He mentioned the part was under warranty - however - the labor was not & quoted 6 hrs to fix ~ ($800).

My question - If a part is under warranty, why would the labor to install not be?

What manufacturer are you inquiring about? Have you called up the company and asked them about this part? I can't imagine anything taking 6 hours to repair. Something is not right with this picture. Have you gotten a second opinion on this unit?

I feel the same way too, but read the warranty, "parts only"

What's the TXV. A good AC tech can replace the entire system in six hours. Get another estimate.

How long should it take to replace the TXV?

TXV = Thermal Expansion Valve. With a discharged system and a very accessible A coil, takes 45+/- minutes. To replace the valve. However, depends on how the access is. The TXV usually sits in the bend of the A coil so you at least have to remove the upper part of the HVAC to access the A coil. Some are sandwiched inside a closet and you may have to pull the whole unit out. Or they are in a 130 degree attic space. Personally 6 hrs seems high, I'd like to make that kind of money but I'm assuming that's to discharge the system, collect the freon and then recharge, in addition to taking out the old valve and braze a new one in. I'd shop around for another person but you may be stuck for a warranty item.

Many hvac units have a parts warranty, but no labor warranty. The standard for labor warranty in my area is one year, and that's from the installer, not the manufacturer. The parts warranty is from the manufacturer, sometimes a year, up to ten years. Believe it or not, it can many times actually take more time to fix a problem in an a/c unit than it takes to install a complete new unit, especially if it is a new 410 unit. But a new unit will cost you a lot more in the unit and materials itself than 6 hours of labor, and that's where you get stuck. With the newer units, you have to purge the system with nitrogen while brazing. You also have to vac the system to a much lower micron, which will take more time. So, I agree that six hours may be a bit long, but I have never seen a bidder short time on a bid, that's is where they lose money. If they just gave you an estimate, and will actually only charge you for the time they spend on the job, it will probably be less than six, but if they are only going to charge you for six, and it goes over six, you win. Here is what should take place. First, they will have to reclaim the refrigerant, or merely pump the refrigerant back into the condenser(if they plan on changing the filter/drier in the condenser, then they will need to reclaim all refrigerant, depending on their equiptment, reclaiming could take anywhere from 10 minutes to an hour). Next, gain accest to txv, this could take a few minute, or an hour, or more, all depending on the accessability of the txv. Then, haul a nitrogen bottle to the condenser, hook up nitrogen, purge system with nitrogen, cut out old txv, braze in new txv. Then, pressure system up to roughly 250 lbs of nitrogen, and bubble check braze joints. All this time, the tech will need to run back out to the condenser adjust flows of nitrogen between purging and leak testing. Once this is done, they will have to hook up the vacuum pump and vac the system anywhere from 1/2 hour(almost never happens that quick) to possibly a couple hours. If they do it correctly, they can be doing the vac on the system while they put the plenum etc all back together. Once the vac is pulled, and vac holds for at least 15 minutes, they can now start to charge the system. If the refrigerant was pumped into the condenser, this should only take a matter of minutes. If refrigerant was reclaimed, it will take a little longer, possibly up to an hour depending on their charging methods. After all, you need to figure in travel time, shop time for gathering equiptment/parts etc.

Final thought, Im not completely sold on six hours, but I most definitely would not call it a rip off either. At least without knowing exactly the work they will be doing, and all the other factors that come into play. A/C systems are a breed all their own, and it really does pay to have them fixed correcty. If you were quoted 2 hours, I would say you were going to regret it in short order, as you most likely would have to call in another tech soon. Six does seem a little high, but not completely out of range.