# PEX solar panels



## 4acrefarm (Mar 26, 2009)

Has anyone seen the homemade solar panels using pex, aluminum fins, and polycarbanate. Gary Reysa has them posted at build it  solar.com. They seem like the purfect cheap do it yourself project.


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## Wallyworld (Mar 26, 2009)

I plan on building some of his copper collectors, built the same way as his pex collectors only using copper pipe


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## Corey (Mar 26, 2009)

Neat.  That is not a bad price.  Though, I have seen advertisements for silicone oven mitts of all types...  http://www.reluctantgourmet.com/silicone_oven_mitt.htm  Which 'will protect your hand from boiling water up to 500 degrees F'.  I'd have to wonder if silicone caulking is the best 'thermal transfer' compound between the PEX and aluminum absorbers.

I'm sure there are a lot of considerations...cost, not attacking the PEX, open working time, etc.  So maybe silicone is the best balance.  Back 'in the day' when I worked with siding and guttering, we had a caulking to fill seams in the gutter.  The stuff was definitely silver, and I would have sworn it was 'aluminum filled' or something of that nature.  Off hand, something like that would 'seem' like it should transfer heat better.  Maybe a person could even mix powdered aluminum in with silicone to boost up the thermal transfer capability?


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## smirnov3 (Mar 26, 2009)

cozy heat said:
			
		

> he stuff was definitely silver, and I would have sworn it was 'aluminum filled' or something of that nature.  Off hand, something like that would 'seem' like it should transfer heat better.  Maybe a person could even mix powdered aluminum in with silicone to boost up the thermal transfer capability?



I would recommend that you NOT try to make your own Aluminum filled epoxy: Aluminum that is fine enough to use as a filler is real pain in the neck - it gets EVERYWHERE


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## eba1225 (Mar 27, 2009)

Have considered the Pex as a collector, but went with copper when I built mine.  This was a flat panel, works ok but not as well as expected.  Am looking to build a parabolic collector this summer.


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## 4acrefarm (Mar 27, 2009)

I also thought of products that would work better than silicone, and came up with the same solutions. I agree the mess is probably not worth it. The gutter caulking does sound like a good choice, but what about cost? You can buy silver roofing tar that has powderded  aluminun in it , but not as easy as a caulking gun.


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## begreen (Mar 27, 2009)

Geocel makes an aluminum colored gutter seal, but I don't think that means that there's actually aluminum in it. I would think that UV resistance would be at least as important than thermal conductivity. It you want thermal conductivity maybe soldering would work better.


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## 4acrefarm (Mar 27, 2009)

This area is hidden from the sun, uv protection is not required.


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## Wallyworld (Mar 27, 2009)

While Silicone might not be perfect, its better than air and cheap. I'm more concerned with silicone corroding the copper over time and with the interaction of dissimilar metals.


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## begreen (Mar 27, 2009)

Good to pick an adhesive sealant that has no acid component to it (neutral cure). Standard silicone has acetic acid I believe. Krylon makes one called white lightning, but I'm not sure about its adhesive properties. Black Dow Corning 995 Silicone Structural Adhesive looks promising. GE1800 Industrial and Construction Silicone is another good one. Geocell has several non-silicone adhesive sealants that might also work, but if adhering PEX be sure the adhesive is not a polyethelyne solvent.


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## Wallyworld (Mar 27, 2009)

The silicone was used for heat transfer not for adhesive. Its to fill any voids between the copper or pex and the formed aluminum. The thought is the silicone transfers heat better than air


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## begreen (Mar 27, 2009)

Link to the project was missing, now I see how he is assembling it and how the silicone is not exposed.

http://www.builditsolar.com/Experimental/PEXCollector/PEXCollector.htm


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## 4acrefarm (Mar 31, 2009)

Thanks for posting the link, I'm new to the site and did'nt know how. One of my concerns with this setup is expanion of the pex. My plans include a 20' wall with each hose going across and back. This puts supply and return in same place but gives a run of 40' per loop. I'm thinking either 3/4 or 7/8 tube.


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## Wet1 (Apr 1, 2009)

Interesting read on making solar panels.  I agree there appears to be room for improvement regarding the use of Si caulking to transfer the heat.


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## 2.beans (Apr 1, 2009)

eba1225 said:
			
		

> Have considered the Pex as a collector, but went with copper when I built mine.  This was a flat panel, works ok but not as well as expected.  Am looking to build a parabolic collector this summer.


 got any pictures of yours? my spring project was to build a panel or two. i would love to to know if im wasting my time.


