Naive Question

[Paul_B]

I cannot understand why the AC output from the invertor does not need RCD protection. I know that it is an isolation transformer but when connected to consumer unit surely there is still potential to get a shock to ground.

Is the assumption made that this would cause the consumer unit RCD to trip, no mains voltage to the invertor would then trip it?

If so, fitting to an old consumer unit without RCD protection would not have this effect and a shock would occur - would it?

Treat me gently!

 

[SolarCity]

If so, fitting to an old consumer unit without RCD protection would not have this effect and a shock would occur - would it?

Under what circumstance?

Just trying to understand what you mean.

 

[Paul_B]

My understanding is that if consumer unit does not meet current standards then best way is to loop meter tails into a garage bar and connect output from inverter via a new mcb into it. If someone then throws main switch off on the consumer unit, the feed from the invertor would still be live and could give a shock not protected by a RCD?

 

[sharpener]

My understanding is that if consumer unit does not meet current standards ... the feed from the invertor would still be live and could give a shock not protected by a RCD?

Yes you are right in that the inverter will continue to supply the grid even if the consumer unit main switch is off. This is desirable so that you do not lose output if e.g. you are out on a sunny day and there is an unrelated fault on one of the house circuits. So for this reason I have a separate 2-way CU just for the inverter and the freezer, with no RCD.

If you have not got an RCD in the existing consumer unit you won't have any shock protection for the house circuits anyway, so installing the PV system has not made it worse even if it has not made it better.

Or do you mean a shock from the inverter wiring? If properly installed there will be much less risk from the inverter wiring than from kettles, toasters and other cheap-and-cheerful appliances with flex connections. Wiring Regs do not require an RCD for the inverter if (amongst other things) it is a dedicated circuit and the cable is not buried in a wall at a depth of less than 50mm, this is to avoid the risk of screws being put through it.

 

[Paul_B]

We have been asked to install in a house that is being seriously renovated. There are a lot of wires that go nowhere and have been disconnected with just a couple of known circuits left live. If we install, I am concerned that someone might interfere with the wiring run from the inverter. Would an Aurora ground fault protection 'according to VDE0126-1-1' be adequate protection?

 

[Earthstore]

If it is that much of a problem, fit the system, commission it,then lock the AC and DC isolators until the wiring in the house is safe.
I am sure the customer will understand if you explain that you have to do this to comply with regs etc, and that it is for the safety of all in the house.
This way they may get the 43.3p tariff. (worded that bit carfully)
Hope this helps

 

[sharpener]

I am concerned that someone might interfere with the wiring run from the inverter.

OK I get more of the picture now...

It sounds like a case for running the PV cabling down the outside of the house in SWA if a good route can be found, or putting it in trunking or conduit, or at least using a distinctive type of cable. Ask the customer have the DNO fit an isolator and then put your Henley block straight after it. If the new CU/rewiring is going to be done piecemeal as the renovation progresses it will be a great help to him anyway not to have to keep pulling the fuse in the cutout.

Am on third Victorian house renovation myself, the fun usually begins with a load of hassle getting a single two-rate meter put in on moving-in day in place of the three meters left from when it was flats, or 3-phase farm supply or whatever, and then starting to look for all the neutral-earth faults which trip the new CU. So I can see exactly where you are coming from!

 

[moggy1968]

and thats after you've had bricks fall into the cavity when you try and chase your boxes out!!

 

[sharpener]

and thats after you've had bricks fall into the cavity when you try and chase your boxes out!!

What cavity would that be, in the typical Victorian house?

Problem is more usually trying to get a secure fixing in the studwork partition walls without having to re-plaster from floor to ceiling! I find Polyfilla Plaster Repair is very useful here because it is so light in weight and clings well (though it does take 48hrs to go off hard).

 

[moggy1968]

Sorry, didn't read that bit! I'm working on a 1950s (I think) place at the minute doing a bit of general sparking and the mortar must have been 9 parts sand to one part water when they mixed it!

I've got an 18month old so not short on stuff that clings well and goes off hard thanks:tongue3: