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Garage_Hermit

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Reply with quote  #131 
er solar usmc,

It might be an idea to create a new thread, in Member Projects, detailing your project ?

just a suggestion,

g_h

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Keith671

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Reply with quote  #132 
Solarusmc,
I guess with the tubes you don't have to worry about stagnation, as you said you turn the pump off after 130 degrees. I like the idea of running the pump longer and getting the extra heat or maybe another tank to store it and use it at night.

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Keith R. in PA.
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Reply with quote  #133 
Hi Keith -

I was doing some surfing today and read this entire thread.  I bought the MaxDTC as well.  How is it working for you?  I will be activating my project in a few weeks. I noticed a couple of things in your setup that I figured I'd comment on.

1.  With regard to the thermistors.  I made "wells" from 3/8" soft copper coil tubing, crimped and soldered the "wet" end and then slid the sensor into the tube.  Note I had to grind down the sides of the rings for them to fit into the tubing.  I've also done a good bit of research on 10k thermistors and it seems that the ones sold by altestore.com should work OK in addition to the ones Brian sells.  I've also seen elsewhere on the web that some have added a bit of non-conductive oil (mineral oil?) to the well for better thermal conductivity.

2.  I have configured my Max for a DON of 18 degrees and a DOFF of 5 degrees.  This means the collector temp must be 18 or more degrees above the tank for the pump to come on.  This will prevent "short cycling" of the pump at the beginning of the collector warm up.  And DOFF at 5 degrees so the pump shuts off when the tank is within 5 of the collector (this allows for any temp loss in the pipe run from the collectors so that the pump does not run too long).

Notwithstanding the above, your optimal settings may (probably will) vary, but thought I'd toss that out there and solicit your opinion of the MaxDTC.

Well done project!
Chris

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Garage_Hermit

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Reply with quote  #134 
Regarding the tee-puller mentioned by Gary at Item No. 20 above,

this technique is also covered in substantial detail in this document:

http://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf

(scroll down to page 59).

G_H

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mclark999

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Reply with quote  #135 
Quote:
Originally Posted by GaryBIS
Hi Keith,
Don't know if you are using a little silicone in the absorber grooves or not?


I think its a good idea for reasons outlined here: 
http://www.builditsolar.com/Experimental/PEXCollector/SmallPanelAirVsSilicone.htm

Basically while the silicone is not a great conductor, its still is ten times better a conductor than air, so any tiny air gaps that get filled with silicone will conduct much better.  It also provides a good flexible bond between the fin and the tube, and it keeps any condenstation out of the gap providing some extra protection against corrosion in addition to the paint.


Once the silicone sets, the screws don't make much difference, because the silicone bonds the absorber fin to the copper quite well (this takes quite a while with the silicone between two metal surfaces) -- so, if the screws rust it does not make much difference.


Gary


Has anyone tried a thermal transfer adhesive like this instead of silicone?   Would it be worth the cost?  http://www.aavid.com/product-group/interface/adhesive

Never mind, I found an article about testing it here: http://www.builditsolar.com/Experimental/SmallPanelTests/ConductiveSilicone.htm


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Denver, CO

Double screen hot air collector
Keith671

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Reply with quote  #136 
Hi Guys,
     I'm back after a couple of years with no communication. I need a little advise on adding a new collector. I now have two collectors 2'X5', built opposite, feeding through a tee between collectors. I would like to add a 4'X8' collector beside these two. My question is since this one is 8' long and the other two are only 5' long, how will this effect the flow? It seems to me that the 5' ones will start to return before the 8' one is full.  As of now I have 1" pex out to collectors with a 1" tee, the tee is capped on end and feeding the two collectors from the tee side necked down to 1/2". I was going to uncap the tee to feed the new collector. Anyone have any ideas or other options?

Thanks Keith

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Keith R. in PA.
stmbtwle

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Reply with quote  #137 
Water seeks its own level so if the tops are all at the same level they should be close. I'd try putting a valve in the fill line to each collector so you can adjust the flow, or shut off a collector for repairs. Once you get it right you can remove the handles to prevent meddling, or wire them in place.

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Willie, Tampa Bay
Keith671

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Reply with quote  #138 
This is a drain back system, so there won't be any water in system to need valves. What if I run it through the 5' collectors first, then through the 8'. this would preheat it before going through 8' and the return would be from the 8'.  Or I could make the collector 5'X8', but this would take more materials because of the odd size.  
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Keith R. in PA.
stmbtwle

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Reply with quote  #139 
I was thinking of the valves more for regulation of the flow than anything else.

Someone else will have to advise about connecting a drainback in series.

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Willie, Tampa Bay
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