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Fitting solar panel onto Romahome Roof?

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  • berwicklaw
    replied
    Fridge from solar panels

    Gas gas is thinking of the original fridges. I have replaced the original 3 way fridge with a compressor fridge which is rated at c 50 watts . It uses c. 4 amps when running but the compressor only runs for about a third of the time. The average is c 1.5 amps . I have c 250 watts of solar panels and 110 ah battery. The panels power everything ( tv , fridge, lights etc) and I have not used ehu in over 2 years. For much of this time I only had 150 watts of panels and this is usually sufficient. I added a panel to give me a margin. A long run of very dull days ( over 5) would necessitate switching the fridge off. It is perfectly possible to run a fridge off solar panels(not of course in winter) and very many people do so. I live in Scotland.

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  • Graham
    replied
    Miriam, if it's a three way fridge you can run it off gas when no electricity is available or electric when on hook up, however you can't run it from the leisure battery unless driving.

    Sent from my iPhone using Forum Runner

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  • gasgas
    replied
    Hi Miriam. The simple answer is no you can't expect a fridge to run off the solar panels on a motorhome roof.
    The quoted power of a solar panel is the absolute maximum it will produce when you are in the south of Spain on a cloudless summer's day with the sun beating down directly at 90 degrees to the panel. In England you will get the maximum power for about one hour a week in the summer.
    Electrically speaking you should remember the simple formula: Watts=Volts x Amps. A (small) fridge takes 10 Amps at 12 volts, and at that voltage will hardly work, it really needs 13.5 volts.
    So to get 10 Amps at 12 volts would need a power source of 120 Watts. Suppose you had a 120 watt solar panel, then at noon on the equator with a cloudless sky, it would work. In theory. In practice the outside temperature would in that case be so hot that the fridge would be struggling to work off any voltage, or gas.

    Suppose you plastered your van roof with say 500 watts of solar panels, then your fridge would work for a couple of hours a day. You would of course have to have five 100 Amp hour leisure batteries, but suppose you did, you would then have to re-wire your fridge and camper electric wiring to overcome the fact that you are feeding it with 12 volts when it is not supposed to be getting 12 volts. The only time the fridge is meant to be working off 12 volts is when the engine is running.

    Forget it. It won't work.

    Do get a solar panel, 80 to 120 watts, but don't expect a fridge to work off it. If it is wired properly with a regulator it will keep your leisure batteries and your engine battery fully charged.

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  • miriam
    replied
    Fridge

    Originally posted by berwicklaw View Post
    I can only give my own experience. I have 2 flexible panels stuck on the roof . One for 2 years and one 1 year. I have had no problems what so ever . Certainly better than faffing around with something propped up on the windscreen! I have 150 watts and power tv lights fridge etc etc indefinitely through the spring summer and early autumn. No ehu at all. Best investment i ever made even IF they need replacing in 5 years . A search of the Internet reveals very little actual evidence of premature failure of these panels. I stand to be corrected if anyone can find more than hearsay.
    Hello, I'm looking into solar options for my new (to me) Romahome, and wondered how you can power the fridge with a solar set up? My understanding at the moment (am very much new to all this), is that the fridge can only be run from 240v when on EHU. I would love to know how it can instead run from the leisure battery, and if so, what would be the minimum solar panel Wattage to run the fridge (plus lap top for 3-4 hours and phone and occasional camera charging). Do you think 100Watts would be enough? Thanks :-)

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  • berwicklaw
    replied
    Originally posted by berwicklaw View Post
    I can only give my own experience. I have 2 flexible panels stuck on the roof . One for 2 years and one 1 year. I have had no problems what so ever . Certainly better than faffing around with something propped up on the windscreen! I have 150 watts and power tv lights fridge etc etc indefinitely through the spring summer and early autumn. No ehu at all. Best investment i ever made even IF they need replacing in 5 years . A search of the Internet reveals very little actual evidence of premature failure of these panels. I stand to be corrected if anyone can find more than hearsay.
    Mea Culpa
    One of my panels 100 watt plastic backed and supplied by Renytek via Ebay has degraded by 50% after 15 months. Renytek have been singularly unhelpful apart from asking me if I wanted to buy another one like it !! I declined in no uncertain terms. The other a 50 watt panel (NOT from Renytek) now 27 months old and aluminium backed is still fine. You might be well advised to stay clear of Renytek.

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  • gasgas
    replied
    I think you will find that Boeing 747s and so on have many parts that are glued together. I know that Vespas have had their side panels glued on for some years now, and car panels as well. And motorhomes come to that. But then, there is glue, and there is glue. I don't suppose Boeing 747 glue is available to you and I in B&Q. I have merely fixed my solar panel to the roof with ornery silicone - well, the most expensive sort. It is used in plumbing joints, and I have a lot of experience in trying to take it apart. Usually I give up and cut through it with a Stanley Knife.

