Renewable Heat Incentive.

No, this is not true. Where there is a wound transformer, there is indeed isolation. The more modern, and slightly more efficient, transformerless inverters do not have isolation.

This has significant implications on the earthing requirements.

Have a look at page 22 (14 of the .pdf), onwards in this document.

"Photovoltaics in Buildings Guide to the installation of PV systems 2nd Edition"

There is a decision chart which I am not going to reproduce, but the key details for average installs are

"...it is the electrical separation of the mains from the d.c. using an isolating transformer that is the key determining factor when assessing the requirement for array frame earthing."

"..freestanding ground mounted, or building roof mounted arrays (away from building metalwork) will normally not be within the equipotential zone."

"Where the incoming supply is PME (the majority of domestic supply arrangements), the PME earth cannot be taken outside the equipotential zone. This is to prevent the potential shock hazard should the supply neutral ever be lost."

"Install & bond to earth spike (Note: do not take PME out of equipotential Zone) (Note: Use 10 mm2 braid or equiv) "

When I was considering options for my installation, the marginally improved efficiency of transformerless inverters was not enough to pay for the additional earthing required.

Kit like this

Ah well remain in ignorance half wit.

There is now a draft 3rd edition around which changes the earthing requirements to what could be summarised as 'hardly ever'. Its issue is imminent, although I note it has been imminent for awhile.

The 2nd edition repeated the fallacy that there is a rule about not exporting an earth outside an equipotential zone. There is not. There may be good reasons not to in some cases, but mostly it can be considered extending the equipotential zone.

As an example, if the whole of a house is an equipotential zone, it is normally barking to say that something on the roof it outside the zone.

I wonder how you go on with ground mounted PV panels? ie easily touched. My array frame is not earthed (roof mounted.) It is transformerless, so earthing the DC side is nor an issue. I believe where there is a transformer earthing the DC side is recommended.

We've been this way before Harry. You have got it round your neck.

Read it once more.

Chris

Not even a fossil fuel power plant at the other end of the plug?

In message , harry writes

You really are terminally stupid

Where does an aeroplane get it's lift from ?

What were you saying about elementary physics ?

Even if he was it would be half more than you

In message , harry writes

Ah - you're talking about a bungalow then

From the pressure difference between the top and bottom surfaces of the aerofoils (wings) created by shoving those aerofoils through the air against the friction of that air.

I think someone dangles a harry above the wing and the empty space sucks it upwards

Actually friction - viscosity - is a necessary component of aircraft being able to fly at all.

"Shoving the aerofoils through the air ..."

not making up for "frictional losses"

Induced drag

Andy