I'm moving into a house with no A/C in a few weeks and am in dire need of A/C education. The room will be 10x12 and will have an excessive amount of electronics producing heat.

From the last thread: http://www.thewolfweb.com/message_topic.aspx?topic=594532 I learned that more BTU's=better. From what I understand, it's easier to cool a medium sized room with a portable unit.

Any thoughts or suggestions?

7/6/2010 12:06:09 PM

jchill2

7/6/2010 12:16:04 PM

Quote :

"I learned that more BTU's=better"

What you should have learned is that more BTU's=bigger (ie more cooling) which is not necessarily better.

As I stated in the other thread, if you buy a unit that is too large it will be inefficient: it will be cycling on and off a lot and will not control the humidity well in the space.

First, lets get some good information to help you properly size a unit. Is this 10x12 room the only room you are concerned with cooling? (The way I am reading it, I am guessing you are renting a room in a house?). Will it be just you renting/sleeping in this room? What do you consider an excessive amount of electronics and what kind of electronics? How often are they running all together vs standby etc.?

[Edited on July 6, 2010 at 12:21 PM. Reason : ]

7/6/2010 12:18:23 PM

I'm assuming that central air is not an option here. If you can't get a small window unit, something like this will do:



You'll need to run the drain hose somewhere.

Check prices here (they vary widely):

http://tinyurl.com/5obbgv

7/6/2010 12:22:32 PM

If you don't necessarily need a portable unit buy this one http://www.google.com/products/catalog?hl=en&q=Frigidaire+FAA055P7A&cid=4516913300157145338&ei=tFwzTOaFG4_03QS0oeyuCA&sa=title&ved=0CAcQ8wIwADgA#scoring=p. I just got it for my medium sized room and it works like a charm. It has the best reviews of any air conditioner as well as energy efficiency rating.

7/6/2010 12:43:27 PM

If you're using a window unit just find a good quality unit that is sized appropriately for the room size. No rocket science here

7/6/2010 1:33:10 PM

if this is a home you own, get yourself a mitsubishi ductless mini split-unit.

7/6/2010 3:45:47 PM

I have a Haier 7,000 BTU portable unit that I bought last summer to use in my pop-up camper at Hatteras for 11 days. It has not been used anymore since, basically brand new. The model is CPRB07XC7-E if you want to look it up. I wrapped the exhaust pipe that goes to the window with fiberglass insulation to increase efficiency. Comes with a remote. 115V

I'll sell it for $225.



[Edited on July 6, 2010 at 3:49 PM. Reason : pic]

7/6/2010 3:48:22 PM

i just bought this

http://www.newegg.com/Product/Product.aspx?Item=N82E16896808031

7/6/2010 6:08:53 PM

Quote :

"First, lets get some good information to help you properly size a unit. Is this 10x12 room the only room you are concerned with cooling?"

Yes, and i'm renting for at least a year.

Quote :

"Will it be just you renting/sleeping in this room?"

Yes

Quote :

"What do you consider an excessive amount of electronics and what kind of electronics? How often are they running all together vs standby etc.?"

I don't put things on standby, I just turn them off.
24/7:
500W Home Server with an efficient CPU, PSU, and 6x HDDs with high activity
Router, 16x Switch, Modem
When I'm home (in the evenings):
Gaming PC with two large monitors, turned off most of the day
DLP HDTV, 5 Floorstanding Speakers, SVS Sub, Onkyo receiver, with either ps3 or 360

Quote :

"i just bought this http://www.newegg.com/Product/Product.aspx?Item=N82E16896808031"

How is it? That was actually the one I was looking at when I made this thread.

7/6/2010 7:04:04 PM

I would say that if you are only trying to cool one room that is 10x12 that a 10,000 BTU unit would be too large. I'm not sure where you live but normally I would say you could get by with a 6000 BTU unit easy in a room that is 120 ft2 even on a west facing wall in an older house (just making some conservative assumptions, I don't know where your house is or it's condition etc.). Now you have talked about the electronics and I don't have numbers off the top of my head to assume for those but I would say a 7500 BTU unit would be more enough (ie probably too large still) for that space.

I don't do any sort of residential stuff and I don't know what the humidity is like where you are at, but like I stated before, you don't want to get one that is too large because of the inefficient cycling and handling of dehumidification.

Keep in mind that the 10,000 BTU unit that ThatGoodLock used is being used for a 1000 ft2 apartment if I remember correctly.

[Edited on July 6, 2010 at 8:37 PM. Reason : ]

7/6/2010 8:33:33 PM

If it is a single bedroom with double-pane windows and no major leaks, like a missing door, then any unit will do fine in 100+ weather. I have a 5000 BTU window unit and it can keep our entire house comfortable on a sub-90 degree day if I give it a head start (our central AC broke a few years back).

