Fusing solar panel cables

[Graham.m]

It falls outside, being an aftermarket addition in the main, and operating at relatively low voltages until very recent improvements in solar panel/mppt technology.

Where boats start to use multiple panels of a domestic size, the installations are still really regulated by the installers own 24/12v boat electrical knowledge and need for reputation to remain good.

Wiring sizes and distance for voltage drop, good connections, correct fusing, reliable and fit for purpose kit( even Bimble were selling a kit earlier in the year that exceeded safe parameters), are all as important as neat wiring and secure brackets.

 

I have seen and corrected a couple of installs this year on newly bought London bound boats that were laughable in their inept installation.

What is recently?

 

I am aware of boat four years ago that had panels that exceeded a 100V output

[nicknorman]

Though not being Matty, I think this is the situation as regards regulations.

Upto a MAX of 50v DC then BS EN ISO 10133:2012 small craft electrical systems DC applies.

For DC voltages higher than 50V would be covered by - I think - IEC60092

Yes it's the over-50v that is the question. As far as I can tell IEC60092 is for ships and offshore installations, with no lower voltage limit. Unfortunately the BSI site is off for maintenance at the moment but my feeling is that this will not be applicable to small craft - apart from anything else it would clash with ISO10133 and 13297 if it did. I don't think 10133 specifically covers solar, it is pretty generic, but I only have an old version available off line.

[Chewbacka]

Yes it's the over-50v that is the question. As far as I can tell IEC60092 is for ships and offshore installations, with no lower voltage limit. Unfortunately the BSI site is off for maintenance at the moment but my feeling is that this will not be applicable to small craft - apart from anything else it would clash with ISO10133 and 13297 if it did. I don't think 10133 specifically covers solar, it is pretty generic, but I only have an old version available off line.

10133 is for small craft with less than 50vDC. If it is not a small craft or is more than 50vDC then it does not apply. Then IEC60092 applies, but I will need to check the BSI site to be sure, and as you say, it is not coming out to play today.

[peterboat]

just a thought, what would happen if a boat with solar panels was hit by lightning, and the controller burst into flames burning said boat to the waterline. now would the insurance company pay up or would they point to installation instructions in my case from the USA which clearly shows disconnects and fuses in the wiring from panels to controller. i think for the cost of fuses, and the lack of regulation for boats, common sense says do what the maker says otherwise you might be boatless

[Loafer]

just a thought, what would happen if a boat with solar panels was hit by lightning, and the controller burst into flames burning said boat to the waterline. now would the insurance company pay up or would they point to installation instructions in my case from the USA which clearly shows disconnects and fuses in the wiring from panels to controller. i think for the cost of fuses, and the lack of regulation for boats, common sense says do what the maker says otherwise you might be boatless

 

I don't think ANY fuse would protect against a lightning strike, Paul. The current surge is so large that not only would the fuse melt and be replaced by a continuous arc, but so would the rest of the cable.

 

20,000A has a good arc-drawing capability.

[peterboat]

well i am in deep do dah then 9 bloody panels glued to the roof have 2 fuses though which clearly wont protect me but midnite say have to be present for warranty purpose.

years ago in the old boat my old controller caught fire it was from china but wasnt anywhere near its maximum load since then i have always bought stuff not from china

[Loafer]

Don't worry. If lightning DOES strike your panels, most of the strike will just leap to the nearest bit of steel hull and go to earth via that. If you're inside the boat, you will be protected by the 'Faraday Cage' effect.

 

Well that's what I reckon anyway.

[WotEver]

Why would lightning want to hit a panel any more than any other bit of steel?

[Loafer]

Maybe slightly higher up?

[John V]

Was in a narrow boat struck by lightning once.....the bang was deafening and you could hardly see along the boat because of the dust.......I thought it was a near miss but we found zig zags in the paint on the flue......it killed the tv stone dead .....but that was the only casualty

[peterboat]

i think we would be safe as loafer and john say faraday cage and he was in a boat but would some of the power go down said cables and fry the controller so while we are thanking out lucky stars we arnt under a tree the electric cupboard is on fire

[Loafer]

Well as John V alluded to, there are always additional, higher-resistance pathways through your hull, like TV aerials, chimneys, solar panel cables etc, yet we don't need to put a fuse in the TV aerial. I don't think a direct strike is protectable really, apart from a 5m high spikey pole connected to your hull. That'll sort it.

