Cooling a small sealed room

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Old 06-21-17, 01:44 PM
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Cooling a small sealed room

I have a 500 Cu Ft room that is inside my garage. When the door is shut it is perfectly sealed (no cracks). I purchased a small 8000 BTU portable air conditioner to cool the room. I would like it to be at least 80 degrees or cooler. The garage can get up to 95 degrees. I purchased a vinyl curtain with magnets to keep it closed and I made an opening in the bottom of the vinyl for the 5 inch vent to exhaust air out. But when I turned the unit on it creates a vacuum that causes the magnets to not hold and thus the hot garage air is being pulled into the room and it it won't cool down. So I thought I would cut an opening in the sheet rock to vent the air back into the garage and then just keep the wooden door closed. Since it is a sealed room will that cause a problem? Do I need a small opening to let some air into the room? If so, how small is enough so I don't have too much of the 95 degree air coming in which seems like it would defeat what I am trying to do. Any advice would be appreciated.
 
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Old 06-21-17, 02:54 PM
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Bet you bought a one hose model not a two hose model. A two hose model won't give you that problem. The one hose units exhaust the room air outside through the single hose to cool the condenser coil. It is inefficient as you can guess because it blows the cold air out and draws hot air in. In the two hose model the second hose brings in outside air to cool the condenser so you don't get the vacuum.
 
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Old 06-21-17, 03:32 PM
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Yes, I bought a one hose model. I did not realize there were other models to choose from. If one hose models don't work, why would they sell them? If I return it and buy a two hose model I'm not sure how that would work? If the two hoses both go to the garage which is 95 degrees seems like the hose that is pulling air into the unit will be pulling hotter air in then what is going out.
 
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Old 06-21-17, 04:20 PM
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The air being drawn into and discharged out of the hoses has nothing to do with air in the room. It's simply intake and exhaust for the condenser.
It's still not very efficient or a great performer but they are better then the single hose models.
 
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Old 06-22-17, 08:08 AM
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I am still trying to understand if what I purchased will work. I was hoping someone on this forum could help me. If single hose air conditioners do not work, why are they being sold? That makes no sense to me.
 
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Old 06-22-17, 08:48 AM
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They are sold because they are cheap and easy for people to setup. Remember, stores sell what they can sell and make money. What's best isn't always what sells best. People want cheap and easy.

If you are handy you can convert your single hose to a double hose. First you need to identify the grills on your unit. Two will be sucking air in and one blows air out. Build a plenum box around the air inlet for the condenser coil. This is the inlet that exhausts it's air outside. Then attach a large flexible hose to the plenum and run it to the outside. That way the air used to cool the condenser coils gets sucked in from outside. Heated by the coils and exhausted back outside.
 
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Old 06-22-17, 11:00 AM
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Dane,
Thanks! I identified the opening from the owner's manual that says "Condenser". So I will try making the plenum box and see how well it works.
 
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Old 06-22-17, 01:21 PM
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I made my first using a cardboard box duct taped to the AC with 6" flex duct. It worked so well I came back and made a more permanent plenum box out of vinyl siding trim stock (aluminum) that I riveted and caulked to the the AC and re-used the duct.
 
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Old 07-12-17, 12:08 PM
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Still having problems....
I was able to return the single hose model and get money back. I then bought a dual hose model (Whynter 14,000 BTU). The room is 8' x 9'. I ran tests and the problem I noticed was that when the room got to 72 degrees the humidity started going up (ranged from 64% to 83%). So I went out and bought a small dehumidifier (Hisense 35 Pint model). I set the the humidity for 50% and it gets the humidity where I want it but now the AC doesn't seem to be keeping the temp where I want it. It was keeping it about 75 degrees and now its up to 79 degrees even though I have it set for 70 degrees. I still have some leakage into the room thru crack in the plastic door I installed. Not sure why the AC isn't doing what it should.
 
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Old 07-12-17, 01:11 PM
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A dehumidifier is a small A/C unit in which the evaporator and condenser coils are both in the same package. With a split A/C, the condenser is outside where it transfers the heat from inside the house (via the evaporator & blower) and expels it to the outside air. Since the dehumidifier has both coils in the same package, it actually is heating the room since it's not 100% efficient. An A/C unit, if properly sized, will both cool and dehumidify the air. That 14,000 BTU unit is much too large for the space in which you are using it, which is why it's not taking the moisture out of the air as well as you would like it to.
 
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Old 07-12-17, 01:49 PM
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Try setting the dehumidifier up higher.... maybe to 60 percent.
The heat from the dehumidifier should help to keep the A/C running.
 
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Old 07-13-17, 04:20 AM
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Bob,
Thanks, I understand your comment about cooling and dehumidifying. But the problem I was having when I just had the AC unit by itself was that it appeared it would gt the temperature to the setting I put in on the control panel (75 degrees) and my temperature and humidity gauge in the room showed that it de this and the humidity was low around 60% but then as I monitored the gauge the humidity slowly started to rise to over 80% in less than 10 minutes. I assume what was happening was the AC unit switched automatically to fan mode once the temperature I set was reached and then once in fan mode it wasn't removing humidity from the room. I want to store my books in this room and I need a stable humidity setting.
 