But what has been linked in this thread are portable units, which often don't have an outdoor air intake, which means their cooling success fades as the temperature of the air sucked into the room increases, because the hot air being pulled into the room is not much cooler than the hot air going out the exhaust.

If you can help it, get a unit with a separate intake, such as a window unit. With a separate intake.

My window unit drew 550watts when operating at a outdoor/indoor temperature spread of 84/74. At a higher spread of 94/74 later in the same day, the power draw grew to 640watts when operating. At the higher spread, the inside vent temperature drop fell measurably, but it seems to me that most of the entropy losses were serviced by the power company, not by reduced cooling capacity, a trick a portable unit without a separate outdoor air intake could never manage. To put it another way, when the temperature rises, a unit with an outdoor air intake just works harder, a cheap portable unit just drowns.

7/7/2010 12:56:31 AM

no A/C unit for a home has an outdoor air intake. Portable as well as window mount units intake indoor air, cool it, and blow it out. The hot air created in the process of cooling is vented outside with both units.

7/7/2010 1:37:29 AM

holy fuck. its 3am and i'm covered in sweat. I'm in a third story apartment built in the 1900s in Boston and we hit 100 degrees today, 8 year high.

Time for a god damn air conditioner.

7/7/2010 3:24:25 AM

Yeah I would have bought a unit as soon as I moved in...regardless of it being Boston.

7/7/2010 9:54:17 AM

^^^ Not true. Many portable units take cool air from the room and use it to cool the condenser coil, heating it up, then exhaust it out the window. This creates a negative pressure in the room, sucking hot air from outside, inside. With a dual-pipe portable or any window unit, the air outside stays outside, only hotter, and the air inside stays inside, only colder.

7/7/2010 1:50:41 PM

the negative pressure created by a single hose design is pretty minimal. In the end the energy consumption is going to be pretty comparable due to the dual hose design being less efficient from the start since the available "cooling" air is hotter. The dual hose design utilizes two separate fans as well instead of one that requires power to run.

In the end it is pretty much a wash.

7/7/2010 2:49:50 PM

7/7/2010 2:55:05 PM

here is a BTU/h calculator on this page.

http://www.mini-split.com/index.html

7/7/2010 5:04:03 PM

^I think that sizer is only to match to a model and the smallest model attached to that calc is a 9000 BTU/H unit.

-I did some really rough and super conservative sizing and came up with 8,500 BTU/h (ie no way should he need or buy anything bigger than this or even as big as this)
-Most your rule of thumb stuff for residential dwellings would probably tell you about 3,000 BTU/h but doesn't take into account a lot of electronics in a small space
-I went in the middle earlier stating 6,000 since I didn't feel like actually figuring out loads for equipment and what was off or on and worst case scenario.

Result? You should be more than fine with a 5000-6000 BTU/h unit like LoneSnark and I suggested assuming you live in Raleigh, don't have a ton of poorly insulated direct-sun glass or poor envelope insulation etc.

[Edited on July 7, 2010 at 6:16 PM. Reason : ]

7/7/2010 6:04:09 PM

I think some of you are making this way more complicated than it needs to be. Just sayin'.

7/7/2010 6:14:00 PM

Well for one room yea, it isn't really a big deal. But when I see the size units some contractor's put on houses it is just silly. People oversize stuff all the time thinking "more BTUs is better..we'll make sure we have them covered" without really thinking about it and then they leave the homeowner with a unit that cycles on and off all the time, not properly dehumidifying, and leaving big temperature gradients in the house. But yea, with one room it isn't as big of a deal but can still lead to higher energy costs and a less comfortable environment. It can also shorten the lifespan of a unit.

Once again, I don't do any residential or commercial stuff for my job but the same ideas apply.

[Edited on July 7, 2010 at 6:25 PM. Reason : ]

7/7/2010 6:21:51 PM

Quote :

"People oversize stuff all the time thinking "more BTUs is better..we'll make sure we have them covered" without really thinking about it and then they leave the homeowner with a unit that cycles on and off all the time, not properly dehumidifying, and leaving big temperature gradients in the house."

This is true.

7/7/2010 6:41:19 PM

I'm going to get the latest Consumer Reports from a friend, as it has a listing of the best window units for the money. The room isn't in direct sunlight nor does it have large windows on multiple walls. I'll go with a 6,500-8,500 BTU model, as recommended.

7/7/2010 6:55:10 PM

wtf? We use 9k heat pumps (specifically Friedrich PDH09 PTACs) in sunrooms under 200 sq. ft. with full glass walls on 3 sides and solid roof. I can't imagine you would need anything approaching that for a 120 sq. ft. stick-built room unless you're running a few servers, plasmas, etc. in there.

*edit* to clarify, I don't know anything about hvac other than what we use, thus the "wtf?" statement. Are portable/window units just that much more inefficient or are people recommending serious overkill?

[Edited on July 9, 2010 at 9:39 PM. Reason : .]

7/9/2010 9:34:40 PM