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mranum

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Reply with quote  #11 
Its alive!!!  [thumb]

We put the ZP through its initial trials yesterday. She needs some tweaking yet but overall I'm happy. [biggrin] The boxes need to get sealed up a little tighter yet but first I need to install a proper switch or controller and change its location. What I have in there now is a spare snap switch from my wood burning fireplace and that doesn't kick in until it hits 120*, and where I have it is in the cold air stream so basically.....it doesn't kick in when it needs too. Live and learn. [rolleyes] So for now the blower is being run manually during the day.

My blower is the blower from my recently deceased furnace from my shop. It is a 4 speed blower and I have it set on the lowest speed. According to the literature I've read it should produce about 590 cfm. I'm running 8" vents with only about 3' of run on the intake and 2' of run at the exhaust. With that amount of airflow the blower cools the collectors just a little more than I want. I will be experimenting with a throttle plate of sorts for the intake of the blower.

The sky was clear with an occasion thin wispy cloud with winds 10-15mph. We got the glass on around noon so my observations were over the next few hours.

With the blower on I had a steady 88* to 90* stream of air entering the shop. If I shut the fan off the collector would max out my thermometers(158*) in a few short minutes. I didnt shut the fan down until 5pm at which time it was still producing 85* air out the pipe.

I have 2 thermometers in the collectors, one in the cold air stream (left side) and one in the middle of the last screen near the exhaust (right side). For checking temps of the duct air inside the building I used my infrared thermometer. I found that with the blower running the temp inside the pipe(in the building) to be within 2* of the thermometer in the last collector.

Needless to say I'm pleased with the results. Still a lot of work left to do like mounting the access door/filter cover, back flow devices, drip rail flashing outside, replace the siding around the collectors...etc etc...so it will be a work in progress for a while yet.

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stmbtwle

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Reply with quote  #12 
Looks great and love the filter setup.  You're right that is a BIG fan.  I think an electronic fan speed control would be better than a "throttle plate", easier to install, quieter, and probably cheaper.
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Willie, Tampa Bay
mranum

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Reply with quote  #13 
I am surprised that the fan doesn't competely overpower it, its really almost matched for it. This thing needs A LOT of air, it is 19' long. Been debating about a speed controller but there is info going both ways as to whether it will work or not because this motor does have a capacitor for starting. There is an electrical motor shop not far from me and I'm going to stop in and talk to them about it and see what they reccommend. Good guys, done business with them several times.

A throttle plate like I was thinking about would be nothing more than a piece of sheet metal anchored at a pivot point that I could slide up or down then lock into place. Really no cost as I have material here.

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mranum

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Reply with quote  #14 
Made a little more progress on my fan control. I ordered a programmable InkBird controller from Amazon and since I'm using a big fan I also picked up a power monitor to go along with it to try and get a handle on power usage. The instructions that come with the controller leave A LOT to be desired [frown] but the unit itself seems like a very nice controller. I need to look online for tips on settings as its pretty confusing.

The way I have it wired the monitor follows the controller so the monitor is off until the controller calls for the fan, then the relay trips...powers on the monitor and the fan at the same time.

I also picked up an anenometer(sp) for calculating my CFM. Preliminary checks looks like I'm putting out 477 to 500 CFM.

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Julian Jameson

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Reply with quote  #15 
That's a beast of a collector, really nice project and it's got me a little intrigued. So I've had a stab at some of the math*

You say the length is 19 feet and I'm assuming the height is 4 feet(?).
Therefore surface area of the entire collector is 76 sq.ft.

To approximate the surface area of the collector elements, you'd take a percentage of the above, for example 90%. 90% of 76 is 68.4sq.ft.

The maximum energy potential from the sun is then 317*68.4 = 21682.8 BTU.
Then factor in an efficiency. 55-70% is a good range to use here, so if we go with an efficiency value of 55%, the maximum output is then 21682.8*.55= 11926 BTU.

I then divided that output by the magic number 1.08 (assuming your location is <500' elevation), giving 11042.

You can then approximate the temperature delta (output-input) by dividing the above number by a CFM factor.

For example, 11042/180CFM is approx. 61F rise (if you have 70F going in, should be around 131F coming out at a measured (i.e. not rated) 180CFM).

You can try that with different CFM values to get a rough idea* of different temperature rises.

Also, if we look at the figures you've already provided, 477CFM with a 23F rise is approximately 11848BTU. So the numbers compare well and and indicate a 59% efficiency value (if 90% of the entire collector collects sunlight).

I suppose fan selection is then just down to comfort, safety, ease of installation etc. Fan noise level is obviously a big consideration, as is power consumption. Also, if the temperature rise is too low, the output air can "feel" colder than the inlet air (as it might blow moisture away from skin, and take away heat in the process), obviously the output temperature should not be so high that it could cause harm to the fan, nearby stuff or living things. Therefore keeping it under 155F is probably a good idea.


tl;dr If you lower the max CFM to under 200, the power consumption of the fan will decrease substantially, noise levels should be reduced, the heat output will remain the same in terms of BTUh and the temperature delta will increase substantially.

*all approximations and errors could easily be present!
mranum

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Reply with quote  #16 
After getting my controller done and getting the controller sensor mounted where I wanted I had some nice clear sky the other day. Here are some observations from throughout the day. When you look at the pics, the thermometer alongside the control box is reading room air temp near the intake on the top, the lower number is humidity. The air temp in my exhaust duct reads within 1 degree of the controller temp. I did no modifications to the fan, still putting out the same CFM referenced earlier. My controller is currently programmed for the fan to turn on at 105 and off at 75. The fan was running steady by 9am but I didn't take a pic of the temps then.

Now that you know what I have for temp readings I'll let the pics speak for themselves.

At 10:00 am...

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At 12:00 pm...

3-11-16-12pm.jpg 
At 3:00 pm ...

3-11-16-3pm.jpg 
At 4:00 pm...

3-11-16-4pm.jpg


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gbwillson

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Reply with quote  #17 
So at noon you were getting a temp rise of about 35 degrees, while pushing 460CFM through your collector? That's about 17,000BTU's per hour using only 250 watts of electricity for the fan. Nicely done! And this is before you tweak things and seal every thing up properly? 

Greg in MN[thumb]

mranum

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Reply with quote  #18 
Well I never ran the numbers but that sounds pretty good doesn't it. All I know is it was throwing good heat all day. [biggrin] Still need to do some more sealing yet. Getting dust in the collector from the fan.
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gbwillson

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Reply with quote  #19 
At noon your numbers looked like this:


CFM x 1.08 x TD
            or 
460(CFM) x 1.08(magic number) x 34.5(temperature difference0
            =

Roughly 17,140 BTU's per hour at the cost of only 254 watts of electricity



Here is a different calculation, but with essentially the same result:

pdf Matt's heat output.pdf     


Realize this is only a snapshot, but it is very impressive! You could slow the fan down to use a little less electricity, but at the cost of soaring collector temps. And hotter collector temps are less efficient and will lose more heat through the cool glazing. 

Greg in MN

PS[biggrin]oes anybody know where the magic number of 1.08 comes from?    

mranum

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Reply with quote  #20 
Thanks Greg! Numbers are better than I expected. [biggrin]
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