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## madrone (Apr 2, 2009)

PEX is known to leach MTBE  and TBA, both nasty chemicals, something which is accelerated by UV and/or heat. I have pex throughout my house, (so much easier for renovations!) but it's in the walls and basement, never gets over 140*. 180* is supposed to be the limit before breakdown occurs. No one really knows the long term effects of high temps, because it's relatively new. I'd personally stick with copper. It's a great design though, otherwise.


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## Wet1 (Apr 2, 2009)

Given the hit in efficiency, durability, and the small price difference, going with copper over PEX in a panel seems like a no-brainer to me.


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## 4acrefarm (Apr 2, 2009)

I was unaware of the mtbe issuse,this would be a closed loop antifreeze design.I like this idea because of ease of installation and price. I plan on 20;40' runs. My system would be vertcal and would hopefully not get over 180*. I May go with copper but i love working with pex. Thanks for the mtbe info, that is nasty stuff.


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## Wet1 (Apr 2, 2009)

I didn't realize PEX is known to leach MTBE and TBA.  Any known studies on this?  The reason I ask is because I have a friend that swears by PEX and he has small children.

Anyway, I would not be all that concerned about it since hot water is typically not used for drinking.  This doesn't mean it's still an issue, but it does lessen the concern a little (in my mind at least).


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## madrone (Apr 3, 2009)

I researched like crazy before replacing my pipes. (You could put your finger through my old steel pipes, and the actual inside diameter was about 1/4") PEX is about the safest pipe, as far as we know. WAY safer than plastic. The amounts of anything leached are small under normal use, too small to really worry about. The problem is that high temperatures and UV are what cause the breakdown. Generally, nobody's system goes over 180*, and people don't usually drink water from the hot tap anyway. Every material has some drawback, and usually some level of health exposure risk. The thing with pex is that it hasn't been around long enough to really know what it does over time. I have small children, and don't worry at all about my pex pipes. I would choose copper in this instance simply because we know exactly how higher temps affects it over time. It might be absolutely fine, but no one knows yet.


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## 2.beans (Apr 3, 2009)

even the potable pex leaches out that stuff?  i thought that was why they made potable to avoid that issue.


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## madrone (Apr 3, 2009)

PEX is far safer than other plastic pipes, but all plastics degrade. pex is just more resistant. Like I said, I'm not worried about using it in my home at all. They've been using it in Europe longer than we have, and Europeans are notoriously stricter environmentally. Here's an interesting study:

http://www2.mst.dk/common/Udgivramm...ikationer/2007/978-87-7052-463-6/html/sum.htm

The temperatures where significant breakdown occurs are well above normal use. I only brought this up because this solar collector is going to get pretty hot. For all I know, any leaching might still be below safe levels.


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## xpertpc (Apr 4, 2009)

I built the copper version from his plans because pex-al-pex is not available around here and the price was not much more. I used very little silicone and only put one small bead down the top of the copper pipe to hold the aluminum fin on. My fins did not come out as pretty as his even though I used my splitting maul to pound them in the jig.

The tests came out pretty good, starting with 10 gallons of 45F street water it took 3 hours to reach 100F when 30 degrees outside, the next day it took another 3 hours to go from 78F to 125F. My unit is no where near as nice as his and is probably at a much lower efficiency but for single guy it will make more hot water then I could ever use.

The night of my test the 10 gallons of 100F water was in a cheap cooler sitting outside with a low temp of 25F and it only lost 22 degrees, the real tank will be super insulated and be in the house and would doubt that I would be starting with anything less than 90+ degrees.

Copper and aluminum will be at odds with each other with galvanic corrosion but that will usually only happen with any appreciable damage when kept fairly wet, I doubt these pipes would ever sweat. Heat transfer silicone does have embedded metal in them but didn't think the cost of it would out weigh the inefficiencies. Using copper sheets rather than aluminum would of cost an additional $400, my complete unit was about $200.

On a early March day while 30 degrees outside the collector reached a stagnation temperature of 145F in about 15 minutes in full sun. I am considering building a few more when I tear up my floor to insulate and put in radiant heat tubing at the same time to augment my wood burner.


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## Wet1 (Apr 6, 2009)

X,
Based on firsthand experience, is there anything you would do different if you were to build another?  How poorly did your fins come out and how snug do they fit the pipe?  How large of a collector and storage tank did you build?  

I'm really considering doing this when I get some time (fall?), I was thinking of using about 64 sq ft of collector (copper/aluminum) with about 225 gal of storage.


