After reading more threads, I think I need to provide more information to get your help:

For the new duct work:

We currently have 14 air supply, 1 return on hallway ceiling, and 2 returns on the wall. We will seal the returns on the wall. The contractor will add one 16" return at the entry hallway, one 12" return in master bedroom, and one supply at the entry.

It will be R8 flex duct.

Thanks everybody!

The furnace and AC are both 2-stage controlled by a true 2-stage thermostat with a 4 inch media filter. This appears to be a good system. The price of the system seems reasonable. It is difficult to judge the price of the duct modifications.

It is interesting the contractor wants to replace your current 5 ton AC with a 4 ton unit. You should ask him how he determined he is able to reduce the size. Hopefully he has done an actual load calculation and not use the some rules of thumb based on area.

The 100K BTU furnace seems large for the Dallas winters. What is the average low during the winter? You may be able to reduce this to 80K BTU.

I assume it is difficult to replace the lineset. Verify the current lineset is the correct size for the new condenser.

I like the contractor has proposed making duct modifications. This is key to a good insulation.

I would ask for a quote for an extended labor warranty if you plan to live in this house for the next 10 years.

Thank you very much, Mike, for the prompt and helpful comment. This contractor seems to know A/C well but I do not. He does not provide the latest Trane model, such as XL20i like other contractors do. Should we go for XL20i or XR15 is good enough? His quote is not the cheapest but we like him best so far. It is good to know his quote is reasonable. I don't want to go with the lowest bid. I'd be concern about cutting corners somewhere during installation.

The avg winter temperature in Dallas is high - 59 and low - 39. I emailed him the questions you want me to ask. Will let you know the result once I get it. Yes, we do plan to live in this house for the next 10 years (or more).

Pete

You are being oversized on furnace.

And if budget allows, I would look at the XV95 80 K 95% eff furnace with the 4 ton rated blower.

In either case, you want a true two stage thermostat like the HW VP IAQ stat over the 802 or 803 Trane stats.

Lineset size should be dbl checked to see if correct size for a 4 ton XR15 which is a good condenser choice.

IMO

the '20' number doesn't indicate it is newer than the '15'. It is indicative of the efficiency rating, not date. The '20' is going to be about %20 more efficient than the '15', but it is going to cost a lot more. It might take several years to make back the extra money spent up front in the monthly electricity savings.

just be aware, the 20 is not even close to 20 SEER in these larger sizes.

While I like Trane, they are guilty just like all others of some marketing deception .

Homeowners should always look up the performance/efficiency numbers from the AHRI Directory and to verify the system quoted is an AHRI matching system. Not to be overlooked.

IMO

Tiger and Weed, thank you very much for great information.

I did some research and cost calculation. You are right. I would not get my money back by buying XL20i ($2,870 more than XR15) in its life span, neither does XL16i ($1960 more than XR15).

With $800 more, I can get XL15i for 2-stage system. I heard that 2-stage compressor can provide better comfort. I am leaning to XL15i. However, some people think overall XR15 is better than XL15i. What are your opinions?

Tiger:

I am emailing the contractor about lineset, XV95 80 K furnace, and thermostat. Not sure this contractor can provide HW VP IAQ stat because he uses everything from Trane. Should this be a deal breaker?

Can investing on XV95 get the money back by saving energy? It really doesn�t get too cold in Dallas.

I am getting AHRI Certified No. from the contractor. Will post the info while I get it.

Mike,

The contractor has not responded to the 10-year labor warranty yet. Will keep you posted.

I just purchased a trane xl 20 I 4 ton heatpump . With the xv 80 furnace with the trane matching coil and a trane 803 thermostat. With out door sensor. It is designed to run as a duel fuel system.
I think the company installing this unit did not have enough experiance in a duel fuel system. They have been back several times and still are having a hard time,
The heat pump was working fine as the temperature dropped to below 32 the unit was not turning over to the oil heat. Also the outdoor temperature on the thermostat was showing 80 degrees.
They just left and they reprogrammed the thermostat and did a few things that have got the themostat to read the correct outdoor temperature. I hope now it will work.
What temperature should the trane heat pump cut off and the oil furnace come on??????
How do I know if this system is installed correctly?
They have come back 6 to 7 times. For this and that. I have lost some what faith in the company.
Should I find a company to come and check there work. This is a dual stage sophisticated system by trane. I did get a great deal but have paid a price in the level of headache. Any suggestions would greatly be suggested.
Thanks.

You have piggybacked onto an old thread. That is considered poor forum etiquette.

This thread is dead.

If you expect help, repost new as your thread.

IMO