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A/C in a small observatory

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#1 nimitz69

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Posted 07 August 2019 - 07:41 PM

I’m in the process of building a small (8’ x 8’) observatory in my backyard.  Since I live in central Florida I plan to install a small floor unit air conditioner which we have left over after putting in an automatic, whole home, auto switchover Generac system.  I also plan to include insulation to help keep the unit from running 24/7 in the summer.  I’ll probably set it to something like 85 deg.

 

so, for those of you who have an a/c unit in your observatory what things do I need to concern myself with as I move forward with the design/build?  My construction log is here:

https://www.cloudyni...nstruction-log/



#2 DuncanM

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Posted 07 August 2019 - 07:56 PM

You might consider using a radiant barrier rather than insulation, because the insulation retains heats and re-radiates it:

 

https://www.amazon.c...B/dp/B00B1HG2NA

 

https://www.energy.g...adiant-barriers

 

 

Also you don't want the observatory cooler than your expected first viewing temperature.



#3 John Fitzgerald

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Posted 07 August 2019 - 08:34 PM

I have this vent fan in my 8 foot Exploradome:

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

It's in this duct:

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

This fan changes the air about 20-25 times an hour in the dome and keeps it at or close to ambient.  It's only 47 watts, on a thermostat set at about 82 degrees.

 

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#4 nimitz69

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Posted 08 August 2019 - 10:01 AM

john-  what are you tops in the summer?  It can be in the 90s here during the summer which would put it easily over 100 degs without some sort of system ...  that would certainly be less electrical use than an a/c unit assuming It could keep temps where I need them to be.



#5 John Fitzgerald

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Posted 08 August 2019 - 10:04 AM

john-  what are you tops in the summer?  It can be in the 90s here during the summer which would put it easily over 100 degs without some sort of system ...  that would certainly be less electrical use than an a/c unit assuming It could keep temps where I need them to be.

The record high here is about 110, but most summers top out at about 96-100, for a few hours in the afternoon, on several days, with dew points between 72-80.


Edited by John Fitzgerald, 08 August 2019 - 10:05 AM.


#6 nimitz69

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Posted 08 August 2019 - 10:05 AM

We have a radiant barrier installed in our house so yeah, i think that’s  probably a better idea



#7 nimitz69

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Posted 08 August 2019 - 10:09 AM

The record high here is about 110, but most summers top out at about 96-100, for a few hours in the afternoon, on several days, with dew points between 72-80.

Thx!  sounds Somewhat similar to here..  what’s your humidity like? The upside of a/c is it deals with The humidity., albeit at a cost ...

 

so anytime the temp hits 82 degs the fan comes on?


Edited by nimitz69, 08 August 2019 - 10:15 AM.

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#8 John Fitzgerald

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Posted 08 August 2019 - 10:19 AM

Humidity is high, but usually only a problem at night.  On nights when I am not using the observatory, a 40 watt bulb comes on about dark under the cover draped over the scope, and stays on until about sunrise.  This controls humidity.  Humidity is not a problem unless it results in condensation.  Our temps drop usually into the upper to mid 60s at night in the summer, much more than yours do.   Heavy dew forms nearly every night, even if it is only partly clear.  Our elevation is about 1,225 feet MSL.  Fans sure are a lot cheaper to run than A/C.  I hope this helps.



#9 nimitz69

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Posted 08 August 2019 - 04:40 PM

Thx.  My 14” Dob stays assembled in my garage under a Gizmo cover & I put a small heating wand under the cover and haven’t noticed any condensation issues



#10 John Fitzgerald

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Posted 08 August 2019 - 09:35 PM

Thx.  My 14” Dob stays assembled in my garage under a Gizmo cover & I put a small heating wand under the cover and haven’t noticed any condensation issues

Is your heating wand a terrarium heater or a "gun cabinet" heater?  Does it have an "on indicator" LED?  I've always used incandescent bulbs for heat because I can tell instantly if they are on or not, but they do tend to attract flying insects at times.



#11 macdonjh

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Posted 09 August 2019 - 08:01 AM

nimitz69, you said the A/C you plan to use is a floor unit, I guess that means the whole thing will be inside your observatory. You will need a hose to the outside for the condensate to drain through.

