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PEX solar panels

Post in 'The Green Room' started by 4acrefarm, Mar 26, 2009.

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  1. 4acrefarm

    4acrefarm Member

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    I was thinking of 200sf on the back of the barn, 64 sf of comercial panels and 100sf on the back of the house. I would build the units right on the wall so there is no heavy lifting. I would also like a 1000 gal tank with pex transfer tied in with my homemade wood boiler. This would be for radiant heat and dhw preheat.

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  2. xpertpc

    xpertpc New Member

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    4acrefarm, having the panels at 90 degrees rather than the recommended latitude + 15 would result in a good amount of efficiency loss, in my area it is 36 degrees + 15 = 51 degree tilt for winter, summer would be -15 but most leave it for the winter angle because the length of day compensates for it.

    I also forgot to mention that when I build my new collectors I will be using a grease used in electrical connections such as DE-OX made by Ilsco, it is designed for aluminum to copper connection and will not only stop corrosion but also aid in heat transfer because from what I understand it to has tiny amounts of metal impregnated in it.

    I just used some to replace my meter base after a falling tree ripped it from the house, the 8oz bottle cost about $20 and looks to be enough to do at least one collector+, it is rated -30 to 300F. There are other names like Alnox and all work the same. Being a retired electrician I had two bottles handy but didn't think of it until my first collector was done.

    Also remember that the thermal expansion of both copper and al-pex is about 2 inches per 100' at 180F, I did not use much silicone caulk and even though it is quite flexible it could cause the plate and grid to deform when hot. My collector makes a fair amount of creaking noise when empty and heating up, kinda like the sound a cooling car engine makes. I think the grease would help reduce any binding and stress on any of the joints.
  3. Wet1

    Wet1 Minister of Fire

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    I was thinking about using anti seize since it contains about 40% to 50% metal (zinc or nickle). It's fairly cheap, withstands high temps well, and resists galvanic corrosion. My fear is that it would not stay in place over time. I think you'd have the same problem (if not more so) with your electrical grease idea. These panels can see routine temps of 250°+ F, plus they are mounted close to vertical, so I suspect the grease would run down in time. If you're thinking about going this route, I'd suggest doing a fair amount of testing before hand to make sure it's not going to run.
  4. xpertpc

    xpertpc New Member

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    Good idea, I will test it first when I build my smaller 3'x4' panel. I had just recently read an article of a man in NZ that has a 30 year old system and he used lithium grease.
  5. xpertpc

    xpertpc New Member

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    Just some thoughts on radiant and dhw: I have not done any of this and will be doing more research before building.

    I originally planned on only building the drain-back system for dhw thus needing no antifreeze or double walled heat exchanger. After building it and seeing how much hot water it can make and also how ugly it looked on my roof peak I changed my mind on usage. I have no heat in this house and since I plan on a floor tear-up and insulation project soon it was a no brainier for radian heat.

    My winter night time lows are around 20F though it does and can get much lower it is usually not for long, this temperature is right on the cusp of a drain back system. The slightest blockage or valve failure would destroy your collector if used in colder weather. Pex however would be much more forgiving if a freeze up were to occur.

    On a radiant heat system I would not use a heat exchanger but pump it directly from the tank the collector circulates thru, a temperature switch would only turn on the collector pump when it is warmer than the tank temperature. The tank would be as big as I could build and be super insulated with a 25% antifreeze mix for my area. A 1000 gallon tank would be about 8000 pounds of water and if heated 50 degrees over the house ambient it could have up to 400,000 Btu's available. My math is always an estimate and for example only.

    If I build a dhw system I will be using my old 40 gal water heater as the storage and heat exchanger, by removing the heating elements I should be able to get a coil of tubing into it, the tubing would then circulate thru the collector with non-toxic antifreeze in it (not the radiant ones) street water would then enter that tank and then fed to the inlet of the new operational water heater. This will always temper the water that needs to be heated and besides standby losses should save a fair amount of electricity.

    This method is not a double walled exchanger and is not legal with most plumbing and municipality codes. Even though I will be using a back flow preventer on the cold water line mixing can occur if both hot and cold faucets are opened at the same time, not likely to be much if any but can happen under some circumstances. I never use hot water as potable and neither should anyone else, If a recipe calls for hot water I heat cold water in the microwave for it.

