RCD's with Photovoltaic's?

[Markc]

How did you find this out?

I have to admit Mr NICEIC inspector!

Fortunately we had fitted a overall 30mA RCD protected board in the garage with the thought to rewiring the garage in 2012. The only circuit on the board was our PV as all the existing was still on the old board. Had left five further ways to use but as yet none are. He couldn't make a observation as there were no circuits requiring supplementary protection connected (sockets etc). Skin of our teeth on that one!

We fit our own board in the majority of cases but there is one or two I have been back to to rectify this issue.

I have tested this on the following inverters, SMA Sunnyboy, Deihl Platinum, Fronius IG & IG Plus, Mastervolt (including my own!!) and Powerone, None tripped in the required time.

Please look into it but also try it for yourself. It might be quicker!

 

[powervan]

these boys have the complete DTI/niceic/health safety/mcs/electricity act/offwatt/beano/dandy/landrover service manual imprinted on there bedroom ceilings! they call it (light reading)

 

[Markc]

these boys have the complete DTI/niceic/health safety/mcs/electricity act/offwatt/beano/dandy/landrover service manual imprinted on there bedroom ceilings! they call it (light reading)

All correct other than the Landrover service manual. Its the Landrover Restoration Manual in my case!

 

[moggy1968]

follow this link
Type B RCDs - Sibert - automated equipment manufacturer and supplier of process consumables
and open the PDFs on the side, they explain everything. I suspect the majority of installations done in the last 2 years don't comply on this basis!!
if you put them on a 16th edition board the easiest solution is to swap the MCB onto the unprotected side, if there's no room then swap it for another circuit, say lighting, so thats on the RCD. of course if that covers the bathroom lighting even better, now you've given them RCD protection in their special location, bonus!!

 

[moggy1968]

Ah yes, the landrover workshop manual, where most chapters begin 'lift and prop the bonnet' my kinda level!!

 

[powervan]

well im shooting tomoz! if i turn her over now the screen will be clear by 8am!!!

 

[Markc]

well im shooting tomoz! if i turn her over now the screen will be clear by 8am!!!

We'll need to be moving to the Landrover forum if we carry on like this!

 

[VMan]

I have to admit Mr NICEIC inspector!

Fortunately we had fitted a overall 30mA RCD protected board in the garage with the thought to rewiring the garage in 2012. The only circuit on the board was our PV as all the existing was still on the old board. Had left five further ways to use but as yet none are. He couldn't make a observation as there were no circuits requiring supplementary protection connected (sockets etc). Skin of our teeth on that one!

We fit our own board in the majority of cases but there is one or two I have been back to to rectify this issue.

I have tested this on the following inverters, SMA Sunnyboy, Deihl Platinum, Fronius IG & IG Plus, Mastervolt (including my own!!) and Powerone, None tripped in the required time.

Please look into it but also try it for yourself. It might be quicker!

I was interested in the disconnection time of my rcd with the inverter generating, im on a TT system with a Ze of 26ohms.

Trip time of 30mA RCD @1 x I (delta) n = 91ms
Trip time @ 5 x I (delta) n = 19.5ms

Its a sunnyboy 1700 was generating about 300Watts to AC ( allowed inverter to start generating again before re test on each side of cycle, made sure meter was going backwards aswell)

I will try it out again once the sun gets a bit stronger.

My MCS install was put on the RCD side of a split board and inspector did not say anything about this! quite concerning really!

Most of our jobs have had dedicated CU with tail block anyhow! (except parents house and my house!)

I will test the parents RCD soon and see the trip times on that ( fronius IG30)

 

[SolarCity]

Your disconnection times are ok but will the PV system actually affect the RCD operation?

The RCD may well operate but effectively the load side of the RCD will still be live outside of the required 0.2s disconnection time. Even on a dedicated RCD, does this not throw a bit of a curve ball on TT systems and effectively make the RCD redundant?

 

[VMan]

Your disconnection times are ok but will the PV system actually affect the RCD operation?

The RCD may well operate but effectively the load side of the RCD will still be live outside of the required 0.2s disconnection time. Even on a dedicated RCD, does this not throw a bit of a curve ball on TT systems and effectively make the RCD redundant?

I think you are right, but surely my megger should still detect the voltage to earth when doing the RCD test anyway, and then show me the reading of this disconnection time when the line becomes the same potential as earth?

 

[BruceB]

It depends how the megger is operatiing: whether it is timing changes in voltages or measuring changes in leakage ac current, or changes in injected dc bias current. It could be any or all. I suspect the latter would normally give the most accurate result and would also show the rcd tripping even with the inverter still pumping out power.
Regards
Bruce

 

[VMan]

hmm, interesting, Bruce, are you suggesting that its possible the megger is detecting the RCD tripping, even if there is still potential difference? and showing me this tripping time, not the time it takes for the voltage potential to get to a safe level?

If this is the case, could this be a problem if you had a fauty RCD that didn't fully disconnect, just made an influence to the current difference the megger looks for??

I only have a 4 way db in my 2 bed cottage, so its RCBO's all they way as i cannot fit a bigger cu in the cupboard! bugger.
As for jobs it will be a dedicated CU for ever installation.

 

[BruceB]

Yes I am. I do not KNOW. But I can envisage a number of ways a tester could perform the task. Measuring currents could be a more reliable way of testing as you are not then vulnerable to stray induced voltages on floating wires. But in the situation described could be giving a false sense of security. You could of course make the opposite argument from a stray inductance perspective.

I am sure there are people on here with a better knowledge of the innards of modern domestic test equipment than me. Accuracy in all scenarios is difficult, complicated and expensive.

Regards
Bruce

 

[VMan]

Yes I am. I do not KNOW. But I can envisage a number of ways a tester could perform the task. Measuring currents could be a more reliable way of testing as you are not then vulnerable to stray induced voltages on floating wires. But in the situation described could be giving a false sense of security. You could of course make the opposite argument from a stray inductance perspective.

I am sure there are people on here with a better knowledge of the innards of modern domestic test equipment than me. Accuracy in all scenarios is difficult, complicated and expensive.

Regards
Bruce

Sorry didn't mean 'suggest' in a bad manor, just cant think of an alternative word. I appreciate your advised and i am concerned about this, i hadn't though how an RCD tester works before and was under the false security that my installations are safe when they may not be!!
I am really annoyed at my MCS inspector for not mentioning this on my MCS installation as it was wired into existing RCD sharing other circuits!!

Thank you for your view on this matter, i will be contacting megger to see if they can shed some light on how my megger works!

 

[BruceB]

It's alright I wasn't taking offence at anything, just trying to be clear. I would be interested if you do get an answer from megger.