Ugh, I'm annoyed to discover the problem which caused me to disconnect
the live to the pond pump circuit for the small pond in the back garden
a while back.

I made sure to use proper IP66 enclosures and protected the supposedly
waterproof PVC mains cable within a flexible plastic trunking and proper
weatherproof grommets etc to the encloser inlets. A Wiska junction box
takes the power (via a second jct box that receives the armoured cable)
and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
(overkill) cable goes to the switch box: live and neutral feeds and
returning switched lives for the filler and the pump/UV. Plus earth. The
switch box has an off/on switch for the pump/UV circuit and a home-made
timer circuit for the filler solenoid.

I tried reconnecting the pump switch but it still tripped the consumer
unit when I switched it on. I then discovered 50V AC on the switched
live. I disconnected that wire inside the switch box but it was still at
50V. Thinking either the junction box itself or the UV/pump might be the
problem, I disconnected the wire at that end too.

Ah....it was still at 50VAC.

The cable is barely 1 metre long. It goes under a wall (part of the low
walling of the raised pond and the flowerbed next to it) and back up the
garden wall to the switch box at waist height. That's it.

How annoying. I /think/ I made it so I can pull the cable out of the
trunking and pull a new cable through. But I do find it odd that the
cable would have this significant leakage if it's protected inside a
conduit and is a proper waterproof PVC flex.

If there is water trapped in the trunking this still shouldn't happen,
should it? Or am I being optimistic? It's less than ten years old.

Michael

Michael Kilpatrick <news@mkilpatrick.co.uk> wrote:
> Ugh, I'm annoyed to discover the problem which caused me to disconnect
> the live to the pond pump circuit for the small pond in the back garden
> a while back.
>
> I made sure to use proper IP66 enclosures and protected the supposedly
> waterproof PVC mains cable within a flexible plastic trunking and proper
> weatherproof grommets etc to the encloser inlets. A Wiska junction box
> takes the power (via a second jct box that receives the armoured cable)
> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
> (overkill) cable goes to the switch box: live and neutral feeds and
> returning switched lives for the filler and the pump/UV. Plus earth. The
> switch box has an off/on switch for the pump/UV circuit and a home-made
> timer circuit for the filler solenoid.
>
> I tried reconnecting the pump switch but it still tripped the consumer
> unit when I switched it on. I then discovered 50V AC on the switched
> live. I disconnected that wire inside the switch box but it was still at
> 50V. Thinking either the junction box itself or the UV/pump might be the
> problem, I disconnected the wire at that end too.
>
> Ah....it was still at 50VAC.

V=IR

If your measuring device has a very large R (as a multimeter typically
does), then a tiny current will cause a large apparent voltage.

As to where the I comes from, you're running one wire parallel with another,
so you get capacitive/inductive coupling between the two conductors. Put
50Hz mains on one wire, you'll see 50Hz appear on the other, if it's
isolated. A current now wants to flow in that wire, and that's why there's
the apparent voltage when you let it flow through the high resistance
multimeter.

However, if you reduce the load resistance (put a resistor between the wire
and neutral) the voltage will collapse, because R got smaller and thus so
did V. There is no source of power able to drive enough current
through the load to hold up the voltage.

TL;DR this voltage is unlikely to be the source of your trip, because this
current is likely to be much less than 30mA. But there may be another
leakage current from live to earth - I suspect somewhere in the pump, given
it gets wet. The 50V is just a red herring.

