When testing a circuit protected by RCBO, do you test at the DB or furtherst point

[Toneyz]

Test either at the D.B or circuit, it makes no difference whatever is the easiest for you. If you are using an RCD tester that does all tests in sequence and you reset trip each time you may need to isolate unplug some loads as when they start up they prevent the next test being compleated.

 

[ipf]

I think we are all aware a ramp test is a separate test that wasn't the question asked and from your reply I assume you don't ramp test any RCD's so therefore don't fully check it's function

The return dumb is for an absolutely stupid assumption.
…...as well as not being able to take a joke!

 

[UNG]

The return dumb is for an absolutely stupid assumption.
…...as well as not being able to take a joke!

I can take a joke but you clearly don't have a problem putting peoples lives at risk by trashing a serious conversation

Yes you can achieve the trip times and still leave a customer with a faulty RCD

Don't bother replying I won't see it you have disappeared from view

 

[ipf]

I can take a joke but you clearly don't have a problem putting peoples lives at risk by trashing a serious conversation

Yes you can achieve the trip times and still leave a customer with a faulty RCD

Don't bother replying I won't see it you have disappeared from view

Whether you see this or not, it seems you are one sad man……..resorting to such a serious and stupid accusation.
Nuff said.

 

[Midwest]

I think we are all aware a ramp test is a separate test that wasn't the question asked and from your reply I assume you don't ramp test any RCD's so therefore don't fully check it's function

I have found on quite a few occasions recently that RCD's / RCBO's can meet the trip times especially when testing at the device while a ramp test has indicated a trip current in excess of the specified 30mA to trip the device
So it is possible that a faulty device can meet the trip times but not within the specified 30mA tripping current

If you carry out the RCD test (e.g. BS EN 61008), for example x 1, the testing device introduces the 30mA current, for which the RCD must detect & disconnect within 300ms.
I can't see how an RCD would pass such a test, but fail because the mA would be too high, as the test current used by the test device is set at 30mA.

A ramp test will measure at what mA the RCD is tripping at. If the RCD was tripping at say 40mA, it would fail the x 1 test, surely?

 

[ipf]

If you carry out the RCD test (e.g. BS EN 61008), for example x 1, the testing device introduces the 30mA current, for which the RCD must detect & disconnect within 300ms.
I can't see how an RCD would pass such a test, but fail because the mA would be too high, as the test current used by the test device is set at 30mA.

A ramp test will measure at what mA the RCD is tripping at. If the RCD was tripping at say 40mA, it would fail the x 1 test, surely?

May be an instance. An existing RCD failed, initially. It tripped at well over on ramp. It hadn’t been tested or operated for a good while. After a few test button operations, it operated fine. Replaced anyway because it was pretty old, but it goes to show.

 

[Deleted member 26818]

Failing the X 1 test is not an issue.
The requirement is for the device to operate within 40ms when tested at a current equal to or higher than 5 times it’s rated operating current.
Assuming of course, that the RCD is intended for additional protection.

 

[Midwest]

May be an instance. An existing RCD failed, initially. It tripped at well over on ramp. It hadn’t been tested or operated for a good while. After a few test button operations, it operated fine. Replaced anyway because it was pretty old, but it goes to show.

But what I am saying is, the tester introduces 30mA (at x 1) nothing more nothing less. If the rcd is faulty and only trips at say 40mA, the test will time out and therefore the rcd will fail that part of the test?

PS the inspector would then move to the ramp test, to verify the issue. Same would go for 1/2 x test.

 

[Deleted member 26818]

But what I am saying is, the tester introduces 30mA (at x 1) nothing more nothing less. If the rcd is faulty and only trips at say 40mA, the test will time out and therefore the rcd will fail that part of the test?

PS the inspector would then move to the ramp test, to verify the issue. Same would go for 1/2 x test.

It doesn’t matter if it fails the x 1 test.
It’s the x 5 test that it has to pass.

 

[DPG]

I think Midwest is responding to the point that UNG made.

 

[Midwest]

It doesn’t matter if it fails the x 1 test.
It’s the x 5 test that it has to pass.

Take your point. I'm trying to make mine about ramp testing.

 

[UNG]

If you carry out the RCD test (e.g. BS EN 61008), for example x 1, the testing device introduces the 30mA current, for which the RCD must detect & disconnect within 300ms.
I can't see how an RCD would pass such a test, but fail because the mA would be too high, as the test current used by the test device is set at 30mA.

A ramp test will measure at what mA the RCD is tripping at. If the RCD was tripping at say 40mA, it would fail the x 1 test, surely?