    Note: I live in the country and don't have municipal water or sewage.
  6. 2.beans

    2.beans Minister of Fire

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    im glad this topic is up. im a lineman in NH and we use stuff called penatrox. its alot like neva sieze ,the gift that keeps on giving. do you think you really need it? is there that much moisture build up in the collector? im gathering parts to build one and didnt think of this.
  7. xpertpc

    xpertpc New Member

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    I don't think enough moisture would be present to cause any severe galvanic corrosion and was thinking of using it more for its heat transfer characteristics.
  8. 2.beans

    2.beans Minister of Fire

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    i was going to use wirsbo plates that 1/2 inch tubing will fit in tight, so i guess i shouldnt have to worry?right?
  9. xpertpc

    xpertpc New Member

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    I searched wrisbro and came across their "Joist Trak Panels" and am thinking they could be used for the entire collector with no other absorber material needed. 3.5"x 4' long for $8, I may look in to buying five of them for the small collector I will be building soon. A 4'x8' collector with 8 copper tubes would need 12 of them at a cost of about $100 shipped. If using pex you would need less because you can not bend it tight enough for 8 runs, I think 7 was the max in his design. You must use pex-al-pex as it is more bendable then regular pex, just ask me - I wasted $25 on pex that could not even make a 10" radius.
  10. Wet1

    Wet1 Minister of Fire

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  11. xpertpc

    xpertpc New Member

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    This where I saw the joist plates for $8 each, they look to be much heavier than the regular fins and think they would be all that is needed to serve as the back and front absorber. I would screw them onto a sheet of metal roofing and just snap the copper pipe grid in them and paint black with bbq paint then cover with the sun-tuff panel.

    I have to email them and see what gauge they are, the super thin aluminum flashing I used cost $50 and took a bit of work and didn't fit all that nice. An extra fifty bucks may be worth it for the increased efficency and ease of assembly.

    http://www.pexsupply.com/Categories.asp?cID=208&brandid;=
  12. 2.beans

    2.beans Minister of Fire

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    when doing heat loss calculating on a house the wirsbo plates lower the required water temp more than the ones blue ridge sells. i dont have the numbers on hand but they are supposed to perform better. i have them installed in some of the rooms in my house and they seem to work great. the rooms heat fast and even with low water temp. if buy buy a box of twenty it saves you a little more.
  13. 2.beans

    2.beans Minister of Fire

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    do you think theres a magic number of tube you need on the exchanger? i was going to use some old aluminum frame sliding glass doors for the front. there 3x6 and using the wirsbo plates ill only be able to have 5 copper tubes per panel.
  14. Wet1

    Wet1 Minister of Fire

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    The $5.53 per sq ft number I gave for the wirsbo plates was for a box of 20, and this is w/o any additional shipping cost or tax. A 3x6 panel is 18 sq ft, they come in a box of 23 sq ft. So if you're doing two panels, you'll need 36 sq ft. I'm sure they would work slightly better, but I don't know that the slight increase in performance is worth 3 to 5 times the price over the cheaper options (the payback would be a VERY long time). I still think those plates are pretty expensive for this application, but whatever floats your boat. Remember, the entire surface of the panel needs to be covered with fins. If they are only 3.5" wide, you'd end up with 10 tubes per panel (assuming the panel will be vertical, 20 tubes if horizonal) to cover the entire surface, and that seems like a lot of tubing for such a small area... and a lot more money in copper. Again, I'd rethink this. Regarding the number or the spacing on the tubes goes, I can't find anything (w/o looking too hard) that would suggest an optimal number. I did not see anything on Gary's site that suggested he has experimented with this either.
  15. 4acrefarm

    4acrefarm Member

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    I have done 2 radiant installations. One using roof flashing to save money and the other using plates bought from Warm toes in Vermont. The cost was $.92 from warm toes and $.24 for roof flashing, for 8"x15". The roof flashing was stiff and hard to work with and don't work as well. The plates from warm toes are soft, pliable and worth the money even for someone as cheap as me.
  16. xpertpc

    xpertpc New Member

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    They just sent me the data sheet (pdf) on the wrisbo trak panel, it looks very beefy and is 0.05" vs 0.019" for the the flashing. I just ordered six of them ($59 shipped) for my 26" x 48" test collector. As far as the number of tubes in the grid I have no idea on the efficiency of going with more, Gary had seven in his design and that is what I also did on my first collector. This next collector will have as many tubes as it takes to butt the trak plates together.

