Another Hot Tub Thread Part 2

[Midwest]

Following on from the last two more technically debated threads:

32A supply for Hot Tub of a PME supply
Another Hot Tub install

I posted a question, in the last one, but didn't get a reply, so starting another one. Hope the Mods don't mind.

So posting my question again, slightly edited.

I’ve been reading lots of threads, about hot tubs & the like, using a PME supply.

I’m thinking of buying one of those inflatable hot tubs Lazy Spa, primarily as a glorified paddling pool for my grandson. I was quite happy to plug into my outdoor socket on my composite (plastic) decking; I have a PME supply.

But since then, I've been reading all sorts things about extending pme (to an outside environment), and I've been contemplating whether to risk it. Manufacturer recommends connecting to equipotential bonding terminal

My options I know, are to either TT just the supply to the tub socket, use my pme supply and try and supplement that with a rod of <20. My sub soil is littered with rocks. Or just use the pme supply without a rod, and don't worry cause its on my plastic decking.

Or just forget it, and keep filling the paddling pool!

Your thoughts?

 

[pc1966]

In terms of effort, putting a DP RCD or RCBO & basic rod to TT the supply is the simplest and least-effort way for peace of mind.

You only need Ra < 200 ohms and you can probably get that with a short rod or a couple of horizontal buried bare 16mm copper wires 50cm down or whatever is practical and safe enough in that region of your garden. E.g. for wire you get it from places such as:

Bare Stranded Copper Conductors

Buy Bare Stranded Copper Conductors online from AN Wallis; number one supplier of your earthing, lightning and surge protection needs. Buy now.

www.an-wallis.co.uk

Unless you have reasonably high water table and long-ish rods I suspect getting Ra < 20 ohms will be a challenge. Or the extra effort for a bigger earth mat style of installation.

The earth mat (or several radial wires) has another attraction, if extending beyond the tub and deep enough down it need not meet 20 ohms for protection as it will still raise the poorly conductive ground above it in that region so [Tub] to [Earth (local)] touch voltage is low enough. But you are looking at a lot of physical effort to do that.

I think the fact you have posted this means you are concerned, and so for peace of mind then a TT arrangement for tub and any outdoor feeding sockets would be of moderate cost and not too much disruption to fit.

 

[telectrix]

no need for any rods. Lazy Spa tubs come with a 10mA RCD built into the lead. it's really just plug and play, whatever earthing system you have.

 

[Midwest]

Thanks. The challenge will be getting an earth rod in, very stony ground. Its too late for an earth mat, as I've had the back garden done.

Of course another alternative might be the ev charger devices. I know there's a little bit of mocking about this, on the you tube sparks, but it is mention at the end of this piece.

 

[richy3333]

@Midwest ive been chatting to Matt-e about this very thing this week. They say their devices are only for ev chargers despite what Super sparks Gifford says.

 

[pc1966]

I found the LazySpa manual on-line and it says the stuff quoted below.

No mention of supply earthing, but they do have an RCD in the lead, not sure if it in effect TT's the tub. Oddly though they warn about not having a grounded socket!

Also odd they warn against using it in the rain! Buggerall use in Scotland then...

=========================================================================

SAFETY INSTRUCTIONS

When installing and using this electrical equipment, basic safety precaution should always be followed, including the following:
READ AND FOLLOW ALL INSTRUCTIONS.

WARNING: RISK OF ELECTRIC SHOCK. Insert the plug only into a properly grounded socket.

WARNING: The spa must be supplied by an isolating transformer or supplied through a residual current device (RCD) having a rated residual operating current not exceeding 30mA.

WARNING: RCD/PRCD must be tested before each use.

WARNING: If the supply cord is damaged, it must be replaced by the manufacturer, its service agent or similarly qualified persons in order to avoid a hazard.

WARNING: To reduce the risk of electric shock, do not use extension cord to connect unit to electric supply; provide a properly located outlet.

WARNING: No part of the appliance is to be located above the bath during use.