I have had this issue on 3 occasions in the the last couple of years
One was a CU installed 6 months previously tested ok at install yet one of the RCD's was found to be faulty 6 months later, the other 2 were brand new CU's where one of the RCD's was not within spec at install

The first CU was found because a quick check at a socket where it had previously been ok failed to trip, tested at the CU it tripped within acceptable times both 1x and 5x although a little higher than I would normally expect decided to do a ramp test at the CU and found it tripped at 37mA I ramp tested it back at the socket but can't remember the exact figure I got but was high enough to cause concern as to whether it is acceptable just to test at the RCD
The other 2 had similar outcomes
On all occasions having contacted the manufacturers the RCD's have been replaced with no problems

It doesn’t matter if it fails the x 1 test.
It’s the x 5 test that it has to pass.

On my MFT on auto test if it fails the 1x then it fails the whole test
Given that ventricular fibrillation can occur at currents as low as 30mA I think the 1x test really matters

 

[Deleted member 26818]

From the current Regulations:
NOTE: Effectiveness is deemed to have been verified where an RCD meeting the requirements of Regulation 415.1.1 disconnects within 40 ms when tested at a current equal to or higher than five times its rated residual operating current.

You want to disagree with what it says, fine.
Take it up with the IET.

 

[Midwest]

I have had this issue on 3 occasions in the the last couple of years

The first CU was found because a quick check at a socket where it had previously been ok failed to trip, tested at the CU it tripped within acceptable times both 1x and 5x although a little higher than I would normally expect decided to do a ramp test at the CU and found it tripped at 37mA I ramp tested it back at the socket but can't remember the exact figure I got but was high enough to cause concern as to whether it is acceptable just to test at the RCD

I'll say this again, & then drop it.

At x 1 my MFT introduces a test current of 30mA (+0% to +10%.) to test an RCD. If it was testing this faulty RCD, its not going to provide it with the 37mA it needs to trip and the test would time out at 300ms, and my MFT would display an error code. I would then go on to conduct a ramp test on the RCD.

Therefore there is no need to conduct a ramp test, in normal circumstances.

 

[brianmoooore]

From the current Regulations:
NOTE: Effectiveness is deemed to have been verified where an RCD meeting the requirements of Regulation 415.1.1 disconnects within 40 ms when tested at a current equal to or higher than five times its rated residual operating current.

You want to disagree with what it says, fine.
Take it up with the IET.

Ridiculous change to the regs IMHO! A working 100mA RCD will pass as a 30mA one.

 

[tudore]

Guidance Note 3 Section 2.6.19 says testing should be at the load side of the RCD, with loads disconnected. I always strive to test at the furthest point on a circuit, as Zs is critical to correct operation, and even correct type of RCD (see Section 411). What is the point of Table 41.3 if circuit resistance can be ignored? I admit if I'm working alone on a big circuit I'll test at the board, but this is very rare as I can usually find a helper for the resets.

 

[Silly Sausage]

Guidance Note 3 Section 2.6.19 says testing should be at the load side of the RCD, with loads disconnected. I always strive to test at the furthest point on a circuit, as Zs is critical to correct operation, and even correct type of RCD (see Section 411). What is the point of Table 41.3 if circuit resistance can be ignored? I admit if I'm working alone on a big circuit I'll test at the board, but this is very rare as I can usually find a helper for the resets.

For the umpteeth time, you are testing the device, not the circuit.
Do test every circuit connected to an RCD?
And, finally, surely you have an instrument that can perform auto testing?

 

[ipf]

For the umpteeth time, you are testing the device, not the circuit.
Do test every circuit connected to an RCD?
And, finally, surely you have an instrument that can perform auto testing?

I wish they did one that does an auto reset
Now that would be an invention

 

[Midwest]

For the umpteenth time plus 1 , the all knowing all seeing IET have this little piece about RCD's; testing is at indent 5.

Inspection and testing of electrical installations: residual current devices - https://electrical.------.org/wiring-matters/issues/50/inspection-and-testing-of-electrical-installations-residual-current-devices/

How do we interpret that? Think it says something similar in GN3.

 

[Ian1981]

For the umpteenth time plus 1 , the all knowing all seeing IET have this little piece about RCD's; testing is at indent 5.

Inspection and testing of electrical installations: residual current devices - https://electrical.------.org/wiring-matters/issues/50/inspection-and-testing-of-electrical-installations-residual-current-devices/

How do we interpret that? Think it says something similar in GN3.

The way I interpreted that is that you test on the load side and that can be anywhere in the circuit covered by the rcd, be it at the CU or at the closest socket outlet or the furthest light.
Your just testing the device only and not the circuit is what the article is saying.
I always test at the CU and until the regulations say different then I always will