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stmbtwle

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Reply with quote  #31 
The problem does seem to be the heater core is too restrictive,  theres's a 30-40 degree drop in air temp going through it, yet I'm getting very little heating of the water (1-2F). So it seems that there's simply not enough air getting through.  I've got plenty of water flow.  There's really no way to measure the actual CFM with the fans installed.

I still have the fan that came out of that heater, but the thing draws 6 amps on 12v, I'd be willing to try it but it's a BIG centrifugal blower and there's no way to fit it to this small collector.  Maybe a bigger one.

I think your idea of a radiator fan might work, and I think they come as small as 7" diameter which would be about perfect and easy to install.  I'll see if I can find one.  Otherwise I'll have to find a larger HEX that allows better air flow, and that means rebuilding the whole collector.

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stmbtwle

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Reply with quote  #32 
Well ordered a 7" radiator fan and an 8x8 hvac HEX. They both may come in today. Problems are the fan draws a lot of power, and the HEX is 3-1/2" thick, which will necessitate some sort of bulge on the back of the collector.
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Willie, Tampa Bay
gbwillson

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Reply with quote  #33 
Being a radiator fan it should be able to handle the back pressure from the HEX. And as long as the back doesn't bulge too much, all is good. If not, a simple reinforcement might be needed. Did this radiator fan have any sort of CFM rating?

Greg in MN
stmbtwle

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Reply with quote  #34 
No, but it does have an amp rating, if it's accurate there's no way I'll be able to power it from PV.

The bulge is to make physical room for the HEX.

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stmbtwle

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Reply with quote  #35 
The problem definitely seems to be I'm not getting enough air through the HEX. I removed the glazing and screen and turned on the fans, but the airflow through the HEX was still not as good as I would expect, there is simply too much resistance in the HEX. However the new one is larger and it will take some time to accommodate it. The new fan would be easier but would preclude using solar to power the thing. I'm at a bit of a quandary here.
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Willie, Tampa Bay
gbwillson

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Reply with quote  #36 
For proof of concept you could use AC current, and if the results look good, switch back to DC. And as far as high volume solar fans, they are available. Here's an example:

https://www.amazon.com/Brightwatts-Galvanized-Prevention-Efficiency-Brushless/dp/B001F6O48M/ref=sr_1_2?ie=UTF8&qid=1487594256&sr=8-2&keywords=solar+gable+attic+fan

Now I don't expect this to fit inside pretty much anything short of a house, but if they can power that kind of CFM capacity via solar, surely you can find something a ┬╝th the size.

Greg in MN
stmbtwle

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Reply with quote  #37 
Bear in mind that those "solar attic fans" are not working against any kind of backpressure.  It's not the CFM that I need, it's the pressure (or a way to do away with the need).  

I think I may get another oil-cooler HEX, they are flat and seem to work pretty well, at nearly 1 sq foot in area.  



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stmbtwle

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Reply with quote  #38 
Well the 7" radiator fan and 8" HEX arrived and while the fan will fit and moves LOTS of air it draws about 3 times what the solar panel can put out. The HEX is simply too big, so I'm getting another oil cooler which I KNOW works well with a computer fan. I'll use the auto fan and the HVAC HEX on the larger ARETHA I plan to build this summer.
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gbwillson

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Reply with quote  #39 
By big, do you mean the HEX is too thick and restrictive?


stmbtwle

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Reply with quote  #40 
I don't think it's too restrictive, but it is physically too big for this little collector. While the HEX itself is 8x8, with all the plumbing it's well over a foot long. Making it fit in this little collector is hardly worth the effort, and I want to put the thing into service and move on. I'll save it for the next project.

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