HVAC questions

[andrea3821]

My expectations may be too high, but if anyone here in HVAC could answer some questions, I'd sure appreciate it.

I just installed a trane xr13 in my home. The salesman said it would cool my house down to 70 degrees. The installers said that I should only expect 20 degree difference from outside. Can anyone let me know what I should be expecting here?

Also, the thermostat is set to be 78 while I'm at work. I came home yesterday and it was 88. This would certainly seem to back up what the installers said.

Should I really only expect to cool my house down to 90 when it's 110 outside? Seems absolutely crazy.

Any advice or direction would be appreciated.

[ntarifi dubai]

I would check the technical specs on the unit - or call a different dealer and ask them what the performance is expected to be.

Frankly - if it's 110 outside - there's no way I'd want to pay for my house to be cooled to 70

if it's 110 outside... i'm selling my house and moving somewhere cooler

I lived in Texas for 11 years, where it was routinely 96 or 98 degrees (with similar humidity levels). We didn't have any problem cooling our house down to any temperature we wanted. I'm guessing we probably had it set in the lower 70's.

[ta7]

pkbutrfli,


About 16 years ago I sold HVAC equipment. I also wrote software that allowed me to run what's called a "Manual J" heat loss/ heat gain calculation on any residential structure. Sizing cooling equipment is always a juggling act. It's almost never sized for the absolute highest temps expected. It really shouldn't be. It's sized such that it does a decent job of cooling and removes the desired amount of moisture from the inside of your home. Your furnace fan generally operates at a higher rpm during cooling. we would shoot for 400 cfm per ton of cooling capacity and expect a 19 degree drop in air temp across the cooling coil.

If the cooling unit is NOT over sized and the stat is set for a reasonable temperature then the unit will run for longer cycles and humidity will be removed from the home. An over sized unit may cool the house but the house will often be damp because the cooling cycles are too short and therefore the unit doesn't have enough time to remove humidity as it should.

If the contractor calculated the cooling load and sized your system accordingly then I would expect you to be comfortable most of the time. It's conceivable that on really hot days the system won't be able to keep up.
I would rather have that than a damp house.

Hopefully this answers some of your concerns.