Edited December 16, 2015 by Loafer

[peterboat]

i was just going to put a fuse in the flu to protect my rayburn against a chimney strike bugger wont bother now but i am keeping my fuses in the solar its got a big warranty to go with its big price so taking no chances

[John V]

Should have mentioned there was one other very very near casualty..........my underwear

[Loafer]

i was just going to put a fuse in the flu to protect my rayburn against a chimney strike bugger wont bother now but i am keeping my fuses in the solar its got a big warranty to go with its big price so taking no chances

 

Absolutely. No point taking 'em out.

[ditchcrawler]

 

I don't think ANY fuse would protect against a lightning strike, Paul. The current surge is so large that not only would the fuse melt and be replaced by a continuous arc, but so would the rest of the cable.

 

20,000A has a good arc-drawing capability.

A long time ago I rewired a church that had taken a lightning strike to the tower. There was not one piece of copper cable left in that church, all the steel conduit was split open and looked similar to a piece of flat steel on the wall. As for the services I can't say as I was only an apprentice boy at the time, but I screwed a lot of pipe.

[John V]

A long time ago I rewired a church that had taken a lightning strike to the tower. There was not one piece of copper cable left in that church, all the steel conduit was split open and looked similar to a piece of flat steel on the wall. As for the services I can't say as I was only an apprentice boy at the time, but I screwed a lot of pipe.

 

Dirty boy.........................Oh !!! you mean threaded......phew !!!

[nicknorman]

I'm reminded of the glider that got struck by lightning near Dunstable. Part of the accident report showed the state of the aileron pushrods that run along the inside of the (group) wing from fuselage to the control surface. The current in the pushrods was so intense that the induced magnetic field caused the pushrods to "implode" ie go from a hollow tube into something much thinner and nearly solid, almost like wire.

 

Edited December 16, 2015 by nicknorman

[peterboat]

i have looked at lightning strikes on solar panels scared me so given up first one on the list was from an insurer who was pretty good but the rest well.............................. lets say because we dont ground our panels they is going to be fried

[peterboat]

[vulpyfox]

I'm using two breakers on mine, one on the + in of the panels and one on the + output of the controller, not much else needed really

 

These also act as isolators at the push of a button ^.^

[nicknorman]

As was explained earlier, the combiner fuses are to protect the panel wiring against a short between the panel and the combiner that could be fed by all the other panels. So if you have a lot of panels in parallel, you either need to have wiring to each panel that can take the total current of all the panels, or fuse them. If you just have 2 or 3 panels / strings of panels with wiring that can take the total current, there is no need.

 

There would certainly be absolutely no point in combining all the panel feeds together and then having a single fuse between the combined panel output and the controller input.

Edited December 16, 2015 by nicknorman

[peterboat]

As was explained earlier, the combiner fuses are to protect the panel wiring against a short between the panel and the combiner that could be fed by all the other panels. So if you have a lot of panels in parallel, you either need to have wiring to each panel that can take the total current of all the panels, or fuse them. If you just have 2 or 3 panels / strings of panels with wiring that can take the total current, there is no need.

 

There would certainly be absolutely no point in combining all the panel feeds together and then having a single fuse between the combined panel output and the controller input.

its just what came with my controller when it came and this was the best picture to show it you know the saying a picture is worth a thousand words.

[nicknorman]

its just what came with my controller when it came and this was the best picture to show it you know the saying a picture is worth a thousand words.

Sure, there's nothing wrong with the picture in fact it shows the issue very well. As I said though, it would be a mistake to "downsize" the picture to say 1 string and still feel the need to have a fuse.

[peterboat]

Sure, there's nothing wrong with the picture in fact it shows the issue very well. As I said though, it would be a mistake to "downsize" the picture to say 1 string and still feel the need to have a fuse.

it does and i only bothered with this thread because my controller came with the said combiner [which i thought was a fuse box], and because i didnt know whether i was going to parallel or series the panels i used it. also hits the problem square on in that there is a need to use fuses in panels which the op asked. because we didnt know how he was going to wire in the panels.

i am not picking a fight but graham did say use fuses in the early posts and looking at the picture he is right