RCD testing - 2 chains of thought.

[Tiny Spark]

Ok so I have 2 chains of thought on RCD testing and I thought it would be interesting to see what you guys thought.

So when carrying out RCD testing I know you are supposed to test at the RCD, Now I was taught (and personally think is more beneficial) to test at the furthest point of the circuit the same as R1-R2 testing.
I believe this as at the end of the day the RCD is there to protect and if it tests ok at the RCD but due to some unknown reason does not test ok at the furthest point then I think this is unacceptable.

Again I dont work in domestic situations but whenever I test RCD's around site I always do them in the above way.

So what are your guys thoughts on it?

Do we have a split or does everyone test at the RCD? if so what is the benefit over testing at the end of the circuit?

Thanks all

 

[Dizzy_Maskell]

Encountered before the later RCD operates fine in DB but when tested at a socket outlet it does not trip,
Technically the RCD passed but I would always recommend further action as yes it works at the DB but not when it's needed at the socket outlet

 

[Aderac]

Apparently the reason for testing at the RCD is because the likes of fridge freezers have a bit of earth leakage do effect the result, or so my assessor told me.

 

[Tiny Spark]

Encountered before the later RCD operates fine in DB but when tested at a socket outlet it does not trip,
Technically the RCD passed but I would always recommend further action as yes it works at the DB but not when it's needed at the socket outlet

Exactly my point, I have never had a fail that was close enough to attempt testing at the board to see if it would pass but I have had a pass which was borderline at the last socket.

Aderac, Why would it matter what was on the circuit if it was unplugged when carrying out the test?

 

[Aderac]

It wouldn't matter if it was unplugged, but if you test at the RCD you don't have to unplug everything i suppose. I'm not talking from experience, its just this subject came up in my assessment briefly this week, but I'm still learning, so please correct me if I'm wrong.

 

[Tiny Spark]

It wouldn't matter if it was unplugged, but if you test at the RCD you don't have to unplug everything i suppose. I'm not talking from experience, its just this subject came up in my assessment briefly this week, but I'm still learning, so please correct me if I'm wrong.

We are all still learning mate

 

[Aderac]

Just read back what i put, the earth leakage would still be running through the RCD no matter where your testing so defo got that wrong haven't i

 

[davethsparky]

I honestly hadn't heard that you are supposed to test at the rcd. At college when I was an apprentice we were taught that you could test it either at the rcd or at any point in the circuit.
The result should be the same wherever its tested, and assuming the circuit passed all other tests.

 

[telectrix]

agreed, it should not matter where you test the RCD, but sometimes there is something in circuit that will give you false readings.

 

[Tiny Spark]

Surely on a radial circuit it should increase the further you go down the line?
Again not something I have ever tried

 

[plugsandsparks]

I use a socket on the cct, preferably near the board, just press the button and stand at the board resetting, if there is no socket to plug into, test at board using the three handed method

 

[Darkwood]

As tel has said the readings tested at circuit points may be false as you can't know background leakage unless you perform additional tests and deduct.. if your reading however pass when doing them at say a socket, lighting point etc then no worries if you have a fail that could be due to additional background leakage then an unloaded test at the rcd can confirm it passes or is indeed faulty.

 

[Guitarist]

Technically, should be done at the RCD, but if it passes at a socket outlet then that's fine.

 

[Des 56]

Other than Plugandsparks reason of convenience,why would you want to use a socket for an Rcd test
Its not a stand alone test,unless there was concern about its ongoing functioning
The dist board will normally be open and available because of the other tests being done

If there are a number of RCDs or Rcbos,you will spend half your day wandering back and forth

The test is done to confirm the operation of that RCD.its not a test of how it reacts on any particular circuit

Another opinion.even if the results are fine,they are false
The installation values are records that are supposed to be accurate,they are also supposed to be for future reference


The correct function and record of the RCD test should be obtained at source

 

[Guitarist]

Other than Plugandsparks reason of convenience,why would you want to use a socket for an Rcd test
Its not a stand alone test,unless there was concern about its ongoing functioning
The dist board will normally be open and available because of the other tests being done

If there are a number of RCDs or Rcbos,you will spend half your day wandering back and forth

The test is done to confirm the operation of that RCD.its not a test of how it reacts on any particular circuit

Another opinion.even if the results are fine,they are false
The installation values are records that are supposed to be accurate,they are also supposed to be for future reference


The correct function and record of the RCD test should be obtained at source

Well, in theory you are quite correct. However, I have tried it on several installations both ways, and the tests came back exactly the same. That said, when I was testing at the socket outlet, everything was already unplugged for R1+R2 tests, so no leakage due to equipment.
So, in summary, by all means test at sockets if it's more convenient, but don't have stuff plugged in or switched on at the time.