Theo

On Sunday, 2 April 2023 at 18:36:26 UTC+1, Michael Kilpatrick wrote:
> Ugh, I'm annoyed to discover the problem which caused me to disconnect
> the live to the pond pump circuit for the small pond in the back garden
> a while back.
>
> I made sure to use proper IP66 enclosures and protected the supposedly
> waterproof PVC mains cable within a flexible plastic trunking and proper
> weatherproof grommets etc to the encloser inlets. A Wiska junction box
> takes the power (via a second jct box that receives the armoured cable)
> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
> (overkill) cable goes to the switch box: live and neutral feeds and
> returning switched lives for the filler and the pump/UV. Plus earth. The
> switch box has an off/on switch for the pump/UV circuit and a home-made
> timer circuit for the filler solenoid.
>
> I tried reconnecting the pump switch but it still tripped the consumer
> unit when I switched it on. I then discovered 50V AC on the switched
> live. I disconnected that wire inside the switch box but it was still at
> 50V. Thinking either the junction box itself or the UV/pump might be the
> problem, I disconnected the wire at that end too.
>
> Ah....it was still at 50VAC.
>
> The cable is barely 1 metre long. It goes under a wall (part of the low
> walling of the raised pond and the flowerbed next to it) and back up the
> garden wall to the switch box at waist height. That's it.
>
> How annoying. I /think/ I made it so I can pull the cable out of the
> trunking and pull a new cable through. But I do find it odd that the
> cable would have this significant leakage if it's protected inside a
> conduit and is a proper waterproof PVC flex.
>
> If there is water trapped in the trunking this still shouldn't happen,
> should it? Or am I being optimistic? It's less than ten years old.
>
> Michael

You don't give enough info. Most likely there is no leakage, you're measuring capacitively coupled microcurrent with a high impedance meter.

On 02/04/2023 20:47, Theo wrote:
> Michael Kilpatrick <news@mkilpatrick.co.uk> wrote:
>> Ugh, I'm annoyed to discover the problem which caused me to disconnect
>> the live to the pond pump circuit for the small pond in the back garden
>> a while back.
>>
>> I made sure to use proper IP66 enclosures and protected the supposedly
>> waterproof PVC mains cable within a flexible plastic trunking and proper
>> weatherproof grommets etc to the encloser inlets. A Wiska junction box
>> takes the power (via a second jct box that receives the armoured cable)
>> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
>> (overkill) cable goes to the switch box: live and neutral feeds and
>> returning switched lives for the filler and the pump/UV. Plus earth. The
>> switch box has an off/on switch for the pump/UV circuit and a home-made
>> timer circuit for the filler solenoid.
>>
>> I tried reconnecting the pump switch but it still tripped the consumer
>> unit when I switched it on. I then discovered 50V AC on the switched
>> live. I disconnected that wire inside the switch box but it was still at
>> 50V. Thinking either the junction box itself or the UV/pump might be the
>> problem, I disconnected the wire at that end too.
>>
>> Ah....it was still at 50VAC.
>
> V=IR
>
> If your measuring device has a very large R (as a multimeter typically
> does), then a tiny current will cause a large apparent voltage.
>
> As to where the I comes from, you're running one wire parallel with another,
> so you get capacitive/inductive coupling between the two conductors. Put
> 50Hz mains on one wire, you'll see 50Hz appear on the other, if it's
> isolated. A current now wants to flow in that wire, and that's why there's
> the apparent voltage when you let it flow through the high resistance
> multimeter.

Yes. With my old boiler, isolating the supply (double-pole switched
spur) upstairs, left 90V ac on the boiler connections. It was certainly
enough to give a good shock when touched, but even a tiny load would
pull it right down to zero.

Michael Kilpatrick <news@mkilpatrick.co.uk> wrote:
> Ugh, I'm annoyed to discover the problem which caused me to disconnect
> the live to the pond pump circuit for the small pond in the back garden
> a while back.
>
> I made sure to use proper IP66 enclosures and protected the supposedly
> waterproof PVC mains cable within a flexible plastic trunking and proper
> weatherproof grommets etc to the encloser inlets. A Wiska junction box
> takes the power (via a second jct box that receives the armoured cable)
> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
> (overkill) cable goes to the switch box: live and neutral feeds and
> returning switched lives for the filler and the pump/UV. Plus earth. The
> switch box has an off/on switch for the pump/UV circuit and a home-made
> timer circuit for the filler solenoid.
>
> I tried reconnecting the pump switch but it still tripped the consumer
> unit when I switched it on. I then discovered 50V AC on the switched
> live. I disconnected that wire inside the switch box but it was still at
> 50V. Thinking either the junction box itself or the UV/pump might be the
> problem, I disconnected the wire at that end too.
>
> Ah....it was still at 50VAC.
>
> The cable is barely 1 metre long. It goes under a wall (part of the low
> walling of the raised pond and the flowerbed next to it) and back up the
> garden wall to the switch box at waist height. That's it.
>
> How annoying. I /think/ I made it so I can pull the cable out of the
> trunking and pull a new cable through. But I do find it odd that the
> cable would have this significant leakage if it's protected inside a
> conduit and is a proper waterproof PVC flex.
>
> If there is water trapped in the trunking this still shouldn't happen,
> should it? Or am I being optimistic? It's less than ten years old.
>
> Michael
>

Have you checked the electronics?

