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Why
are inches inches? Miles miles?
I think it all has to do with an arbitrary edict issued by
a pharaoh, long, long ago, about the length of his knuckles
or some such. Is that really how “standards” get
started? The same conclusions could be drawn about much of
the way we approach greenhouse engineering these days. Though
not quite as exotic as measuring ancient pharaoh’s
body parts, we in the horticultural engineering community
have conspired to create such nonsensical “rules of
thumb” on our own. Case in point— here is why
we have settled on 3/4" tubes (or the metric equivalent)
on
12" centers for greenhouse floor heating.
So much of what we do in our daily lives is the result
of “myth and legend”, we plod away not questioning
the “whys” behind the things we do. A little
reality check and rudimentary analysis from time to time
are healthy, don’t you agree? Some might say, “heck
if it ain’t broke, don’t fix it.” You
know what? That’s what Henry Ford said about the
Model T. He made more than 14 million of them, and found
great success in doing so, but in the end, his refusal
to change his car allowed his competitors to catch up.
| Converse to
what you might think, here are the facts:
Fact 1: In a 1 acre greenhouse
1/2" tubing, placed on 9" centers,
can transfer 12.3% more energy.
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| Fact 2: In a 1 acre greenhouse
1/2" tubing, placed on 9" centers, will
have 41% less water volume.
Cost: 1/2" tubing, placed on
9" centers, should cost only 3.1% more
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Startling Facts about Greenhouse Floor Heating Revealed!
Well, in the scheme of things, this may not really qualify
as “startling”.
I mean we are dealing with a pretty mundane subject here. Or are we? Do you
realize that fuel efficiency and heating system response can have a huge effect
on your bottom line? Making good decisions about the way you outfit and equip
your greenhouse now will have far-reaching effects on the profitability of
your operation for it’s entire economic life.
A wise man once said, “The devil is in the details”. That statement
gives a very concise and eloquent view of the importance really “small” things
have in the process of specifying the environment systems for your greenhouse.
Ok, enough lofty stuff. Here’s the bottom line:
1/2" floor heat tubing may work better for you than
3/4"!
The limitations come about in the form of maximum length.
For best efficiency, 1/2” tubing is limited to floor
areas of 250’ long or less, but that’s a healthy
500’ round trip or “loop length” and
should be fine for most projects.
One Grower’s Experience:
A grower with probably more experience with heated floors
than practically anyone is Bill Swanekamp of Kube-Pak.
A large plug and finished crop producer
in Allentown, NJ. Besides being excellent growers, this is one of the best
run businesses around. Just ask anyone familiar with Kube-Pak and they will
remark about how this operation is a model of efficiency on many fronts. Bill
did his first 1/2" tubing on 9" centers floor about 8 years ago
and hasn’t looked back since. It’s become the standard at this
operation.
Bill reports that the heating response at the floor level
is quicker and that the actual tempertures measured across
the surface are more even. It works. It costs pretty much
the same, and it can make your facility
more efficient. Pretty hard to find fault with that.
Next time you plan a floor heat installation, give 1/2"
tubing on 9" centers
a thought. Even though it’s a little “non-standard”, it could
be a good investment for you!
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