electric shock from solar panels

[Bill Wright]

A warning to aerial installers! My son Paul removed an old aerial from the chimney and put it down on the roof, where it happened to touch the frame of a solar panel. When he picked it up he received a severe electric shock and he was lucky he wasn?t thrown off the roof. Obviously the solar installation wasn?t properly earthed. Needless to say he warned the householder that his solar installation was faulty, which didn?t please him at all. I suggest everyone working on roofs treats solar panels as a lethal shock hazard until proven otherwise. The last thing you want when working at heights is an electric shock.

In the early days of television every TV and radio aerial was assumed to be ?live?. Maybe we need to go back to those days and work in rubber gloves.

It was quite serious. Paul said the shock felt like 240V 50Hz, so it's likely the whole installation wasn't earthed. The high voltage from the panels is DC of course, but Paul said he definitely felt the 50Hz! I asked how many Hz he counted before he let go but he said he wasn't sure!

Of course the solar industry is full of bloody cowboys, so it's no surprise. Some of the roof fixings they've used (that we've seen) are terrible. There's going to be a legacy of leaking roofs in a few years. That'll extend the payback time to infinity I should think!

Bill

[Tim Watts]

On Wednesday 03 July 2013 15:18 Bill Wright wrote in uk.d-i-y:

If it helps, a nearby bungalow has PV panels and I can see 2 green/yellow earth bonding wires coming off the panel frame. Looks like 6mm2 +/-

So yours sounds like a buggered installation.

[harryagain]

Not quite as simple as that. It is a controversial topic. Bit here on the subject.

There's no reason why a roof should leak if the job is done properly.

[Chris Hogg]

Harks back to the thread a couple of weeks ago about the fire crew who weren't allowed to tackle a fire in a building that had SPs on the roof. In view of the above, you can see why.

[Brian Gaff]

I blame the squirrels myself, always eating away outdoor wires, can't see what they see in them. Brian

[Bill Wright]

Well, any penetration of a roof is likely to fail eventually. But I did mention my suspicion that the job hadn't been done to the highest standards.

I think the problem with solar panels is that there is a large number of small holes made, so the chance of failure on a whole installation is high.

Without doubt a 'clean' roof with no attachments or penetrations is likely to prove the most reliable, and cheapest to fix if there is a problem.

Bill

[dennis]

There shouldn't be any new holes. The idea is too remove a tile/slate and fit a hanger bracket. The tile/slate is then refitted without any new holes. Repeat as required.

The rails fix to the brackets and the panels to the rails.

[Bill Wright]

dennis@home wrote:

You can't 'remove' individual tiles (and even more so slates) if the roof has been properly nailed. A good slate roof is as tight as my brother-in-law. No, sorry, I'm exaggerating. But it really is tight. Believe me, I've been trying to find ways to route cables through roofs for the last 40 years. If you start lifting individual tiles and slates (even if you can, which on a well-nailed roof you won't be able to) you'll never get the roof back to as good as it was before. What happens if you try to force the issue with a nailed roof? Well you will break a lot of tiles or slates. If you do manage to slide a hanger bracket under a tile you won't be able to nail it, and it's no good saying you'll go in the loft to do it because of the roofing felt. So the only thing stabilising the hanger is the weight of the tile. Wind gets under tiles and lifts them, and I've no doubt it will get under solar panels. Constant movement is the enemy of a sound roof. On roofs with a gentle pitch there's always the danger of rain blowing up under the slates, or getting sucked though due to pressure differentials. Seen this many a time. Even a slim hanger bracket will make this much more likely. I've seen a lot of solar installations fixed by drilling holes through the slates above the rafters and inserting a long bolt-thing with a screw tip. Waterproofing is by a tight-fitting rubber grommet. It's obvious that this arrangement is going to fail long before the panels are worn out. When you stand on the ground and look up at panels they look OK. But climb up there and get hold of them and you'll often find they're quite loose, and can be lifted up with ease, bringing tiles with them. The solar panel job, like the aerial job, is difficult for the customer to have a close look at, so bad work is rife.

