Hot tub installation !

D

devonsparky

This is a follow up to a thread I started yesterday.

I have been working all day installing a hot tub situated outside on a patio slabbed deck.

Contrary to what I was told, it was TN-C-S supply so here is how I have wired it.

  • From Henly blocks - 25mm tails to a one way board (Main Sw RCCB - 50A MCB)


  • 10mm 3 core SWA from board to 63A rotary isolator and from rotary isolator to hot tub


  • Earth rod with 10mm G/Y back to one way board and then used one core as an earth to the hot tub and connected the armour to the earth bar too.



Time beat me today so I have not connected into the Henly blocks yet and tested .......................... Is this how you guys would have done it. 10 years in the game and an approved electrician and it's still nice to get feedback off of this forum !! ha ha
 
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Engineer54 said:
If the hot tub was located on bare ground or grass, i think i'd be also installing a rod, even if it was a TN-S supplied installation. Your still going to get a potential difference between true earth and the DNO TN-S earth.....


As for the Regs, i think they state somewhere, that a TNC-S supply can be used, for supplying hot-tubs and the like provided an earth electrode of a certain value is also provided.... I think that value was around 20 ohms, but i wouldn't swear to it...
Click to expand...

Nothing like PME E54, i very much doubt you would feel any sensation on a TN-S.

As for an Electrode on a PME, for it to be any use you would be looking at very low single figures.

A lot of these Hot Tubs are class II as well.
 
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Further back in this thread it was mentioned that someone had a small tingle while getting in and out with tncs to that why I've decided to tt. As long as I can get less than 199 ohms.

- - - Updated - - -

Only kidding about the 199. Don't start biting me
 
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keithsims said:
I replied in the other thread, I installed my tub using the supplied tncs earthing arrangement also putting a rod in at the tub end. This rod was well below 22 ohms as stated in the regs, the only problem I had was when you got out the tub and one leg was on the floor and one in the water you could feel a shocking feeling, slight difference between true earth and suppliers earth, therefor I disconnected the suppliers earthing and made the tub tt. Alls fine now so that's how I install them from now on!
Click to expand...
From page 2 also he said the voltage between the water and earth rod was only 2 v
 
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Will Pickard said:
Further back in this thread it was mentioned that someone had a small tingle while getting in and out with tncs to that why I've decided to tt. As long as I can get less than 199 ohms.

- - - Updated - - -

Only kidding about the 199. Don't start biting me
Click to expand...

On a PME, yes its very possible, its also possible if you TT it to, be careful where you put that rod:)

If it class II where's the risk?
 
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I may be wrong here but...l even if it is class two would the element still be in contact with the water, anyway the one I'm doing this week is class one, no exposed metal but when you open the cover the pump and heater unit are metal

Back to the post I copied, personally I don't think youd feel the 2 v so the insulation in the heater is breaking down when getting hot. 2 nod thing the rcd should trip at a max of 50 v probably less
 
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SPARTYKUS said:
If you're getting a tingle somethings very wrong
Click to expand...

I believe its because everything is bonded back to an earth bar in the control box, including the pumps casings and frame, elements heating tubes etc, there is a little earth leakage from the heating element and in turn you feel it when you touch suppliers earth (in this case the water is included as its being heated and running through the heating pipes and being pumped) and true earth (in this case the concrete floor ( I had not finished the decking) not enough to hurt but enough to feel it! Iv heard of it before, a boy sat in the tub and his girlfriend who was standing on the bare ground and she gave him a kiss and got the tingles lol!
Anyway mines all fine now it's TT. Even when it was tncs with earth rod I still got the 2v pd so I isolated the suppliers earth at the hot tubs consumer unit
 
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Chr!s said:
Nothing like PME E54, i very much doubt you would feel any sensation on a TN-S.

As for an Electrode on a PME, for it to be any use you would be looking at very low single figures.

A lot of these Hot Tubs are class II as well.
Click to expand...

I didn't say it was anything like PME. However, there is still a real difference between an electrical supply TN-S earth and true earth. A potential difference will be present. Now if were talking about this hot tub being located on wooden decking, i wouldn't bother with installing a rod at all, but on bare ground or grass, ...always better to air on the safe side.

You could well be right about some of these tubs now being Class 11, but i've personally never come across one to date...., But then most of the units i've worked with or come across, have been American and Canadian jobby's and most of those are supplied with an earth rod as part of the installation kit... Also, most of those hot-tubs have integral RCD's in the control panel...
 
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Engineer54 said:
Also, most of those hot-tubs have integral RCD's in the control panel...
Click to expand...

if they are USA / Canadian built then the rcd's arent going work with a UK supply.

Anyways , the hot tub install i mentioned earlier was all wood construction with metal internal control boxes that can only accessed by removing a panel using a tool
i consider this a class 2 piece of equipment , dont know how others may feel ?
 
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biff55 said:
if they are USA / Canadian built then the rcd's arent going work with a UK supply.

Anyways , the hot tub install i mentioned earlier was all wood construction with metal internal control boxes that can only accessed by removing a panel using a tool
i consider this a class 2 piece of equipment , dont know how others may feel ?
Click to expand...

All higher powered equipment in the States like cooker ranges, tumble dyers, etc etc, are 220/240 volts.... Hence ALL hot tubs in the States and Canada are 220/240 volts... Never seen a 115 volt hot tub anywhere.
 
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Will Pickard said:
Take it in the USA they have 115v 2 phase supply then do they? Or do they gat all 3 phases to the house?
Click to expand...

It's called a 3 wire single phase supply, in essence it's a split phase and neutral supply.... 220/240volts between the split phases and 115/120 volts between phase and neutral/earth...
 