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## xpertpc (Apr 6, 2009)

My fins turned out kinda crappy and did not fit tight at all around the copper pipe, I used pretty thin aluminum flashing material and lined the box with a double layer of three strips 20" wide, 50 feet was $40. The fins were made with a jig like he shows and used 6" wide flashing which may of been my problem but couldn't find anything else.
I have since found the heat transfer plates online $150 for 100 pcs - 24"x5" plates which is enough for 2 collectors.

I initially built the box as he shows but it was getting too heavy for me to move so I started over with 1x4s instead and used metal corner braces, the osb board was very heavy and replaced that with 1/8" masonite which is pretty flimsy but used three 1x2s for back support. it is 8x4 or 32 square feet.

I lined the box with al then laid in the pressure tested copper grid then siliconed the fins to the copper with just a single bead on the top of pipe and a squiggle down the wings of the fins to the back al then drilled and used about 100 al pop rivets right thru the 1/8" masonite, basically pegboard with no holes in it and only $5.

I don't have a southern roof so I built what looks like a rocket test stand on the 1-1/2 story peak, it looked so goofy that I took it down and have since put a 10' addition onto my shed with a beefy flat south roof to hold the collectors and plenty of room for a 500 gallon tank for the radiant floor heat.

Just remember you can't skimp on the heat exchanger pipe unless you don't use much hot water, the 300' of 1" is a huge coil and requires a big tank, I bought 100' of 1/2" and was gonna use a fifty gallon tank because I only have an attic and no basement plus I would never use more then 10 gallons at any given time. 300' of 1" holds 12 gallons and 300' of 1/2" only holds 3 gallons.

If I were to build the other 2 collectors for the radiant floor heater I would check into using metal 2x4 studs or the floor channel for the studs because they have no pre-punched holes in them for the side frame and use corrugated metal roofing for the back plate.

Since both the corrugated roofing and sun-tuff panels only come in 26" widths and knowing how much more heat this baby puts out when you track the sun rather than leaving it point straight south I thought about making the narrower panels and give a slight arc to the collector array.


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## 4acrefarm (Apr 6, 2009)

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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## xpertpc (Apr 7, 2009)

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.


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## Wet1 (Apr 7, 2009)

xpertpc said:
			
		

> 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 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.


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## xpertpc (Apr 7, 2009)

Wet1 said:
			
		

> xpertpc said:
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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.


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## xpertpc (Apr 7, 2009)

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.


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## 2.beans (Apr 7, 2009)

xpertpc said:
			
		

> Wet1 said:
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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.


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## xpertpc (Apr 7, 2009)

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.


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## 2.beans (Apr 8, 2009)

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?


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## xpertpc (Apr 8, 2009)

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.


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## Wet1 (Apr 8, 2009)

If I'm reading this right, those wirsbo plates will cost a pretty penny.  23.3 sq ft of this material is $130 or $5.53 a sq ft.  The RHT plates might not be quite as nice, but they are only $1.72 per sq ft.

http://www.blueridgecompany.com/radiant/hydronic/316/rht-heat-transfer-plates


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## xpertpc (Apr 8, 2009)

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;=


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## 2.beans (Apr 9, 2009)

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.


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## 2.beans (Apr 9, 2009)

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.


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## Wet1 (Apr 9, 2009)

2.beans said:
			
		

> 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.



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.


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## 4acrefarm (Apr 9, 2009)

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.


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## xpertpc (Apr 9, 2009)

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.


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## Wet1 (Apr 9, 2009)

xpertpc said:
			
		

> 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*.


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


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## xpertpc (Apr 9, 2009)

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.


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## 2.beans (Apr 9, 2009)

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?


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## xpertpc (Apr 9, 2009)

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.


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## 2.beans (Apr 10, 2009)

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.


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## 4acrefarm (Apr 16, 2009)

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?


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## Wet1 (Apr 16, 2009)

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.


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## xpertpc (Apr 19, 2009)

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.


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## 2.beans (Apr 20, 2009)

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


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## xpertpc (Apr 20, 2009)

That looks pretty nice so far and went to town with 10 copper pipes, what did you use as a backer board to screw the plates to? don't forget to mount with a slight slope so the tubes will drain.


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## 2.beans (Apr 21, 2009)

first i used a scrap piece of 1/2 inch plywood, then topped that with 1 inch foil back insulation, then laid the wirsbo plates on top and screwed them down thru the insulation to the plywood. i ripped down the scrap insulation and lined the inside sides with it. i just need to paint it and drill and screw the glass door on and im done. what did you mean to keep it tilted so the tubes will drain? thanks


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## Wallyworld (Apr 21, 2009)

Looks nice, are you going to paint the inside with flat black barbeque paint?