I’d be looking for a fault there rather than in the cable - at least unless
there are signs of damage etc.

If you can isolate the cable, try testing it with DC. That will rule out
coupling but, in 1m, coupling is most unlikely to be enough to be
noticeable.

Well, I had a rotator cable that worked at low voltage have issues, but it
was all outside and had a bend where it needed o go to the motor. I thin in
that case it was heat an cold cycling that dit it it bent around nearly 90
degrees. However on such a short piece, I'd suspect the local rodents.
Assuming they managed to find a way into the conduit.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Michael Kilpatrick" <news@mkilpatrick.co.uk> wrote in message
news:u0ceen$2j7hu$3@dont-email.me...
> Ugh, I'm annoyed to discover the problem which caused me to disconnect the
> live to the pond pump circuit for the small pond in the back garden a
> while back.
>
> I made sure to use proper IP66 enclosures and protected the supposedly
> waterproof PVC mains cable within a flexible plastic trunking and proper
> weatherproof grommets etc to the encloser inlets. A Wiska junction box
> takes the power (via a second jct box that receives the armoured cable)
> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
> (overkill) cable goes to the switch box: live and neutral feeds and
> returning switched lives for the filler and the pump/UV. Plus earth. The
> switch box has an off/on switch for the pump/UV circuit and a home-made
> timer circuit for the filler solenoid.
>
> I tried reconnecting the pump switch but it still tripped the consumer
> unit when I switched it on. I then discovered 50V AC on the switched live.
> I disconnected that wire inside the switch box but it was still at 50V.
> Thinking either the junction box itself or the UV/pump might be the
> problem, I disconnected the wire at that end too.
>
> Ah....it was still at 50VAC.
>
> The cable is barely 1 metre long. It goes under a wall (part of the low
> walling of the raised pond and the flowerbed next to it) and back up the
> garden wall to the switch box at waist height. That's it.
>
> How annoying. I /think/ I made it so I can pull the cable out of the
> trunking and pull a new cable through. But I do find it odd that the cable
> would have this significant leakage if it's protected inside a conduit and
> is a proper waterproof PVC flex.
>
> If there is water trapped in the trunking this still shouldn't happen,
> should it? Or am I being optimistic? It's less than ten years old.
>
> Michael

Not so sure about that. It is true that the voltage will vary with load, but
does the device that trips itself have sufficient load to avoid this voltage
detected? In the case of my rotator, it seemed that the rotation of the
aerial would gradually creep out of resolution with the knob. However taking
it down and using short bits of wire did not show a fault. I seem to recall
that the leak varied as you flexed various bits of the hardened cable.

Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Theo" <theom+news@chiark.greenend.org.uk> wrote in message
news:Hcq*UBNcz@news.chiark.greenend.org.uk...
> Michael Kilpatrick <news@mkilpatrick.co.uk> wrote:
>> Ugh, I'm annoyed to discover the problem which caused me to disconnect
>> the live to the pond pump circuit for the small pond in the back garden
>> a while back.
>>
>> I made sure to use proper IP66 enclosures and protected the supposedly
>> waterproof PVC mains cable within a flexible plastic trunking and proper
>> weatherproof grommets etc to the encloser inlets. A Wiska junction box
>> takes the power (via a second jct box that receives the armoured cable)
>> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
>> (overkill) cable goes to the switch box: live and neutral feeds and
>> returning switched lives for the filler and the pump/UV. Plus earth. The
>> switch box has an off/on switch for the pump/UV circuit and a home-made
>> timer circuit for the filler solenoid.
>>
>> I tried reconnecting the pump switch but it still tripped the consumer
>> unit when I switched it on. I then discovered 50V AC on the switched
>> live. I disconnected that wire inside the switch box but it was still at
>> 50V. Thinking either the junction box itself or the UV/pump might be the
>> problem, I disconnected the wire at that end too.
>>
>> Ah....it was still at 50VAC.
>
> V=IR
>
> If your measuring device has a very large R (as a multimeter typically
> does), then a tiny current will cause a large apparent voltage.
>
> As to where the I comes from, you're running one wire parallel with
> another,
> so you get capacitive/inductive coupling between the two conductors. Put
> 50Hz mains on one wire, you'll see 50Hz appear on the other, if it's
> isolated. A current now wants to flow in that wire, and that's why
> there's
> the apparent voltage when you let it flow through the high resistance
> multimeter.
>
> However, if you reduce the load resistance (put a resistor between the
> wire
> and neutral) the voltage will collapse, because R got smaller and thus so
> did V. There is no source of power able to drive enough current
> through the load to hold up the voltage.
>
> TL;DR this voltage is unlikely to be the source of your trip, because this
> current is likely to be much less than 30mA. But there may be another
> leakage current from live to earth - I suspect somewhere in the pump,
> given
> it gets wet. The 50V is just a red herring.
>
> Theo

