Hot tub tripping, but also working… crossed Neutral?

[Refinedgent]

Hi Guys
just recently bought a new house that came with a hot tub! Fun times,
after filling it up and switching it on, it works a treat huzzahh!

HOWEVER
The tub has its own 32Amp fuse on an RCD fuse board in an outbuilding, nothing else is on this fuse, tub only.
The wiring from this then goes outside to the tub to another smaller IP65 RCD with a DIN rail and 40A 30mA breaker.
This breaker switch does not function… regardless of switch on or off, Tub remains on.
(if the 32Amp fuse in main outhouse is switched tub powers on/off as it should)
I didn’t think too much of this and guessed the exterior fused switch was dead or it simply wasn’t wired up Or some such.

Upon isolating the supply and opening up the exterior British General box, I replaced the fuse with a like for like swap 40A 30mA fuse….
still nothing.. the new fuse wasn’t switching anything…. Tub was working great but this switch was doing nothing…

I then checked the tub itself just on off chance it was wired incorrectly and sure enough
Live was correct, but Neutral and Earth were swapped, hence switch wasn’t vitally switching anything. Odd I thought… I swapped them round so now correctly wired….
now main breaker is tripping.

I’m guessing I have a Neutral or Earth that is touching the live somewhere along the wire somewhere?
Or could it be the hot tub is drawing too much power upon start up and tripping the RCD? (I disconnected tub heater and pumps and tried switching on but still same issue, so I don’t think it’s anything wrong with the tub as it wouldn’t be drawing much power at all)

It appears whoever lived here prior had this issue of tripping and just swapped the earth and neutral to get around the issue, which doesn’t seem terribly safe)

any advice much appreciated, thanks all

 

[ericmark]

Hot tubs outside need careful earthing. electrical installations outdoors a supply to a detached outbuilding. and Broken Pen go into it more, it is not really a DIY job.

 

[Refinedgent]

Hot tubs outside need careful earthing. electrical installations outdoors a supply to a detached outbuilding. and Broken Pen go into it more, it is not really a DIY job.

Wow, there’s some bed time reading….

the tub is an American model (arctic spa cub) and I understand these often get down rated so I wonder if this has something to do with it. Tub is somewhat elderly and been in situ and in use for many years, wired up as outlined above.

it does appear to be fully RCD protected at 32Amp from the main CU in the outbuilding on its own circuit, so maybe this is fine (I understand since I think the tub was installed it’s now preferred to have a Rotary switch located close by for maintenance etc, I assumed the double pole 40Amp that is on the sealed DIN rail served this purpose as was switched but as it didn’t function this threw up my concerns.
will the current wiring with swapped earth and neutral mean RCD protection is now not in place?

 

[JohnW2]

....a new house that came with a hot tub! .... , it works a treat huzzahh! … regardless of switch on or off, Tub remains on.

I then checked the tub itself just on off chance it was wired incorrectly and sure enough ... Live was correct, but Neutral and Earth were swapped, hence switch wasn’t vitally switching anything. Odd I thought… I swapped them round so now correctly wired…. now main breaker is tripping.

Unless I'm misunderstanding, something there does not add up. The tub was clearly working, but if the N & E connections to it were 'swapped', then any RCD protecting the circuit would have tripped immediately the tub tried to draw any current.

As I see it, if there were no N-E fault (faulty connection between the two) all of the L current would be going through an RCD, but none would be going through the other side (meant to be neutral, but connected to the tub's earth), since all the return current would be going through the E, so any current drawn by the tub would immediately trip the RCD. At the other extreme, even if there were a 'dead short' between N & E in the tub, at least some of the current would be returning to the CU through what was meant to be the earth conductor, hence not all of it would be going through the RCD - so, again, the difference between current in the two sides of the RCD would cause an instant trip.

I therefore think that it would require at least one other fault (e.g. a break in the neutral somewhere) in addition to the swapped N and E for the tub to work without tripping an RCD. Do I take it that you are sure that at least one of the two RCDs actually works?!

What is the 'main breaker' that is now tripping - are you referring to an MCB or an RCD?

Kind Regards, John

 

[bernardgreen]

the tub is an American model (arctic spa cub)

What colour are the wires in the cable to the spa ?

American wiring colours are :-

Live BLACK
Neutral WHITE
Earth GREEN ( but not always )

I understand these often get down rated

American supplies can use two 120 V phases to achieve 240 V for large appliances. The heating element is connected between two phases and does not use a Neutral from the supply

The same appliance in the UK will have the heating element connected between one phase and Neutral.

 

[ericmark]

I agree with @JohnW2 if it was working seems unlikely neutral swapped. We can have TN or TT supplies to our homes, and with TN often TN-C-S which can have loss of PEN problem, using an earthed mat under the hot tub one can ensure the area around it is earthed to same polarity as hot tub, the same if using TT, but one can't assume because it has been working for years it is OK.

