Replacing home A/C unit ?

[fishrdan]

For the HVAC guru's, I have a couple questions about replacing our old home AC unit. It's a combo AC / gas heat, roof mounted model, not sure of the manufacturer as it doesn't say. Our house is just under of 1700 sqft, 2 story, old windows that are leak air like a sieve. We are located in Las Vegas, NV.

- What brands of AC units are good, bad, "best bang for the buck"
- Any specific features to look for, 2 speed?
- Best SEER rating, purchase price VS cost savings (14?)
- What would the SEER rating be for our old 1984 or 1988 AC unit
- Does a 3 ton unit sound appropriate (survey will be done)
- Anything I need to ask the installation company before buying
- What should I avoid, in concern to the installation company
- I'm probably going to pay cash, would this affect the purchase price, negotiating?
- Realistically, how much should we save by installing a 14 SEER (August AC bill is around $225, $325 total electric bill)

This old unit is still working well, though over the years many things have been replaced; blower motor, several condenser motors, caps. Last year it stopped cooling well so I pulled all the panels off and found the evaporator coil about 50% plugged. After cleaning it's been working much better. (When we bough this house, ex-rental, there was no house filter, so that would explain the plugged coil.) Right now the compressor relay sticks from time to time, it's on the to-do list, but I have a feeling we are on borrowed time with this old unit.

The local utility is starting an AC rebate program and I want to see if I can get our old AC unit replaced before it dies. I don't have any details on the program as it hasn't started yet, not sure if this is even going to be a factor in buying the unit... $100 Woo Hoo

Thanks, Dan

 

[Cofe]

Re: Replacing home A/C unit ?

I would personally recommend a Trane AC unit that is energy efficient enough to write off on taxes. If your windows are leaking, replace them with energy efficient windows and also write them off on taxes. Newer AC systems use a lot less power than before. And with a combination of replacing your AC and windows, you could pay for the total system in a few years savings on electricity. I overrated my SEER rating on my AC on my last upgrade, and the AC keeps up easily.
Living in Nevada, it should be dryer there most of the time. So I do not think that upgrading the SEER rating will matter that much in your climate. Also call around to the installers in the area and get quotes before you decide what to do.

 

[lncoop]

Re: Replacing home A/C unit ?

Cofe, to what extent did you exceed your SEER rating? I'd like to hear your thoughts on that since I too am close to having to do something and we're both Arkies. Our climates differ a little, but not much, especially during the months AC is needed.

 

[Cofe]

Re: Replacing home A/C unit ?

Cofe, to what extent did you exceed your SEER rating? I'd like to hear your thoughts on that since I too am close to having to do something and we're both Arkies. Our climates differ a little, but not much, especially during the months AC is needed.

When I upgraded last year, I went with the next higher SEER rating than what was calculated for my house. It is important to note that your air handling unit must match the output from the out side unit. Duct size and number are other factors in calculating the correct size unit. Where I live the weather is not supposed to get extremely cold, so I went with a heat pump system. I use a wood stove most of the time during winter months.
As far as AC goes in my climate, the humidity can get very high during hot summer months. There are times that I have to run the air handler unit to defrost the A-coils. No matter what SEER rating, the humidity has a lot to do with overall efficiency. Replacing my windows with new energy rated windows, was the best decision I made to control heating and cooling costs.

 

[hrdwrkingacguy]

Re: Replacing home A/C unit ?

Seer rating in a unit from 1984 doesn't exist...Whats important is that the unit is sized properly...1700 sq/ft with crappy windows more then likely will be a 4 ton by everyone's "rule of thumb" half *** load calc...A real load calc will tell you what you need...You can run an over sized 18seer unit and it will cost more then a properly sized 13seer...Trane, Carrier, York, Amana, Day and night, heil, tempstar, all make decent units and have their pro's and con's...In Vegas it isn't much different from where I live...Most units are two stage heat, single stage cooling...Variable speed fans are nice only in that they dehumidify at lower speeds then ramp up to take care of the sensible temperature...Also they deliver true CFM due to static pressure compensation...That means if you have a oversized duct system the ECM in the motor will speed up to deliver true CFM...

My feeling is most salesmen will come into your house see 1700sq ft and try and sell you either a 4 ton or a 5 ton...Have a real load calc done with manual J and see what it says...An over sized unit won't dehumidify(not that humidity its an issue in LV) and will short cycle at mild times...Typically when the temperature is over 100 degrees a properly sized unit should run for 20-25minutes at a time...To small of a unit from the start will be way to small when the temperature goes north of 95degrees...Units loose capacity as the temperature goes up...A unit that is 5 tons at 85 will be a 3 ton when its 118...