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All the ones ive installed ive installed on a TNCS supply if thats on the house and they are fibre glass and the only metalic parts are within the TUB none have integrated RCD's, main switch RCD and 40 amp MCB if you get a neutral fault then this will cause an imbalance and trip the RCD , in the area i am if you can get an earth rod in more than 300mm you'll be lucky , non of the manufacturers instruction have stated that they require an RCD and i understand about exporting the earth , bit like roding a wooden garden shed supply
 
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nickblake said:
All the ones ive installed ive installed on a TNCS supply if thats on the house and they are fibre glass and the only metalic parts are within the TUB none have integrated RCD's, main switch RCD and 40 amp MCB if you get a neutral fault then this will cause an imbalance and trip the RCD , in the area i am if you can get an earth rod in more than 300mm you'll be lucky , non of the manufacturers instruction have stated that they require an RCD and i understand about exporting the earth , bit like roding a wooden garden shed supply
Click to expand...

Dont just think of the tub construction material when talking about Class 11, you have pumps and heaters, then think what will pass through them, ..yes water, ...but not just your standard tap water, the water will be treated with chemicals to correct Ph values and others for disinfection to keep it crystal clear, such as Bromine, Algaecide, flocculates, etc etc... Which i would think, will make the water far more conductive than your standard water will be....
 
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Engineer54 said:
Dont just think of the tub construction material when talking about Class 11, you have pumps and heaters, then think what will pass through them, ..yes water, ...but not just your standard tap water, the water will be treated with chemicals to correct Ph values and others for disinfection to keep it crystal clear, such as Bromine, Algaecide, flocculates, etc etc... Which i would think, will make the water far more conductive than your standard water will be....
Click to expand...

Blinking good point E54. Water on its own, rubbish conductor.
 
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nickblake said:
All the ones ive installed ive installed on a TNCS supply if thats on the house and they are fibre glass and the only metalic parts are within the TUB none have integrated RCD's, main switch RCD and 40 amp MCB if you get a neutral fault then this will cause an imbalance and trip the RCD , in the area i am if you can get an earth rod in more than 300mm you'll be lucky , non of the manufacturers instruction have stated that they require an RCD and i understand about exporting the earth , bit like roding a wooden garden shed supply
Click to expand...


Its not just about a fault on the tub, you should TT a hot tub, its all about the potential difference between true earth and the MET (PME)

Its the failure of the PME thats the worry here,

Plus class 1 fittings in and around the tub could be a problem.

personally i would TT a hot tub
 
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yes i do understand so why are we using PME at all because if you loose the supply neutral in a house that has a shower above the a cast iron bath then you have an even worse scenario every piece of bonded metal will become at a potential of around 110 volts so realisticall every PME installation shold be TT just in case
 
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OldeSparky said:
Its not just about a fault on the tub, you should TT a hot tub, its all about the potential difference between true earth and the MET (PME)

Its the failure of the PME thats the worry here,

Why? because 1 in ten million have temporarily lost the neutral that is subsequently fixed pronto?

Plus class 1 fittings in and around the tub could be a problem.

personally i would TT a hot tub
Click to expand...

So you prefer to rely on a device thats proven to be unreliable and subject to high failure rates (the RCD) for disconnection! Theres a lot more chance (probably several orders higher) of the RCD failing than the PME neutral being lost.


Don't get me wrong I am not a fan of PME (TNS all the way) but .... the logic puzzles me. Loss of neutral is unheard of. And fixed quickly the miniscule few times it happens. RCD failure is rife and often never checked, fixed or found. Especially when they're fitted by a "friend" that has 'acquired' the board and RCD and has no registration, invoice, and more importantly, test equipment. Changed a few things for a mate who had the board changed 8 years ago, as above, RCD was kaputt. Probably never worked. How would we know? It was never tested.
 
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SPARTYKUS said:
So you prefer to rely on a device thats proven to be unreliable and subject to high failure rates (the RCD) for disconnection! Theres a lot more chance (probably several orders higher) of the RCD failing than the PME neutral being lost.


Don't get me wrong I am not a fan of PME (TNS all the way) but .... the logic puzzles me. Loss of neutral is unheard of. And fixed quickly the miniscule few times it happens. RCD failure is rife and often never checked, fixed or found. Especially when they're fitted by a "friend" that has 'acquired' the board and RCD and has no registration, invoice, and more importantly, test equipment. Changed a few things for a mate who had the board changed 8 years ago, as above, RCD was kaputt. Probably never worked. How would we know? It was never tested.
Click to expand...

How would you know if the Earth was lost on a TN-S? That's one advantage of PME, the DNO are alerted to it.

Each system come's with risk, non are infallible.

Broken PEN'S, it hapens, quite rare

RCD'S failing, it happens, more down to not testing the RCD quarterly or the system to which it connects to than the RCD itself.

TN-S loss of Earth, it happens, though very little TN-S in most area's now, certainly Domestic anyhow.
 
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Hi Chr!s

good point re loss of earth on TNS. Not sure. Assume most losses would be because cable is severed or damaged, isn't the outer usually the earth on TNS?

I'm just a cynic and suspect they dropped the idea of having 3 hard lines back to the sub station as it is (clearly) cheaper to have 2 instead.... all about money.

I agree, nothing is infallible.

Not sure about the quarterly testing. I have come across a few that operate satisfactorily on the test button, but do not operate when tested (ramp, x1, etc) and have been replaced). So as mentioned, nothing is infallible including the test button!

TNS a dying breed.

Don't know much about the construction, etc between a house and substation of a TNS cable. Would love to though!:D
 
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