Hot Tub Help!

[hoppy]

Been to look at a job.

Existing hot tub, been in for over year.

There are no manufacturers instructions, it is sited on concrete, about 25m from fuse board.

The customer is having problems as it is currently fed by what looks to be 1.5mm twin and earth, keeps tripping out when they turn the temp to certain point, also they can smell a fishy smell - the cable melting.

the hot tub came with a 230V industrial plug on it.

from what I can see from the panel inside the tub it requires a 32A supply.

The house is a tns no room on existing cu.

So, I am going to split tails, feed a new 2 way rcd unit, 32A mcb type c, 6mm 3 core swa to 32A rotary isolator.

With regards to earthing, I have read many posts on this but cant decide what is best.
Should I use the house tns earth on its own, or put a rod in also at the rotary isolator, or keep the hot tub separate and just tt the isolator.

I know some instructions ask for a rod, but I cant find them so I am asking what you more experienced guys would do for the best!

Thanks Guys!

 

[amberleaf]

in my limited experience, Hot tubes

Information Only . 2008:

Introduction
The increasing use of hot tubs and garden spas, in both indoor and outdoor locations, has brought with it an increase in the number of questions posed about the safety requirements for the associated electrical installations. The questions raised result from the need to know what particular requirements of BS-7671 should be applied to a given situation. For example, should the requirements set out in Section 701, Section 702, or both, be applied in addition to the general requirements ?

The product specification relevant to hot tubs and garden spas is BS-EN 60335-2-60: Specification for safety of household and similar appliances: Particular requirements for whirlpool baths and whirlpool spas.

Indoor hot tubs

Where a hot tub is placed in a location containing a bath or shower, the requirements of Section 701 have to be met. However, where a hot tub is located indoors, it may be placed in a room other than the bathroom. Where a hot tub is located in a room other than a bathroom, whether on the ground floor or elsewhere indoors, the location will be subject to similar electrical safety considerations as a bathroom. In such cases, the electrical installation designer may decide that the requirements of Section 701 should be applied in full.

Garden spas

Where the garden spa is housed in a purpose-made spa-shelter , the location will be subject to similar electrical safety considerations as a bathroom, and the most appropriate requirements to apply are likely to be those of Section 701.

Increased risk of electric shock

As with rooms containing a bath tub or shower basin, the indoor hot tub introduces an increased risk of electric shock due to the reduction in body resistance, particularly contact resistance, due to immersion, or partial immersion, in water. For hot tubs located outdoors and garden spas, the risk of electric shock is further increased because contact with the general mass of Earth is likely. (Touch voltages under earth fault conditions are increased due to persons being in contact with ‘ true ’ Earth, i.e. the ground.)

Protective multiple earthing (PME)

Where earthing is by PME, it should be noted that electricity distributor’s notes of guidance often contain particular requirements relating to electrical installations in locations containing swimming or paddling pools or the like, or do not permit PME earthing to be extended outside buildings in which there is an insulated floor and main protective bonding is provided.

 

[amberleaf]

BS-EN-60335-2-60:2013 + A12:2010
Household and similar electrical appliances , Safety . Particular requirements for whirlpools baths and whirlpool spas

 

[hoppy]

Thanks amberleaf!

 

[davesparks]

The only thing I am aware of in the regulations is that they recommend an earth electrode with an Ra of less than 21ohms be connected to the protective bonding system of the installation if a swimming pool is supplied via TNCS.
And that outdoor hottubs should be treated as swimming pools.

No special requirements are given for TNS, but with the trend for DNOs to convert TNS systems to a bodgeit TNCS whenever they feel like it it may be worth consideration.

My interpretation of it is that you install the earth electrode and connect a main bond to it from the MET, other interpret it differently but I would not personally be happy with an earth rod connected to the isolator.

 

[edexlab]

Just done first hot tub circuit , tub not delivered /installed yet
after reading up and looking at various information ie regs, GN7 , DNO, manufacturers info, various forum posts and the Nic techline.

