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SkyShed POD Air Conditioner Installation
Posted: 22 June 2017
Updated: 29 June 2017

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In late June 2017 southern Arizona experienced an extended heat wave with ambient air temperatures near and above 110°F for several hours in the daytime here in Oracle (elevation 4350'). This resulted in temperatures over 130°F inside my observatory. Such high temperatures had never been seen before in the previous almost 8 years of use. I decided it was time to install an air conditioner inside the SkyShed POD. I purchased a Frigidaire 8,000 BTU Portable Air Conditioner (~$300) from a nearby Best Buy store.

On Thursday, 22 June 2017, I went to the observatory about sunrise (0520 MST) to install the AC unit in one of the SkyShed POD bays. I went out so early to get started on the project before the current heat wave made it too hot to work outside.

Here is the AC unit and my tools outside of the observatory before I began the work:

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I unboxed the air conditioner, plugged it into the observatory power, and did a quick check that the unit worked. As expected it worked fine.

I then removed a shelf unit from one bay and reconfigured it so that it would fit next to the AC unit. I moved another shelf unit to the bay just vacated. Next, I moved the AC unit into the now empty bay to check the position where I would make the hole for the hot air duct. I removed the AC unit from the bay and drilled out a large hole in the bay wall for the duct. Here is the resulting hole, seen from the inside and outside:

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0800 MST: finished making the hole. The outside air temperature was 98°F.

I used a bay for the AC unit that was partially under the POD Zenith Table (PZT) and made the hole high on the bay wall so that the PZT table would provide some protection from rain for the duct opening on the outside.

I added an extra screen with a finer mesh to the duct to keep critters out:

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With the hole now made the supplied duct was connected to the AC unit and the AC unit moved into the bay. It was placed on a small piece of wood (the unit has castors so a flat surface was needed). Then the duct was routed to the hole:

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I then cut the supplied "window sliding kit" to be the length I wanted and mounted it to the exterior bay wall:

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The bottom photo shows the duct closed to provide additional protection from rain and snow. The closed position will only be used when the AC is not needed.

1006 MST: installation of the air conditioner was completed. I turned the unit on and left it set for 72°F. Wow, did that feel good! The outside air temperature was 105°F.

By this time and with the heat, I was too pooped to continue working in the observatory and seal the duct opening. I would finish those later in the day. I put my tools away.

1150 MST: closed the observatory with the AC running.

1426 MST: returned to the observatory to check on the "cooling". The AC was running. The outside air temperature was 108°F and the inside temperature was 102°F. That's about 30 degrees cooler than it would have been without the AC.

1810 MST: went back to the observatory to finish up the installation. The outside air temperature was 99°F. I added sealant on both the inside and outside of the hot air duct hole. I then set up the shelf next to the AC unit with the observatory clock, shortwave radio receiver, and some other items. That completed the installation.

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The last thing I did was to set the AC temperature to 85° to avoid the unit running all night long during this heat wave as the minimum outside air temperature currently would get down to 80°F.

I am glad I installed an air conditioner in Cassiopeia Observatory. It will really help with this new hotter trend in southern Arizona.

Update 29 June 2017

At the recommendation of SkyShed Observatories I purchased a 20' section of 3/4" backer rod ($7) from Home Depot:

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The backer rod is pushed into the narrow air gap between the top of the POD walls and the bottom of the dome, as seen in these photos:

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It only took a couple of minutes to insert the rod all the way around the dome.

The purpose of the rod is to keep the cooled air inside of the observatory. Otherwise, the air conditioner will be overworking trying to cool down the entire neighborhood.

One 20' section was enough to go almost entirely around the dome circumference. Since the rod had to go over the dome brackets and lock knobs, as seen in the photos above, there was a 3" wide gap not filled by the rod at the end of the rod, as well as the open gaps at the brackets and knobs. Cutting the rod into smaller sections would likely eliminate all of these gaps. I may do that eventually.

So did the backer rod improve the cooling inside the POD or reduce the workload on the AC? Hard to say on either. Certainly the theory behind using the backer rod is sound: keep the cool air inside. I will continue to monitor temperatures this summer to see if I can determine any specifics.


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Copyright ©2017 Michael L. Weasner / mweasner@me.com
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