RCD test results

[Clinchy]

I did a board change this week and fitted a BG dual RCD.

Carried out all my testing before hand and everything checked out ok.

Fitted the board and did my post live tests and both RCD's trip at 4.8ms at x 5 and 8ma on the ramp test.

So I though maybe a dickie batch of RCD's, swapped them over for 2 new ones and still 4.8ms and 8ma.

Removed the busbar and N out on the RCD's and tested at the RCD and still 4.8ms and 8ma.

Anyone have any idea's?

 

[pc1966]

Have you checked your MFT against some other RCD?

 

[ChrisElectrical88]

As stated have you got all your test settings right and not accidentally pressed a button?

Also learn a lesson that BG is woeful kit.

 

[James]

Take one home with you, test it on the bench at home. Compare to a known good one.

 

[Dustydazzler]

As above rig up at home and test

 

[Dartlec]

I did a board change this week and fitted a BG dual RCD.

Carried out all my testing before hand and everything checked out ok.

Fitted the board and did my post live tests and both RCD's trip at 4.8ms at x 5 and 8ma on the ramp test.

So I though maybe a dickie batch of RCD's, swapped them over for 2 new ones and still 4.8ms and 8ma.

Removed the busbar and N out on the RCD's and tested at the RCD and still 4.8ms and 8ma.

Anyone have any idea's?

Were all loads disconnected at the time? Sounds like something going on with the existing loads - though both doing it seems unlikely unless there's a borrowed neutral somewhere.

It's not impossible you've got a dodgy batch both times, but I'd be wondering about the tester - worth testing it on some other installation (even your own at home) to see if it's giving expected results.

Also if you're using a plug socket/lead to do the tests, try it with the separate leads and directly at the RCD. I had a Megger plug in lead just fail suddenly on me with no visible sign of damage earlier this year.

 

[Clinchy]

I had all loads disconnected and tested at the RCD's.

I've just tested my RCD's and they test as expected.

I've fitted quite a bit of BG and never had an issue before.

I'll have to go pull one out next week and bring it home, or I can try chucking in my van one in quick and see if that tests Ok at the clients.

Cheers guys, I'll report back.

 

[telectrix]

sure you had MFT set on 30mA and not 100mA?

 

[Gavin John Hyde]

Not wanting to hijack the thread but I have had issues the last few weeks or so with Steeple Type A RCDS, all 4 I have fitted have tripped when carrying out a no trip Loop Zs test using a KT64DL.. RCD tests as fine but trips on no trip loop testing and no trip PFC.
have had to link out rcd to measure these results, test at the terminals inside the EV Charger to get a true Zs rather than via an evse adaptor too.
Have asked Alan Towler the tech guy at kewtech for thoughts? He is looking into it.
MFT is calibrated and works fine on other brands and RCDS. just this batch of Steeple Type A RCDS. made me wonder if they are overly sensitive to the MFT and something its pumping out.

 

[James]

If I remember correctly, testers often inject dc into the circuit when doing no trip test. The theory behind it is that it saturates the coils in the rcd preventing it tripping.

 

[Vortigern]

Have you done any test for earth leakage? It may be that existing leakage is at 15-20 ma and that is why such a low result.

 

[Dartlec]

Not wanting to hijack the thread but I have had issues the last few weeks or so with Steeple Type A RCDS, all 4 I have fitted have tripped when carrying out a no trip Loop Zs test using a KT64DL.. RCD tests as fine but trips on no trip loop testing and no trip PFC.
have had to link out rcd to measure these results, test at the terminals inside the EV Charger to get a true Zs rather than via an evse adaptor too.
Have asked Alan Towler the tech guy at kewtech for thoughts? He is looking into it.
MFT is calibrated and works fine on other brands and RCDS. just this batch of Steeple Type A RCDS. made me wonder if they are overly sensitive to the MFT and something its pumping out.

I think the new method of No trip testing uses something like 15mA on the Meggers, presumably similar on others - so wouldn't need much existing leakage to trip if the Steeples are particularly sensitive - Do they ramp test at lower than other RCDs?

 

[Gavin John Hyde]

I think the new method of No trip testing uses something like 15mA on the Meggers, presumably similar on others - so wouldn't need much existing leakage to trip if the Steeples are particularly sensitive - Do they ramp test at lower than other RCDs?

I have found they trip at lower levels compared to say MK or Hager.
If you test through the charger it trips everytime due to the on board DC monitoring. It detects at 6ma.
With EV charging it's a radial with RCD before the charger. I always do testing for as at the incoming terminals before the actual charging bit to avoid the tripping.
I tested one of the type a RCDs this morning and it tripped at 21ma which is on the low side.