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Author Topic: SMA SB3300 inverter tripping CU mains RCD  (Read 3784 times)
Westie
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« Reply #30 on: September 29, 2018, 10:18:52 AM »

The point the OP has made is that the RCD that's tripping isn't even feeding the SunnyBoy that he is convinced is the cause of the nuisance trip!  

So, is it possible that a residual DC current component from the SB is in a 'ground loop' with another inverter type device that is fed via the RCD? ie. there's a small DC current circulating between the SunnyBoy and another device that is fed by the RCD, so that DC current path would be back thro the RCD and maybe causing the nuisance trip. This would be difficult to prove but if it was the case then replacing the old AC RCD with a Type A may solve the problem.....  

Of course the even more confusing bit is that this SB is an old transformer inverter which is galvanically isolated so there should be any residual DC current component!

eabadger.... That was an interesting link to the proposed 18th Edition regarding RCD selection, the comments were even more interesting and confirmed what I've thought for a while now, namely that the appliance manufacturers must provide integrated earth leakage protection. Certainly for our UK ring main system there's no other way that's going to work given the number of inverter drives now being supplied in our appliances.

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Scruff
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« Reply #31 on: September 29, 2018, 10:26:18 AM »

Certainly for our UK ring main system there's no other way that's going to work

 facepalm

Use two radials.

Two radials!

If you have to ask why; use two radials!
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eabadger
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« Reply #32 on: September 29, 2018, 10:50:33 AM »

i am amazed the copper shortage "fix" ring final circuit still is ongoing, that and reduced size of earth conductor.
norm here is radials, i have gone one per room, except bigger rooms where i have two.
special items like cooker, washer, dishwasher, fridge, freezer each require there own circuit, special items as a rule protected by type A rcd's.
lights on there own circuit, again i have done one per room, that way most trips only kill one area not the whole upstairs.

when i came here from uk i hankered after t&e and ring mains till i looked in to it a bit more, now am convinced this is better

but back to the radom tripping, my victrons are transformer inverters but still i had issues until changing to type a.
only trips now are self inflicted, like leaving extension lead out and it filling with water, right in the middle of watching telly!

steve
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Scruff
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« Reply #33 on: September 29, 2018, 11:31:33 AM »

i am amazed the copper shortage "fix" ring final circuit still is ongoing, that and reduced size of earth conductor.

 banghead
That's a fairytale. How is circumnavigating a room going to use less copper than running two sides instead.  wackoold


4.6 AC Electrical System
AC Electrical System shall meet the following requirements;
- The AC system must be tested and certified by a Registered Electrical Contractor and a
Safe Electric certificate must be provided
- The AC system must comply with ET101:2008
- Where the PV system does not have at least simple separation between the AC and
DC side protection for domestic PV systems at the main domestic consumer unit must
be via a dedicated Type B RCD protective device, rated for 25A (or larger where
required).
- Where the PV system cannot, by reason of its construction, feed DC currents into the
electrical installation (i.e. AC system), a Type B RCD shall not be required, and
electrical protection of the AC circuit shall be in accordance with ET101:2008.
- An AC isolator (2 pole, switching live and neutral) must be installed between the
inverter and the consumer unit, and accessible from the inverter location
- AC isolator must be labelled – “PV System MAIN AC Isolator”
- The main incoming point of the dwelling (typically the meter box) must contain a
warning label indicating the presence of a separate source of electrical supply to the
building.
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Westie
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« Reply #34 on: September 29, 2018, 11:35:27 AM »

i am amazed the copper shortage "fix" ring final circuit still is ongoing, that and reduced size of earth conductor.
norm here is radials, i have gone one per room, except bigger rooms where i have two.
special items like cooker, washer, dishwasher, fridge, freezer each require there own circuit, special items as a rule protected by type A rcd's.
lights on there own circuit, again i have done one per room, that way most trips only kill one area not the whole upstairs.

when i came here from uk i hankered after t&e and ring mains till i looked in to it a bit more, now am convinced this is better

but back to the radom tripping, my victrons are transformer inverters but still i had issues until changing to type a.
only trips now are self inflicted, like leaving extension lead out and it filling with water, right in the middle of watching telly!

steve

Yep, I agree, it's a better system, I spend a bit of time in Majorca now my son lives there, his place is wired in exactly the same way as you describe. It's especially useful when tracing nuisance trips as there are so many more points of isolation.

Glyndwr98, you problem is a strange one but if I were you I'd be replacing your old AC  RCD with a type A, just in case there is any residual DC backfeeding going on ...
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Westie
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« Reply #35 on: September 29, 2018, 11:43:02 AM »

i am amazed the copper shortage "fix" ring final circuit still is ongoing, that and reduced size of earth conductor.

 banghead
That's a fairytale. How is circumnavigating a room going to use less copper than running two sides instead.  wackoold




IIRC the reasoning was to double the load capacity, ie. a 2.5mm radial would be able to carry a max load of 16A, but a ring would be ok for 32A.  Then of course you applied the magical 'diversity factor' which meant you could add sustantially more load than 32A becuase you'd never be using all the applances at once wackoold
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eabadger
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« Reply #36 on: September 29, 2018, 11:45:25 AM »

scruff: you are right, but done for costs, https://en.wikipedia.org/wiki/Ring_circuit
or so it says.
our sockets here are 16a
however doesnt logic say that radial individual circuits beat ring?
the gizmos we can fit in our CU is massive.

one odd thing we are meant to have a data CU, where phone is terminated and the adsl router and switch, meant to, but the box's are so expensive i dont think many fit them.

steve
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Scruff
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« Reply #37 on: September 29, 2018, 01:00:51 PM »

2 x 16A radials = 32A!

As regards the RCD, I'd make absolutely sure the inverter isn't downstream before getting carried away.
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glyndwr1998
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« Reply #38 on: October 02, 2018, 04:29:45 PM »

Checked the mains incoming consumer unit rcd, it was an AC type 80a 30ma.

Jut purchased a type A 80a 30ma to replace it.

It wasnt expensive, so we`ll change this first to see if anything improves. Funny enough, we havent had any trips now for the last week plus!

Anyhow, we`ll change the rcd and go from there, if we still get nuisance trips, we`ll swap out the inverter.

Thanks for the support on this one guys.
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Scruff
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« Reply #39 on: October 02, 2018, 11:32:47 PM »

Turn off the RCD. (when the house is at low load during daylight).

See if the inverter enters anti-islanding mode.

If the inverter doesn't enter anti-islanding mode then it has nothing to do with the inverter.
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