Search results

IIRC it was 48. something it dropped to which triggered the load shedding

Wait, so you've had 6 out of 6 BG RCBO's 'fail'? or could it be -

What 'requires' all work to have certificates?

If the earth loops/fault currents are identical L-N and L-E it suggests PME

try disconnecting the neutral from the circuit which has the live disconnected

Fluke T110, T130, and T150 testers https://www.fluke.com/en-gb/support/safety-notices/tpt-recall I'm on my 3rd T-150 so it's nice to see them finally admitting the design flaw and hopefully my 4th T-150 won't break after a few months

It's UK forum so anyone reading the thread later could have reasonably made the mistake that the answers applied uk-wide had nothing been said. Appliances can't be easily isolated if the socket is concealed behind a unit or appliance, and the DB isn't readily accessible.

"Where socket outlets are concealed, such as to the rear of white goods in a kitchen , separate switching should be provided in an accessible position, to allow appliances to be isolated." Scottish building regs

411 is ADS, not limited to TT supplies 411.4 is about TN supplies 411.5 is about TT 411.4.9 is about using RCD's in a TN installation to satisfy disconnection times

Supplies for things 100's of metres away from the nearest source are not at all unusual in a temporary event or other temporary scenarios (credible real world situations). The supply may only be for a small load, such as LED lighting, or small device charging and so volt drop less of an issue...

According to my calculations a 77amp fault current with 2.5mm cable would take 13.9 seconds* to overheat and reading the graph (C16) would take about 15 seconds to disconnect. A 77amp fault current with a 1.5mm cable would take 5 seconds to overheat (still about 15 seconds to disconnect). So...

What is not credible about using 1.5 or 2.5mm cable with a C16?

No, it was an exercise in looking at what happens in long cable runs under fault conditions Not compliant with what regulation?

Yes for 4mm, but if you look at 2.5mm cable and 1.5mm cable in the otherwise same scenario things look a bit different! Both (depending on install method etc) have a CCC in excess of 16 amps.

Yes, sorry 36seconds Yes I had already noticed that, so in this example we can see that the 4mm cable, aside from volt drop, will actually comply.

On the last course I did, a BS7909 course taken by James Eade, we looked at long runs of cable (unit 3 - power distribution) and the resultant problematic fault currents. It was accepted that RCD's would take care of an earth fault, and volt-drop aside, the question was asked whether a 4mm cable...

515.1.2 says that RCD's cannot be the sole method of protection, and refers to section 411 which says RCD's can be used so long as overcurrent is accounted for per chapter 43

411.4.4 says quite clearly that RCD's can be used for (earth) fault protection in TN systems, nothing about only for additional protection or exceptional circumstances, am I missing something?

Those are disconnection times for L-E faults, which can be covered by an RCD, I'm looking at L-N faults where the loop impedance exceeds the given values. I said "...disconnection will occur before the cable overheats" it's another way of saying exactly what you said. Are you just trying to...

John ^ I'm sure you'll correct me if I'm wrong but there does not appear to be any requirement that a L-N fault is disconnected within a given time or using the "magnetic part" of the breaker but rather only that the disconnection will occur before the cable overheats. In practical terms with...