Best way to replace a central air conditioning system?
February 17, 2010 11:16 AM   Subscribe

How do I get the best out of a new central air conditioning system?

I am very close to spending a pile of money on a new central air conditioner and furnace system for my house. I have the quote and the rebate amounts, and it all seems reasonable. I'm having the work done while it's still cool, and the curent system is over 15 years old, so it's a good time to get it done. Our heating/cooling efficiently will improve, and our utility bills will drop. I even have a good feeling about the company doing the work.

I just want to make sure I'm not overlooking anything.

Have you had an air conditioner and/or furnace replaced in a home recently? Is there anything you'd have done differently? Any questions you wished you'd asked before the work began? Help me not have any regrets with this major home improvement project. Thanks!
posted by the matching mole to Home & Garden (12 answers total) 3 users marked this as a favorite
Do you need central and a furnace, or could you get by with just a heat pump? If you're doing mostly cooling and your outside temperatures don't get too cold, you may be able to skip the furnace.
posted by electroboy at 11:32 AM on February 17, 2010

Best answer: I just got central air installed in my house this summer, and you need to make sure you get a programmable thermostat (which are pretty common). That way you can set the temperature to a level where the unit won't have to do much work when you're out of the house and have it set to a comfortable temperature when you're in the house. For air conditioning, my schedule is:

6 a.m. (an hour before I wake up): 72 degrees
8:30 a.m. (not long after I leave home): 83 degrees (the house won't warm up past that, so the unit stays off)
4:30 p.m. (half hour before I get home): 72 degrees
11 p.m. (just after bedtime): 76 degrees

After everything's installed, you should also invest in super-cheap draft blockers for the doors.
posted by moviehawk at 11:38 AM on February 17, 2010

Don't forget the tax breaks (in the USA). Keep receipts for when you file.

I'd also look at a programmable thermostat. I'm looking at the white-rogers line myself, but waiting on the IRS refund to purchase.
posted by bach at 11:38 AM on February 17, 2010

IS the current system gas or oil. My parents moved from gas to oil and save a ton of money on heating costs now. Got rid of the oil tank and oil burner for a unit literally half the size.
posted by majortom1981 at 12:30 PM on February 17, 2010

I mean from oil to gas.
posted by majortom1981 at 12:31 PM on February 17, 2010

Response by poster: @all, thanks for the input. keep it coming!

@electroboy, thanks for the question. but the furnace is old, leaking, and very inefficient, so it'll be replaced.

@moviehawk, those are great suggestions about tax breaks and draft blockers.

@majortom, the system is currently gas, so I'm good on that front.
posted by the matching mole at 1:57 PM on February 17, 2010

@electroboy, thanks for the question. but the furnace is old, leaking, and very inefficient, so it'll be replaced.

I meant that you could remove it altogether. Heat pumps supply heat pretty efficiently, and since it appears that you're in Texas, you probably don't have much need for a separate heating system.

That said, heating by gas may be cheaper now, and setting aside what you think gas prices will do in the future, it's not a bad idea to have a backup. But given that the furnace part is going to run you around $1000 or so, you might want to consider going heat pump only. It shouldn't be much more expensive than just AC.
posted by electroboy at 2:07 PM on February 17, 2010

Get the most efficient system you can reasonably afford. By "reasonably" I mean do a little analysis - go with the cheapest model (which is going to be loads more efficient than your 15 y/o unit) and then compare how long it would take to make up the price difference of the more expensive models (with increased efficiency) to how long you think you're going to be in the house.

New units should come with a programmable thermostat. Try utilizing the Energy Star guidelines at a minimum.

While they're there, have the HVAC guys check your ducting for air leaks and seal them if they can.

