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recently saw some "click" c/u advertised at a bargain price at a large local dealer, bought 2 and thought about a bit of extra profit on next job....great. installed one in cumbria (60 mile drive), when i came to test the rcd, it would not trip, either on test button or test instrument. well, i suppose thats life, but i am ok, cos i have a spare in the second c/u. went back to cumbria and fitted new rcd. exactly the same, would not work. tried excersing it etc to no avail.thought it must be me, rechecked all connections, all ok, rcd working as a manual 2 pole isolator ok,all other test, polarity earth loop etc all ok, then connected a supply to both units on the bench, niether would trip on test button, am i missing something?
i returned the faulty rcd to scolmore who make them with explanatory note, they returned it later no fault found. again, tried it on the bench and it wouldn't operate. bought a different make for my third trip to cumbria, tried it on the bench and it worked fine.
the rcd is a "click" DB300 63A 30ma unit. has any one else had problems with these, or is there some unusual method required to test them?
i would add, i have been doing this job for some considerable time and this is first time i have had 2 new units fail to operate.
 
The test button creates an internal imbalance and has nothing to do with your testing equipment, just as long as the RCD is connected correctly.
They should behave in exactly the same way as any other RCD, so if you have tested other makes and they are all fine, it sounds like these click units are faulty.
Ask scolmore what tests they carried out and what the trip figures were. Not saying they weren't tested, just worth asking :)
 
interesting point about what they tested, they did not include a written response, but did phone me to tell me the unit worked fine, but went on to say, rather strangely, that they didn't have the test equipment, but their engineer had managed to put a load accross it and it worked ok. the guy who phoned me was more likely sales/customer care, defo not an engineer, but he did say he had witnessed it working. i have never heard of an rcd that needs a load to operate, but maybe someone else has?
 
As guitarist says, sounds like faulty rcd. The only time I've come across an rcd that wouldn't trip, was when the circuit neutrals fed from the rcd were in the wrong bar. Once I swapped them the the right bar, the rcd worked fine (trip button aswell).
 
going back tomorrow with a new rcd, will have another look at neutral wiring, already rechecked it once, but it was cold wet and miserable. (c/u is outside)
 
interesting point about what they tested, they did not include a written response, but did phone me to tell me the unit worked fine, but went on to say, rather strangely, that they didn't have the test equipment, but their engineer had managed to put a load accross it and it worked ok. the guy who phoned me was more likely sales/customer care, defo not an engineer, but he did say he had witnessed it working. i have never heard of an rcd that needs a load to operate, but maybe someone else has?


Sounds more like they simply checked that it "didn't" trip when connected to a load, as they may have thought you meant it was faulty by tripping all the time. Always hard when dealing with office people.
 
RCD failures of all types is just par for the course!! No matter what some would argue here, they are just not as reliable as one would expect them to be!! And why a S type upfront (or replacing the main isolator) should ''Always'' be fitted to a TT installation. Relying on a single 30mA RCD each side of a CU is just asking for trouble, especially with numbty Ra values!! lol!!
 
Still at least it didn't explode when you pushed the test button,there was an article in P E last year,April I think it was and a few people had had this happen to them.
 
quick dash to cumbria, fit cheap replacement rcd, works first time and passes all tests. both scolmore units bench tested, both u/s including the one they tested and returned. beggars belief, thought i was going senile. thanks for all your posts. had'nt heard of the exploding one, must have made some poor sparky re check his connections. will stand well back next time!!
 
I bought a BG garage unit and had the same problem took it back and the guy gave me a replacement out of his stock thats when I found the replacement was a better build quality as the test button was dark yellow and the garage RCD was bright yellow so its back to Wylex for me .

Also remember when you send it back it goes to the sales people who push the test button and say fine so when you send it back tell them to ramp,x1x5 test as well
and if you are still not sure change the CU out free of charge why because your reputation is on the line
 
Don't know if anyone else has seen the arcing through the casing on some the RCDs when testing them , usually in dark cupboard .
 
The internal arcing might just be because there's a load current when it trips.

Ask to see their paperwork and test sheets for the returned items. If I returned something with a fault report to a supplier and they handed it back after testing it and saying it worked then I'd give them an invoice for the traveling and labour time if I went back to site and it still wasn't working. I wouldn't be shy with the prices either, using salesmen or office staff to test returns doesn't fly with me I'm afraid.
 
I agree that using RCD's should be no reason not to still use a belt and braces approach. They're a very useful safety device but they're not an alternative to having good electrical design.
 
I bought a BG garage unit and had the same problem took it back and the guy gave me a replacement out of his stock thats when I found the replacement was a better build quality as the test button was dark yellow and the garage RCD was bright yellow so its back to Wylex for me .

Also remember when you send it back it goes to the sales people who push the test button and say fine so when you send it back tell them to ramp,x1x5 test as well
and if you are still not sure change the CU out free of charge why because your reputation is on the line
yes....and this is what the O/P should`v done before returning the item....at least that way he had the info available....should any salesman crap start to surface...
 
when I worked in BMS systems the service guy tested the outstation alarm by initiating it on the PC but this did not prove the actual input at the outstation he thought it was smart I thought it was lazy now you think when you return the RCD they would have a calibrated tester on hand but I dont think plus the majority of these are built in the far east so that tells me their QC is not very good plus it would bother me if someone got hurt because I saved £15 on a CU
 

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