RCD issues / question

[gbrown100]

Hi everyone.

Some background first, I have a CU in the house from Wylex that's maybe 15 years old. It's been added to over the years but has always been stable with one exception. We've been having a lot of power issues lately because of some faults in the street, anyone I have spoken to have their lights flicker and a few issues with some devices turning off when this happens however our RCD trips, constantly. This is quite annoying!

Anyway, roll forward a little and ongoing issues have frustrated me enough that I bought a 6kva refurbished ups for my office which is in my detached garage from a reputable source. There's a 32 amp supply from house cu (rcd side) to the garage. A CU in the garage (with RCD) and currently said UPS is on a 20 amp radial circuit shortly to be upgraded to 32 amp. The load on the UPS will be a max of 10 amp (plus another 10 for charging) although currently is zero.

With the UPS switched on and powering something from battery all is fine. 20amp circuit on all is fine, the UPS has its own 40amp switch on the supply side, within seconds of the ups switch being flipped (not immediate) the RCD in the house trips. If I turn the rcd on again a second or two and the rcd trips. I can see no issues with the wiring or plugs.

So my question is, is this really a problem with the UPS at this stage or is it likely the setup I have is contributing to an already sensitive rcd tripping?

Any thoughts appreciated, I'll probably get an electrician out to check this out!

 

[ericmark]

What type is the RCD? In the main to supply an UPS it needs to be type A or better, my UPS does not have a RCD on the feed, the RCD's are on the output of the UPS. Again type A.

 

[gbrown100]

It say 80A 30ma WRS80/2 which reading up is a type A.

Also, I should mention that I have another 3 UPS's ranging from a 1600, 1000 and 750va dotted around (all APC) and my understanding is that UPS's can cause a certain amount of earth leakage.

I've also read that the UPS removes rcd protection on the load side so I just probably install one? It's feeding 6 uk sockets running 3d printers.

 

[AndyPRK]

1. Is the wylex RCD test button yellow or black ?
2. You could install RCBOs in the consumer unit. So if there is a build up of earth leakage across all the circuits, it would reduce that problem.
3. Little point adding an RCD on the output of UPS. I assume they are isolated, so you can't get a shock off them. And the usual reasons for fitting an RCD don't really apply to 1 office room with surface cabling

 

[gbrown100]

The button is yellow.

Just confirmed, I unplugged the 1600 and 1000 ups and nothing is tripping. Now actually I could just run all of that off the 6000 va anyway and remove the other two.

The issue with the RCBO's is that the two I just isolated are also on the same circuit heading back to the CU in the house

 

[AndyPRK]

FAO Eric = Yellow button RCDs are type AC

 

[gbrown100]

FAO Eric = Yellow button RCDs are type AC

OK, so the specs all said A but yet colour denotes AC. OK, so this doesnt make much of a difference in this instance does it?

 

[hllns]

3. Little point adding an RCD on the output of UPS. I assume they are isolated, so you can't get a shock off them. And the usual reasons for fitting an RCD don't really apply to 1 office room with surface cabling

That it's isolated is quite the assumption with anything modern, a number of them run in an ECO bypassed mode as switch mode power supplies are usually fine with the few ms of interruption, a number of designs also don't have galvanic isolation with the neutral referenced from the input:

Isolation in a UPS system - KOHLER Uninterruptible Power

Isolation in a UPS system - KOHLER Uninterruptible Power

www.kohler-ups.co.uk