One unit or two? That is is the question (Air Conditioner)

[theonlyski 3]

billeisele

I have 2800 sq feet, 2 story. Monthly bill is $129. The units are properly sized. The neighbors house is almost identical. Their bill is $300+. The units were "upsized" because more is better BS. Normalize these 2 houses to account for variables, thermostat setting, lifestyle, etc., and his bill is about 70% higher.

I think that my Nest thermostat has paid for itself. https://nest.com/

It was very easy to set up and once you set it, you can forget about it. Forget to turn your AC to away mode going out of town? Do it from the airport, too easy.

My last month's power bill was $91.61 for a 1500 sqft house in central Florida that I keep chilly at night and I have a bunch of electronics on all the time.

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[billeisele 122]

JerryBaumchen

Hi bill,

Quote

HVAC guy in the house

I like learning from you type of guys.

On 'Ask This Old House' this evening on PBS they had some guy who a previous contractor had put a 4-ton unit in his house, which was either 1300 ft or 1500 ft.

The 'Old House' guy said that his unit was way too large for the size of house and it kept freezing up. So they tore it out & put a new 3-ton unit in.

From the small amount of studying that I have done on heat-pumps and/or a/c units; in an a/c unit you usually do not have to upgrade the ductwork if your heating system is something like nat. gas or oil. However, if you're using a heat-pump for heating, then you should upsize the ductwork. Heat-pumps move the heated air at a slower velocity than the heated air from systems such as nat. gas or oil. They need to move a larger volume of air at a slower velocity vs other systems.

JerryBaumchen

Mr Jerry - unit sizing is site specific, weather conditions make a big difference, that type house in SC would be 2 - 2.5 tons, assuming normal % of windows and good construction, if it was an old leaky house then the first steps would be to stop the leaks, insulate and ventilate

the duct work should be sized for the equipment being installed, long discussion of this in my reply to John

not sure about your description on duct sizing based on the type of system, bottom line is you don't want a draft especially in heating, if the heat pump is delivering 100 degree air and it is blowing on you it will feel cold, natural gas heating delivering 115 degree air will also feel cold because of room air mixing

what I didn't talk about too much is the quality of the installation, we're seeing a lot of flex duct poorly installed, it is supposed to be stretched out, and hung with minimal sag

for anyone having work done I'd put in the contract that the unit sizing and duct work to be designed and installed following ACCA Manual J & D and the manufacturers recommendations

after the installation is done ask for the Manual J load calculations and the duct design (for your file), when they don't have it say Breach of Contract, and let the fun begin

a little more info on my house, I'm the second owner, prior owners were a retired couple, I did some "energy efficiency" work, some repair work on the duct system and installed properly sized the units, with 4 people in the house the bill went down about 40%

Give one city to the thugs so they can all live together. I vote for Chicago where they have strict gun laws.

[Krip 2]

Great job HVAC dude

If I might make one suggestion add a clause in the contract that the installation of the ductwork has to pass a inspection specified third party so and so.

The inspections can be done for free if you live in the right
art of the country. John Mitchell if you want to know the peeps send me a pm and I can put you in touch with our electrical coop guy.

He knows the peeps that do the free inspections. The fly by night contractors hate those guys. You might have a problem finding a contractor willing to sign
the contract.

Some county inspectors are sharper than others. You may try Bates tech school and see if they have a hvac program. Who ever you choose to do the inspection they need to be listed in the contract.

One Jump Wonder