Beat the Heat With This External A/C Controller
strip for the high voltage connections. I
then laid out the transformer and the
relay to fit. The green ground wires were
attached to the inside of the project box.
The only connections that were soldered
were the toggle switch contacts and the
connections to the transformer. All other
connections were made using crimp
terminals. Refer to Figures 4 and 5 for
views of the wiring.
After I had rechecked all of the
wiring, I put the lid on. I plugged the A/C
cord into the socket on the controller
box, I set the power switch to OFF. I set
the fan control to HI FAN and the TEMP
control to 6. I plugged the cord into a
wall socket. I then turned on the power
switch; so far, so good. I then flipped the
bypass toggle switch to ON. And
success! The A/C came on and ran
normally. Refer to Figure 6 for the
installed view. The thermostat can be
programmed for days of the week
and the weekend. It has the option for
several temperature settings for the
day. I settled on the following:
five feet away from the A/C unit and
out of the air flow. Refer to Figure 7
for a view of the thermostat. The bedroom is large being about 30’ x 15’!
The bed is located at least another 10
feet away from the thermostat. I used
a datalogging thermometer to measure the temperature at two locations:
one two inches behind the thermostat
and the other on the nightstand next
to my bed. The results exceeded my
wildest expectations. Refer to Figures
8 and 9 which show the temperatures
at the thermostat and at my bedside.
As I had mentioned earlier, details
were not provided for the components of
the controller. Part of the reason is that
such components can be hard to find to
exactly duplicate the design. And part of
the reason is that rooms and air conditioners can vary widely. You should make
adjustments to fit your situation. NV
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Rather than mounting the thermostat on the wall, I mounted it on a
heavy aluminum plate that serves as a
base. I placed the thermostat about
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❑ An aluminum project box —
6” x 4” x 4”.
❑ A relay whose A/C contacts
were rated at or about 10 amps,
with a coil voltage of 24 VAC.
❑ A sub-miniature single pole
single throw toggle switch.
❑ A power on/off switch rated at
125 VAC and 10A.
❑ A transformer for converting
line voltage to 24 VAC.
❑ A four foot A/C extension cord.
❑ An AC receptacle.
❑ Misc. hardware including wire,
terminal strips, nuts and bolts,
and crimp connectors.
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