop for 4mm cable would be 5.7V, which is acceptable. the MCB should be selected to be < the current capacity of 4mm cable, so 32A is the max. allowable.. . you need to fit a IP65 outdoor socket. also, i imagine that the tub has an inline RCD in it's lead. here our outdoor socket is a double, so facility for use for lawnmower etc.

bear in mind that while you could lay the cable, under instruction, this work is notifiable and should be undertaken by a qualified electrician.

 

[marcuswareham]

Fitting a socket that far down the garden, It is also important to look at your supply earthing arrangements as that will be outside of the equipotential zone.

This is particularly important on TN-C-S / PME due to the fact that if there is a loss in supply natural it can cause your earth conductor to become live with dangerous voltages even under fault-free conditions.

Is the hot tub double insulated? as using a class 1 outside with water on PME is risky.

and as telectix mentioned: due to the fact you are asking which MCB is appropriate makes it sound as if you will be adding a new circuit to you C/U which is notifiable.

Thanks Marcus

 

[Shaun matthews]

Fitting a socket that far down the garden, It is also important to look at your supply earthing arrangements as that will be outside of the equipotential zone.

This is particularly important on TN-C-S / PME due to the fact that if there is a loss in supply natural it can cause your earth conductor to become live with dangerous voltages even under fault-free conditions.

Is the hot tub double insulated? as using a class 1 outside with water on PME is risky.

and as telectix mentioned: due to the fact you are asking which MCB is appropriate makes it sound as if you will be adding a new circuit to you C/U which is notifiable.

Thanks Marcus

Fitting a socket that far down the garden, It is also important to look at your supply earthing arrangements as that will be outside of the equipotential zone.

This is particularly important on TN-C-S / PME due to the fact that if there is a loss in supply natural it can cause your earth conductor to become live with dangerous voltages even under fault-free conditions.

Is the hot tub double insulated? as using a class 1 outside with water on PME is risky.

and as telectix mentioned: due to the fact you are asking which MCB is appropriate makes it sound as if you will be adding a new circuit to you C/U which is notifiable.

Thanks Marcus

Hi Marcus
Yes I have a rcd on the hot tub and also the socket has an rcd built in ,
Can I not use the armour of the swa cable as an earth or do I need to add a separate ground rod , if so where do I stop the earth from main supply

 

[marcuswareham]

Hi Marcus
Yes I have a rcd on the hot tub and also the socket has an rcd built in ,
Can I not use the armor of the swa cable as an earth or do I need to add a separate ground rod , if so where do I stop the earth from main supply

Hi Shaun

You need to obtain if your house is TN-S, TN-C-S or TT earthing arrangement. A way to check is to look at where you supply cable comes into your house just before the electric meter where the main fuse is (service head):

TT: if you have an earth rod at your house and the earth from that rod goes into your consumer unit, and all you have coming in from the grid is L and N
TN-S: if your earth is connected to the incoming supply cable via an earth that looks to come out of the cable before the main fuse and is the sheath of that cable

TN-C-S: if you earth is connected to the incoming supply service head next the the N like this picture (alot of times there will be a sticker saying PME/Protective multiple earth also)

This is a guide and to really be sure you should test it or get an electrician to

Now if it is TN-C-S like the last one this is where the problem can be, due to a broken PEN conductor on the supply

View: https://www.youtube.com/watch?v=JRHyqouJPzE


Here might be another option:
I have looked on google images for the lazy spa hot tub and it looks as if the electrical unit at the side of the hot tub is made of plastic (likewise so is the tub) this could mean that it is double insulated / class 2 to check this look for a symbol on it like this

If this is the case and this symbol is on it then the risks of a broken N on TN-C-S has gone away, however the fact that there would still be a 13A socket down the garden means that someone could plug something else into it and that thing could be a class 1 item and the risk has returned, so in this case, if that outlet is only every to be used for the hot tub you could change the hot tub 13a plug & 13a socket outlet for another connecter to avoid any other equipment being used by that outlet (I would suggest a ture1 connector ( https://www.neutrik.com/en/neutrik/products/powercon/powercon-true1/powercon-true1-cable-connectors ) we use them all the time in my industry and they are solid and IP rated to be outside) (I wouldn't recommend a 16a ceeform connector as this still looks like a standard outlet and is not obviously for one use)

Yes very important to have RCD protection not just for the hot tub but also for the cable, it seems as if you have that already, and yes you can use the amour of the SWA cable for your earth conductor


So in summary this is what I would do:

- If I had TN-S supply: I would put an IP rated socket at the end of the garden using the amour as the earth and have it all protected by an RCD

- If I had TT supply: I would put an IP rated socket at the end of the garden using the amour as the earth and have it all protected by an RCD and add an additional earth rod at the garden socket outlet

- If I had TN-C-S supply & I only wanted to use that outlet for the hot tub: I would put a true1 outlet (F) at the end of the garden using the amour as the earth and have it all protected by an RCD and then change the 13A plug on the hot tub for a true1 male connector (and label the outlet as for class 2 items only)

- If I had TN-C-S supply & I wanted to use the garden outlet for alot of different things: I would put an IP rated socket at the end of the garden and make it its own TT island. I would connect the SWA amour to the house earth but then would isolate that earth from the 13a outlet (using a plastic junction box) then the 13a outlet earth would connect straight to a local earth rod and this must all be protected by an RCD

Please note if you are installing earth rod they need to be tested, you need a multi-function tester to test the earth rod resistance, your earth loop impedance. And if you were using TT then you RCD is critical so you would also want to check RCD disconnection times.