WARNING: Parts containing live parts, except parts supplied with safety extra-low voltage not exceeding 12V, must be inaccessible to a person in spa pool; Earthed appliance must be connected to the fixed socket which is permanently connected to fixed wiring. Parts incorporating electrical components, except remote control devices, must be located or fixed so that they cannot fall into the spa pool.

WARNING: The plug of spa shall be more than 3.5m away from the pool.

WARNING: It is necessary to have the plug accessible after installation of the pool.

WARNING: TO AVOID ELECTRIC SHOCK, DO NOT USE THE SPA WHEN IT IS RAINING.

WARNING: This appliance is not intended for use by persons (including children) with reduced physical, sensory or mental capabilities, or lack of experience and knowledge, unless they have been given supervision or instruction concerning use of the appliance by a person responsible for their safety. Children should be supervised to ensure that they do not play with the appliance.

WARNING: To reduce the risk of injury, do not permit children to use this product unless they are closely supervised at all times.

WARNING: Water attracts children; Always attach a spa cover after each use.

WARNING: Do not bury cord. Locate cord to minimize abuse from lawn mowers, hedge trimmers, and other equipment.

WARNING: To reduce the risk of injury, replace damaged cord immediately.

DANGER: Risk of Accidental Drowning. Extreme caution must be exercised to prevent unauthorized access by children. To avoid accidents, ensure that children can not use this spa unless they are supervised at all times.

WARNING: RISK OF INJURY. Never operate spa if the suction fittings are broken or missing. Never replace a suction fitting.

WARNING: RISK OF ELECTRIC SHOCK. Install at least 1.5m from all metal surface.

WARNING: RISK OF ELECTRIC SHOCK. Never operate any electrical appliance when in your spa or when your body is wet. Never place any electric appliance, such as a light, telephone, radio, or television, within 1.5m of spa.

CAUTION: In order to avoid a hazard due to inadvertent resetting of the thermal cut-out, this appliance must not be supplied through an external switching device, such as a timer, or connected to a circuit that is regularly switched on and off by the utility.

WARNING: During pregnancy, soaking in hot water may cause damage to the fetus. Limit use to 10 minutes at a time.

WARNING: TO REDUCE THE RISK OF INJURY:

A. The water in a spa should never exceed 40°C (104°F). Water temperature between 38°C(100°F) and 40°C(104°F) is considered safe for a healthy adult. Lower water temperatures are recommended for young children and when spa use exceeds 10 minutes.

B. Since excessive water temperatures have a high potential for causing fetal damage during the early months of pregnancy, pregnant or possibly pregnant women should limit spa water temperature to 38°C (100°F).

C. Before entering a spa, the user should measure the water temperature with an accurate thermometer since the tolerance of water temperature regulating device varies.

D. The use of alcohol, drugs, or medication before or during spa use may lead to unconsciousness with the possibility of drowning.

E. Obese persons and persons with a history of heart disease, low or high blood pressure, circulatory system problems, or diabetes should consult a physician before using a spa.

F. Persons using medication should consult a physician before using a spa since some medication may induce drowsiness while other medication may affect heart rate, blood pressure, and circulation.

 

[Midwest]

no need for any rods. Lazy Spa tubs come with a 10mA RCD built into the lead. it's really just plug and play, whatever earthing system you have.

My primary concern, is the loss of pen conductor. The appliance is Class 1, so potentially it could become live through the water heater > water > grandson then stepping onto floor. Long shot I know, but a possibility.

PS, got me links muddle up, I'll post the link for their advice for bonding the pump, when I can get on their web site.

Page 11


Hmmm, cancel my thread. Its now saying the apparatus is Class II

 

[pc1966]

You sure? Page 11 of that manual has:

Using an extension lead or multi plug adaptor with the spa heater can cause the plug to overheat, causing damage to the equipment and surrounding items. The spa is a class 1 electrical appliance and must be connected directly to a grounded socket. It is recommended to only use a socket which is resistant to humidity and capable of high power loading. Regularly check the plug and socket for signs of damage before using the spa – do not use the spa if the plug or socket is damaged. If you are unsure about the quality of the electrical supply, please consult a qualified electrician before use.

