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....

 

[edexlab]

This Tub is direct on a patio which has dabs of mortar onto bare earth and a few inches below a mix of backfill rubble, this has made driving the rods in difficult and its several metres before the rod clears the rubble and is driven into earth

Having not seen the connection point in the tub I don't know if there is a terminal where a cpc to the board and conductor to a rod can be accomodated, so I've taken the rod conductor to the isolator 2 metres away

The possibility of an internal Rcd and an upstream one ?
I did ask the customer. before I started but he hasn't been able to tell me if there is or not

I was thinking discrimination isn't an issue here really, unless the Rcd within the tub is able to be tested, and if it is we agreed that I would temporarily link out or change the upstream Rcd for a main switch to enable testing of the downstream one
If it turns out there will be 2 Rcd's protecting, it would surely be preferable to having one which could fail ?

 

[Engineer54]

This Tub is direct on a patio which has dabs of mortar onto bare earth and a few inches below a mix of backfill rubble, this has made driving the rods in difficult and its several metres before the rod clears the rubble and is driven into earth

It could still well be conductive, especially when the area around the hot tub is wet from splashing water and people exiting the tub etc. Are the clients using chemical additives to the tub water such as bromine and PF correctors, which will in effect make the water more conductive??

So what sort of Ra values are you achieving with the earth rod install?? If it's particularly bad values, you may have to find a another location that is rubble free away from the patio, to drive your earth rod...

 

[edexlab]

Current reading is 45 ohms with 7 coupled rods down, close to the building wall,
I managed to get 2 in on the other side of the tub but I think there's probably 2m in rubble and whats left in clay? before a complete stop.
There are 2 locations where I can drive more into , 1 which is the closest is 5 m away. on the next level 3m down (as the property has several levels /stepped)
the other is 12 m away, again 2 m lower,
I was thinking that at these distances between rods, although it may lower the overall reading , will it actually have a positive effect or could it actually lead to a false sense of security,
I did think about using an earth electrode tester as I can borrow one, but with the location being on a patio partly on soil with building rubble and a few metres away is an underground room, so a layout of rods across the area was not practical , and I was thinking "mat" from the start but agreed to look at installing rods first to see how it went.

 

[Engineer54]

Wow, 7 Rods already and still only at 45 ohms!!!

What type of earth rods are you using here, not those 3/8 thin 1.2m twiggs i hope?? You seem to have a lot of rubble around this property, and to be honest you have positioned your earth rods in just about the worst place possible, next to walls where you will Always encounter old builders construction rubble/debris. You need to find a decent rubble free position, where you can couple 2 or even 3 X 5/8'' rods together to get a minimal depth of 2.4m. Perhaps it may be a good idea if you excavate say around 1m X 1m X 1m pit at the chosen position to get rid of any debris etc (will also confirm no services present that you may otherwise hit) You could also apply a conductive clay (Bentonite) or even a chemical enhancer in the excavated pit, though i'm not a lover of chemical enhancers, as they need reapplying on a regular basis as they dissipate into the surrounding ground....

 

[edexlab]

5/8 coupled 7 rods straight down by hand!
I know there will be limited contact here while the soil consolidates where the couplers have made the hole bigger
As for siting rods next to the building I know !
I lifted the slabs and tried different areas and managed an average of 16 inches , this one kept going , so did I lol

Although as I've said before there is a lot of rubble approx 2 - 3m and this one is now clear of that and presumably into clay ( house is on a riverbank)
Will having a rod further away be a problem?
I know it'll reduce the overall value but I'm thinking as the ground immediately around the tub is poor
I can definitely get some in on the side of the property which is around 14 metres away lovely soft ground!!

 

[Engineer54]

5/8 coupled 7 rods straight down by hand!
I know there will be limited contact here while the soil consolidates where the couplers have made the hole bigger
As for siting rods next to the building I know !
I lifted the slabs and tried different areas and managed an average of 16 inches , this one kept going , so did I lol

Although as I've said before there is a lot of rubble approx 2 - 3m and this one is now clear of that and presumably into clay ( house is on a riverbank)
Will having a rod further away be a problem?
I know it'll reduce the overall value but I'm thinking as the ground immediately around the tub is poor
I can definitely get some in on the side of the property which is around 14 metres away lovely soft ground!!

Are you saying you have 7 rods coupled together going down 8.4 metres?? If this is a riverside property, then you must of hit the water table at that sort of depth. I'm not sure if it's going to be a worthwhile exercise going for another position, if you only achieve 45 ohms going down 8.4 metres. Nothing to stop you trying mind, if money/costs is not going to be a problem. Maybe try excavating around the existing rod and treat with a generous amount of Bentonite....

 

[edexlab]

Yes 7 coupled together plus 2 in a nearby position, it is a riverbank
but I reckon the rods point will be just about the same level as the river now as the house is on a steep bank roughly 7/8 metres higher than the river bank edge

It was quite frustrating as I always keep putting rods in until I can't do anymore and aim for a highest reading of 20 ohms but if I can put more in I do and usually get it a lot lower, this has been for Domestic or Agricultural