In the main out door electrical equipment is class II, lawn movers, etc, so it does not matter what earth is used as it does not use the earth, even some hot tubs are class II.

However the earthing or bonding of outdoor electrical equipment is complex, and you would be better not to DIY the out door supply, in Wales it is considered as a special location and the work needs registering, for some reason I don't know why, this was removed in England, even in Wales I have seen errors made with out door supplies, where caravans have been plugged into a TN-C-S earthed system, which is against the rules. But less likely to happen when installed by an electrician.

With equipment from USA I have seen errors made, it is possible an isolation transformer is used, but some transformers have the core earthed to one winding, it just gets too complex to cover all possibilities.

 

[Harry Bloomfield]

it does appear to be fully RCD protected at 32Amp from the main CU in the outbuilding on its own circuit, so maybe this is fine (I understand since I think the tub was installed it’s now preferred to have a Rotary switch located close by for maintenance etc, I assumed the double pole 40Amp that is on the sealed DIN rail served this purpose as was switched but as it didn’t function this threw up my concerns.

I would suggest that you supply good, clear photos of all connections, RCD's and MCB's with the covers removed, including one of the name/rating plate itself, on the tub.

 

[Refinedgent]

Unless I'm misunderstanding, something there does not add up. The tub was clearly working, but if the N & E connections to it were 'swapped', then any RCD protecting the circuit would have tripped immediately the tub tried to draw any current.

As I see it, if there were no N-E fault (faulty connection between the two) all of the L current would be going through an RCD, but none would be going through the other side (meant to be neutral, but connected to the tub's earth), since all the return current would be going through the E, so any current drawn by the tub would immediately trip the RCD. At the other extreme, even if there were a 'dead short' between N & E in the tub, at least some of the current would be returning to the CU through what was meant to be the earth conductor, hence not all of it would be going through the RCD - so, again, the difference between current in the two sides of the RCD would cause an instant trip.

I therefore think that it would require at least one other fault (e.g. a break in the neutral somewhere) in addition to the swapped N and E for the tub to work without tripping an RCD. Do I take it that you are sure that at least one of the two RCDs actually works?!

What is the 'main breaker' that is now tripping - are you referring to an MCB or an RCD?

Kind Regards, John

This is what I find weird,
see attached pics which may help in explanation
1/ first pic shows the CU in outbuilding - RCD protected B32
2/ pic shows wiring to the smaller IP65 box adjacent to tub (feed coming in the top, wiring to tub going out the bottom)
3/ pic shows inside the tub, the wiring set up. Top ‘box’ diagram shows an earth symbol (obscured by that bundle of wires), then in descending oder ‘LINE 2, LINE 1 (with brown wire) , N (with black wire) and LINE 3’. (I’m assuming Line 1 = LIVE and LINE 2 + 3 unused) as you can see form this it appears earth and neutral are swapped in the tub.

The 40Amp double pole switch 100% works as is brand new
and the B32 switch also definatley ‘functions‘ as an on off switch and also ‘trips‘ if tested

 

[Refinedgent]

I would suggest that you supply good, clear photos of all connections, RCD's and MCB's with the covers removed, including one of the name/rating plate itself, on the tub.

Ahhhhh

upon trawling the internet… I think I may have found the issue…
found the instruction manual for tub…
in the current set up LINE 1 is assumed as LIVE…. Looks like it’s actually LINE 2 that should be connected?
anyone any thoughts on this before I go do something stupid….

looks as if it was connects as if it was set up for 2x 16amp in stead of 1x32…. Would this be the reason for the trip?

 

[EFLImpudence]

The supply line(live) and load(tub) line are connected and don't go through the RCD.

 

[Refinedgent]

The supply line(live) and load(tub) line are connected and don't go through the RCD.

View attachment 310475

how did I not spot this…. Duh!
So load (tub) should be connected to underside left hand side of the RCD?

 

[EFLImpudence]

as you can see form this it appears earth and neutral are swapped in the tub.

They appear to be - but could there be a junction box somewhere where the wires are swapped (for some reason)?
OR
Does that plastic cover come off and perhaps the tub wiring is wrong?

So load (tub) should be connected to underside left hand side of the RCD?

Yes.

 

[bernardgreen]

The RCD in picture 2 need to have the Live to the tub to be connected to the Load side of the RCDView attachment 310476

 

[bernardgreen]

 

[Refinedgent]

They appear to be - but could there be a junction box somewhere where the wires are swapped (for some reason)?
OR
Does that plastic cover come off and perhaps the tub wiring is wrong?



Yes.

Found this diagram handily on reverse of tub panel….

appears that brown LINE 1 wire should indeed actually be in LINE 2 socket,
maybe this is causing the trip as it’s mistakenly trying to 2x16amp power and causing issues?