    I will let everybody know how it all works out, but am also in the middle of major house renovations so I am a bit slow to get on task. I also spent some time on google reviewing the different plates and this one was always mentioned as good. If not I get to add $60 worth of crap plates to my $25 worth of wrong pex - which is why I went with copper instead, I do hvac so I can't screw copper up or can I ? out of 42 silver soldered joints only one leaked and then only at 40 psi, should of known better because it was a sloppy inside street elbow.

    At first I just did a static test like Gary did though I think he made mention otherwise, it passed with flying colors, then I said what the heck I have the gauges, so did an extended pressure test and good thing I did albeit it may of never leaked being an open air system but it made me feel better.
  17. Wet1

    Wet1 Minister of Fire

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    You'll have 7 tubes/traks in your 26"x48" panel.
  18. xpertpc

    xpertpc New Member

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    err ah six tubes because that is all I ordered, the online dimensions said 3.5" wide while the pdf specs said 4" wide, which would leave 1" on each side for latitudinal hydrostatic global warming thermal expansion. Then again it is morning drink time here in Kentucky and math is not prevalent in these parts.
  19. 2.beans

    2.beans Minister of Fire

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    i got a box of 20 and just opened them up. theyre 3.5 inches wide. my plumber sold to me cheaper than pex supply. i hope to build it this weekend. any thoughts on using the sliding glass doors?
  20. xpertpc

    xpertpc New Member

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    Hey 2.beans, is it two or toot? do they seem pretty heavy duty? The spec sheet they sent me is a 2005 right from wirsbo, heard they were bought out so I guess I'm gonna be spacing mine.
    I used the polycarbonate sun-tuff from Lowe's $18 for 26"x8' sheet (used 2), it is corrugated and a bit of a pain to seal but I did it. I would like to use tempered glass but there is none to be had around here, anything that is cheap or free is holding a mobile home together. And don't even bother looking for visqueen, that's high end roofing material.

    The nice thing about sun-tuff panels is that it is a virtual 2 dimensional solid, it has no thickness or weight and is also virtually indestructible being 20 times stronger than fiberglass or so says their website.
  21. 2.beans

    2.beans Minister of Fire

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    its two one for the wife and one for my daughter. i laid it out on plywood tonight. the plates laid out perfect covering the entire surface area. the 1/2 copper fits nicely. are you buying fittings or are you "welding/brazing" thing together. from what ive read so far it sound like your using silva? ive practiced drilling pipe and welding copper pipe back together. its not too bad just need the right amount of heat.
  22. 4acrefarm

    4acrefarm Member

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    how about ideas for glassing? My first plan was to use salvaged sliding glass doors. I think this would yield the best result. Fixed sizes and heavy weight will make more work in assembly. The suntuff panels seam easier to work with but they are single pane. I think I have settled on the extruded panels that they sell for greenhouses. These are extremer easy to work with and light weight. You can cut them with snips or skillsaw, and they drill and screw easily. They are double layer, their only drawback is the UV transmittance is only about 78 percent. What do you all think?
  23. Wet1

    Wet1 Minister of Fire

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    I wouldn't use those double layer panels. With only 78% UV transmittance, you're leaving a lot on the table... I'd go with the proven Sunturf.
  24. xpertpc

    xpertpc New Member

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    The suntuff panels are 26" x 8' and takes two panels to make a 4'x8' collector for $36, they have no weight to them and according to manufactures specs are 20 times stronger than fiberglass and are also hail resistant. The only problem I had was sealing the panels because they are corrugated, $10 closure strips and silicone so far has solved that problem - they may not last the 20+ years the commercials units do but by then a new technology will be about, plus you are saving $1500 per unit.

    I received the joist plates as mentioned in an earlier post and they look really nice, much better than any aluminum flashing could ever be, too busy re-roofing and putting siding on to mess with the second collector now. Plus I just bought all the lumber for my new chicken house, being the proud farther of 4 more chickens I have to expand - what can I say, me and the pit bull ie pig bull loves egg muffins.
  25. 2.beans

    2.beans Minister of Fire

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    heres were im at so far. i hope to finish up tomorrow night. ill have better pictures then.

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