Testing Screwfix RCD adaptors

You should not PAT test any RCD. An RCD adapter is not considered as a portable appliance so I don't know why you are trying to test it. The tests you are doing using the Metrel is the correct way to test an RCD. Or am I getting the wrong end of the stick here? If the RCDs have failed the test then yes they could be faulty. That is why we test. Have confidence in your testing!

 

The Code of Practice for In-service Inspection and Testing of Electrical Equipment does not agree with you - they should be subjected to RCD tests (which many PAT testers are capable of).

Oh, and by the way, the Code of Practice (and therefore so-called "PAT testing") is not, nor has it ever been, restricted to portable appliances.

 

Splitting hairs mr risteard. RCDs should not be exposed to insulation tests, it says so on the RCD. They should be tested for compliance with tripping times as required by BS7671. If a PAT testing instrument has those capabilities then fine. Use them. Don't just go through all of the tests by rote as you could damage the RCD. No insulation testing is necessary.

 

What make are the ones that you are finding faulty - a colleague also found that a plug-in RCD wasn't tripping with a dedicated RCD tester. The RCD in the CU tripped fine within specification.

I assume the RCDs on the tools are plug-in types?

 

It's not splitting hairs because there is a defined procedure for PAT testing RCD adaptors (which are not subject to BS 7671 as they are not part of the fixed installation), and they therefore should be tested in accordance with the Code of Practice. Most (or certainly many) PAT testers have an RCD testing capability for this reason.

 

I have one of them and it has always passed the RCD tests it has been subjected to by my Megger PAT450.

 

I think the one that my colleague had that failed was also a Masterplug one - guess they can be a bit hit and miss!

 

Great little post this if a bit old or stale recently got myself a second hand Robin rcd tester to carry out these tests (as the pat tester I'm using (not mine only on loan from the charity I'm testing for) can't do rcds great bit of kit though to be sure I repeat the rcd tests at each level required both at the 0setting and the 180 setting (I think it's 180 don't have the machine in front of me right now) 3 times so normally that's 12 times as I like to get accurate results

 

It is 180 deg. You’re testing at the peak of the positive, then negative of the AC cycle. 180 degrees apart.

Older RCD testers won’t test the newer type A RCDs correctly.

With most RCDs used for supplementary protection, the main result you want to check is that it trips within 40ms at x5.

 

Thanks, that explains a lot as I'm new to this testing any further advice would be greatly appreciated both for plugtop/ plug through/ socket face types as well as main board types as well as appropriate trip times for 30ma and 100ma (as those are the two types I'm most likely to come across)

 

Some RCDs will not trip on the negative half cycle of the current.

In the UK the frequency is 50 Hertz, that’s 50 cycles per second.

So as there is a 1000 milliseconds in a second as full cycle lasts 20 milliseconds (1000 divided by 50) and a negative half cycle lasts 10 milliseconds (1000 divided by 100).

Therefore the RCDs that won’t trip on the negative half cycle, 180 degrees, may take an additional 10 milliseconds to trip when tested on the 180 degree setting.

If a RCD won’t trip at all it’s probably ######, do they trip using the built in test button?

 

Thanks yes so far the 3 I've tested all trip using there test button only had one older type power breaker (with the reset button underneath so has to be unplugged to be reset with sleeved pins, have a older version with bare pins as well) fail to trip on the negative test

 

The older version with the bare pins fails for having bare pins.

 

Yeah know that it's part of my personal collection not in use for domestic or commercial purposes just simply a collectors item just stating that I have two versions of the white powerbreaker type with the reset button underneath meaning it has to be unplugged to be be reset, haven't tested the bare pin model as well technically its all ready failed due to bare pins however for ***** and giggles I may end up testing it just to see how it reacts (see if the partial test fail is a flaw of that particular model to keep an eye for in future)

 

Why? Regs are not retrospective.

 

I am sure your copy of the 5th edition Code of Practice for In-service Inspection and Testing of Electrical Equipment is in the post. When it arrives I am confident you will be able to advise us correctly. I would use mine but I do not have access to it online at present.