Hot tub tripping, but also working… crossed Neutral?

[JohnW2]

The point is @Refinedgent has not stated if TN-S, TT, or TN-C-S and if he does not know, then not safe for him to do the work.

In terms of "the work" that is being done (attempting to identify and correct suspected wiring errors) I'm not sure in what sense the OP (or anyone else) would do anything differently, regardless of whether the installation's supply was TN-S, TN-C-S or TT.

It is, of course possible that the tub was not originally installed in a manner which was safe with regard to the supply type. That's a potential problem with any 'inherited electrical installation' and, in this case, had it not been for the seemingly anomalous behaviour (non-hehaviour) of the second RCD the OP would have had no reason to be looking into the matters that he has reported here. I suppose you could therefore argue that anyone inheriting an electrical system should have it 'inspected' to make sure that it had been installed correctly, and was ;'safe'?

The issue is not even restricted to 'inherited electrical installations'. What if the OP (or anyone else) had himself had the tub installed by an 'electrician'? Very few members of the public would have any way of knowing whether it had been installed "safely with regard to the type of supply" - so should they be advised to always get a second electrician to inspect the work, to make sure that the first one has done it 'safely', or what?

As an aside, I also somewhat suspect (from the terminology he has been using) (although I obviously may be wrong) that the OP may well 'know' more than you are seemingly assuming.

Kind Regards, John

 

[Refinedgent]

In terms of "the work" that is being done (attempting to identify and correct suspected wiring errors) I'm not sure in what sense the OP (or anyone else) would do anything differently, regardless of whether the installation's supply was TN-S, TN-C-S or TT.

It is, of course possible that the tub was not originally installed in a manner which was safe with regard to the supply type. That's a potential problem with any 'inherited electrical installation' and, in this case, had it not been for the seemingly anomalous behaviour (non-hehaviour) of the second RCD the OP would have had no reason to be looking into the matters that he has reported here. I suppose you could therefore argue that anyone inheriting an electrical system should have it 'inspected' to make sure that it had been installed correctly, and was ;'safe'?

The issue is not even restricted to 'inherited electrical installations'. What if the OP (or anyone else) had himself had the tub installed by an 'electrician'? Very few members of the public would have any way of knowing whether it had been installed "safely with regard to the type of supply" - so should they be advised to always get a second electrician to inspect the work, to make sure that the first one has done it 'safely', or what?

As an aside, I also somewhat suspect (from the terminology he has been using) (although I obviously may be wrong) that the OP may well 'know' more than you are seemingly assuming.

Kind Regards, John

Thanks John,
and yes you are bang on.
I inherited the current tub set-up which has been in situ for years (over a decade in fact)
filled with water switched on and bobs your uncle it works a treat.

It’s only as frankly I tinker with things and I’m nosy that I even bothered to check the tub fuse board and open up the tub to check its wiring. I’d wager 99% of individuals would turn on tub, fill with water and be done with it. Why check a perfectly good hot tub that’s working beautiful and has been there for years? (when staying in a hotel, air BnB, etc etc does everyone here also check the electrical installations of their accommodation and hot tubs… I think not. Though I’m sure we’re about to get inundated with members who will not step inside a structure without their multimeters at hand)


any way. I have now ‘correctly’ connected the tub up (with the live travelling through the 40Amp as it ‘should‘ be (amd not bypassed!) , and the tub LINE 2 used as main Live in (it can be set up for 3 phase but I don’t have 3 phase) . And sure enough it’s tripping the RCD. Indicates To me likely culprit is some component in the tub that is drawing too much power or there’s some earth fault somewhere (Not terribly surprised as the tub is elderly. I tried isolating heaters and pumps as this often highlights which component is duff, but to no avail.)

I suspect the previous owner when also seeing the tub was tripping the RCD simply by-passed the local RCD and then decided to swap Neutral and Earth, which is obviously bad practise, but perhaps they had a laise-fair attitude to electrics, who knows, and they just really wanted the tub to work and bugger the RCD protection. I believe I’m correct in saying with the current set up (i.E. Live to Live, and Neutral and Earth swapped at the tub in theory RCD protection is currently NOT in place? Though I do find it weird the tub is functioning perfectly with no trips…

anyway I now have a technician from Arctic spa coming on Friday to check it over and see what’s what, maybe a motherboard fault (my guess)


also it’s a TNCS

 

[EFLImpudence]

any way. I have now ‘correctly’ connected the tub up (with the live travelling through the 40Amp

More correctly "the 30mA".

as it ‘should‘ be (amd not bypassed!) , and the tub LINE 2 used as main Live in (it can be set up for 3 phase but I don’t have 3 phase) . And sure enough it’s tripping the RCD. Indicates To me likely culprit is some component in the tub that is drawing too much power

RCDs don't trip on "too much power"; they trip on tiny amounts of current in the wrong place; i.e. missing from the correct place.

or there’s some earth fault somewhere

Well possibly. Have you figured out the apparent N and E reversal yet?

