consumer unit

[geebee]

hi
if the lighting side of a split consumer unit was fed by the PV would the other power side of the consumer unit still use the free electric generated by the PV

 

[TedM]

Yes. But there are usually better ways of wiring in the inverter output.

 

[moggy1968]

on a twin RCD consumer unit I generally try and avoid putting the PV on one of the house RCDs. sometimes it's unavoidable but if I can I don't. Some of the inverters don't like 30ma RCDs

 

[infinity]

But if the cable is buried in the wall for instance there is no choice but to install an rcd?

 

[Markc]

sometimes it's unavoidable but if I can I don't. Some of the inverters don't like 30ma RCDs

You may want to reconsider this. The regulations state you are not permitted to fit PV to a communal RCD protection device. The other outgoing circuits on the same device may need the <40mS protection offered by the RCD. The inverter when in generation MAY not loose its voltage from the terminals within this time period. G83 only requires 5 seconds. So in a trip condition the inverter will still feed for over <40mS. This is considered as MAJOR none compliance and putting the occupants at risk. A complaint (Or worse) would be upheld. Inverters should never be connected via a 30mA communal RCD protection device.

Now the 30mA requirement for cables embedded in a wall at less than 50mm a RCBO is considered for the inverter, yet the same condition applies. The inverter will hold voltage for >40mS not <40mS. So a earthed sheathed cable is the only option?

On the next one try this. Before setting the inverter into operation test the RCD as per BS7671, (6 tests + functional test) Then wait for the inverter to go into generation and test the RCD again. Wait between each trip for the inverter to go back into generation before tripping again. I suspect the reading will be >40mS. i.e. NO Supplementary protection offered.

 

[geebee]

im sorry if i have caused confusion here but what i ment to say is if the PV is fed into a 16A curcuit breaker on the lighting side of a split consumer unit is the other power side of the consumer unit going to get free electric ?

 

[GaryM]

Yes it will.

 

[powervan]

just a note! the consumer unit shoudnt have a side just for lighting! dual rcd units should have a MIX of ciruits both side! ref rcds we been putting them on one side or other of rcd for quite a while! never had probs(touch wood) and niceic mcs inspec never picked it up on the first job !! but thanks for info much appreciated!!

 

[SolarCity]

I think this may be a split load board where one side is protected by an RCD (sockets etc.) and one side isn't (lighting etc.) rather than a split load RCD board (commonly known as 17th edition boards)

 

[moggy1968]

thanks for the info mark C, food for thought!!!
I suspect not a lot of people know that!!
can you point me in the direction of that particular reg.
As I understand it there is no requirement for an RCD on PV anyway as long as you have physical seperation of AC and DC circuits (and of course the cable isn't burried, which we have never had).
putting the PV on it's own garage board or a non RCD way tend to be our preferrred option but I think we have a couple of jobs where it has been on a shared RCD where we couldn't fit a sub board in the space available.
The only inverter I have had so far that routinely tripped a 30ma RCD was the 4000TL. that was on an older RCD main switch and I ended up having to fit a 100ma RCD on a garage unit

 

[powervan]

advice!thought!views! u cant beat this forum for that!

 

[moggy1968]

and bottom twitching latest news:grouphug:

 

[Markc]

Its in the green regs now as I had it waved under my nose by my inspector two weeks ago. Regardless of that the RCD still will not trip at <40mS regardless of the regulation number.

Once I get the green regs I will post it.

 

[GaryM]

I think this may be a split load board where one side is protected by an RCD (sockets etc.) and one side isn't (lighting etc.) rather than a split load RCD board (commonly known as 17th edition boards)

That's also the conclusion I came too. His installation would probably have been pre 2008 and therefore designed to the 16th edition where split load boards (made up of 5 or 6 RCD protected ways and 5 or 6 non RCD protected ways) were common practice

 

[GaryM]

Its in the green regs now as I had it waved under my nose by my inspector two weeks ago. Regardless of that the RCD still will not trip at <40mS regardless of the regulation number.

Once I get the green regs I will post it.

I've just had a quick look and can't see anything in section 712. It's probably hidden elsewhere.