Re: [GBlist] oversz air/heat unit?

["David Porter" <dporter@porterarchitects.com>]

> Just got off the phone with a  aircondition/heat contractor to set up
>      an appt. for an estimate  to install  air/heat.
> He said off the top of his head that  I would need a   2 or 2.5 ton
> unit.
>
> Alarms went off in my head cause i know  you are suppose to put
> some effort into   " sizing" the unit correctly;  especially in my
> humid climate.
>
>  My question is,  how  can I make sure he is selling me the correct
> size unit?     any advice would be helpful.

The one misnomer about A/C that I can tell you about is do not oversize the
unit.  Even in the air conditioning capital of the US here in South Florida,
I get clients all of the time who tell me to bump up the A/C unit size that
I specify by 1/2 ton.  If anything, you want to slightly undersize the unit.
An A/C unit, to be most effective at dehumidifying, which is what it is
really meant to do, needs to run a lot.  An oversized unit will kick on for
brief periods, quickly cool down the interior and trip the thermostat off.
It hasn't run long enough to dehumidify the interior.  Our bodies are more
attuned to uncomfortable humidity conditions than we are to temperature.

By accurately sizing or slightly undersizing the A/C unit, it runs for a
longer period of time, thus allowing the system to dehumidify the space as
best possible.

And, I wouldn't hold it against an A/C contractor who might tell you that
you need a 2 or a 2 1/2 ton A/C unit over the phone.  Unless you have an
unusual house of all glass, sizing from one "typical" house to another is
really determined a lot by SF and volume.  Yes, solar orientation does play
a role in the exact sizing of a unit but most experienced A/C contractors
can tell you from experience what size your house will need.

David Porter AIA
Palm Beach Gardens, FL USA
dporter@porterarchitects.com
www.porterarchitects.com




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