Connecting Honda EU20i generator to shore power system

[BabaYaga]

This is a typical internal circuit diagram for a RCD.

As you can see the test button connects the live to earth through a resistor to fudge a line to earth leakage so creating a difference in current flowing through the Line and neutral

I would have thought the test circuit of a RCD would more typically be connected between L and N (rather than L and E).
Are you sure this is correct?

 

[PaulRainbow]

I would have thought the test circuit of a RCD would more typically be connected between L and N (rather than L and E).
Are you sure this is correct?

The RCD is for protection against shock, by monitoring for an imbalance between L & N. The test button creates a small leak (thanks to the resistor) from L to E, tripping the RCD.

 

[rogerthebodger]

I would have thought the test circuit of a RCD would more typically be connected between L and N (rather than L and E).
Are you sure this is correct?

A connection between L and N would cause the same current to flow in both Line and Neutral so would not cause any imbalance so no trip of the RCD.

As Paul discribes

 

[VicS]

The RCD is for protection against shock, by monitoring for an imbalance between L & N. The test button creates a small leak (thanks to the resistor) from L to E, tripping the RCD.

But an RCD in a consumer unit does not have an earth connection to it, just L and N.
ITYWF that the test button, and resistor, links the load side of one with the input side of the other to create an imbalance.

 

[BabaYaga]

But an RCD in a consumer unit does not have an earth connection to it, just L and N.
ITYWF that the test button, and resistor, links the load side of one with the input side of the other to create an imbalance.

Yes, this is also my thinking.
Some further googling suggests that the schematic in post #39 might actually show an earth leakage circuit breaker (ELCB) which does about the same thing as a RCD, but is not what boat owners (or home owners) usually encounter.
▷ Earth Leakage Circuit Breaker (ELCB)

 

[PaulRainbow]

But an RCD in a consumer unit does not have an earth connection to it, just L and N.
ITYWF that the test button, and resistor, links the load side of one with the input side of the other to create an imbalance.

I'm aware of that, which is why the test button only tests the RCD, not if it will work in a fault situation, like i said in post #38 .

My reply in post #42 was regarding the schematic Roger posted.

 

[rogerthebodger]

Yes, this is also my thinking.
Some further googling suggests that the schematic in post #39 might actually show an earth leakage circuit breaker (ELCB) which does about the same thing as a RCD, but is not what boat owners (or home owners) usually encounter.
▷ Earth Leakage Circuit Breaker (ELCB)

You are correct maybe this s a better diagram

The dotted line is an external earth from the case of the supply and appliance.

The only thing this is not clear on is the neutral earth connection at the supply side.

Also there is often a wired connection duplicating the dotted line connection through the earth.

The previous diagram I posted is just another of doing the same thing which does require an connection to an earth that could be in the distribution box.

The above diagram uses less components so will be cheaper to manufacture and buy.

 

[VicS]

I'm aware of that, which is why the test button only tests the RCD, not if it will work in a fault situation, like i said in post #38 .

My reply in post #42 was regarding the schematic Roger posted.

My point was that you said "The test button creates a small leak (thanks to the resistor) from L to E, tripping the RCD. " That is wrong. That is not how the test button works.. It cannot when there is no earth connection to the device.

The test button does create an imbalance situation so does up to a point test that the device will trip i a fault situation but what it does not do is test or confirm that the device trips within the specified time and current ranges

 

[PaulRainbow]

My point was that you said "The test button creates a small leak (thanks to the resistor) from L to E, tripping the RCD. " That is wrong. That is not how the test button works.. It cannot when there is no earth connection to the device.

The device in Rogers diagram has an Earth, i was referring to Rogers diagram, that is how the test button works with that device.

The test button does create an imbalance situation so does up to a point test that the device will trip i a fault situation but what it does not do is test or confirm that the device trips within the specified time and current ranges

On a standard RCD the test button only tests that the RCD functions. The limitations of the test button have little to do with time or current ranges, more to do with the fact that all it does is to test the functionality of the device itself. It does not prove that it will trip if there is a fault. Suppose the earth wire has become detached from a socket or somewhere on a circuit, if there is a fault the RCD will not trip. As i've already said, the only way to check for that is with a RCD tester.

If it was possible to test an installation for full RCD operation/protection by pressing the button on the RCD i could save the hundreds of pounds of test equipment i carry, not to mention calibration costs.

 

[Graham376]

If it was possible to test an installation for full RCD operation/protection by pressing the button on the RCD i could save the hundreds of pounds of test equipment i carry, not to mention calibration costs.

As a test, a light bulb across earth and live socket pins will trip it, if it's working but won't provide necessary data.