(Not terribly surprised as the tub is elderly. I tried isolating heaters and pumps as this often highlights which component is duff, but to no avail.)

I suspect the previous owner when also seeing the tub was tripping the RCD simply by-passed the local RCD and then decided to swap Neutral and Earth, which is obviously bad practise, but perhaps they had a laise-fair attitude to electrics, who knows, and they just really wanted the tub to work and bugger the RCD protection.

I'm confused. Is the RCD tripping or not?

If it is not then the N and E cannot be reversed - despite the colours.
If it is then perhaps the N and E are reversed - despite the colours.

I believe I’m correct in saying with the current set up (i.E. Live to Live, and Neutral and Earth swapped at the tub in theory RCD protection is currently NOT in place?

Why not? Where is it?

Though I do find it weird the tub is functioning perfectly with no trips…

Then N and E cannot be reversed - despite the colours.

 

[ericmark]

I remember with my parents house as a boy I managed to blow the fuse when the line touched the earth, so I know at that time there was an earth, I was around 14 year old, 72 now.

But when many years latter I came to wire up a wet room, the only earth I could find was the one installed by the GPO for the party line phone, there was no sign anywhere of there ever being an earth. I called the DNO and asked what earth I should have, and they didn't know so sent some one out, who gave us TN-C-S.

I have also seen the reverse, where a house was TN and was rewired by my son with no power to the house while being rewired, and when the supply was reinstated they were given TT so no earth. Errors can be made, which is why we should have an EICR every 10 years (5 years with rental).

The problem is TN-S can be made into TN-C-S without the owner even knowing, and within the home it does not really matter, only in the garden is there a problem. And only then with a loss of PEN, I seem to remember seeing a report saying around 250 cases a year, so one would be very unlucky for it to happen while one was in the tub.

I was looking at where I work, technically a TN-C-S supply, but the building is a metal frame, and is connected to the railway lines, so even with a loss of PEN unlikely the voltage would raise much, and the railway lines connect the buildings and there is more than one transformer supplying them so would need multi loss of PENs to be a danger.

In the main the big problem with loss of PEN is fire, where gas pipes melt, due to earth bonding wrong side of isolator block, when I have been studying my C&G 2391 nothing was said about testing to ensure the bonding was not corrected to wrong parts, so not sure even with an EICR faults would be found, as I only realised the danger in University I must have missed that day in collage.

Today with EV charging and PV solar panels we are more aware, but still easy for even an electrician to miss it.

 

[JohnW2]

In the main the big problem with loss of PEN is fire, where gas pipes melt, due to earth bonding wrong side of isolator block ....

You say that but, as an electrician (and regardless of what regs may seem to say), you surely do not agree with that statement about "the wrong side of isolator block", do you ?

As an electrician, you surely must understand that to main bond gas pipework on the consumer's side of an (electrically) 'isolating block' is not only totally unnecessary/pointless but could, in some circumstances, leave unbonded exposed extraneous-c-ps within the building that could represent a risk of electric shock to the occupants?

Kind Regards, John

 

[bernardgreen]

In the main the big problem with loss of PEN is fire, where gas pipes melt,

More likely to be an undersized bonding wire to a metallic service pipe ( gas and/or water ) that overheats.

While there are "not many" cases of a lost PEN lasting for several hours there are many cases of transient voltage excursions on the Neutral in the network pulling the CPC potential away from local Ground potential. A person touching both CPC and Ground will be affected,

 

[EFLImpudence]

BUT - isn't what Eric is meaning by the wrong side, the supplier's side, which is actually the correct side for the bonding conductor to be connected?

 

[JohnW2]

BUT - isn't what Eric is meaning by the wrong side, the supplier's side, which is actually the correct side for the bonding conductor to be connected?

Maybe - but, if so, why did he call the (electrically) correct side "the wrong side"?

As things are, there is clearly a 'conflict of interest' between electrical and gas considerations. If there is touchable pipework which qualifies as an extraneous-c-p entering a building, the measures frequired to minimise the risk of electric shock would be those which increased the risk of a gas pipe 'melting' (if that ever happens).

The only way of avoiding that would be insistence that there was always an ';insulating section' before the pipework entered the building - in which case no bonding of anything would be required and, even if the internal gas pipework were bonded (which would almost never do any 'harm', since such pipework is almost inevitably earthed, via CPCs, anyway), that would not pose any risk to the gas supply pipe.