Sorry that's a bit long, hope this helps

Thanks Marcus

 

[Midwest]

Wouldn't it also depend on where the said hot tub is located, for example in a shed or on some decking.

Ive just visited the lazy spa hot tub site, to have a look at the spec’, but there’s a waiting time for their site. Most be lots of people staying at home at the moment!

 

[telectrix]

with lazy spar, you just plug it in. no worries about earth rods and all that crap. as long as the supply circuit is RCD protected and fit foruse.

 

[marcuswareham]

Wouldn't it also depend on where the said hot tub is located, for example in a shed or on some decking.

Ive just visited the lazy spa hot tub site, to have a look at the spec’, but there’s a waiting time for their site. Most be lots of people staying at home at the moment!

Good point, Yes I was prusming it was going to be on some grass or somesuch

 

[davesparks]

- If I had TN-C-S supply & I only wanted to use that outlet for the hot tub: I would put a true1 outlet (F) at the end of the garden using the amour as the earth and have it all protected by an RCD and then change the 13A plug on the hot tub for a true1 male connector (and label the outlet as for class 2 items only)

- If I had TN-C-S supply & I wanted to use the garden outlet for alot of different things: I would put an IP rated socket at the end of the garden and make it its own TT island. I would connect the SWA amour to the house earth but then would isolate that earth from the 13a outlet (using a plastic junction box) then the 13a outlet earth would connect straight to a local earth rod and this must all be protected by an RCD

That's an impressive mountain you'veade out of a molehill there!

And why on earth would you want to fit a true 1 connector? Those things are nasty, flimsy crap and get a dangerous once they've got a bit worn.

 

[marcuswareham]

That's an impressive mountain you'veade out of a molehill there!

And why on earth would you want to fit a true 1 connector? Those things are nasty, flimsy crap and get a dangerous once they've got a bit worn.

Hahaha yes it is, I am a specialist at that! although should a hot tub be class 1 I would think thats a fairly large risk

Strange you have that experience with ture1. I have done a 2 year worldwide concert tour with about 3000 true1 connectors, on the back of an LED video screen built every day and driven hundreds of miles each night or flown, etc and in that time we only replaced around 35 of them.

I am guessing as lazy spa company don't say anything about power requirements or PME (just had a look at a manual for one, I also cant see anything saying if its class 1 or 2
all it says is: Parts containing live parts, except parts supplied with safety extra-low voltage not exceeding 12V, must be inaccessible to a person in spa pool; Parts incorporating electrical components, except remote control devices, must be located or fixed so that they cannot fall into the spa pool.
• The spa must be supplied by earthed power source.
• RISK OF ELECTRIC SHOCK. Install at least 2m from all metal surfaces)
, I guess it must be double insulated or any tingles or injuries are on lazy spa then

 

[Midwest]

I'd say its just a plug & go one, like Tel said. Might need to exercise some sense where the bathers are getting in and out of the thing, but I suspect all the electrics are spirited away anyway, from unsuspecting users.

I'd be more concerned about the users ability to carefully control the different chemicals levels in the thing, and trying not catching disease's from it.

 

[davesparks]

Hahaha yes it is, I am a specialist at that! although should a hot tub be class 1 I would think thats a fairly large risk

Strange you have that experience with ture1. I have done a 2 year worldwide concert tour with about 3000 true1 connectors, on the back of an LED video screen built every day and driven hundreds of miles each night or flown, etc and in that time we only replaced around 35 of them.

In the past when I installed a supply for a hot tub I would just install earth rods as advised in the note in the regulations concerning outdoor pools.

I've seen many of them come through with tours in the local theatre which are broken, or damaged by mishandling.
The other problem is that once they are well used they wear in such a way that they can be connected incorrectly and short L-E etc. I believe this is the hidden reason behind Neutrik discontinuing the true 1 connector.
Which is another good reason not to fit them, they are discontinued!

 

[Shaun matthews]

How about the volt drop though wouldn't that affect the earth aswell with the distance from the house

 

[davesparks]

How about the volt drop though wouldn't that affect the earth aswell with the distance from the house

Please explain what you mean by this?

 

[marcuswareham]

In the past when I installed a supply for a hot tub I would just install earth rods as advised in the note in the regulations concerning outdoor pools.

I've seen many of them come through with tours in the local theatre which are broken, or damaged by mishandling.
The other problem is that once they are well used they wear in such a way that they can be connected incorrectly and short L-E etc. I believe this is the hidden reason behind Neutrik discontinuing the true 1 connector.
Which is another good reason not to fit them, they are discontinued!

Fair enough about the discontinued, I had not realized that I just get given them by hire companies. , I have not found them to brake anymore than any other connector really. That is a fair point on the risk of connecting worn ones incorrectly thats true they can go that way, the method I mentioned could be any connector, true1 was just what popped into my head

 

[Shaun matthews]

Please explain what you mean by this?

Well with the cable being 40 metres long , there would be a volt drop in the supply , wouldn't there be a chance that the earth could become live ,

 

[davesparks]

Well with the cable being 40 metres long , there would be a volt drop in the supply , wouldn't there be a chance that the earth could become live ,

I still don't understand, how will voltage drop cause the CPC to become live?
Voltage drop will cause the voltage between L and N at the far end of the circuit to be reduced, it won't disconnect the CPC and reconnect it to the line!