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## Wet1 (Apr 21, 2009)

It looks nice (although quite costly for DIY)!  What insulation did you screw the plates down to?  The reason I ask is because the panels will reach temps in excess of 250° and your insulation will need to be rated above this temp since they are in direct contact with the plates.

You'll want to tilt the tubes or collector so everything has a slight slope to it, this way everything drains back during the coldest weather... The bottom headers MUST be sloped so everything drains back.

Since you've gone top of the line with this collector(s), you might want to spend the extra money on a selective coating rather than black bbq paint.


Nice job, I'm looking forward to your seeing your results!


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## 2.beans (Apr 21, 2009)

im at $226 so far. thats with buying enough screws and 1/3 of the wirsbo plates to build the next one. im not sure on the heat rating of the insulation, i didnt put that much thought into the 250 plus temp. thanks for pointing that out. i dont know if i could change it now without breaking something. i already bought the high heat paint and used some so i guess ill stick with it. if it fails i can always take the glass front off and repaint. thanks for the much needed input.


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## 2.beans (Apr 21, 2009)

without sounding too dumb about the drain back, i planned on draining this in the winter. this would give me room to add treatment to my system every spring. each collector holds 1 and 1/4 gallons of water. the collectors are going to be at my shop which is 250' from my 1000 storage tanks. when my super store tank (dhw 45 gallon tank) calls the panel will directly heat the dhw, if there is no call it will dump into the 1000 gallon storage. i guess im not to sure on how the drain back works. i wasnt planning on doing it with a drainback because i burn wood in the winter. in the worst case if this doesnt work like i hope i can put the panels down at my pool and try to heat that. thanks.


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## Wet1 (Apr 21, 2009)

2.beans said:
			
		

> im at $226 so far. thats with buying enough screws and 1/3 of the wirsbo plates to build the next one. im not sure on the heat rating of the insulation, i didnt put that much thought into the 250 plus temp. thanks for pointing that out. i dont know if i could change it now without breaking something. i already bought the high heat paint and used some so i guess ill stick with it. if it fails i can always take the glass front off and repaint. thanks for the much needed input.


Regarding the cost of the solar system, checkout the following link.  It does a good job showing how big of an impact cost is when considering the payback.  You'll need to know some basic info about your system to get accrate numbers, but either way it's kind of neat to see how build cost impacts payback.

The heat paint should be fine.  The idea of using the selective coating is to increase efficiency, but you'll be fine w/o it... and it should hold up well over time.



> without sounding too dumb about the drain back, i planned on draining this in the winter. this would give me room to add treatment to my system every spring. each collector holds 1 and 1/4 gallons of water. the collectors are going to be at my shop which is 250’ from my 1000 storage tanks. when my super store tank (dhw 45 gallon tank) calls the panel will directly heat the dhw, if there is no call it will dump into the 1000 gallon storage. i guess im not to sure on how the drain back works. i wasnt planning on doing it with a drainback because i burn wood in the winter. in the worst case if this doesnt work like i hope i can put the panels down at my pool and try to heat that. thanks.


You kind of lost me here.  How are you going to configure your system?  Is it going to be a batch, thermosyphon, drain back, or closed loop system?  Here is a LOT of info on solar hot water heating design which you might find very helpful...
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

Also, if these panels are going to be located 250' away from your storage tanks, I would think you would have huge losses given the delta T and distance.


BTW, those small panels will not do much for heating a pool, unless it's pretty small.


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## 2.beans (Apr 21, 2009)

its going to be a closed loop system. im going to try to ball valve my boiler off or out of the system, and circulate the water thru two panels with a taco 011 to the storage. the undergroud piping is 1" pex. i would like them down at the house but i dont have a real good place for them besides at the pool. that also is an option, id have to dig up the lawn and run a new line into the house. you think ill loose too much heat in 250' feet with a 011? i dont loose any with the wood boiler, i know its apples and oranges though. ive been reading on build it solar, i did find one estimate for a yearly payback. at that rate it could pay for itself in a coulple years if i run it the way id planned. thats good right? if it gave me june, july, and august off from messing with wood that would be priceless. i think im enjoying the learning part more then any savings that this could offset. ive definitely wasted more money on worse things.