 

[Midwest]

I'll have to contact them and clarify. Web page definitely says Class 2. The manual for the Barbados is not available.

220-240V~50Hz, 2,060W at 20°C, Class II

Barbados

 

[pc1966]

That page also says:

SPA PUMP EQUIPOTENTIAL BONDING TERMINAL
It is recommended to arrange for a qualified electrician to connect the spa pump to an equipotential bonding terminal using a minimum 2.5mm2 solid copper conductor

Where can we find someone like that? <joke alert - in case anyone takes offence>

 

[nicebutdim]

I'm guessing that PDF manual is for a particular product, but the 'barbados' model is of different construction?

 

[Midwest]

That page also says:

SPA PUMP EQUIPOTENTIAL BONDING TERMINAL
It is recommended to arrange for a qualified electrician to connect the spa pump to an equipotential bonding terminal using a minimum 2.5mm2 solid copper conductor

Where can we find someone like that? <joke alert - in case anyone takes offence>

Yep I posted that before, except I mixed up me links. Also can't see why a Class 2 device would need a PRCD? It does say on their web sites that their tubs are Class 2, but the instructions suggest Class 1.

I've emailed them, they've confirmed my enquiry. I'll post when they come back to me.

 

[bigspark17]

i cant belive someone hasnt come up with a contactor that is now allowed to disconnect the L N and cpc of this circuit much the same as the new ev chargers. This would elimate all this confusion.
for my 20pence worth. I use the pme earth unless otherwise stated in manufacturers instructions. If it is required i will isolate cpc (pme)@ the isolator and install a 3/8 rod below the isolator.

 

[Midwest]

i cant belive someone hasnt come up with a contactor that is now allowed to disconnect the L N and cpc of this circuit much the same as the new ev chargers. This would elimate all this confusion.

I've just watched John Wards vid on ev chargers (June 2020). He's not convinced that those devices will disconnect on all occasions, with a pen disconnect.

I've been trawling around the web, to find a nice looking garage size CU, for my hot tub supply, if I need that. It will have to be located in my down stairs toilet, to keep away from other TN-C-S earths in the house, and close enough for socket location.

Found the FuseBox one, which looked ok. But then came across the Schneider Resti 9 & Easy 9, which you can customize the cover. But Schneider don't seem to do a Type A RCD in those ranges?

It also says not to use their surge protection on TT supplies; my garage unit will be fed from a SPD CU?

 

[bigspark17]

Why not use existing way in existing cu to rotary isolator and TT from this location?

 

[Midwest]

Why not use existing way in existing cu to rotary isolator and TT from this location?

Are you saying use the pme, and add a local earth rod?

 

[bigspark17]

Are you saying use the pme, and add a local earth rod?

no isolate the pme in rotary then continue with the electrode.

 

[pc1966]

One though I had was to use a 4-pole RCD after the usual 2-pole RCD/RCBO to allow the supply to trip including CPC if there was a stray current in the CPC. But that has several issues in practice, such as needing enough volts to trip the RCD and no normal earth currents to confuse it.

Also the PME-derived earth for a hot tub also has the issue that it could be 5-10V above true Earth without any fault which is enough to make a wet person notice it.

 

[Midwest]

no isolate the pme in rotary then continue with the electrode.

I'm confused as to how that would work. Upstream RCD might notice imbalance, but earth fault down that earth rod? Suppose it would make no difference where the RCD was, compared to where the earth rod is.

 

[pc1966]

I think @bigspark17 suggestion is you break the CPC at the rotary isolator, so your CU has a DP RCD and the SWA out has the PME-derived CPC, but there is a different earth system from the isolator to the tub (and any related sockets).

Of course you need to make sure there is no metalwork, etc, in touchable range that is on a different earth system (e.g railings with a PME-derived earthed floodlight, CCTV camera, etc, mounted on them etc).

Stand alone metalwork in contact with the Earth is fine, as that is your TT rod's system anyway. No harm in bonding to the rod just in case though.