Solar Panel installation details

I've finally got round to ordering some panels. 2x 50W rigids from Photonic. Was intending to do this last year and decided to go travelling instead!

To mount them I'm planning to get some aluminium angle, with screws through the panel frame and glue onto the roof with Sikaflex. So a few questions:

1) Has anyone had corrosion problems using stainless steel bolts through aluminium? I was wondering whether or not to use some plastic washers.

2) Once glued down, the nut (or bolt head depending on orientation) won't be inaccessible so can't be released at a later date. Has anyone bothered making theirs de-mountable for later replacement or do you just live with it and hope you can drill it out if it ever needs replacing or cable fault etc?

3) Is Sikaflex 512 the right one to use (the alternative seems to be 221 but that doesn't seem to be as suitable)?

4) Most charge controllers, and especially the MPPT ones, documentation says they need good ventilation for heat dispersal and not to be mounted on a flammable surface - there are not exactly many non-flammable surfaces inside a campervan. What are your experiences of heat generation/dispersal around these controllers?

5)  The panels will be inline with skylights as far as possible but not entirely out of the airstream. Is it better for the aluminium mounting rails for the solar panels to run across the van (blocking high speed airflow underneath when driving) or parallel to the direction of travel (preventing passing trees poking underneath and tearing the panel off). Does the bracket orientation change impact noise?

Thanks,
Joe

JandJ wrote:I've finally got round to ordering some panels. 2x 50W rigids from Photonic. Was intending to do this last year and decided to go travelling instead!

To mount them I'm planning to get some aluminium angle, with screws through the panel frame and glue onto the roof with Sikaflex. So a few questions:

1) Has anyone had corrosion problems using stainless steel bolts through aluminium? I was wondering whether or not to use some plastic washers.

2) Once glued down, the nut (or bolt head depending on orientation) won't be inaccessible so can't be released at a later date. Has anyone bothered making theirs de-mountable for later replacement or do you just live with it and hope you can drill it out if it ever needs replacing or cable fault etc?

3) Is Sikaflex 512 the right one to use (the alternative seems to be 221 but that doesn't seem to be as suitable)?

4) Most charge controllers, and especially the MPPT ones, documentation says they need good ventilation for heat dispersal and not to be mounted on a flammable surface - there are not exactly many non-flammable surfaces inside a campervan. What are your experiences of heat generation/dispersal around these controllers?

5)  The panels will be inline with skylights as far as possible but not entirely out of the airstream. Is it better for the aluminium mounting rails for the solar panels to run across the van (blocking high speed airflow underneath when driving) or parallel to the direction of travel (preventing passing trees poking underneath and tearing the panel off). Does the bracket orientation change impact noise?

Thanks,
Joe

Joe

Limited info here as my solar is also Photonic, but semi flex and glued to the roof..............

Answers.........

1 My background is underwater engineering using remotely operated vehicles, in,,,,,,,,,salt water. No probs using SS bolts through aluminium, but be sure the bolts etc are A4 grade, lesser grade will be problematic.
2 Don't know
3 Sikaflex should be fine, but I just bought some 3M double sided tape, VHB, google it, I reckon I could more or less lift  the truck off the ground via my solar panels!! But the correct primer as well though and use it as per instructions
4 My charge controller is NOT MPPT but also from Photonic, just a simple dual battery one. It is screwed to a plywood plate just in front of the LB under the driver seat, so I hope it isn't flammable!! Been there for 2 yrs now and no smell of burning!
5 I am sure that any airgap, irrespective of orientation will be just fine. My semi flex one (140w btw) is glued to a 10mm thick polycarbonate sheet, the stuff conservatory roofs use and its "ducts" are inline with the airflow, no probs there either.

I don't know how to do this, Paul or another moderator will know, but I wrote a comprehensive post of my solar installation some time back, if you can access this it may well assist further.

Good luck, IMHO a motorhome with no solar is a van! We virtually never do EHU and both batteries are full all winter.

Bw

IanH

Although not a moderator any more, I think this is the thread IanH refers to.....

[You must be registered and logged in to see this link.]

Thanks Ian,

Noted about A4 grade stainless.
As my roof isn't flat VHB may not be thick enough but sikaflex will bridge/fill the gaps.
Controller - I was going to fit in same place but on a metal bracket.

Cheers,
Joe

Paulmold wrote:Although not a moderator any more, I think this is the thread IanH refers to.....

[You must be registered and logged in to see this link.]

