Padilen wrote:Our hot humid weather just broke. It's going to be about 10* cooler and less humid. Maybe I don't need AC after all
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Isn't your two weeks of summer just about over there?


Padilen wrote:Our hot humid weather just broke. It's going to be about 10* cooler and less humid. Maybe I don't need AC after all
.
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Hader wrote:"Now an AC question. I've read that AC's(window/portable) are not designed to handle more than 15-20* differential. I've read claims of 90*+ outside and 65* inside. What is truthful don't expect more than 15-20 or can 25-30 be possible? "
We had a 5k window unit that we installed in a not-so-tight 22' Hi-Lo (the roof unit was to much noise). The window unit did just fine in South Texas!
Hader wrote:"Now an AC question. I've read that AC's(window/portable) are not designed to handle more than 15-20* differential. I've read claims of 90*+ outside and 65* inside. What is truthful don't expect more than 15-20 or can 25-30 be possible? "
We had a 5k window unit that we installed in a not-so-tight 22' Hi-Lo (the roof unit was to much noise). The window unit did just fine in South Texas!
m.colley wrote:Hader wrote:"Now an AC question. I've read that AC's(window/portable) are not designed to handle more than 15-20* differential. I've read claims of 90*+ outside and 65* inside. What is truthful don't expect more than 15-20 or can 25-30 be possible? "
We had a 5k window unit that we installed in a not-so-tight 22' Hi-Lo (the roof unit was to much noise). The window unit did just fine in South Texas!
Hader,
Yes, 15-20 degree diff is common, even in site built homes per Manual J load calcs. Truthful depends on who you ask. About the only way to get a larger differential is by cutting your"heat gain" to next to nothing & keeping you humidity levels to very low levels. In AC mode, heat gain & humidity infiltration control pretty much control your differential. Thats were variable speed blowers come in. They will allow you to lower your fan speed to run a colder evaporator coil and pull off more moisture/humidity while not running so low that your evap coil freezes. Some higher end window units actually have a dehumidification mode that simulates this.
In designing HVAC systems, Manual J allows you to set your design parameters like OA temps, differentials etc. Manual J then tells you how much latent vs sensible btu's you need to achieve your design. This where the fun comes in because MOST manufacturers won't warranty equipment that is mis-matched or doesn't meet THEIR specs, so your stuck using their equipment whether it meets your needs or not.
Thursday I had to design a custom refrigeration system for a local "beverage company" that builds "on site self contained event trailers" (portable beer keg coolers". A 4x8 cargo trailer with one inch thick foamed walls, 2" foamed floor and roof sandwiched between aluminum skins. It had to be able to maintain 35 degrees inside even if its 100 degrees outside and it had to be able to run on a portable generator. Our Cooler load calc program wouldn't recognize the parameters so I had to do alot of math. It took over 3 hours and mismatching equipment from 3 different manufacturers to come up with a combination that would WORK. YES in this case it takes a 65-70 degree differential to keep that beer cold in those conditions.
Martin
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