If you don't want to do it yourself, you can have them further insulate your attic space using either blown cellulose or fiberglass batts. If you have a crawlspace you'll want to insulate that as well, along with putting down ground cover. These things will do the most to reduce your heating and cooling bills beyond the new HVAC unit.
posted by squorch at 2:14 PM on February 17, 2010

I haven't personally bought a new AC or anything but as someone with a background in Architecture and specifically the Building Envelope system you definately want to consider checking ALL your windows and doors (including attic and basement access) for air leaks. You would be surprised how much money the average person could save on heating and cooling just by caulking their windows or (if you wanted to take on a whole other project afterward) replacing them with new better insulated windows. There is no point in spending hundreds or thousands on an amazing system if all your hard work is going to go straight out the window (pun not actually intended, but I like it)

With the whole sustainability movement in architecture there are more and more companies who specialize in home energy audits these days. If you do a quick search you will likely find lots of information on this. They will tell you exactly how to optimize the heating and cooling in your house.
posted by LZel at 2:28 PM on February 17, 2010

Changing windows might be good while you are at it. My parents changed out a huge single pane window with 2 half sized tripple pained windows (both together equaling the size of the old one) and it made a huge difference.
posted by majortom1981 at 3:12 PM on February 17, 2010

Best answer: I have in the past year installed new central heat and air in one house and just replaced the furnace in my rental.

Make sure the company gives you a reasonable warranty; parts and labor should be 3 years, and get all of the paperwork. Make sure the warranty is transferable should you sell the house or the company gets bought out by a competitor.

Have the guy doing the installation show you how to do all of the following:

1. Check the drain pan to ensure it's level at least once or twice a year, once preferably before you start using the a/c regularly; you don't want it tipping or rusting and forming a hole, because then condensation can drip out onto the sheet rock below, which will weaken the ceiling (and you'll end up with a pile of sheet rock caving in somewhere like the top of your car in the middle of the night in the garage, like I did).

2. Have them show you which breakers are connected to the a/c unit and the furnace in case you need to check something, including how to safely remove the cover and check the condenser coils for rust, and at least once check the fan motor and blades to make sure they are level and not moving around enough to hit each other and bend/dislodge anything inside the casing of the a/c unit

3. Get a quote and recommendation on frequency of service, i.e., checking your ducts for leaks, adding freon and what the costs would be for regular service vs. emergency services (nights, weekends and holidays) and of course have those numbers handy.

4. At least once a year, if you have an outside A/C unit, have them come and clean out the vents for dust, leaves, etc. (You can clean the unit yourself by removing the top section's screws and blowing out debris with a pressurized hose from the inside out). However, they can also clean the debris out with an enzyme cleaner, which is far more effective and less difficult.

5. Make sure dust and dead bugs, etc. don't pile up around the furnace, it could cause a fire hazard.

6. I'd go for at least a 15 seer unit; a 23 seer unit is probably the most seasonally efficient thing you can buy, and it's a huge investment upfront, but it'll cut your bills massively if you live in an area where you run the a/c 6-9 months out of the year (which is common in Texas).

Of course change your air filters every 30-60 days too. If your a/c suddenly is blowing, but NOT COOLING, it could be overheated and the condenser coils will have ice on them if this is the case. If you suspect this is happening, turn the a/c off. Throw the breaker. Climb up into the attic, take the casing off like they showed you, and check for ice on the condenser coils. If they're frozen over, leave everything off for two hours (go to the movies or the titty bar where it'll be REAL cold). Come back, make sure the ice is gone, put the cover back on and turn the a/c back on. It should work OK and cool down after about two more hours.

The best way to avoid overheating the unit when it's hot as hell outside is the programmable thermostat + not going below 72 degrees during the day. If you can bear it, leave it on 78; 76 is where I set mine and it worked okay.

In addition to my experience with pricing, buying and watching the units being installed and serviced (both the original ones and the upgraded replacement units), my stepfather worked in HVAC both residentially and commercially for 15+ years so I do know a little about this stuff ($3500-$7000 sounds like a massive amount of money until your bills during both seasons are cut in half for a few years, and yes, definitely write it off on your taxes!).

Good luck!
posted by Unicorn on the cob at 7:27 PM on February 18, 2010 [1 favorite]

Response by poster: Thanks for all the excellent info and advice, folks. I've got a 16 SEER unit on its way and am confident I'll get the best out of it.
posted by the matching mole at 4:03 PM on February 20, 2010

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