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## Wet1 (Apr 21, 2009)

Well if you're doing a closed loop system, drain back/tilting the collectors is irrelevant.  I would suggest using a non toxic antifreeze, but since you switch over to wood in the winter, there's no point... just make sure it's easy to drain the solar system.

I would think you'd have a lot of heat loss running that distance.  Remember, this is something that only runs a few hours each day, so it's not steady-state like your wood boiler basically is.  If the collectors are over sized enough for your application, then you can probably get away with it, but I would think it's far from ideal when you consider the flow and amount of time these solar systems operate at.

Your payback of a couple years could be right, I have no idea what your numbers are.  With that said, the delta T on the DHW during the summer is much lower than it is in the winter, plus you're only talking about three months of the year, so I would think the payback might be significantly longer... especially when you factor in the cost to run the Taco 011 for several hours each day.  BTW, watch the flow rate with that pump and those relatively small panels.

Either way, it looks like your panel is coming out very nicely.  It's a neat project and a real slick learning experience, I'm looking forward to seeing more pics as the project progresses.  :coolsmile:


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## 2.beans (Apr 21, 2009)

i have my system setup with a three way zone valve at the tank side if the 250' run. the zone valve is controlled by the boiler temp or the panel temp. i im installing a temp sensor on the panel thats immersed in the water so it will only turn the circulator on when it hits its desired temp. then when the circulating water is to temp it will open the three zone valve. i dont know yet what to adjust things to but im sure that will be a learning curve on its own. so until the zone valve opens id be heating maybe 10 gallons of water. does that make any sense?  i do this to stop the mixing of the water in the storage tanks. it seems to help my stratification by only letting hot water into the tank. i filled my panel with water to check for leaks and fixed the two that i had. i was going to paint it but now im getting chicken. im thinking i need to add some pressure to it to make sure im really all set.


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## Wet1 (Apr 22, 2009)

I see what you're doing.  That should work fine in theory.  What I suspect might happen in reality is the circulator and zone valve might end up being cycled a lot due to the losses from the long run and the relatively low temps we're talking about with two small panels and high rate of water flow with that circulator.  Either way I'm sure it will work, you're just going to be taking a pretty significant hit in efficiency/performance.

Since you're using a closed loop system, you should absolutely pressure test your panels since they will see pressure in the field... it will be a PITA to fix leaks within the panels once they are painted and buttoned-up.


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## xpertpc (Apr 22, 2009)

I pressure tested mine (just the grid) while sitting in the full sun for several days, one leak didn't show up until the grid expanded and contracted many times. My pump is a 4 gpm and although it seemed to work it was slow to heat, I throttled it down to 1 gpm and it worked much better. Most commercial unit specs I have looked at were rated between 0.5 - 1 gpm.

Are you putting street water or tempered preheated water back into the collector? The 250' pipe will hold 10 gallons and may not completely empty into your dhw tank if the collector cools down and pump stops. I see exactly what Wet1 is saying in the above post happening. At least you would be preheating the dhw inlet and should save a bit of money.

To stop short cycling you would need a temperature controller with hysteresis so you can turn the pump on at 120F and off at 90F or there about or maybe even an off-delay timer to keep the pump running for 10 minutes after the temperature is satisfied, neither would work in a open dhw loop unless you are recirculating that water too.


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## Wet1 (Apr 22, 2009)

I would think he'd want around 2 gpm flow rate for his system.

xpertpc... he's using a closed loop system with a HX in the tank(s).  His system will not be draining into the tank, it will be pressurized.


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## 2.beans (Apr 22, 2009)

to correct the gallon per minute flow thru the collector i can install a smaller pump  that is just controlled by the temp controller on the panel. it will be pushing thru the 011 that would be off. ive read that taco said that that wont hurt the 011. i have a 006 bronze that i could use. that would really slow things down in a 250' run, then maybe id have some heat loss in that length of run. the water is pre heated that goes back into the collector. the temperature controllers i use are ranco's. they can be set for heating or cooling, operate from 30 to 220 and the differential can be set from 1 to 30. the controller can be up to 400 feet away from the sensor.


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## 2.beans (Apr 26, 2009)

saturday morning i started out with 42* water, at the end of the day it was at 106*. we had a daytime high of 86* the tank is a 45 gallon unisulated tank so i dont know how much that heated up on its own. i started out with the pump at 1.5 gpm and around one o'clock i slowed it down to 3/4 gpm. that made the output water temp increase from 94* to 105* in a half hour to finally top the tank out at 106* today im going to add a gauge to the panel supply line and add the ranco controller to see if i can get the tank hotter.


