Bad shock off Hot Tub.

[Pufferfish1992]

Got called out to look at a hot-tub. (reasonably new I think) which client was getting a shock off. Have tested everything up to the panel in the Hot Tub. RCD is fine although hasn't tripped when under load. It is when the main motor kicks in that water become's live. Most likely a fault with the Hot Tub itself but with the callout charge I want to make sure. Anyone have any experience with this. What else could it be?

 

[telectrix]

rigourous testing will find. does sound like a hot tub fault. any road. customers that can afford the leccy to run these things deserve shocking.

 

[UNG]

What supply type do you have and how have you tested that the water becomes live
How is this hot tub earthed and what is the Zs of the supply?
How are the pump(s) and heater earthed?
Have you checked for earth connections / continuity on the electrical equipment on the hot tub

 

[HappyHippyDad]

What supply type do you have and how have you tested that the water becomes live
How is this hot tub earthed and what is the Zs of the supply?
How are the pump(s) and heater earthed?
Have you checked for earth connections / continuity on the electrical equipment on the hot tub

6 questions within 4 sentences, not bad.
The answers will be interesting.

 

[Gavin John Hyde]

Given the amoutn of hot tubs that have been bought since this pandemic began and number of enquiries I get regards running a circuit - i am usually too busy thankfully . It is about the right time we start getting threads on the forum about them causing issues. either poorly installed or dodgy parts in them.
Sadly I wouldn't be surprised if somebody does get a fatal shock one day as I was told for one I did quote for that I was too expensive and some fly by night outfit did it for £150 - the materials would have been £80 mind..

 

[UNG]

6 questions within 4 sentences, not bad.
The answers will be interesting.

Should I have asked more??

One of the big issues is earthing and the "just knock a rod in and TT it" brigade. All well and good not exporting the earth if understand what you are doing but just putting a rod in can create other problems if a fault occurs when you have water and wet people in the area around the rod and tub

 

[Pufferfish1992]

What supply type do you have and how have you tested that the water becomes live
How is this hot tub earthed and what is the Zs of the supply?
How are the pump(s) and heater earthed?
Have you checked for earth connections / continuity on the electrical equipment on the hot tub

The supply is PME which initially made me think that it could be broken PEN but tested and it seem's fine.
Hot tub wired in armoured all the way. Plastic board. Armoured glanded into box above CU. Earth on sheath wasn't earthed but have put that right today.(was picking up about 50-60v off the sheath.) Induction most likely. Armoured run is about 15m from the house into a rotary isolator. Isolator look's ok. Zs seemed within normal range if slightly higher than expected. They have spurred off the hot tub supply to feed some light's in the decking. (fused spur next to rotary iso) which made me think could that be anything to do with it (bit dodge). DIdn't even start looking at the hot tub itself. Just wanted to confirm it wasn't the wiring before calling an engineer out. Was debating putting an earth rod in but will see what the engineer says first. In the hot tub itself the armoured is just in a cord grip no gland needed wouldn't know where to start with pump's ,heater etc. Never encoutered such thing ever before it was like the wall and the ground was all live pretty worrying/playing on my mind tbh.

 

[Midwest]

@Pufferfish1992 what make/model is the tub?

 

[UNG]

The supply is PME which initially made me think that it could be broken PEN but tested and it seem's fine.
Hot tub wired in armoured all the way. Plastic board. Armoured glanded into box above CU. Earth on sheath wasn't earthed but have put that right today.(was picking up about 50-60v off the sheath.) Induction most likely. Armoured run is about 15m from the house into a rotary isolator. Isolator look's ok. Zs seemed within normal range if slightly higher than expected. They have spurred off the hot tub supply to feed some light's in the decking. (fused spur next to rotary iso) which made me think could that be anything to do with it (bit dodge). DIdn't even start looking at the hot tub itself. Just wanted to confirm it wasn't the wiring before calling an engineer out. Was debating putting an earth rod in but will see what the engineer says first. In the hot tub itself the armoured is just in a cord grip no gland needed wouldn't know where to start with pump's ,heater etc.

Have you actually confirmed the hot tub is properly earthed as it reads like you have only checked Zs at the isolator

Have you tried an earth leakage clamp on the mains to check if there is any earth leakage or at what level it is at

If you treat the hot tub as an appliance and test it as such what results do you get especially the testing of the earth bond from the supply point to the heater and pump(s)

Never encoutered such thing ever before it was like the wall and the ground was all live pretty worrying/playing on my mind tbh.

Have you confirmed this as a fact

 

[Pufferfish1992]

@Pufferfish1992 what make/model is the tub?

It's a Canadian Spa. Hot Tubs, Swim Spas, Replacement Covers - Built for Canadian Winters - https://www.canadianspacompany.co.uk/

 

[Midwest]

Looks like a reputable make. If the final circuit tests out ok, the next step is for the manufacturer to test its product. What do you get when the water becomes 'live'? How old is the tub?

 

[littlespark]

Oh brilliant. That’s the make ive got!

Mines is a small model that comes with 13A plug and 10mA inline rcd, but I know they come in the bigger variety’s.

 

[D Skelton]

Is it me or is there a direct correlation between the number of "what's the best way to wire up this hot tub" threads and the number of "shock off a hot tub" threads?

 

[i=p/u]

does seem quite popular thread, Section 702 applies..