Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
PSA
Member Login

Site Notices
Posted: 4/30/2011 7:35:57 PM EDT
I have bought a 16X10 wood framed portable building for a shop.

I am insulating it with R30



I am wanting a small AC unit that I intend to mount in the wall, not the window.

given that the space is only 160 square feet and insulated well, would a 5000 BTU AC keep it cool even in Texas?



I was looking at the specs on some and most of those pull under 5 amps running which would not cost alot to operate at all.




Link Posted: 4/30/2011 7:49:33 PM EDT
I think I'd go with 10,000 just to be sure.  It would allow the unit to kick off once in a while and not work so hard.

BTW: I'm not a HVAC guy, I could be off by 11,000 BTUs either way.  I do, however, prefer to overdo things, rather than wish I'd bought the next size bigger.
Link Posted: 4/30/2011 8:00:30 PM EDT
I know about overkill, I usually build things that way.  But I want to keep the electricity bill in check as well




Link Posted: 4/30/2011 8:00:50 PM EDT
Originally Posted By skunk-ape:
given that the space is only 160 square feet and insulated well, would a 5000 BTU AC keep it cool even in Texas?


According to the chart at this website, looks like it would come pretty close to doing the job.

I was looking at the specs on some and most of those pull under 5 amps running which would not cost alot to operate at all.


Going with a bigger unit means that the compressor won't be running as much - which means that the operating costs may not be any higher than with a small unit that runs all the time.
Link Posted: 4/30/2011 8:06:48 PM EDT



Originally Posted By Skibane:



Originally Posted By skunk-ape:

given that the space is only 160 square feet and insulated well, would a 5000 BTU AC keep it cool even in Texas?




According to the chart at this website, looks like it would come pretty close to doing the job.




I was looking at the specs on some and most of those pull under 5 amps running which would not cost alot to operate at all.




Going with a bigger unit means that the compressor won't be running as much - which means that the operating costs may not be any higher than with a small unit that runs all the time.


man, big difference from 5000 to 6000

I have a chance to get a pretty nice 4 yr old 10,000 BTU unit from a friend for a good price, but I think that would be a waste



 
Link Posted: 4/30/2011 8:14:00 PM EDT
Sizing based on area alone usually only applies to conventional construction, meaning vented attic space, vapor barriers an common walls with like living spaces.



A shed will have much higher humidity gain, leading to considerably more latent heat issues.  Since all 4 walls and ceiling will be hot, there is no insulation which will stop this heat gain, R30 only slows the heat gain.  And without ventilation, the temperature difference (gradient) will be much higher, leading to decreased insulation performance.



Now a 5000 Btu unit will function fine as a dehumidifier.  But it will be significantly under sized.
Link Posted: 4/30/2011 8:16:39 PM EDT
Originally Posted By skunk-ape:
I have a chance to get a pretty nice 4 yr old 10,000 BTU unit from a friend for a good price, but I think that would be a waste


If it runs 50 percent of time to produce the same amount of cooling as a 5,000 BTU unit that runs 100 percent of the time, the electricity costs of both units are likely to be almost identical - in which case your used 10,000 BTU unit might turn out be a bargain.
Link Posted: 4/30/2011 8:17:10 PM EDT



Originally Posted By Keith_J:


Sizing based on area alone usually only applies to conventional construction, meaning vented attic space, vapor barriers an common walls with like living spaces.



A shed will have much higher humidity gain, leading to considerably more latent heat issues.  Since all 4 walls and ceiling will be hot, there is no insulation which will stop this heat gain, R30 only slows the heat gain.  And without ventilation, the temperature difference (gradient) will be much higher, leading to decreased insulation performance.



Now a 5000 Btu unit will function fine as a dehumidifier.  But it will be significantly under sized.


wow, thanks Keith... should I try and vent the building somehow?

one good thing is the building is shielded from the afternoon sun by a tree canopy

I guess I am going to look at that 10K unit then



 
Link Posted: 4/30/2011 8:38:09 PM EDT



Originally Posted By skunk-ape:





Originally Posted By Keith_J:

Sizing based on area alone usually only applies to conventional construction, meaning vented attic space, vapor barriers an common walls with like living spaces.



A shed will have much higher humidity gain, leading to considerably more latent heat issues.  Since all 4 walls and ceiling will be hot, there is no insulation which will stop this heat gain, R30 only slows the heat gain.  And without ventilation, the temperature difference (gradient) will be much higher, leading to decreased insulation performance.



Now a 5000 Btu unit will function fine as a dehumidifier.  But it will be significantly under sized.


wow, thanks Keith... should I try and vent the building somehow?

one good thing is the building is shielded from the afternoon sun by a tree canopy

I guess I am going to look at that 10K unit then

 


Shade helps a lot.  Windows hurt the other way, especially when they are aluminum framed single pane.  Massive heat gain through those.  If you are in a more humid part of the state, the 10k is a better deal, it will run on a lower duty cycle as Skibane stated, resulting in an identical energy load.  But that 5k will likely last only a few years before the compressor dies from overwork.
 
Link Posted: 4/30/2011 8:43:11 PM EDT
For a room that small I would say that would be fine. you don't want to over size the unit, that is just about as bad as under sizing it, if you over size it will cycle off before removing the humidity in the air. Here's you a link to check out.

Linky.

Link Posted: 5/1/2011 4:24:19 AM EDT
Well, I need to decide what to do.



I can get a 5000 BTU unit just about anywhere for $100-125  or I can get the nice used 10,000 BTU used one for about $50-$75

The used one is in a buddy's workshop and is only a few years old.  It only was used when he was in the shop so the hours on it should not be too high. It is a window unit and I hope the cabinet is small because I am going to mount this in the wall of my shop and not the window.  



I guess I need to be shopping for an 8000 BTU unit instead of a 5000 and make the comparison between that and the used one.

At this point, I am figuring the 5000 will be over worked.



I will only run this when I am in the shop during the summer, but if I end up using it for food storage as well, I don't want it getting 90 plus degrees in there and hurting my food supply.  So I might leave it on the high setting to just maintain a 85-90 degree temp



BTW, Keith I live 3 hours west of DFW, so humidity is relatively low here.
Top Top