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## Wallyworld (Apr 26, 2009)

You need to use a differential controller, which I assume the ranco controller is. Mine turns on at 15 degrees warmer than water temp and kicks off at 5 degrees warmer. I have 2, 3 by 8 panels, copper collectors and I hit 160 degrees yesterday. I'd say your collector did pretty well


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## 2.beans (Apr 26, 2009)

Wallyworld said:
			
		

> You need to use a differential controller, which I assume the ranco controller is. Mine turns on at 15 degrees warmer than water temp and kicks off at 5 degrees warmer. I have 2, 3 by 8 panels, copper collectors and I hit 160 degrees yesterday. I'd say your collector did pretty well


 so if your tank temps at 100* the pump turns on at 115* and shuts off at 105*? does it automatically rise as the tank temp rises? when you say that you hit 160* yesterday was the collector temp or storage temp? the ranco is a differential controller im not sure if its the best one for the this application though.thanks


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## Wallyworld (Apr 26, 2009)

2.beans said:
			
		

> Wallyworld said:
> 
> 
> 
> ...



If the tank is a hundred my pump turns on at 115, if the suns goes in and the collector cools off, it would shut off at 105 assuming the tank temp is still 100. My tank temp got to 160 yesterday,


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## 2.beans (Apr 26, 2009)

what kind of controller is it? thats how id like to run it.


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## Wallyworld (Apr 26, 2009)

Its a solarmetric, think they are out of business though. The controller is 18 years old. They make them now where you set the differentials you want. This one is one choice


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## 2.beans (Apr 26, 2009)

i adjusted the ranco higher and got the tank to 120* today with low sun until 2 o'clock this afternoon. i think im going to need a better controller and install the panels closer to the house.


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## Wallyworld (Apr 26, 2009)

I heard my pump start running at 8:55 this morning and it was still running at 4 pm when I went out. Collectors' temps at 4 were around 152; tank temp in the high 140s.


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## steviep (May 1, 2009)

I live here in NH and I plan on making solar heater for my DWH. I really like your designs and wouldn't mind looking at them but a better idea would be a list of materials. I am planning on putting a spare electric hotwater heater as storage in line before my gas hotwater heater. I would like to know what buy for a controler and where to buy it reasonable. I have also thought about getting a 12 volt circulator and running it off of a small solar collector .


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## xpertpc (May 1, 2009)

2.beans said:
			
		

> what kind of controller is it? thats how id like to run it.


In Gary's article under "pumps and controls" he uses the Steca differential controller, They seem to be $100-$200 depending on needed features, I just google searched and came up with this http://www.stecasolar.com/index.php?Steca_TR_0502_en


http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm


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## 2.beans (May 2, 2009)

im going to look in getting one. ive wathched this work for a week now and achieved 120* in my uninsulated tank. on the hottest days we had it melted some of the plastic fittings off so i didnt get good results on those days. it was putting out 150* water onto the ground, it would have been better in the tank. i knew it was going to be slow but i didnt think it was going to be this slow. so with that said im going to put these down at my house and dig a ditch across my lawn again and add a second panel maybe a third and a second super store tank, or build one. heres some pics. ive have about 10 seconds into placing the panel so im guessing my results could be increased. thanks


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## begreen (May 3, 2009)

2.beans. Thanks for sharing your evolving experience. I'm learning a lot serendipitously through your trials and errors. Wallyworld, thanks for the continued input. This is good feedback.


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## steviep (May 8, 2009)

instead of wisbo plates I am thinking of trying corrigated roofing panels. I started an experimate using a 2x2 piece of roofing a piece of plywood and 4 - 3' pipes. the roofing really holds the pipe down tight. I painted it black and set it out in the sun. I have a meter with a tempator prope, the outside tempator was 71 within minutes the inside of the pipe  tempature rose to 82. I guess its time to start building.


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## Wet1 (May 8, 2009)

Could you please show a drawing or picture of exactly what you have in mind?


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## xpertpc (May 8, 2009)

Yes please post some more information, did you use corrugated 26" wide galvanized steel or ridged aluminum?


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## steviep (May 9, 2009)

I am trying the 26" galvinized roofing , when I figure out how to post pitchures I will do it. Basically I am going to build it the same way everyone else is doing with the wisbo plates . I am just trying to make one with as much materials I have laying around.


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## 2.beans (May 9, 2009)

theres a thread at the top of the forum that walks you through. thats how i learned. its pretty easy. more pictures the better. good luck


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