Why does the Carrier unit need to be replaced?

13 SEER is the minimum efficiency for outdoor units made today. Likely won't get 13 SEER when paired with a 10 SEER coil, so don't look for energy efficiency when doing it this way.

R-22 units are no longer manufactured and harder to find. You'd certainly want to avoid R-410A if you're reusing your existing indoor coil.

If you can find a 13 SEER R-22 unit, preferably Carrier, this might work, but you can't expect any real savings or enhanced performance when mismatching equipment.

ryanhuges is partly correct
Your asking for trouble on a heat Pump
13 SEER is the least efficient available and only 410A.
If you can find a R22 Condenser and install it you wont get near 13 SEER and more than likely your heat will suck when in heat mode. You will not qualify for any rebates. Code enforcement has gotten real strict with matching systems. You now have to have an engineering firm certify that you did not diminished the SEER rating of a existing unit. Good luck doing that!

DONT GAMBLE
You are not the only one who is finding out that the EPA is creating a greater $$ burden on the consumer. This is only the beginning

Code enforcement has gotten real strict with matching systems. You now have to have an engineering firm certify that you did not diminished the SEER rating of a existing unit. Good luck doing that!

Perhaps where you are, but certainly not everywhere, and probably not most places.

Thanks a ton for the fast replies!!

ryanhughes "Why does the Carrier unit need to be replaced?"

The heat pump(outdoor condensor unit)needs to be replaced as the compressor is going. Started making terribly load noise, making the walls vibrate with this pulsating sound, extremely loud. They checked "everything" else and said it was the compressor. I was told it alone can be replaced for $1500-$1700, and hence figured it may be best to just get a new one, until I found out about all this R22 vs R410, mis-matching etc. The tech who said it needed to be replaced is from my regular AC service company who does my 2 x year prevent. maint. on the units.

My parents have a 9 Seer Air handler that is going on 20 years and they replaced their condenser several years back (2002) with a 14 seer, no change to the air handler, he saw huge savings on their electric bill and has had no trouble with the unit. How is that explained?

Due to the tight space where this one air handler is and poor lay out up there, it is going to be extremely costly to get down and get a new one in. May need dry wall work and reinforcement up there. Dad is adament that I do not need to change the handler, but hey, he's not an HVAC guy just someone who didn't replace and is seeing great benefit and no problems. The first HVAC guy who came yesterday said he could replace the outdoor unit with a 12 seer max (if he can find one) but not to expect much of any savings, but better to replace with a 10 seer again. ($2400) Why spend that kind of money and see no efficiencies? Having 2 more estimates on Monday. He said he could also replace just the compressor for $1500.00. This is why it seems like it may be best to take a plunge and replace everything, but really I do not have 6K.

If I get another R22 outdoor unit, what happens if the air handler goes in 3 years, then what? I have to replace this new 3 year old condenser and an air handler? There went the $2400 out the door. Or are there air handlers that can handle both, just not condensers that can?