Well worth setting the alarm for Sunday morning

[ARW]

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.

[Andy Burns]

It takes much, much less than that to keep me away ...

[ARW]

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

[Brian Gaff]

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

[Harry Bloomfield]

ARW explained :

Are you sure of that???

[ARW]

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

[soup]

Hey hey settle down. No need to go that often.

Soto Voce "tad keen this one".

[Harry Bloomfield]

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.

[ARW]

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.

[Archibald Tarquin Blenkinsopp]

Surely that does not apply to an RCD?

There used to be earth leakage trips that would respond to any current flowing to ground through a relay coil, but I assumed these were all history now.

AB

[ARW]

I think it is a C2 on an EICR if they are fitted.

[Harry Bloomfield]

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.

[Harry Bloomfield]

It certainly does, an imbalance between the current flow through L when compared to N (or N compared to L) is the whole principle of an RCD operation. The imbalance is what they are designed to detect and trip on.

[ARW]

Did you miss the words "RCD main switch"?

[ARW]

If there is no live as all the MCBs are turned off there is no possible current flow.

[Archibald Tarquin Blenkinsopp]

If I understand you correctly I am surprised, I thought existing installations did not have to be upgraded. Even if you might have to isolate the kitchen sink from ground :-)

After all ELCB's dont rely on this new fangled electronics. One near miss when Trump and his chums start throwing nukes around will zap all your RCD's yet your leakage trips will carry on regardless:-)

AB

[ARW]

Voltage operated circuit breakers are the ones that I mention.

[Archibald Tarquin Blenkinsopp]

+1

AB

[Archibald Tarquin Blenkinsopp]

Yes, by that I assume you mean RCD's?

although I would suggest that the sense coil of an ELCB has to have a Voltage across it to function.

Do all ELCB's need upgrading now when found as part of an inspection?

I replaced a faulty unit a few years back with a modern device, this was outside the main fuseboxes and had been supplemented by RCD's in a few other areas.

As I didn't know the system fully at the time, and had only a few hours before pulling out, my initial reaction was to replace like with like. I was forced into the RCD route though due to there not being any antique shops in the area.

I should really look into the protection as I provide power in one of the out buildings for a farmer, I do have the supply coming from two RCD's plus the local consumer unit RCD also.

AB

[T i m]

Cheers, T i m