Also, if it is really an A/C and not a dehumidifier, you'll need some duct to the outside for the hot air from the condenser coil to escape through.
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#12 DeanS

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Posted 09 August 2019 - 08:13 AM

I have a small window unit in my warm room, I run it on a timer.  I set it to run depending on temps outside.  I leave the door from warm room open into the scope room and a fan to circulate the air.  I do the same in the winter with a small radiant heater.  The idea is to keep the scopes at about whatever the evening temps will be so that scopes are already cooled down, or warmed up in the summer ;)

 

I tried just the radiant barrier in the roof but it was not enough.  I ended up using some 1" foam panels between the rafters/joist and that has helped keep the heat out.  My walls are not insulated in the scope room, only in the warm room.

 

This system has worked well for over 10 years.  Cost is minimal, perhaps $20-30 per month.

 

Dean



#13 nimitz69

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Posted 09 August 2019 - 11:14 AM

Is your heating wand a terrarium heater or a "gun cabinet" heater?  Does it have an "on indicator" LED?  I've always used incandescent bulbs for heat because I can tell instantly if they are on or not, but they do tend to attract flying insects at times.

It’s not an aquarium heater but I don’t remember it being called a gun cabinet heater either .... its just a metal wand with no LED indicator.  Been using it for over a year without issue



#14 nimitz69

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Posted 09 August 2019 - 11:17 AM

nimitz69, you said the A/C you plan to use is a floor unit, I guess that means the whole thing will be inside your observatory. You will need a hose to the outside for the condensate to drain through.

Also, if it is really an A/C and not a dehumidifier, you'll need some duct to the outside for the hot air from the condenser coil to escape through.

Agreed.    It comes with all Those Items & we’ve set It Up before so I’m familiar with that aspect of the unit.  It actually has 2 modes: dehumidifier or a/c



#15 nimitz69

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Posted 09 August 2019 - 11:23 AM

I have a small window unit in my warm room, I run it on a timer.  I set it to run depending on temps outside.  I leave the door from warm room open into the scope room and a fan to circulate the air.  I do the same in the winter with a small radiant heater.  The idea is to keep the scopes at about whatever the evening temps will be so that scopes are already cooled down, or warmed up in the summer wink.gif

 

I tried just the radiant barrier in the roof but it was not enough.  I ended up using some 1" foam panels between the rafters/joist and that has helped keep the heat out.  My walls are not insulated in the scope room, only in the warm room.

 

This system has worked well for over 10 years.  Cost is minimal, perhaps $20-30 per month.

 

Dean

Thx.  I’ll probably do both types of insulation as well.  I’ll also probably install the recirc fan mentioned earlier and then set the a/c to come on only if inside temps bust some upper limit so the a/c isn’t running all the time. No heater required here as temps rarely drop below 50 deg in winter at night ...



#16 macdonjh

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Posted 10 August 2019 - 07:12 AM

Agreed. It comes with all Those Items & we’ve set It Up before so I’m familiar with that aspect of the unit. It actually has 2 modes: dehumidifier or a/c


Then you are good to go. Good luck.

#17 andrew.abrah

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Posted 24 May 2021 - 01:46 PM

What a great idea you have, I also always dreamed about building my own observatory. I wish you good look and hope all your plan will become a reality. I always had problems with high temperatures, as I am a super sensitive person and I have health problems like blood pressure. My mother told me to try airconservicing.org, she was hoping this can help me.  And I really liked this service. But now I think about moving into another country, I am a bit scared because I can lose my work, but my family sustains my idea and I feel very motivated. I hope my plan will become reality soon, because I think the change of climate would help me.


Edited by andrew.abrah, 24 May 2021 - 01:47 PM.


#18 GrandadCast

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Posted 24 May 2021 - 11:17 PM

I went with a large A/C unit, fully insulated walls R13, R13 floor, and love it. Going into the observatory for me is not just for nights. The heck with sweating while I play inside. If metal roof then keep a gap between the metal and ceiling insulation to allow venting. I will be adding another layer of foam, the pink 1" board to the ceiling just to make it a bit better. Also I can paint the pink board and it is tough stuff so unlike the current insulated foam board which is too brittle to handle pokes. I like the dry feeling too. Not as humid as your location. Cactus grows here so it's dry and 1330 feet. But I still can feel it. I keep it at 80 when not inside the observatory and 70 when inside during the day. If I plan to image that night I put the temp to what my imaging time outside will be for two or three hours before sunset.

 

Jess


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#19 Christopher Erickson

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Posted 25 May 2021 - 01:29 AM

NEVER use an aquarium heater out of water.

 

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