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I had committed to an electric greenhouse. The only alternative in
our area is bottled gas, and open flames and pressurized tanks make
me nervous; also I didn't like the idea of a vent. Of course, electric
bills and the threat of power outages --- an all-too-common occurrence
here, at any season --- also make me nervous. Several of my home circuits
can be switched to a small generator during outages, and I suppose that's
the course I'll eventually take with the greenhouse, once my bank account
recovers.
Electricity is supplied via a (huge!) 2-gauge cable running from the
main in my house, through the attic, to the garage, out the back wall
of the garage, and through an underground conduit to the greenhouse.
| I decided to concentrate the electrical
entrails in the corner to the left of the door. Here the electrician
has just installed the circuit panel (lighter gray), and the relay
box (darker gray). Above the relay box, on the side wall, is the
controller. The relay box sends signals from the controller to the
various electric applicances, turning them on or off. For example,
at the bottom right of the relay box you can see the short, curved
line going from the relay to the motor of the intake louver. (Outside
the door is Nimrod, taking a break from hunting.) |
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About 25 years ago I replaced the old fuse-box in
my house with a circuit-breaker panel, and clearly remember the
electrician driving a 10-foot grounding rod into the ground by hand
(well, actually by sledge-hammer). So when this electrician pulled
a grounding rod out of his truck, I anticipated a gruelling task,
especially since our severe drought situation has dried out the
ground to a depth of several feet. I said as much to him, and he
laughed as he hoisted his trusty hammer-drill. By the time I had
run into the house to get my camera, the rod was more than half-way
in. |
Inside, all the wiring is enclosed within conduit,
and the connections are weatherproof. Four greenhouse systems require
electrification: 1) Overhead lighting, outlets, and water heater;
2) the HAF (horizontal air flow) fan; 3) the ventilation system;
and 4) the heaters.
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For general lighting, I decided on two 4' regular fluorescent
shop lights hung over the main aisle. One of them is offset somewhat
toward the side, so that it illuminates the work area. And I was
determined to --- for once --- have enough electric outlets, so
put two on each side wall, and one at each gable end. These are
outdoor type fixtures, and are GFI protected; part of one is seen
at the top of the next photo:
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| I used an extra piece of polycarbonate (actually,
sawed off from one of the incorrectly sized panels described in
Part 10) for mounting the controller,
seen here. In addition, a variable-speed control for the HAF
fan will be mounted on this piece, and eventually, a timer for
an HID (high-intensity discharge) light. In other words, all the
gadgets that I can adjust to control the greenhouse environment
will be grouped here. |
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The left-hand photo below shows a close-up of the controller,
which automates the ridge vent, the
exhaust fan, intake louvers, and
the heaters. It looks fearsomely complicated, but like all such
electronic creatures, it can be tamed and then loses some of its
intimidation. Different temperature schedules can be programmed
for daytime, nighttime, and a morning period in between called
"Dif." I'm not using this "Dif" stage, but
for now have set the controller for a target temperature of 55°
at night, and 65° during the day. After a prolonged period
of record-setting warmth this fall, we're finally, in December,
experiencing more normal temperatures in the 30 - 50° range;
so far, I've noticed that the controller regulates the greenhouse
temperature within ±5° of the desired point.
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| When Temp. = |
55 |
60 |
65 |
70 |
75 |
80 |
| Heater 2 |
On |
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| Heater 1 |
On |
On |
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| HAF Fan |
On |
On |
On |
On |
On |
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| Ridge vent |
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Open |
Open |
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| Intake louver 1 |
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Open |
Open |
| Intake louver 2 |
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Open |
| Exhaust fan |
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On |
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I have two electric heaters, each one capable of providing 17,065
BTU's, and requiring 240 V. They are very compact units, and I've
mounted them near the floor, at the ends of the greenhouse, kitty-corner
from each other; their air flow goes the same direction as the
current generated by the HAF fan.
As shown in the table above, one heater turns on as the temperature
drops to 60°, and then the second one at 55°. After I
gain some experience with how the greenhouse works, I may be able
to lower these limits, for economy's sake.
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Now that there's light at the end of the tunnel, on with the plumbing!
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