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Old 07-13-17, 04:24 AM
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Ok. I will try that. But I am trying to get this room ready to store about thirty boxes of books. I was told humidity should be around 50% for book storage. I am Ok with tempreature around 78 degrees or lower but I just want these values (Temp & Humidity) to be somewhat stable and not any wild fluctuations.
 
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Old 07-13-17, 04:54 AM
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If you need humidity control more than temperature control, then you will need a humidifier in conjunction with an A/C unit. As you have found, to control humidity, the unit needs to run almost full time. Long "off times" allow the humidity to creep back up. That's why having an oversized A/C unit is bad for getting the humidity down. It cools the room so quickly that it doesn't run sufficiently long enough to reduce the humidity significantly.

A combination of dehumidifier to maintain a fairly consistent humidity and an A/C unit to control temperature should give you what you want. However, since the dehumidifier adds additional heat to the room, you may need to get a larger A/C unit to get the temperature down to where you want it.
 
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Old 07-13-17, 05:22 AM
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For book storage is temperature your primary concern? I would expect humidity is the key for storage and in that case a dehumidifier would be your best choice.

The first step for an environmentally controlled room would be to properly vapor seal your room. If it's just wood or sheetrock walls, even with insulation you may have a significant amount of moisture/humidity that can enter the room independent of temperature. This will especially be an issue in winter when the room may never warm to where an air conditioner needs to turn on.

If you want to absolutely control both temperature and humidity I think you need something more complex than just a standard air conditioner and/or dehumidifier. You might get close for the warmer part of the year with a properly sized air conditioner which has already been pointed out. Simply going for a big AC is not the answer as you've already found out. You specifically want an AC that has to run a significant amount of the time which for your size room will be about the smallest you can buy.
 
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Old 07-13-17, 05:25 AM
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Bob, Thanks for the input. But I am stuck with the unit I bought (14,000 BTU) as it was the smallest I could find that had the dual hoses as everyone previously told me I needed. So I now have both the Dehumidifier rated at 35 pints per day and the AC unit. I just need to find a way for them to operate together in the same room. The dehumidifier appears to do what it is advertised to do (set a Humidity and keep it there). I just need to figure out why the AC unit is no longer doing what it is supposed to do. So it sounds like even though I have a small room (9x10) the heat from the dehumidifier is more than the AC can handle and I may need to accept a higher temperature. Like I said previously the room is completely sealed with a wood door and is located inside a large garage. Right now I have a plastic door with magnets to easily get into the room but even with the dual hose AC unit I still have a vacuum pulling in hot air from the garage. At some point I plan to cut an opening in the sheet rock to vent the AC hoses but I first wanted to see if I could get both the units working together.
 
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Old 07-14-17, 03:45 AM
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You are trying to create a museum like environment on a shoe string budget.
The air conditioner you have is simply too big as has been said.
Air conditioners designed for this purpose are very closely matched to the size of the load and have specialized controls to be able to control humidity and temperature.

Being closely sized to the room, the ability to control fan speed to control capacity and an electric heater element to be able to give the air conditioner a load when it needs de-humidification but not cooling is what it takes.

A key element of the preservation of documents and objects is stability.
Having your books in an uncontrolled environment will not always be in the correct temp/humidity range but it would less harmful than one that fluctuates as much as an ineffective system.

Even with environmental control your books should not be in boxes.
They need to be placed upright on shelves with space around them for air circulation.
 
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Old 07-14-17, 04:35 AM
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Greg,
Thanks for your reply. Let me explain a little more... This is an attempt to offset the cost of storage at an off site location at $109/month. We plan to move to east coast in about 18 months where I will have room for all the books within a house. We are temporarily in an apartment. I have a very large garage and within it is this small storage room. There is no way I can vent the AC unit to outside air. It can only go to the interior of the garage. My experiments so far indicate that in order to get the temperature where I want it I am going to have to abandon the idea of the plastic door with magnets since its letting too much hot and humid air back into the room. That means cutting thru the sheet rock and keeping the wooden door closed which will completely make the room air tight. If I do that I will need to repair the opening before we move out which will be an expense. I just hate to go to the trouble of cutting the opening for the hoses and then find out that it still will not work. So if you are certain that the AC unit along with the 35 pint/day dehumidifier will not work please advise and I will not waste any more time trying to do this.
 
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Old 07-14-17, 08:00 AM
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If you have a facility that can provide a proper storage conditions for that kind of money I would jump at it.
Even if you can cobble somethig together you would not likely spend the money to do it.
Like I said.......leaving your books without any temperature control is more stable and better for the books than a poorly operating system.

This is how museum curators and archivists handle HVAC problems.

Can you give us a clue as to what you might have?
 
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