Need constructive critique on my idea for a solar hot water panel , please

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On Jul 8, 3:29 pm, .p.jm.@see_my_sig_for_address.com wrote:

I addressed the UV light problem in my OP , and it wont be a problem the way im going to do it.
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On 7/8/2011 2:48 PM, snipped-for-privacy@gmail.com wrote:

Just enough to flush an older toilet. ;-)
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On Jul 8, 1:58 pm, "Stormin Mormon"

Thanks much. Ill get hold of him.
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    My grandmother is more help than you, and she's dead.
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1. Use of double pane will reduce inflow of heat rays.
2. Use of foil will reflect some heat from being 'conducted' through pex. Try to find foil with dull side and face to sun.
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yup.... thereby negating any efficiency at all.
Thats ok tho.... its his soap and he can wash it just as fast and as hard as he wants to.
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On 7/9/2011 3:58 PM, HankG wrote:

Just paint the Pex black..Lay it on Galvanized barn tin also painted black. This project is a waste of time.

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.
Your suggestion here shows me that it is you that doesnt know what you are doing ! You cant paint Pex Tubing per the manufacturer of any Pex Tubing . Further you have to shield Pex from UV rays ,and lastly, I dont need 180 f. water for a shower from Pex laying out in the sun unregulated . Stop being arguementative and dont reply to posts if you are inundated with negativity and/or jealousy . This will conclude my dialogue in this thread as there have been no good constructive info disemminated other than Mr. Stormin's link (and you all need to stop badgering this Guy .. you sound like a bunch of attacking Parasites) . End.
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On Sun, 10 Jul 2011 06:59:48 -0700 (PDT), " snipped-for-privacy@gmail.com"

    Geez - is this national 'pissy little bitch' day ?
    Tell you what - go take your little PEX shower and STFU.
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Your suggestion here shows me that it is you that doesnt know what you are doing ! You cant paint Pex Tubing per the manufacturer of any Pex Tubing . Further you have to shield Pex from UV rays ,and lastly, I dont need 180 f. water for a shower from Pex laying out in the sun unregulated . Stop being arguementative and dont reply to posts if you are inundated with negativity and/or jealousy . This will conclude my dialogue in this thread as there have been no good constructive info disemminated other than Mr. Stormin's link (and you all need to stop badgering this Guy .. you sound like a bunch of attacking Parasites) . End.
Gotta love 'moaners that want to use "presidential solutions" instead of doing somethng right. We all know that it won't work, and its going to be nothing but wasted time and money, with all of the associated problems.
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1. I never stated this at all.
2. Im using foil only to shield the PEX from UV rays ; Yes, ill paint it flat black for the Box to absorb heat when i want full sunrays coming thru as regulated by the sheetmetal plate that will be (fully or partially) placed on the front of the window .
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1. I never stated this at all.
Per your original post: "A double pane window in frame measuring 36" sq. od (without any inside bars) will be fastened on top of the box for a greenhouse effect. "
While a double pane window might retain more heat (greenhouse), it (heat) has to get through the double pane first.
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On 7/11/2011 4:33 PM, HankG wrote:

This may seem counter intuitive, but if possible you want to block IR in your glazing.
Very little of the light hitting the solar collector is IR, or heat.
http://en.wikipedia.org/wiki/File:Atmospheric_electromagnetic_opacity.svg
What happens is that plain old visible like strikes the collector and is turned into heat. You want to block the heat/IR from escaping in better collectors. This is the idea behind selective coatings. Best applied to the collector surface.
If I were the OP, I'd have a layer of polycarbonate with a UV shield in it (SunTuf or equivalent) and then multiple layers of mylar. You'll lose light transmission but it will be more than made up by cutting losses. The higher the temperature difference between the collector and ambient the greater the loss, for hot water, more than space heating, this is significant.
Also, don't use styro type insulation, it will not survive stagnation. Something like polyisocynaurate is better, which is widely available, usually with a reflective surface to cut radiative losses.
j

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On 7/8/2011 12:11 PM, snipped-for-privacy@gmail.com wrote:

The thermal conductivity of PEX is not great.
I will set this in a box which i will construct

4 inches is probably overkill. Your loss out the glazing is far greater.
A 32" square sheetmetal plate painted with

Why?
The coiled Pex tubing will be wrapped in

Painting would work.

Define direct contact? The thermal contact between the PEX and the back plate is likely to be low.
A double pane window

OK.
I'd ditch Plan A. Try something from here:
http://www.builditsolar.com
j
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On 7/12/2011 5:12 PM, j wrote:

That is not great, somewhat less than 1 m^2 which matches up with this chart:
http://www.solarpanelsplus.com/solar-insolation-levels /
So, about 3 1/2 or 4 1/2 kWhr /day. You'll lose some in the glazing.
Your efficiency will be about half or less. Probably much less. You'll gain a bit by having your collector tilted.
You should be looking at a collector at least 4 times as large. And you have no pumping to storage, so you will only heat the amount of water in the pipe, which I believe someone figured as 6 gallons.
Why don't you do a batch heater? That is just a tank in a glazed insulated box. You'll have substantial night time losses with any system that doesn't pump to an insulated storage.
j
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On 7/12/2011 4:12 PM, j wrote:

Damned? Is that why those suppliers have been selling it to us as radiant heaters? They told us it was invented for that. Wow..I have a lot of installations thats bound to be pissed at me. Some of those install are decades old.. I wonder why they still call me for repairs etc?

They walk among us. ;-p

Is that why those crooks at the supply house sell us metal mounting plates that radiate under the floors of the spaces to be heated?

I have a better idea..Go to Johnstone Supply and buy a PEX design and install guide video for Hydronic heat systems. And then don't let the door of this NG hit you in the ass.

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    Because you haven't fixed it yet ?
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On 7/12/2011 9:16 PM, .p.jm.@see_my_sig_for_address.com wrote:

No sense wrecking job Security. When the pex expert gets his Shower going, I have an Idea that a Hotwater Heater installer is gonna get a service call. ;-p

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On 7/12/2011 9:11 PM, PaxPerPoten wrote:

Don't be silly.
The heat flux in radiant heating is much lower than it is in a solar collector. PEX is fine for radiant. The temperature drop, and hence the loss, is therefore much less. Note also the much greater insulation levels on the "back" side of radiant that keeps the heat from escaping. PEX may be suitable for low temperature low efficiency collectors such as you might use at a pool, not for domestic hot water.

Maximum contact area is important. The OP's plan had no provision for that. This is far more important with a low conductivity material like PEX than it is with copper. The thermal conductivity is several orders of magnitude less.

The only collector in a flat plate you will find there is this one:
http://www.stiebel-eltron-usa.com/sol25.html
Not a bit of PEX in that, or any other commercial collector for DHW.
You never seem to mind being a jerk. I think you just like to complain and assume everyone else is dumber than yourself. You'd do yourself and everyone else a big favor if you weren't so smug. It's not too late.
j

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    Damn - I'm all out of popcorn.
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