Growing Spaces

[new user]

We built one of your greenhouses last year and we love it! Our kids ate a
spinach and lettuce salad in mid-January which was wonderful. We do have
one lingering question, however, about the undersoil fan. From reading all
of the literature, it seems the idea is to take hot air from the dome which
would direct it into the ducts. When we wired it up, however, it pushes
air out from the soil instead. When we tried to flip the connections, the
fan didn't work any longer. Which way is the fan actually supposed to
blow? And if it is truly supposed to be blowing into the soil, do you have
any suggestions for making that happen?

Thanks!

Amber Lancaster
YES-2-Tech Project Manager
Saint Louis Science Center

[udgar.]

Dear Amber,
Thank you for your question and I am glad to hear that you are
enjoying your growing dome. We used to have the fan wired up so that
it blew the air into the soil at the south side of the dome. However,
a solar engineer told us that the growing dome has its own natural air
circulation. The hot air rises at the south side of the dome where it
is warm, and sinks down at the north side of the dome where the water
tank is making it cool. Our early fans, he explained to us, were
fighting the natural circulation. Because the fan circulates the total
amount of air through the dome every ten minutes, the air is getting
thoroughly mixed and this way we augmenting the natural circulation. I
hope this explains what is going on.

Sincerely,
Udgar
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[joe]

Udgar:
So the fans should be on the South side of the dome? My intake is on the North and fans are on the South. I just want to make sure that is correct.
Joe

[udgar.]

Yes, the fan is on the south side of the dome and the intake(s) are on the North.
If you look at our temperature graphs,
http://www.geodesic-greenhouse-kits.com/temperature.php

you will see that the fans can put the soil temperature up by 10 degrees on a sunny day.
Enjoy
Udgar
_________________
Become the change you want to see

[DAdkins]

First of all, Thanks Amber for setting me up online & the welcome...

OK - I'm confused on this one... On the original post Amber said, "When we wired it up, however, it pushes air out from the soil instead..."

This seemed strange to me... I haven't gotten my own dome YET, so maybe this makes sense to those of you that have one... However, from the pictures that I've viewed online - it looks like located on the southern wall is a box (w/fan) - apparently that sucks the air from open pipes near the water tanks on the northern wall...

So if I understand, Amber had it wired backwards at first & I don't guess had open pipes on the north wall...??? These questions didn't seam to be answered throughout the other replies...

Secondly, I'm not an engineer, but it does seem strange sucking the cooler air from the northern side to HEAT the soil... I guess that's why originally the sub-soil airflow was reversed... I guess the natural flow out ways 'common sense'... But that's why I love these forums!

THANKS to all the info & I look forward to being a fellow partner...

[joe]

KAdkins:

Hi. I asked the same question and, if I understood it correctly, it has to do with utilizing the heat from the water tank/heat sink. At any rate, that is how I have mine wired. It is currently +3 with a wind chill of -7 and the temp in the dome (in the shade because the top is covered with snow) is +50f. The spinach looks like a forrest but the bananas are a little sallow.

I have chosen not to add supplemental heat because - well - I just have.

On a related note, I have had the dome 4.5 years and just this last month have had to replace the fan boxes and fans. I elected to use a different set-up. First, I used computer fans similar to the ones that came with the dome. I got them at the local Radio Shack, but there are probably 100 different places to get them. Maybe even a used computer store.

I removed the boxes (which were rotten) and used a black plastic sump-pump well turned upside down. Simply cut a hole out that matched the fan and mounted it inside. Now I have an indestructo housing with the fan pointed sideways instead of up (which got watered too easily). The top is flat to accomodate plants and the black helps to heat air in the body of the plastic even more before discharge back into the dome.

Hope this helps someone.