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Garage_Hermit

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Reply with quote  #31 
@mattie

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What would be really nice here is to set up remote monitoring of the system, from a webpage that you could check from a smartphone or laptop


Nice idea, Mattie !

I have started a new thread HERE... http://simplysolar.supporttopics.com/post/home-automation-6817854?pid=1282053757#post1282053757

G_H

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JoeK

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Reply with quote  #32 
I can't remember where but I've seen setups that transmitted via wifi and could be monitored real time from any location with internet.
This unit has a serial plug that I think is now obsolete on newer computers.  You can get USB adapters or whatever you need to accommodate.  I believe you just plug it in to a laptop and pull the data off, then clear it for the next monitoring cycle. I hope it's that easy anyway. Would be so smooth to set up some kind of transmission for remote monitoring, but I don't have the knowhow for that. Nor the time to learnhow.  It's gonna have to suffice to just pull the data every so often for now.

I hooked up the 12",12V, radiator fan today and tested it out in the system. Results were excellent.  Even though I took a lot of airspeed measurements they are hard to translate to actual airlfow since the laminar effect is pronounced and its difficult to determine the average airspeed in the duct/plenum accurately.  The fan was clearly not having any trouble with static pressure though. I think the plenums are sufficient it doesn't seem to affect the fan performance at all as far as I can tell.  I did not detect much difference in airflow between pushing with the fan or pulling. Neither subjectively nor with the anemometer. I think the rated airflow of 1400CFM is in the right ballpark, likely 1000-1200CFM at least.  Without a doubt this fan alone could be slowed down and still easily handle the circulation needs for this application, but I'll probably just make the outtake plenum for the 16" fan anyway since I've already got the fan and I need to make a plenum regardless.  I still need a 12" fan for the exhaust vent too so that will be good.  I may not bother with two fans just for the SHCS as previously considering. Unless they are tuned just right I think the weaker fan might just interfere with the other, and stress one or both motors. A measure of redundancy/security would be nice, but seems an unnecessary cost at this point.  I may test it out with two fans still though just to see how it does.  If there doesn't seem to be interference issues I could always pick up another 12" fan after all.

I did the testing sort of late in the afternoon after it got a bit cloudy, so the intake temps were between 46-50*, air exiting the system was a steady 39.2*F with hardly any variation. RH In was ~27-30% and coming out ~38-50%. I think the RH would stabilize too but it was the first time running air through and there was definitely some musty moisture hanging out down there.  The longest I ran the fan at once was probably 5-10 min. Even though the charger was set at 2A trickle charge there was not any noticeable draining/diminishing of power.  Volts at the battery terminals were reading 12.66 and measured at the fan connectors 12.38

SHCS and exhaust fans both will definitely be regulated to run at lower velocity. At full power the 12" fan, ducted as shown, makes a sound very much like a vacuum cleaner, but much quieter. I'd say less than half the noise of a regular domestic/shop vac.
3-23-14fantest2.jpg

Garage_Hermit

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Reply with quote  #33 
Hi, Joe,

Nice reading, glad U R getting set up !

Quote:
Unless they are tuned just right I think the weaker fan might just interfere with the other, and stress one or both motors.


Sounds good - I recently read (somewhere ?) that if U use two fans in series, they should be the same rating / same type, for exactly this reason.

Just looking at your stack, it looks very near the roof -- I guess this is intentional to intake the warmest air. However, it also looks very near the bulkhead  -- I am wondering if you won't get some system effect there ?
Just a thought.

G_H


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ChrisJ

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Reply with quote  #34 
http://www.welserver.com/intro.htm

This system is used a lot on ground source heat pumps.

Are you looking to control things via WiFi? or just monitor?

Chris 



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mattie

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Reply with quote  #35 
Hello Joe
You mention
"RH in was ~27-30% and coming out ~
38-50%. I think the RH would stabilize too but it was the first time running air through and there was definitely some musty moisture hanging out down there."

I can hear what your saying here and perhaps its just a process of
cycling the system over time to allow the greenhouse and the SHCS to stabilize.

Could this also point to the system was working well and that some energy has been taken on by the subsoil? With the dry bulb temperature higher inside the greenhouse
the RH or ratio is greater ,could this point to why the percentage is the lower value of 27-30% at the input?

The RH out percentage at the output
is higher because the airs capacity to store water vapor has been reduced(energy released) hence the higher value of 38-50%?

Just a thought,it will be best to run a few more tests to see if this is a repeatable result.
Regards Mattie
JoeK

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Reply with quote  #36 
GH, Seems there is plenty of clearance for the duct to avoid any issues of flow restriction. Was there some other sort of system effect in mind? Yes it is intentionally high up there for warmest intake, and because the preformed 4ft section was just the right length...

Chris, thanks for the link that looks like a great monitoring system.  I'm not actually looking to do anything via wifi on this just now. Certainly not in the budget at this time. The datalogging will just have to be downloaded with a wire for a while.

