My first time here and I'm not sure if this is the right forum to post this thread. I have a couple of 4 pole RCDs controlling at least 5 miniature circuit breakers each with a common input for them all. I had the neutral to all the RCD output tied to the bar and when i push the test button they don't trip individually. Is it safe to remove all the RCD neutral output and take the neutral from the supply to the load directly ? With the neutral input still available

 

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The RCD should normally be effective without the neutral present, as the live conductors would still be referenced WRT earth GND.
You would have to test it to ensure the RCD supports it.

 

This is out of my wheelhouse, so I don't recognize what the term RCD is referring to. At first I thought it might be some kind of motor drive, but from the context, it appears to be some kind of fault protection device similar to a GFCI?

 

This is out of my wheelhouse, so I don't recognize what the term RCD is referring to. At first I thought it might be some kind of motor drive, but from the context, it appears to be some kind of fault protection device similar to a GFCI?

RCD = Residual Current Device, = GFCI , term used more often in UK etc.

 

This is out of my wheelhouse, so I don't recognize what the term RCD is referring to. At first I thought it might be some kind of motor drive, but from the context, it appears to be some kind of fault protection device similar to a GFCI?

A Residual Current Device (RCD)is a sensitive safety device that switches off the electricity within 10 to 50 milliseconds if there is an electrical fault. An RCD is is designed to protect against the risks of electrocution and fire caused by earth faults. Wish i could get an answer to that. I live in Dartford London

 

Thanks, both of you. Now I can follow the discussion better. Max is definitely someone to listen to for these kinds of questions, and that's doubly the case for questions specific to U.K. codes and usage.

 

and that's doubly the case for questions specific to U.K. codes and usage.

It has been a fair few decades since I worked with UK reg's, I suspect many things have changed!

 

Is this page specific to US standards?

 

Is this page specific to US standards?

Not as far as I Know!
Just that it is N.A. based, and quite a few members are also.
But we will talk to anyone!

 

The RCD should normally be effective without the neutral present, as the live conductors would still be referenced WRT earth GND.
You would have to test it to ensure the RCD supports it.

RCD's do not have ground/earth input. It's just 3 phase and neutral and it definitely won't function properly without a neutral input

 

Not as far as I Know!
Just that it is N.A. based, and quite a few members are also.
But we well talk to anyone!

Not sure what N.A means

 

Not sure what N.A means

N.A., in this context, means North America, primarily the U.S. and Canada, though we certainly have members from Mexico as well.

 

RCD's do not have ground/earth input. It's just 3 phase and neutral and it definitely won't function properly without a neutral input

Yes you are correct, the neutral is used to power the internal electronics, usually I assume the supply is 3ph star connected source supply, with the star point grounded, ?

 

My first time here and I'm not sure if this is the right forum to post this thread. I have a couple of 4 pole RCDs controlling at least 5 miniature circuit breakers each with a common input for them all. I had the neutral to all the RCD output tied to the bar and when i push the test button they don't trip individually. Is it safe to remove all the RCD neutral output and take the neutral from the supply to the load directly ? With the neutral input still available

The neutral must go through the RCD. Otherwise it cannot detect "residual" current, which is the difference between the live and the neutral i.e. any current that has gone astray - presumably to earth and hopefully not via a person.
On a well balanced 3-phase supply there will be no neutral current, so the sum of the live currents will equal zero.
On a not-so-well-balanced 3-phase supply, neutral current will be present. If this does not go through the RCD it will trip.

 

The neutral must go through the RCD. Otherwise it cannot detect "residual" current, which is the difference between the live and the neutral i.e. any current that has gone astray - presumably to earth and hopefully not via a person.
On a well balanced 3-phase supply there will be no neutral current, so the sum of the live currents will equal zero.
On a not-so-well-balanced 3-phase supply, neutral current will be present. If this does not go through the RCD it will trip.

Yes, the neutral must go through the RCD .is it necessary to take the neutral from the output of the RCD to the load ? I did combine all the neutral (6 RCD) to the output line and when i push the test button multiple RCD trips. So i ignored the output neutral of all the RCD since the neutral input is available for the protection circuitry to function

 

A Δ-connected load would need no connection to the RCD output terminal. If there were a fault in which current flowed to earth, it would still trip the RCD as the net current (vector sum of the three live currents) would no longer be zero.
If the load is balanced and star-connected, the theoretically, no neutral connection would be required as there is no neutral current, but I think it would be bad practice to ignore it.
if the load is three separate single phase loads, I.e. unbalanced, then the RCD would trip immediately if the neutral were not connected via the RCD.
The trip button operates by connecting live at the output to neutral at the input through a resistor, allowing a current of ΔI (the tripping current) to bypass the current balance transformer thus simulating a fault current, so the trip button would not work without a neutral connection.