I decided that the overwhelming concensus of opinion was to isolate the earthed armour of the submain via adaptable box and to put in an Isolator > 30mA Rcd Cu > Mcb/final circuit as a TT install

In this case there are no other circuits /accessories with Pme earthing nearby and physically the tub location outside is a short distance from the house via a large attached conservatory containing a swimming pool

My interpretation of that note re Pme in 701 was the same davesparks ie that Pme earth is ok as long as the electrode/mat is "installed and connected to the equipotential bonding"

but I've spoken to several people more qualified than me who all said to TT ,
any other opinions?

 

[Engineer54]

The only thing I am aware of in the regulations is that they recommend an earth electrode with an Ra of less than 21ohms be connected to the protective bonding system of the installation if a swimming pool is supplied via TNCS.
And that outdoor hottubs should be treated as swimming pools.

.

If were talking about a tradiitonally in-ground concrete built swimming pool, the steel reinforcing is the earth electrode (Ufer earth), which is also cross bonded to include any S/steel pool ladders, diving boards etc... Absolutley crazy to then go and drive a rod in the ground . As with any pool installation this steelwork will need connecting to installations MET be it TN-S, TNC-S, or TT.

 

[Engineer54]

Just done first hot tub circuit , tub not delivered /installed yet
after reading up and looking at various information ie regs, GN7 , DNO, manufacturers info, various forum posts and the Nic techline.

I decided that the overwhelming concensus of opinion was to isolate the earthed armour of the submain via adaptable box and to put in an Isolator > 30mA Rcd Cu > Mcb/final circuit as a TT install

In this case there are no other circuits /accessories with Pme earthing nearby and physically the tub location outside is a short distance from the house via a large attached conservatory containing a swimming pool

My interpretation of that note re Pme in 701 was the same davesparks ie that Pme earth is ok as long as the electrode/mat is "installed and connected to the equipotential bonding"

but I've spoken to several people more qualified than me who all said to TT ,
any other opinions?

Probably because they don't know any different!! lol!!

There are very few swimming pools in the UK compared with many other warmer countries, so it's very unlikely the average UK electrician has any pool installation experience whatsoever, including those that you asked for advice..

So what did the manufacturers information, and the NICEIC tech line come up with to help you ??

 

[DPG]

Get it right! Let's not have a repeat of the other thread on here. Daz

 

[Engineer54]

Get it right! Let's not have a repeat of the other thread on here. Daz

It would be helpful to know what the hell you're talking about and to who you are referring too?? lol!!

 

[DPG]

It would be helpful to know what the hell you're talking about and to who you are referring too?? lol!!

Sorry Eng! The swimming pool electrocution thread that was posted today. lol etc. !!!!! lol Daz

 

[SPARTYKUS]

TNS. KING of earths.

the reason its being replaced is because the new idea is cheaper, not because its better (IMO).

money, not safety.....

 

[edexlab]

I spoke to several agents of manufacturers based here and they didn't know much other than most installers TT them , and they advised using C type Mcb.

 

[edexlab]

The techline chap certainly knew the regs and what page, paragraph to refer to etc
and basicly said in my case as described to him that using the swa armour for the cable , then isolating it, with a TT install supplying the tub locally was the best way to go

I spoke to him on 3 occasions about this clarifying a few things as , everytime I read that note in the regs it clearly suggests bonding from an electrode/ mat to the "installation" protective bonding which if your using the TN earth would mean the MET

He said it actually meant bonding to any extraneous parts near to the tub and not to the MET of the property

 

[Engineer54]

The techline chap certainly knew the regs and what page, paragraph to refer to etc
and basicly said in my case as described to him that using the swa armour for the cable , then isolating it, with a TT install supplying the tub locally was the best way to go

I spoke to him on 3 occasions about this clarifying a few things as , everytime I read that note in the regs it clearly suggests bonding from an electrode/ mat to the "installation" protective bonding which if your using the TN earth would mean the MET

He said it actually meant bonding to any extraneous parts near to the tub and not to the MET of the property

As far as an above ground hot tub install, that is sitting on bare ground or concrete, i would probably TT the tub install taking the rod earthing conductor directly to the hot tubs internal electrical panel. If the tub is sitting on wood or other non conductive material that would take at least 3 to 5 steps/strides before that insulation material ends, then there really isn't any need to TT.
Many of these hot tubs/jaccuzi's will on the newer models have integal RCD protection, so check first, before providing an upstream RCD....