Cooling a detached garage in Houston, TX – Problems?????
I have 600 sq ft insulated detached garage that I am having trouble getting adequate cooling. I use it as a woodworking workshop and find working in 85+ degree heat unbearable. Drip marks on my projects etc etc etc… The garage is exposed to the sun most of the day. In Houston we have many many days over 90 degrees.
I have a 3 ton (yes, 3 ton) large portable air conditioning unit (Air Rover) in the garage. I had the unit serviced and everything is in proper working order. These air units are mainly used for spot cooling in large computer rooms and data centers. I have an electronic thermostat on the unit which is functioning fine as well.
I insulated the garage, drywalled it and put in a ceiling creating an attic space. The ceiling is insulated as well. I also insulated the double garage door. Since the attic air gets extemely hot in the summer I added quite a few extra soffit vents to go along with the ridge vent at the top of the garage itself.
The air unit is large enough that I should be wearing icicles when I am in the garage. For instance my home has two 3.5 air units that cools 3700 sq ft of space adequately. This 3 ton unit should be overkill for my 600 sq ft garage. Why am I not brrrrr’ing???????
For instance yesterday the air temp outside was approx 90 degrees. With running the air unit for a number of hours I could only get the temp down in the garage to 80 degrees. Meanwhile my home was a comfortable 70 degrees.
I am trying to figure out if I have air unit set up correctly or there might be a pressure problem??? Maybe I need evacuate some air from the garage to the garage attic and forcing the air out of the garage attic with an electronic vent system so that I reduce the extremely hot air from the attic space which might be having an effect on the garage workspace itself.
On the air unit I have the air intake (16″ diameter input) taking air from the top of the garage workspace and vent the hot air outside via a 16″ exhaust. The cold air has 3 (6 inch) ports that I blow into the garage workspace. It has a 30amp 240v motor which intakes and blows a huge amount of air. Should I be taking the input air from the garage workspace or should I be taking it from outside or even from the garage attic? I have had conflicting opinions on this.
I also thought about putting a fan in the ceiling to blow garage workspace air into the attic and then use an electronic vent to blow the hot air out of the attic. This would work in conjunction with how I am running the air unit. I do not wan to try this approach until I get some solid advice in terms what might work.
I know I can get a qualifed air expert to my property but I am trying to figure this out. Once I have the proper advice I can do all the work myself
Sweating and confused in Texas!!!!!!
Any help would be appreciated.
Replies
Recirculate
Rob,
You need to recirculate the air from the shop through the package unit so it is not trying to cool 90 degree air. Just like the unit in your house does. You don't say what kind of insulation but if it's fiberglass a radiant barrier would help.
Three ton package unit cools my 1500 foot shop with very little insulation.
KK
recirculate
I am recirculating the air from the shop through the air unit and blowing cold air back into shop and exhausting the hot air outside. logic being that I am conditioning already conditioned air which means the air unit will not work as hard. Someone suggested I needed to bring the air from outside but my feeling is that then I would constantly be trying to condition 90 degree air.
I am using fiberglass insulation between the studs on the walls and ceiling of the garage. I cannot remember the r value but it was the highest I could get from one of the big box stores.
Regards
Get yourself a humidity gauge.
In houston the humidy is very high and generally is always high.
Again, I am currently drawing all the air from inside the shop and none from the outside unless it is leaking in through porous garage doors etc...... I vent the exhaust outside. I also have run a tube to the outside where the water flows during the dehumindification process. It appears to be drawing humidity from the air as there is a constant water flow as one would expect.
I vent the exhaust outside.
What are you venting? If you are venting exhaust air outside, it has to be made up by something, like hot moisture laden air from outside.
okay. 1st order of business is a humidity gauge. I will monitor how the humidity changes/drops when I run the air unit.
I might have to invest in a dehumidifier assuming one can work quickly and efficiently enough to make a difference to ease the load on the air unit.
thanks for the responses.
Regards
The dehumidifier won't really work any better/less expensively than the AC. It's basically just an AC with the hot and cold sides connected.
What might help is painting all that new drywall -- drywall is like a giant sponge, and lets off A LOT of moisture, especially when "fresh". A coat of paint (maybe VB paint) would cut the amount of humidity getting into the air. (The concrete floor likely also contributes a lot, BTW.)
Contact their customer support.
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Call us toll free: 1-800-858-6287
customer support.
okay. I will.....
thanks again.
I think the customer support will be better than the opinions of the last 10 or so hangers on on this forum. I tried to find installation manuals online, but striked out.
The condenser has to be vented both to/from the outside! You can duct it to the unit, or you can 'open a door' so to speak, but you have to provide air to it if you exhaust air from it. How long are your exhaust ducts? Minimize the 'supply' and 'exhaust' ducts to/from the condenser, so you're not impacting your load from them also.
Sounds like maybe minimal supply air ports ... 3 ducts 6" diam doesn't seem like much for what did you say ... 3 tons? I'd say a total of 18" square would be more like it. What's the size of the coil/discharge of the unit? You shouldn't restrict that.
Ideally, you should have your compressor and condenser outside ... otherwise all that heat is making life heck for you.
Without the proper setup, you are spinning your wheels and not getting anywhere. You say it's a spot computer unit, but if you don't set it up right, it really won't work well. Remember, you're using it differently than it was intended, so something isn't right. One possible problem w/ a spot cooling unit is that it may be dumping waste heat into the space surrounding the computer. Normally a data center application will use a split DX cooling system where the compressor and condenser are outside.
Problem solved !!!!
It appears that the problem is now solved. We will wait and see during todays hot hours.
Taking your suggestion and also phoning Air Rover technical support I have to bring the input air from either the outside or the attic space and not from the shop itself. Basically what I was doing was taking the air conditioned air and dumping it to the outside. My logic was that I would air condition already air conditioned air which would make the unit more efficient. I was wrong!!!! This was clearly due to a lack of understanding of the air conditioning process and how this unit works.
The preference is to bring the air from the outside and not from the attic as that air temp is lower. Due to my garage organization the easiest way was to bring the air from the attic getting is as close as I can to a ridge vent.
It worked like a charm. Basically dropped the garage temp from 87 degrees to 75 degrees withing approx 20 min.
I will run the unit today to see how it handles 90 degree heat of houston. Air inside the garage is usually 6-8 degrees warmer than the outside air due to radiant heat from a car etc in the garage. Since I am pulling attic space air which will probably be around 120 or more we will see how efficient the air unit is. If it struggles to keep up I will find a way to bring the air in directly from the outside.
Many thanks for all the input. Without this forum I would probably still be scratching my head.
I am also attaching a picture of the final setup. You can see from the ductwork that air comes in from the attic and vents to the outside wall. Previously I was just bringing the input air from the shop.
I would not pull air from the attic.
By pulling air from your attic you will decrease the efficiency by blowing hotter air over the condensor. Also you will be pulling a lot of humid air into the attic, which could be a problem. I'm happy it's working for you.
okay
Okay. I will pull the air from the outside. This clearly will make it more efficient.
Thanks for the feedback.
Personally, I'd lose the flex ducts as much as possible. Looking at your pic, you could lose all of that using standard hard duct and adjustable elbows (assuming you can get them that large). But that's a detail. The intake from the attic is pretty straight, but the exhaust through the wall is a bad bend, dude. Restricted air flow will affect your efficiency. You could take your intake through the roof if you didn't mind a roof penetration.