Detecting Earth Leakage from Inverters

[ScottishGasMan]

So this is just more of a curiosity.

With inverter driven heat pumps, you may have a 30ma Type-B RCD. Specced so that if there was variable frequency earth leakage it would trigger at different times. i.e if its was earth leakage at 50 Hz it would trip at or above 30mA. If it was above 1 kHz leakage then the trigger point would be 150mA etc.

So if you had an RCD intermittently tripping on a heat pump system as above, you might put clamp round the L&N feeding the appliance and see 100mA of a difference.

How could you know if this was happening at high frequencies and everything's working at normal, or lower frequency's and the RCD should have already tripped?

Can you know? Is there more advanced testing equipment available than the standard earth leakage clamp to test for this sort of thing?

 

[endecotp]

Is there more advanced testing equipment available than the standard earth leakage clamp to test for this sort of thing?

Clamp and an oscilloscope.

 

[EFLImpudence]

if its was earth leakage at 50 Hz it would trip at or above 30mA.

Actually it could be anything above15mA, usually around 26mA.

 

[ericmark]

Very few times have I had an oscilloscope at work, and to be frank, not even a clamp on to measure in increments of 1 mA or DC, and as to high frequency AC most seem to stipulate 50/60 Hz.

But to install EV charging points, solar panels, and heat pumps, is rather specialist, one needs to return to collage and retrain. And I know from reading trade literature there has been a problem with EV charging points, where some built in RCD's do not comply with UK well in fact EU as well rules.

With some makes of charging points being banned in their own country. Also rules as to sharing an RCD with other equipment, as yet heat pumps in this country are not that popular, mainly due to rules and regulations over grants, so can't heat and cool, and clearly if fitting due to global warming rather silly if only one way.

But I will guess once we start to push, as with electric cars, we will start to see the problems, in the main to date it is the efficiency, with anywhere between 200% and 600% with electric at 400% cost of gas and oil, some heat pumps are giving the good ones a bad name, well it seems to be more down to how selected and fitted.

We saw the same with gas boilers, but 75% to 90% was not so noticeable, so bad installers got away with it, and most of the bad installers seemed to be surviving by fitting under government grants, people getting something for nothing are less likely to complain.

But be it a mechanic working on an electric car, or a plumber working on an electric heating system, the reason I became an electrician was I was a useless mechanic, found out before apprenticeship ended so moved over, but because good with one trade, it does not mean good with another, and having seen a so-called Gas Safe tradesman seal a flue with gaffa tape, even the schemes do not seem to be ensuring poor tradesmen will be weeded out.

I hope you get an answer, but not seen any special allowance for heat pumps using 150 mA, I would question if they can be used in the UK?

 

[Murdochcat]

22 mA is a very typical tripping current