Mattie, et al. the soil is certainly taking on energy that's clear enough from the temp drop. And simply lowering the temperature DOES in fact raise the RH. As you state this is because colder air has a lower saturation point for water vapor. Thus colder air containing the same amount of water vapor would be at a higher RELATIVE humidity than warm air of equivalent moisture content. That's relative humidity in a nutshell sort of as I understand. It is a measure of how close to saturation with water vapor the air is. no vapor=0%, saturation =100%.

However I think the RH readings in this case were subject to greater influence by stagnant moisture underground. I don't think the temp drop of 10*F would result in that great a change in RH.  It was clear that the first blast of air was displacing some musty, humid air that had been stagnant down in the system.  I think the soil moisture is greater than the dry air aboveground and the air was actually picking up moisture from the system.

This is the OPPOSITE of what you would hope for during successful operation. BUT that's because during normal operation the aboveground air in a greenhouse with growing plants would become very humid and warm. The greenhouse currently is missing a bunch of windows and a portion of wall, and has no plants either so in the case of my test the air aboveground was fairly cold and dry, just a bit warmer than atmospheric.  The main reason for the test was to ensure the fan could provide sufficient airflow.

IF the air I pumped under were 80*F and 70-80%RH (common conditions in the sunspace garden) then it would have reached dewpoint underground, and water vapor would condense to liquid. That would lower the RH more significantly than the lowering temperature naturally raises it. Thus the air would return from the system cooler, and drier than when it entered the system. Though it might still read 40-50%RH, that will be much lower than the intake.
Because warm air can hold much more vapor than cold air the dewpoint should easily be reached underground as the air cools and the vapor readily condense out. This is very desirable.
mattie

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Reply with quote  #37 
Thanks Joe
Looks like its simply a case of getting the greenhouse enclosed and running the system again when conditions are better.Is there a number of cycles or an average time period with newly installed systems before they reach stability or ideal operating conditions(Tell those plants to grow faster [smile] )
Thanks again for all the answers its great watching how this develops.
Regards Mattie
Garage_Hermit

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Reply with quote  #38 
Joe, if U R creating moisure underground, how do you drain it off ?

I am asking because I have the same problem with my very modest KW (Kitchen Window) ground loop:operational view.jpg

The way I have been handling it, is to remove the ventilation (curved) standipipe, and soak it up wth a sponge - the maximum I have seen is 1 cm of water in there -- around a couple of liters I guess.

I designed the system this way, it is not perfect, but for the other method I really wanted - in-ground drain to a soakaway - I was not fully confident that it was a good idea...
========
regarding system effect, I posted on this previous, citing: http://ateam.lbl.gov/Design-Guide/DGHtm/ductworksystemeffect.htm

This bit in particular bought my eye:

"provide uniform straight flow conditions at the fan inlet and outlet"

because I was in the process of designing an UN-UNIFORM intake for myself !

Anyhow, great to hear about your system tests, keep the info coming , I am riding on your shirt-tails !

G_H

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JoeK

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Reply with quote  #39 
Mattie, I don't know what a typical time is for conditions to stabilize. I think with the fan running the humidity would sort itself out in a couple days, though it will always fluctuate some based on many factors. I think the subsoil should warm up in 2-3 wks since we're getting into warm sunny days and nights are rarely below 20*F anymore.  That's simply speculation though.

GH, The top of the duct stack is ~7" or so on the left side of the pic, nearest the curve of the glazing.  I think it is open enough on the whole to provide virtually unobstructed flow. Probably a slight system effect, but only very slight if not negligible.  The plenum in that picture is actually two barrels tall, so plenty sufficient to avoid effect there, and the 4ft duct length above the fan seems to be working great.  Thanks for mentioning it and including that link as it has led to some rethinking of the outtake plenum and fan arrangement. I may end up sticking with a 12" fan, since it is totally sufficient and easily ducted without significant system effect to speak of.  Seems a bit more difficult to arrange the 16" fan so easily. still looking at options.
As for draining off water there is no need. The black drain pipes are perforated and will allow water to drain out into the subsoil. I think the bottom layer of pipes might lose much of that water to downward percolation into the sub-sub soil (technical term).  Generally though the water is simply absorbed back into the soil and can achieve a significant measure of water recycling, especially with some perennial plants rooting down below the first foot or two of topsoil, they will be able to help bring the water up closer to the surface.  Capillary action should bring some water up on its own as well. Once the plants get growing I think that even if most of the roots lie in the top 1-2ft of soil the drawing effect will pull water up from the deeper soil layer.  I believe the top layer of pipes lies ~2.5ft below the surface, with the second layer ~1ft lower.

Priority is still getting the structure fully enclosed...
Garage_Hermit

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Reply with quote  #40 
Thanks, Joe !

I sure do learn something every day, on this site !

So when I get the chance, I will perforate my in-ground pipe after all (my echiums (echia ?) ill do the rest, therefore [cool]
[echium_1]

cheers,

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
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