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  • mikeroch
    replied
    Originally posted by chrisg149 View Post
    Thanks Mike. My small roof is fibreglass and I've put an expensive rubber coating down called "EPDM Liquid Rubber". Could I bond on top of this uniform skin or would I need to clean right down to the base fibreglass and by doing so break the existing skin?
    I think we've been here before! I'd carry out a small-area test about the size of as 50p coin at the site of one of the mounting pads. Sikaflex is itself 'rubbery' so may bond perfectly ... BUT the fear is that your sealant skin will act like the release agent in a GRP mould creating a weak point. The safest approach in terms of bond strength would be to accurately remove patches of roof covering the shape of your mounting pads right down to the fibreglass and then bond to that. Any small potential leakage points between the pads and the waterproofing skin could be sealed with a bead / fillet of Sikaflex or even some more of your EPDM sloshed on thereabouts too.

    Jim's mechanical fixing solution is without a doubt the equal of a successful bonded approach, but you can't un-drill holes and once the gel coat surface is breached, GRP becomes vulnerable to water ingress, as well as being visually scarred should the panel ever be removed. Personally I'd always try the non-destructive approach first.
    Last edited by mikeroch; 20-09-2015, 16:42. Reason: add detail

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  • Twolitre
    replied
    Undoubtedly adhesives have come a long way in my lifetime. But I am still very reluctant to rely on any exposed to changes in temperature or the elements.
    Accordingly, almost nothing I fix does not have a secure fastener (as the trades call nuts, bolts and rivets etc.).
    Not happy to perforate any weather-proof surfaces anyway, I decided my solar panel would not be fixed, but would stand alone in the best place to benefit from sunlight even in shaded areas.
    I cannot help but wonder, with my reservations about adhesives, whether anyone has ever lost a solar panel while cruising on motorways with the air-wake/turbulance produced by heavy vehicles trying to rip them off?
    Jim.

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  • chrisg149
    replied
    Originally posted by mikeroch View Post
    I just stuck 'em with white SIKAFLEX 512! The roof has to be absolutely clean and unpolished, having washed and dried the roof first I then gave the areas to be stuck a good buffing with a meths soaked rag (don't use cellulose thinner it's too aggressive). The pads have a decent gluing area and Sikaflex is seriously sticky stuff, you can relax as regards the security of the panel ... absolutely no need for screws into your precious roof!
    Thanks Mike. My small roof is fibreglass and I've put an expensive rubber coating down called "EPDM Liquid Rubber". Could I bond on top of this uniform skin or would I need to clean right down to the base fibreglass and by doing so break the existing skin?

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  • mikeroch
    replied
    I just stuck 'em with white SIKAFLEX 512! The roof has to be absolutely clean and unpolished, having washed and dried the roof first I then gave the areas to be stuck a good buffing with a meths soaked rag (don't use cellulose thinner it's too aggressive). The pads have a decent gluing area and Sikaflex is seriously sticky stuff, you can relax as regards the security of the panel ... absolutely no need for screws into your precious roof!

    I had the option to self-tapper screw the pads to the aluminium edge of the panel, but chose to stick the panel to the mounts by the same means, surplus Sikaflex wipes off with turps when doing the job. Were it the case that you needed to remove the whole system from the roof a thin blade worked in and gently levered will eventually peel the sikaflex joint apart.

    Hope this helps. Mike R

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  • chrisg149
    replied
    Originally posted by mikeroch View Post
    I got mine from Electra-mek http://www.electramek.com
    Boss' name Jim Stratford
    01760 723953 or 07795 063888

    120w Framed panel product code EMK10-09 came with mounting pads and a tube of Sikaflex for £210 (2013 NEC show price).
    Interested to see your photos and links. Did you stick or drill the mounting pads/legs onto your roof?

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  • mikeroch
    replied
    Originally posted by Jimblob1978 View Post
    Mike can you tell us make / model of yours and what the fixings are? Thanks
    I got mine from Electra-mek http://www.electramek.com
    Boss' name Jim Stratford
    01760 723953 or 07795 063888

    120w Framed panel product code EMK10-09 came with mounting pads and a tube of Sikaflex for £210 (2013 NEC show price)

    I (stupidly, because I hadn't done my homework) failed to buy a Charge Controller at the same time, so he mailed me a 'Sunsaver Duo' (charges both car and leisure batteries separately) Product code EMK 24-20 for £99.95. An essential piece of kit otherwise your batteries will be damaged and the system will run inefficiently.

    Prices may have changed of course, but I found the guy very personable and helpful. I've attached the Charge Controller user guide ... perhaps you will download it so I can delete it from my attachments file fairly soon in order to save space?

    Afterthought: Passing the PV wire to the inside of the vehicle may possibly be achieved by going through an existing portal (eg. roof ventilator) but if drilling the vehicle skin becomes necessary consider purchasing a proper waterproof cable gland or junction box.
    Attached Files
    Last edited by mikeroch; 14-09-2015, 09:20. Reason: add Afterthought

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  • Jimblob1978
    replied
    Mike can you tell us make / model of yours and what the fixings are? Thanks

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  • mikeroch
    replied
    That's what I've got!

    My own installation is just like yours lifted up off the roof on proper pads ... solid as a rock and well ventilated.
    Attached Files

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  • gasgas
    replied
    I don't think they would help the heating problem Mike. Solar panels do generate heat as they work, my house ones are set a few inches above the roof tiles for that reason. When you buy a rigid solar panel for a MH you should get some stand-off brackets, which are polycarbonate blocks which you fix to the panel, and then to the roof. They lift the panel off the roof allowing air underneath.

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