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RCD v RCBO v MCB


grahamsmythe

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How should a DC Inverter be protected in a Consumer Unit?

 

Currently our inverter has a 16amp MCB on the non-RCD side of our Consumer Unit.

 

1. Should it be moved over onto the RCD side?

2. Should the MCB be replaced with an RCBO? Would the electricity flowing the opposite way cause an RCBO to behave differently?

3. Should it just stay as it is?

 

Any suggestions would be gratefully received.

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5 hours ago, grahamsmythe said:

Should it be moved over onto the RCD side

Can depend on inverter, RTFM on that one.

5 hours ago, grahamsmythe said:

Should the MCB be replaced with an RCBO

Not had any experience of that.

5 hours ago, grahamsmythe said:

Should it just stay as it is

Was it wired and then a test certificate issues?

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Some inverters can cause nuisance tripping of devices containing RCDs. It can be to do with leakage currents associated with EMF suppression in the inverter. You can get drives without EMF suppression but from memory these can't be CE marked.

 

Schneider do their Si RCDs (that aren't time delayed) and in my experience solve the issue completely. Of course some inverter brands cause less trouble than others!

 

si RCD.pdf

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2 minutes ago, Onoff said:

Some inverters can cause nuisance tripping of devices containing RCDs

Think that was the problem with the SMAs.  Some had a transformer and some didn't.  Seem to remember that the TL range should not have an RCD as it caused problems.

 

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Just now, SteamyTea said:

Think that was the problem with the SMAs.  Some had a transformer and some didn't.  Seem to remember that the TL range should not have an RCD as it caused problems.

 

 

You might find the manufactures say don't fit an rcd just to save themselves problems and comeback from their customers. I've a longstanding relationship with a major inverter / motor manufacturer. Back when we were experiencing a +25% tripping rate, on start up, of installed machines I took them to task. Their initial, ludicrous suggestion was to either fit 100mA RCDs or ones without EMF suppression. I persevered digging and asking and found the Schneider units did the trick. In a quirky twist about 2 years later this major manufacturer came onto me, in writing, to ask if I'd ever solved the problem. Other companies were turning away from them and fitting other drive makes because of it. Somewhat peeved I rang them and found they had just supplied 200 inverters to one customer who built pay kiddie rides as seen in shopping centres everywhere. The breakdown rate through nuisance tripping was ridiculous. I put them onto Schneider and the rest is history. Handy as whenever I need free help I remind them of this.

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55 minutes ago, Onoff said:

Their initial, ludicrous suggestion was to either fit 100mA RCDs …

 

Dunno about ludicrous - that is (or was - while since I've taken much notice of the subject) a common requirement for PV inverters. It might well be what the OP finds if he reads the fine manual. Doesn't give quite the shock protection that a 30 mA RCD would give but still gives decent protection against supposedly earthed things being at a higher than ideal potential better than no RCD.

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2 minutes ago, Ed Davies said:

 

Dunno about ludicrous - that is (or was - while since I've taken much notice of the subject) a common requirement for PV inverters. It might well be what the OP finds if he reads the fine manual. Doesn't give quite the shock protection that a 30 mA RCD would give but still gives decent protection against supposedly earthed things being at a higher than ideal potential better than no RCD.

 

In my situation it was. In effect portable equipment with trailing leads vulnerable to damage. A short term solution proposed by one site's insurer was to fit 100mA rcd and a totally non standard mains plug socket arrangement on the basis that only the controlled kit with the inverter issue could be plugged in and that was used by trained operatives. Didn't help ref the trailing lead issue but they convinced themselves it went some way to solving the issue. All fixed long since with 30mA Si units and back to normal plugs & sockets.

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5 minutes ago, Onoff said:

In my situation it was. In effect portable equipment with trailing leads vulnerable to damage.

 

Sure, but wouldn't want the OP to read his manual, see it says 100 mA RCD, and think that's a ludicrous solution for the fixed wiring in a loft or where ever. Of course, 30 mA would be better but 100 mA RCDs are manufactured for good reasons.

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1 hour ago, SteamyTea said:

Going to pop that on the Kindle, will also show that screens at night don't disturb sleep I am sure.

 

The 2010 version I have here has even more pages if you want that? ?

 

Type 4 is indeed an old school circuit breaker designation rated at 50 x In. There were Type 4 rcbos made by Square D I remember. 

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