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stmbtwle

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Reply with quote  #441 
"I really need to replace that with something proper this year. Of course I said that last year as well..."

Yep, I know how that goes... :D

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay

SolarInterested

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Reply with quote  #442 
Quote:
Originally Posted by jamieF
Since it gets asked every time I update the poly tank liner still looks fine.  It's discolored but that may be from the water. It's not brittle at all.   The poly on the collector is fogged over.
Thank you [biggrin]

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jamieF

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Reply with quote  #443 
birthday money came in from my inlaws with some specific must use requirements on it so I bought glazing today.   dear god this stuff is expensive...   Anyways it's installed collector.jpg 
I'll need to see it on a hot day to adjust the trim that holds it in.  I think it's likely a bit too tight at the moment and will warp when expanding.   

The twinwall is definitely more translucent than the faded poly it replaced. I've been seeing the collector max out at 80C when the pump is running with the poly.  Hopefully it'll get a bit hotter now.   3 or 4 days of pure sun predicted starting this sunday.   I'm looking forward to it.   Next part of this project is wiring clean up for the solar panel, battery,...  

gbwillson

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Reply with quote  #444 
Very nice looking Jamie!

Twinwall expands greatest in the direction of the ribs. Check on the manufacturers website for installation instructions where you should be able to find the specific amount of thermal expansion for the given product. And don't do what I and a few others have done and forget to remove the protective film from both sides before the collector gets hot. Even after a few minutes, the film can be very difficult to remove.

Greg in MN
jamieF

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Reply with quote  #445 
thx,   the film is off.  I made the mistake on the first panel I put in of taking the film off, getting it all in place and then realising I had the non UV side out.  I love this hobby enough to do everything twice right?
gbwillson

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Reply with quote  #446 
Measure once, cut twice..."

Since you can't tell the difference between the UV protected side and unprotected, I mark the glazing on one of the corners, not with a sharpie as it fades in a year. I scratch a mark so it lasts. My first collector needed a little TLC inside, so I removed the glazing, and couldn't figure out which side was protected when I put it back together. I think I got it wrong, as the polycarbonate became very brittle about a year ago before I sold it. 

Greg in MN
jamieF

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Reply with quote  #447 
The sun was out today for a few hours. I figured the glazing was tight and I was correct. The glazing instantly expanded a lot and I had to fix the trim as everything was bulging.  Sadly I was away and couldn't watch it but now that it's cloudy again the trim seems to all be in place and it didn't bulge out to the point of breaking or anything.   

I had left the trim somewhat loose today so that may have let heat escape but the readings are interesting.   The surface maxed out at 66C when it would max out at close to 80C with the poly.   The tank however gained 3 degrees in a little over 2 hours.  It normally gains 1 degree per hour.  I'm not sure why that would be.  The fluid also gained 4 degrees between the collector inlet and it's outlet which is 1 degree more than normal.   That would make sense if the collector was hotter but the surface readings were lower than normal.   I'm aware that 1 set of readings isn't enough to make a conclusion but I found it interesting.


stmbtwle

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Reply with quote  #448 
Is the tank cooler than normal? In my experience, water input temperature affects the collector temperature.

Otherwise it sounds like a good clear spring day. If your pump is solar powered it would probably be running a bit faster, increasing heat transport to storage.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
jamieF

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Reply with quote  #449 
pump isn't solar powered.   the tank may have been a bit cooler than normal but not by much.  Of course the increase was only a bit as well.   Either way we've got a nice few days coming up so hopefully I can get some good readings.
jamieF

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Reply with quote  #450 
I've had some beautiful sunny days lately. At first I noticed that the expansion was still causing issues resulting in a bow at the top in the middle which was letting out a lot of very hot air.  That was limiting temperatures to the high 60's.  I corrected that(famous last words) and then I stagnated the collector.  Temperatures quickly climbed over the 80C mark and I turned the pump back on.  temperatures maxed out in the 70C range and fairly quickly dropped back to 60-65C.  It looks like the pump running is greatly reducing temperatures in the collector which of course is what we want.  

Max temperatures in the collector don't seem any different with the glazing. What is different is I hit useful temperatures earlier in the day.  about an hour earlier.     My collector is partially shaded at first and it seems like enough heat is retained for the pump to kick on and be useful.  I'm still gaining about 1 to 1.5 C per day just for longer.


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