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BubbaKlinton
@comcast.net

BubbaKlinton to scooper

Anon

to scooper

Re: one story vs two story houses - pos vs neg?

said by scooper:

When the wife and me bought this house (a 2400 sq ft singlestory contemporary),...

We have a single unit heatpump / propane furnace - a 4 ton heat pump and a similarly sized furnace in the crawlspace.

Unless you are in AZ near the Mexican border, that heat pump is WAY too big. Even there, it is too big. AC makes us feel comfortable by controlling humidity -- plus heat. You will be MUCH more comfortable at 85 degrees and 40 percent humidity than 70 degrees and 80 percent humidity.

Next time you replace the system (and that happens about every 16 years or so unless it is ground source) have a mechanical engineer look at the numbers.

It wouldn't surprise me that some previous owner got some idiot HVAC contractor to install a hugely oversized unit.

Going smaller will save you in power bills too.
scooper
join:2000-07-11
Kansas City, KS
·Google Fiber

scooper

Member

We were the ones who put this in in 1997 - the previous unit had failed. Being relative newbies to this (and not much internet about this), we took the contractor's recomendation. Next time - we'll be having a Manual J calculation done , but it wouldn't surprise me if we are a little oversized - we can hold 70 degrees inside on a 100+ degree day outside (and with NC humidity, to boot) - and we aren't running 100% duty cycle to hold 75 inside in those conditions.

djrobx
Premium Member
join:2000-05-31
Reno, NV

djrobx to BubbaKlinton

Premium Member

to BubbaKlinton

We have a single unit heatpump / propane furnace - a 4 ton heat pump and a similarly sized furnace in the crawlspace.

Unless you are in AZ near the Mexican border, that heat pump is WAY too big. Even there, it is too big. AC makes us feel comfortable by controlling humidity -- plus heat. You will be MUCH more comfortable at 85 degrees and 40 percent humidity than 70 degrees and 80 percent humidity.

I dunno. I'm in an LA suburb. It gets hot but nothing like Arizona. We have a 4 ton on our 2083 square foot 2 story. It seems to be sized pretty appropriately, it just barely keeps us cool (thermostat gets up to 78 and it runs endlessly) when it's 105+ out. Granted, it's old, so it's not as efficient as it used to be, but it's certainly not crazy oversized. Our neighbors have a slightly larger house and just put in a 5 ton unit.

Our old 3.5 ton unit installed into our 1400 square foot two story home was a bit oversized. I wouldn't go less than 3 in that house though.

BubbaKlinton
@comcast.net

BubbaKlinton

Anon

said by djrobx See Profile
dunno. I'm in an LA suburb. It gets hot but nothing like Arizona. We have a 4 ton on our 2083 square foot 2 story. It seems to be sized pretty appropriately, it just barely keeps us cool (thermostat gets up to 78 and it runs endlessly) when it's 105+ out. Granted, it's old, so it's not as efficient as it used to be, but it's certainly not crazy oversized. Our neighbors have a slightly larger house and just put in a 5 ton unit.

Our old 3.5 ton unit installed into our 1400 square foot two story home was a bit oversized. I wouldn't go less than 3 in that house though.
[/BQUOTE :

I think you need to check the freon charge in your unit.

Having your HVAC run continuously when the outside temp. is 105 is just fine. Even at 100 it is fine, and 95 is OK. You should not and can not expect more than a 30 degree drop. If it is there, the humidity will not be low enough on normal days, and you are both uncomfortable and paying far too much for electricity. You will be forced to set your thermostat FAR too low to be comfortable.

In much of Nevada, the temp. will go to even 115. MANY houses don't have AC. They use evaporative coolers. These are basically chimneys that have humidifier pads in the top, and they are kept wet. The evaporation of water cools it drastically, and that cooler air comes down the "chimney" and the air goes out either vents at the base of the walls, or out slightly open windows. Since the outside air is nearly totally dry, the "cooler" air with still dry humidity makes us comfortable. I am happy in Las Vegas at 115 when I am in the shade. It is DRY.

Dry beats cool or cold any day.

From both a comfort and energy cost standpoint you are MUCH better off with an undersized unit than an oversized unit.