On 02/04/2023 18:36, Michael Kilpatrick wrote:
> Ugh, I'm annoyed to discover the problem which caused me to disconnect
> the live to the pond pump circuit for the small pond in the back garden
> a while back.
>
> I made sure to use proper IP66 enclosures and protected the supposedly
> waterproof PVC mains cable within a flexible plastic trunking and proper
> weatherproof grommets etc to the encloser inlets. A Wiska junction box
> takes the power (via a second jct box that receives the armoured cable)
> and it has the pump, UV and solenoid, connected to it. A 5-core 2.5mm2
> (overkill) cable goes to the switch box: live and neutral feeds and
> returning switched lives for the filler and the pump/UV. Plus earth. The
> switch box has an off/on switch for the pump/UV circuit and a home-made
> timer circuit for the filler solenoid.
>
> I tried reconnecting the pump switch but it still tripped the consumer
> unit when I switched it on. I then discovered 50V AC on the switched
> live. I disconnected that wire inside the switch box but it was still at
> 50V. Thinking either the junction box itself or the UV/pump might be the
> problem, I disconnected the wire at that end too.
>
> Ah....it was still at 50VAC.
>
> The cable is barely 1 metre long. It goes under a wall (part of the low
> walling of the raised pond and the flowerbed next to it) and back up the
> garden wall to the switch box at waist height. That's it.
>
> How annoying. I /think/ I made it so I can pull the cable out of the
> trunking and pull a new cable through. But I do find it odd that the
> cable would have this significant leakage if it's protected inside a
> conduit and is a proper waterproof PVC flex.
>
> If there is water trapped in the trunking this still shouldn't happen,
> should it? Or am I being optimistic? It's less than ten years old.

Without looking it up how much, there will be some capacitive cross-talk
between conductors. A DVM has a very high input impedance, in the M-Ohm
region, and so may well see 50VAC.

In article <u0ctn5$2lb4t$1@dont-email.me>,
SteveW <steve@walker-family.me.uk> wrote:
> Yes. With my old boiler, isolating the supply (double-pole switched
> spur) upstairs, left 90V ac on the boiler connections. It was certainly
> enough to give a good shock when touched, but even a tiny load would
> pull it right down to zero.

Was the cable to the boiler bunched together with other live cables? I've
certainly seen stray volts using a Hi-Z DVM, but never felt them.

--
*Very funny Scotty, now beam down my clothes.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

On 03/04/2023 15:37, Dave Plowman (News) wrote:
> In article <u0ctn5$2lb4t$1@dont-email.me>,
> SteveW <steve@walker-family.me.uk> wrote:
>> Yes. With my old boiler, isolating the supply (double-pole switched
>> spur) upstairs, left 90V ac on the boiler connections. It was certainly
>> enough to give a good shock when touched, but even a tiny load would
>> pull it right down to zero.
>
> Was the cable to the boiler bunched together with other live cables? I've
> certainly seen stray volts using a Hi-Z DVM, but never felt them.

I could certainly feel this. My conclusion was that it was picking up
from parallel cables - there is no choice in the run as it has to go
between a joist and a wall, under a tiled bathroom floor and then drop
vertically in a duct in the corner of the hall below, so a whole host of
cables have to run the same route, as there is nowhere else accessible.