Thanks Paul
Ian

JandJ wrote:I've finally got round to ordering some panels. 2x 50W rigids from Photonic. Was intending to do this last year and decided to go travelling instead!

To mount them I'm planning to get some aluminium angle, with screws through the panel frame and glue onto the roof with Sikaflex. So a few questions:

1) Has anyone had corrosion problems using stainless steel bolts through aluminium? I was wondering whether or not to use some plastic washers.

2) Once glued down, the nut (or bolt head depending on orientation) won't be inaccessible so can't be released at a later date. Has anyone bothered making theirs de-mountable for later replacement or do you just live with it and hope you can drill it out if it ever needs replacing or cable fault etc?

3) Is Sikaflex 512 the right one to use (the alternative seems to be 221 but that doesn't seem to be as suitable)?

4) Most charge controllers, and especially the MPPT ones, documentation says they need good ventilation for heat dispersal and not to be mounted on a flammable surface - there are not exactly many non-flammable surfaces inside a campervan. What are your experiences of heat generation/dispersal around these controllers?

5)  The panels will be inline with skylights as far as possible but not entirely out of the airstream. Is it better for the aluminium mounting rails for the solar panels to run across the van (blocking high speed airflow underneath when driving) or parallel to the direction of travel (preventing passing trees poking underneath and tearing the panel off). Does the bracket orientation change impact noise?

Thanks,
Joe

Joe, there have been several instances of Solar Panels detaching from roofs and flying down the motorway. Sikaflex have been involved in inspecting some of them, due to insurance claims and 'Adhesive' warranty issues.
In all instances the wrong adhesive was used or the surface not prepared properly.

They say a structural adhesive, like 292i, should be used not the usual 'sealant' adhesives, Sikaflex say 512 must not be used.


We worked with two Sikaflex Technicians to create a guide on how to fit Solar Panels, including surface preparation to Sikaflex guidelines. 
It covers everything including the recommended fastenings, Adhesive Bead thickness, spacers, paint protection finishes, etc. see here :  [You must be registered and logged in to see this link.]

It even answers your question re 'Wind lift' and the special fitting technique that overcomes the much debated issue re 'screwing into wafer thin' Aluminium which avoids the requirement for Nuts on the bolts.


One surprising thing from the investigation was that over 50% of detachments were 'professional' fits.


The best MPPT regulators, like the Votronic MPPT 165, don't generate much heat as they regulate the power drawn at source.

Hmm very useful reading. Interesting that the van suppliers often only have 221 or 512, will need to look for another source.

Personally I have always preferred to use RivNuts to fix into the skin as opposed to any form of self tapping screw.

HairyFool wrote:Personally I have always preferred to use RivNuts to fix into the skin as opposed to any form of self tapping screw.

JandJ, Sikaflex 221 is described by the Sika documentation as -
 "a high-quality multipurpose non-sag 1-C polyurethane sealant that cures on exposure to atmospheric humidity". 

Sika 512 is also a Sealant, therefore some thing that Caravan and Motorhomes businesses will have around anyway, that might explains why many sell it as suitable when Sika say it isn't.



Hairfoool, Rivnuts are brilliant when used 'dry', but require some expertise to be used safely and easily, especially when covered in a thick Bead of adhesive with a short setting time. 
One of the issues with rivnuts is applying enough adhesive to bond it into the Aluminium and then also running a fat bead of adhesive over the rivnut (effectively hiding it) for both adhesion/sealing. This makes it hard to locate a bolt into the rivnut after the panel is in place and adhesive is squeezing out everywhere.

The fitting process suggested on the web page, ensures a lot of adhesive is squeezed into the Roof space itself, below the thin Aluminium skin, which then acts like load spreading 'washer' beneath the skin. This creates a larger surface area for the the easy to use 'Self Tapper' than even a rivnut can supply.  
Obviously the sealing effect with such a major covering of adhesive/sealant should be pretty much perfect as well.  

 
The Solar panel fixing article was about creating a practice that was both safe and easy for all to adopt with the most basic of skills.

True, it helps being an aircraft engineer when choosing how to do a job and there are lots of different RivNuts to use.

As far as load spreading behind the skin goes I have even seen Peel rivets used but that didn't result in enough adhesive thickness under the fitting. Once the edge bead peeled off water got under the fitting.

As to the adhesive some components would be stuck to the aircraft skin. They came with the glue already on them as a hardish lacquer, we would wipe the skin with a activator liquid and the glue surface then place accurately as it bonded instantly. Good for 600mph for a few years.