I live in New Orleans, LA and since hurricane Katrina prices for everything have gone up.

6 years ago I had a new Bryant central heating system installed (company did not have Trane units at that time). Also had new coils installed at the same time. The company installed Carrier coils.

I need to replace a 3 ton central A/C unit (outdoor part). The company that installed my heating system 6 years ago (now only has Trane units) quoted a price on a 3 Ton Trane XR13 of $3,416 installed. This price includes:

1. Outdoor unit installed
2. Replace pistons on indoor coils to make new Trane unit more efficient with the Carrier coils

3. Install electrical breaker at condenser for service disconnect

4. Extended warranty added to price which makes it 10-10-10 (Labor, Parts and Compressor)

A quote from a second ccompany will install the Trane XR13 for $2,582. This does NOT include replacing pistons on Carrier coils nor installing a breaker at condenser. It just states "material and labor".

Opinions on this would be greatly appreciated.

The breaker at the condenser should be a cheap part of the equation; I wouldn't guess more than $100.

... so seems you're looking at whether to pay $800 to replace the pistons.

We do have a couple great HVAC folk here who may pipe in, but in the meantime I'd ask the first guy for more specifics on the benefit and/or need of replacing the pistons... and ask the 2nd guy why he would NOT replace them.

Breaker at the condenser... $124
Change piston... $192
Extended warranty (10-10-10 labor, parts, compressor)... $353

If I read your figures the second bidder is actually only beating the first bid by $165 if you add the cost of the Breaker and the changing of the piston and the warranty that is listed.
I sell Carrier but the first bid for the Trane is fair if he is installing the 13 S.E.E.R. unit that only can be manafactured after the first of 2006. Some companies still have the 10 or 12 S.E.E.R. left in stock and it is leagel to seel. So make sure what you are getting.

Would the model number 2TTR3036 indicate the Trane is a 13 SEER?

First of all a piston change should not be done! Since the new style equiptment is on the market now you need a Thermostatic expansion valve installed on the older Carrier coil to make it match the new unit. A thermostatic Expansion valve is the only way to make suer you get all the efficiency out of the unit. I have stated just the facts. BTW the Expansion valve that will mount on the inside (evaporator) should be sized to the outside unit in tonage. Any thing else and you are not getting your moneys worth and can cause future compressor failure due to slug back of liquid in the suction line. A TX valve will make sure your insud evaporator is properly loaded at all times for maximum cooling.

Do you have a ball park figure amount as to how much this "Thermostatic expansion valve" can cost?

Ad probably 150.00 to the price. What everyone does not uinderstand is that you cannot properly install a new 13 SEER unit on a old 8 to 10 SEER coil without one. Actually the indoor coil should be replaced with a new one MATCHED to the new outside unit. The newer coils are larger to allow the higher SEER numbers and save you electrical cost but the Expansion valve will help with this match but no a complete energy saving match.

The compnay told me about having to change the pistons to make the new Trane unit run a little better/a bit more efficient with the Carrier coils.
Thanks. I'll have to check with the company on this.

You probably should consider replacing the coil with a new one---the price to change the coil probably will not be much more than the cost to install TXV on old coil. With the new 13 Seer outdoor unit when you install it on an old air handler it is like trying to put 3 pounds of dirt (the new outdoor unit freon) into a 2 pound bucket (the old coil inside). Some companies will not install 13 Seer unit on an old air handler, period. It just does not work properly. The Trane model number is a 13 Seer unit. Don't try to save $200.00 by dealing with price only--check the companies reputation and call the local mechanical inspections department for your county and ask how many complaints or violations this company has had. You might be surprised at the answers you get.