Hello Folks,
Since the good people on these forums have been of great help in the past, lets see what insight can be garnered now. 🙂
I live in a 2-story home on top of a daylight basement. The AC/Heat for the first and second floors are zoned. Specifically, the 2nd floor cooling has a 3-ton unit while the 1st floor has a 2-ton unit. This was told to me by an HVAC person at my home today.
The HVAC person was at my home today to fix a leak in a freon line, at a weld location, for the 2nd floor zoned unit. This was warranty work so it was at no-charge to me. Thank you!
Anyway, during a part of our general conversation, this individual stated that in Georgia and during the Summer months the best someone could expect from a correctly-sized heat pump was a 17-18 degree (F) differential to the temperature outside when it got over 90-F.
Yesterday, it got to 93-F in my neighborhood, which means the correctly-sized unit would only be ‘expected’ (capable?) of cooling down the zone by 17 degrees F, and I should not expect the unit to be able to cool it further (below) than (93 – 17 = 76)F.
I was surprised at this, but also understood that my home being new construction almost certainly came with a builder that sized the unit to minimum specification or allowance in order to minimize building costs (and maximize their profits), but I would hope that if it got to 100F outside I could expect a unit more capable of getting the temperature on the 2nd floor down to 80F or below.
So, what do all of you think? Should I take his statement with a grain of salt, take it as gospel, or … ?
Replies
You should take his statement as that of someone who does not know how an air conditioning system (or probably any HVAC equipment) is sized. The design conditions inside and out must be taken into account, as well as the building construction, color, exposure, occupancy, etc.. Whether the outside design temp is 110 or 90, the system should be sized to cool the inside to 75 degF and 50% relative humidity (normal conditions for comfort). You think in Pheonix that would find an indoor temperature of 92 degrees accptable on a 110 degree day? NOT. A lot of (most?) builders and HVAC installer/contractors should, but seldom actually run load calculations to size systems properly, but just guess, or worse, oversize the equipment at a waste of money (yours) and energy (i.e. more of your moneey).
The summer design conditions for Geoergia, BTW, range from 93 to 97. If your AC won't cool your house to 75 on any day less than 100 (which would be what I would design to), it's not sized correctly. On the other hand, on that 100 degree day, a properly sized AC unit/system should run continuosly.