On Wednesday, June 18, 2014 4:39:03 PM UTC-4, rangerssuck wrote:
On Wednesday, June 18, 2014 4:15:38 PM UTC-4, mike wrote:

On 6/18/2014 9:00 AM, rangerssuck wrote:



My house is about 90 years old, a ~1500 sq foot three bedroom colonial. I'm in Northern NJ, and it's getting pretty hot outside. I currently have not enough window units to keep the whole house cool, and I'm thinking it's time to do something.







I've had three AC people in to make their sales pitch. what they have offered (and all of the pretty similar in price is:







a)Split system to just do the first floor (18000 BTU). Outside unit in back yard under the window that now has the big AC, inside unit on living room wall. A couple of fans as needed. ~$3500 (minus $500 state rebate)







b) Same as A, but with a second inside unit in the ONE bedroom (30,000 BTU). ~$5500 (no rebate)







d) Same as C but with a third inside unit to hit a second bedroom (40,000 BTU). $8000







d) Central system (3.5 ton). Outside unit in same place, inside unit in attic, ductwork in 3 upstairs closets, vent in EVERY room first & second floor, return in upstairs hall. ~$7500. 1 year parts & labor, 10 years parts warranty.







I'm at a loss as to which is the right thing to do. Assuming I can afford any of these (I can), what would be the relative advantages/disadvantages of each? How about the relative cost of operation?







Thanks - I want to get this done ASAP, because my other option is to move to Antarctica.







I think you'll regret NOT doing the whole house.



I think so, too. But I'm concerned about the cost of operation. The guy yesterday said that with the mini split, you could let the house heat up quite a bit, turn it on and the room would be cool in a half hour or so. With the whole house deal, he said that if you let the house heat up, it could take hours to cool off the house to 74 or so. So he recommends that you set the thermostat to 80 when going out. So, that gets me thinking about energy usage.



In reality, I work at home, so I'm here most of the day, but only in one or two rooms.

I don't think there isn't anything magic about one system cooling the house faster than the other. And I would think 3.5 tons in a 1500 sq ft house
is going to cool it off pretty quickly, unless it's poorly insulated, has
a lot of sun exposure through windows, etc. I can't imagine it taking hours.
And just an hour can already make a big difference in the perceived temp,
because it takes out the humidity. Sometimes I put on my system because
it's 75, but it's too humid. In just 20 mins or so, you can feel a difference
in the humidity.

There is a difference though in energy usage if you just cool one or two
rooms with a mini-split or cool the whole house.

The good news is that these systems are a lot more efficient than they
were 20 years ago. A 14 SEER system on a 1500 sq ft house shouldn't
cost that much to run. You can keep the house at 76, and with the
reduction in humidity, I find it quite comfortable. I think the difference
in electric cost isn't going to be that great, and if you make a decision
based on that, it would be a mistake. Plus in NJ, it's only going to
be used substantially for 3 months of the year.

BTW, in comparing those systems capacities, one ton is 12K BTUs.