What exactly happens during an RCD test? (Methods 1 & 2) Discussion ThreadWhat exactly happens during an RCD test? (Methods 1 & 2) Electrical Advice
Sorry this is a bit of a long read but I’d be extremely grateful if someone can help me understand RCDs and testing methods of them.
I know RCD test applies a fault current but in what way? I understand how continuity/IR and the other test work so it helps me know what to do, what’s going on, what to look for etc but I’m a bit stuck on RCD testing. I have attached a picture which is for test method 2 both 2 lead and 3 lead)
Annoyingly there are no pictures for test method 1 but it says between line load side of that circuit and the associated cpc.
Q1.Would this be a 2 lead test only? Is there 3 leads test for method 1?
Q2.So my guess is that the instrument is probing onto L and transferring I^n at 0.5/1/5 (15/30/150ma) to Earth which then the RCD detects the imbalance between (L)-N to Earth and then trips? (Only for 1x and 5x I^n)
Q3.The instrument then detects the time it took to cut the power whilst sending that fault current which tells you the tripping times?
Q4. This test is preferred when you can carry out an EFLI of that circuit/s before this RCD method as you know the exposed conductive part is connected to earth and there won’t just be a floating fault current on the exposed conductor right?
This method is if you have no upstream RCD.
Q5. If there is an upstream RCD: As the L from the upstream is feeding this RCD it’s also leaking that L to E which measures the imbalance of either that RCD or this RCD? Which is why it’s not preferred as you’re unsure which RCD the instrument is reading?
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Test method 2 upstream/downstream method where there’s an upstream RCD like the scenario in Q5…
For both 2 lead and 3 lead I’m kind of stuck on how it stops the upstream RCD from tripping and only measures this RCD…
Read my guess on below. If it is correct then I think I’ve answered Q6 and Q7 but I’m still stuck on Q8 why 3 lead test is needed
GUESS: I’m going to have an educated guess though I’m...
Read more
What exactly happens during an RCD test? (Methods 1 & 2) for the original thread on Electricians Forums
Sorry this is a bit of a long read but I’d be extremely grateful if someone can help me understand RCDs and testing methods of them.
I know RCD test applies a fault current but in what way? I understand how continuity/IR and the other test work so it helps me know what to do, what’s going on, what to look for etc but I’m a bit stuck on RCD testing. I have attached a picture which is for test method 2 both 2 lead and 3 lead)
Annoyingly there are no pictures for test method 1 but it says between line load side of that circuit and the associated cpc.
Q1.Would this be a 2 lead test only? Is there 3 leads test for method 1?
Q2.So my guess is that the instrument is probing onto L and transferring I^n at 0.5/1/5 (15/30/150ma) to Earth which then the RCD detects the imbalance between (L)-N to Earth and then trips? (Only for 1x and 5x I^n)
Q3.The instrument then detects the time it took to cut the power whilst sending that fault current which tells you the tripping times?
Q4. This test is preferred when you can carry out an EFLI of that circuit/s before this RCD method as you know the exposed conductive part is connected to earth and there won’t just be a floating fault current on the exposed conductor right?
This method is if you have no upstream RCD.
Q5. If there is an upstream RCD: As the L from the upstream is feeding this RCD it’s also leaking that L to E which measures the imbalance of either that RCD or this RCD? Which is why it’s not preferred as you’re unsure which RCD the instrument is reading?
Test method 2 upstream/downstream method where there’s an upstream RCD like the scenario in Q5…
For both 2 lead and 3 lead I’m kind of stuck on how it stops the upstream RCD from tripping and only measures this RCD…
Read my guess on below. If it is correct then I think I’ve answered Q6 and Q7 but I’m still stuck on Q8 why 3 lead test is needed
GUESS: I’m going to have an educated guess though I’m...
Read more
What exactly happens during an RCD test? (Methods 1 & 2) for the original thread on Electricians Forums