It will end in tears believe me. Give it a few years and the shit will hit the fan.

Bill

[John Rumm]

With a proper slated roof, then you can use a tool called a "slater's rip" to cut through the nails in one slate and free it such that it can be slid out. You then need to use a repair bracket (or lead strip) to refix it since you can't get the nails back in once its in place.

[Cash]

Hello John,

To add if you don't mind?

On a properly constructed tiled roof, only 1 in 5 courses of tiles are actually nailed (there are a few exceptions to this though which allows those 'loose' tiles to be pushed back - and just having spent around 4500 for a new roof, I can confirm that this is still the practice (and is no different to my time working on the bloody things).

Before you ask, I'm too bloody unfit now to clean the 'winders' of a ladder, let alone fit a new roof myself - age is a bloody good excuse to let others do it without being nagged by SWMBO about the cost. A very big grin here.

All the best

Cash

[dennis]

Sorry but you don't appear to understand roof construction or working methods.

I have just had some of the tiles removed and a mains pressure cylinder dropped in and its pretty easy to remove tiles as they aren't nailed every row.

Roofers frequently remove and repair slates too, using a slate ripper.

[Bill Wright]

Yes I've seen it done. It leaves the slate loose. It definitely reduces the integrity of the roof.

Bill

[Bill Wright]

It's putting them back that's the problem, not removing them. And they are often nailed every row. Fact is, if you mess about like that with a roof on the grand scale needed by solar panels damage will be done; the roof will not be as good as it was before.

Bill

[John Rumm]

Not at all ;-)

Yup... I think the only time they usually do more is in very windy or exposed locations, where they might nail every other course.

[Bill Wright]

It doesn't make any difference. A well constructed roof will be too tight for it to be possible to lift slates without doing damage. Slates are fragile and if you start prising them up they will break. I guess there are a lot of broken slates now in the UK, with the break hidden from the owner by being pushed up under the next row. You just can't mess about with slate roofs like that without spoiling them.

Bill

[Bill Wright]

It doesn't make any difference. A well constructed roof will be too tight for it to be possible to lift slates without doing damage. Slates are fragile and if you start prising them up they will break. I guess there are a lot of broken slates now in the UK, with the break hidden from the owner by being pushed up under the next row. You just can't mess about with slate roofs like that without spoiling them.

Bill

[harryagain]

You are exactly right Bill. I have a (fake) slate roof and had that experience. (My installation was an early days one)

Slates have to be removed with a ripper, the brackets fitted and lead flashing put on.

There is at least one other person here has holes drilled. This was done initially on mine but I was very suspicious & checked next time we had heavy rain. There were several slight drips you might easily miss. It could only get worse and any leak can cause rot.

So Imade them come back and remove the lot and fix properly.

However the brackest they use on interlocking tiles are pretty well foolproof, I don't see there being a problem with those.

[harryagain]

Arfa, The facts are these. The Pv panels produce electricity when the sun shines on them. This can only be stopped by covering them up. (Not very practical)

If the mains power goes off for any reason the inverter shuts down/isolates it'self The PV is still active. And all the DC wires to the inverter. Up to

1000volts depending on how many panels, the inverter voltage and how it's wired

[Nightjar]

I have found it to be a surprisingly strong material, but then I have only ever used best Welsh slate.

You can, if you know what you are doing and have the right tools although, as John says, you cannot re-nail a slate that you have removed and replaced, but have to use a slate hanger to fix it in place.

Colin Bignell

[Nightjar]

On 04/07/2013 07:37, harryagain wrote: ...

What you mean is it should shut down, assuming it is not faulty and has not been damaged by the fire. The Fire Brigade cannot assume that and have to work on the principle that the house may still have live mains inside.

Colin Bignell