Well worth setting the alarm for Sunday morning

Not.
As per the other post. I had a job in Sheffield for Sunday morning.
No power to a flat that the customer has just rented. Did the usual stuff over the phone on Friday but was told that the main switch would not stay up.
Well even if it was a RCD main switch then that should not trip if all the MCBs are off. I even covered the MK RCD main switch scenario that trip to a halfway position and need to be pushed down before being pushed back up.
A case of slack customer syndrome springs to mind so I arranged to go this morning and sort it out.
A bog standard 16th edition CU with a 100A main switch in the OFF position awaited me. Turned out that the customer was just not shoving the main switch up hard enough.
Still, it keeps me from going to Church.
--
Adam

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ARW wrote:

It takes much, much less than that to keep me away ...
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On 14/10/2018 11:38, Andy Burns wrote:

I go once a year unless some relative or friend decides to get married or buried in one.
--
Adam

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On 14/10/2018 11:41, ARW wrote:

Hey hey settle down. No need to go that often.
Soto Voce "tad keen this one".
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Why bother with once a year ? You'll burn regardless, boy.
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wrote:

<weg>
Cheers, T i m
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On 14/10/2018 11:38, Andy Burns wrote:

I only go because of Remembrance Sunday and the Scouts.
--
Adam

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If the switch has never been moved much they can be a real pain. I am often reminded about our house when we first moved in, my late father had to use a clamp to extend the arm of the switch to shift it to the on position. One of those very old metal lever switches. Quite a piece of mechanics. On the other extreme, some of the plastic engineered ones from the 70s break of when you try to move them. Hopefully the designs have changed by now. Brian
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ARW explained :

Are you sure of that???
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On 14/10/2018 11:45, Harry Bloomfield wrote:

Yes. No current flowing means there is a zero imbalance between live and neutral.
--
Adam

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ARW explained on 14/10/2018 :

You are overlooking - MCB, disconnects L only. If N has a short to earth, imbalanced current will flow through RCD, causing it to trip. Depends to some extent on PD between N and E.
The above catches many people out.
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On 14/10/2018 12:25, Harry Bloomfield wrote:

If ALL the MCBs are turned off then the current flow is (or should be) zero. You can apply any pd between N and earth you want to but that will still not trip an RCD as an RCD has no reference to earth.
--
Adam

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ARW wrote on 14/10/2018 :

An RCD needs no reference to earth to trip, just some current to flow through either L or N, which does not flow through the other pole - to cause it to trip. I'm surprised you are not well aware of that Adam. It caught me out just the once, when RCD's first appeared, but ot since.
I would suggest if you doubt it, that you try it.
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On 14/10/2018 12:45, Harry Bloomfield wrote:

Did you miss the words "RCD main switch"?
--
Adam

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ARW has brought this to us :

Your point being?
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On 14/10/2018 14:04, Harry Bloomfield wrote:

If you have a NE short what is the PD between N and E?
--
Adam

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ARW expressed precisely :

Zero or close to zero, depending on the path resistance.
However, prior to the N to E short....
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On 14/10/2018 15:35, Harry Bloomfield wrote:

There is a RCD not connected to earth?
--
Adam

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ARW presented the following explanation :

Yes, why would it need an earth?
They work quite simply on a current imbalance, which is what the C in RCD stands for current. If the RCD sees a difference in current flow between it L & N connections, it trips and safely disconnects the supply.
At this point I will point out that you do fully understand, are fully aware why an N to E trip will cause the RCD to trip - but unable to accept you made an error, that you are attempting to still score a point.
Quite easy to prove, drop all of the MCB's out and short N to E on any of the sub-circuits. No more to be said, I think.
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On 14/10/2018 16:40, Harry Bloomfield wrote:

Multiply zero by any number and you get zero.
A 30mA RCD needs a minimum of 16mA to cause a trip.
--
Adam

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