On 02/04/2023 20:47, Theo wrote:
> Michael Kilpatrick <news@mkilpatrick.co.uk> wrote:
>>
>> Ah....it was still at 50VAC.
>
> V=IR
>
> If your measuring device has a very large R (as a multimeter typically
> does), then a tiny current will cause a large apparent voltage.
>
> As to where the I comes from, you're running one wire parallel with another,
> so you get capacitive/inductive coupling between the two conductors. Put
> 50Hz mains on one wire, you'll see 50Hz appear on the other, if it's
> isolated. A current now wants to flow in that wire, and that's why there's
> the apparent voltage when you let it flow through the high resistance
> multimeter.

> However, if you reduce the load resistance (put a resistor between the wire
> and neutral) the voltage will collapse, because R got smaller and thus so
> did V. There is no source of power able to drive enough current
> through the load to hold up the voltage.

Hmm. It seems unreal for a cable barely more than a metre long. And you
wouldn't expect to see the same result for the two situations (1) both
ends of that 1m long core wire are disconnected and (2) one end is
connected to the UV bulb and the pump motor via the terminal block in
the junction box?

Of course it's conceivable that both pump and UV bulb are now presenting
an open circuit. I should hard-wire the pump to test it.

>
> TL;DR this voltage is unlikely to be the source of your trip, because this
> current is likely to be much less than 30mA. But there may be another
> leakage current from live to earth - I suspect somewhere in the pump, given
> it gets wet. The 50V is just a red herring.

I have ordered a slightly large junction box - it's a bit cramped anyway
and yesterday I accidentally pierced one of the silly membranes on one
of the unused inlets, so its waterproofing is now compromised. That's an
hour or two of rewiring to begin with.

I will also extract my circuit board from the switch box. The on/off
switch for the pump does make use of a terminal block on the circuit
board because the (weatherproof but nice-looking) switch has awfully
delicate connectors, so I didn't want to connect the 5-core cable
directly to it. However, the only track on the circuit board adjacent to
the pump switch signal is the neutral. I should still inspect it,
though. There's bound to be something obviously I simply haven't noticed
yet.

All this faff just for a pond pump!

Michael

On 03/04/2023 07:56, Brian wrote:

> Have you checked the electronics?
>
> I’d be looking for a fault there rather than in the cable - at least unless
> there are signs of damage etc.
>
> If you can isolate the cable, try testing it with DC. That will rule out
> coupling but, in 1m, coupling is most unlikely to be enough to be
> noticeable.

That's what I thought! There is bound to be something I've missed that's
causing this if it's not the pump itself, and, as per my reply to Theo
above, I've now got to change the junction box anyway, so I'll be
rewiring the whole damned thing! What a pain.

Michael

On 02/04/2023 18:36, Michael Kilpatrick wrote:
> Ugh, I'm annoyed to discover the problem which caused me to disconnect
> the live to the pond pump circuit for the small pond in the back garden
> a while back.

Oh, silly me!!

I really should have tested more of the components individually
yesterday. I was convinced I must have made a bad job of the wiring or
the circuit board - or possibly water ingress to the junction box or
damaged cables, etc.

But it turns out it's the UV bulb. The pump is fine (at least briefly).

What happened before I disconnected it some time ago was that it ran for
a bit and then tripped the circuit breaker in the consumer unit after a
little while. Whatever the problem with the UV unit was, it has clearly
degraded, as it trips immediately.

I'll just get rid of the silly thing.

Michael

On 03/04/2023 17:50, Michael Kilpatrick wrote:
> There is bound to be something I've missed that's causing this if it's
> not the pump itself, and, as per my reply to Theo above, I've now got to
> change the junction box anyway, so I'll be rewiring the whole damned
> thing! What a pain.

Sometimes valour is the better part of discretion.

Faced with the need to add some more disco lights to what was a rat's
nest of chocolate blocks in a biscuit tin, I horrified my boss by
demanding a hacksaw, and removing the cancerous growth surgically.

A new DIN rail box went in and as pairs of wires were identified first
with an ohmmeter, and then some live mains applied, the pairs were
documented and terminated neatly on the rail connector.

It only took an hour or so.

--
The biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.