When to buy a new central air system?

[q1100q]

I live in Houston, and have a 3-1/2 ton Rheem unit that is probably at least 15 years old. System runs about 12 hours a day during Aug/Sep and keeps the house about 77 F, with a RH of ~55%.

Im trying to explain to one of my coworkers that I plan on buying a new system in April 07, prior to selling my house in 08. He thinks its stupid and that I wont get any return on my investmsent at selling time.

Question - Why does the system efficiency decrease over time (loss of compressor efficiency?)?

Also this guy thinks it makes more sense to run the system to total failure before replacing. I dont want to be stuck in August with no AC for a day or two and pay premium pricing for replacement.

Any statistics on how long an average system should last, and the experts opinions on when to replace.

THanks

[johnl45]

Originally posted by q1100q
I live in Houston, and have a 3-1/2 ton Rheem unit that is probably at least 15 years old. System runs about 12 hours a day during Aug/Sep and keeps the house about 77 F, with a RH of ~55%.

Im trying to explain to one of my coworkers that I plan on buying a new system in April 07, prior to selling my house in 08. He thinks its stupid and that I wont get any return on my investmsent at selling time.

Question - Why does the system efficiency decrease over time (loss of compressor efficiency?)?

Also this guy thinks it makes more sense to run the system to total failure before replacing. I dont want to be stuck in August with no AC for a day or two and pay premium pricing for replacement.

Any statistics on how long an average system should last, and the experts opinions on when to replace.

THanks Your getting close to the life cycle of that unit. A new system would be a + if I was buying your home.

[star882]

Replace it during the winter, when demand is low.

[allstar08]

it sounds like it needs to be serviced. systems to not drop off that much over time. if it worked well in the past, it should work the same now. it may be low on charge or other problems that r not letting it keep up with demand. upgrading will not give you that much on resale. a central ac is a central ac for the potential home buyer.

[fl1]

New system will use a lot less energy,depending on it's rating SEER/HSPF/AFUE,so keeping it till it dies is costing you X dollars a month.Factor that in to replacing it,along with and repairs you make ,until it's just not worth repairing anymore.

[dnt]

Expect about 50% payback on your new system when you sell. Then if you happen to get 75% you can celebrate and have a couple of beers. Your coworker is exactly correct IMHO you are throwing money away by doing this. If your system is still working well (which it probably could be with a Pro service call). Now my background is in landlording we dont spend a dang dime unless there is a return on that cash so I may be a bit opinionated on repair/replacement issues LOL.

[watercop]

12 hour/day run time in hot humid weather isn't necessarily bad. Long run times are desireable for dehumidification.

77 deg / 55% sounds fairly comfortable, is it?

Are you getting killed with electricity bills? Yours may be higher owing to post-Katrina increases in fuel prices to utility companies. Mine claims not to have raised rates but the fuel adjustment charges have increased bills by a third or more.

If it hasn't been checked and coils cleaned in awhile, definitely get that done.

I'm skeptical of return on investment at sale. If you are definitely selling the house in <2 years I'd get a good preventive maintenance service done and run for luck.