Kind Regards, John

 

[Harry Bloomfield]

As things are, there is clearly a 'conflict of interest' between electrical and gas considerations. If there is touchable pipework which qualifies as an extraneous-c-p entering a building, the measures frequired to minimise the risk of electric shock would be those which increased the risk of a gas pipe 'melting' (if that ever happens).

It can happen. When I was quite young, it set fire to the home I lived in. A bare earth wire, run in close contact to a gas pipe. Obviously there was a PD between pipe and earth wire, which abraded the pipe over the years, and was enough to ignite the gas. I walked in from school, just in time to see the smoke, flames coming up through the floor, and turn the gas off, plus extinguish the fire.

 

[EFLImpudence]

Maybe - but, if so, why did he call the (electrically) correct side "the wrong side"?

You had better ask Eric.

 

[JohnW2]

You had better ask Eric.

That's essentially what I was doing in my reply to him, wasn't it?

Kind Regards, John

 

[JohnW2]

It can happen. When I was quite young, it set fire to the home I lived in. A bare earth wire, run in close contact to a gas pipe. Obviously there was a PD between pipe and earth wire, which abraded the pipe over the years, and was enough to ignite the gas. I walked in from school, just in time to see the smoke, flames coming up through the floor, and turn the gas off, plus extinguish the fire.

Sure, I can well imagine joints becoming loose, or even the pipe cracking, with a consequent ignition of the gas (although I suspect even that would require an exceptionally low impedance path to earth for there to be enough current to do those things - but it was the 'pipe 'melting' that I was wonder whether ever happens.

If it ('melting') did happen, I imagine it would have to be the consequence of 'electrical heating' of the pipe, by an exceptionally high current, since the evidence of gas cookers and soldering etc. seems to suggest that a gas flame would, in itself, probably not be hot enough to melt a steel/iron pipe?

Kind Regards, John

 

[Refinedgent]

More correctly "the 30mA".


RCDs don't trip on "too much power"; they trip on tiny amounts of current in the wrong place; i.e. missing from the correct place.


Well possibly. Have you figured out the apparent N and E reversal yet?


I'm confused. Is the RCD tripping or not?

If it is not then the N and E cannot be reversed - despite the colours.
If it is then perhaps the N and E are reversed - despite the colours.


Why not? Where is it?


Then N and E cannot be reversed - despite the colours.

Nope I mean the 40Amp. (which is adjacent to tub)

when connected up as in Theory it ‘should‘ be (ie live through the 40A RCD and Neutral to N, Live to LINE 2 and Earth to earth it trips….

if I connect it back up to how it was when I found it (ie bypassing the local 40Amp, but still on the B32 Amp RCD in outbuilding away from tub and the Live to Live and Neutral and earth swapped, everything works fine.
so frankly it’s all bloody weird. Surely if N and E were swapped it just shouldn’t work….but it does.

I even tried connecting tub up as it ‘should’ be and bypassing local 40A RCD and this too caused a trip on RVd in outbuilding . I wonder if the fact the tub CAN operate in 3 phase may have something to do with it (see attached circuitry diagram, bottom left where it appears Line 1 and Line 2 appear to be connected

 

[Harry Bloomfield]

Sure, I can well imagine joints becoming loose, or even the pipe cracking, with a consequent ignition of the gas (although I suspect even that would require an exceptionally low impedance path to earth for there to be enough current to do those things - but it was the 'pipe 'melting' that I was wonder whether ever happens.

It was I suppose - electrical spark errosion, probably over several years, due to there being no bonding of the pipe, to the earth.

 

[SpecialK]

Nope I mean the 40Amp. (which is adjacent to tub)

when connected up as in Theory it ‘should‘ be (ie live through the 40A RCD and Neutral to N, Live to LINE 2 and Earth to earth it trips….

if I connect it back up to how it was when I found it (ie bypassing the local 40Amp, but still on the B32 Amp RCD in outbuilding away from tub and the Live to Live and Neutral and earth swapped, everything works fine.
so frankly it’s all bloody weird. Surely if N and E were swapped it just shouldn’t work….but it does.

I even tried connecting tub up as it ‘should’ be and bypassing local 40A RCD and this too caused a trip on RVd in outbuilding . I wonder if the fact the tub CAN operate in 3 phase may have something to do with it (see attached circuitry diagram, bottom left where it appears Line 1 and Line 2 appear to be connected

Are Neutral and earth crossed or does it change over mid way? On the RCD black is earth and grey is Neutral. In the hot tub Grey is earth and Black Neutral?