HELP! Building a new house. Am I getting the bad hand of a deal or what?

[home4us]

:( Ok. First of all, I am not a HVAC know-it-all, just a mom, wife, teacher, and an anxious new-home buyer. We are purchasing a 2 story, 2407 (+/-) sq. footage home in Dayton, Texas, north east of Houston. Our downstairs includes master BR and bath, powder room, dining, living room, utility, and kitchen. Upstairs: 4 bedrooms, bathroom, and a game room. We have a total of 17 windows on the house. Our builder's AC contractor has put in 1 XT80 Single Stage Furnace and coil model no. 2TXFH054S3HHAA. We have had conflicting stories from the builder, contractor, upper management, and so on over what exactly we have installed in our home to tonnage issues. I was under the impression that we would be just like every other homeowner in this subdivision that has a 2 story home, especially the ones who have the exact floor plan as us, that we would have 2 units inside and out. The contractor told us that the 1 unit was a variable speed, zoned, dampers, and it would be sufficient for our home, whether it was a 4, 4.5, or 5 ton AC. We have called a local AC Trane dealer who told us differently. One unit will not be cost effective and the upstairs will not cool, and the compressor will run continuously. I have searched the Trane website and as far as I can tell...the XT80 is NOT a variable speed furnace. Which brings me to you...are we getting the raw end of the deal here? Can you shed some light on this? I am totally at a loss for words. I have internet searched for answers but I am not a HVAC person! Help! Many thanks!

[ptcooper]

The XT80 is not a variable speed. The XV80 is the variable speed model.

It is acceptable to have one system with zone capability. The XV80 should work well, but not the XT80. The size/capacity of the equipment is required to be determined by a heat lost heat gain calculation. Ask your builder to give you a copy of the calculations. By the way, all your conversation should be with the builder and not the HVAC contractor.

To say that one unit will not be cost effective and will be insufficient is only a guess. Again, the load calculation will tell the story. The builder is required to have a system installed in your home that provides a temperature difference of not more than 3° in ANY room. Bedroom, bonus room, first floor, second floor, it does not matter which room.

Also, in the Houston area, the system is normally designed/required to provide 75° inside at an outside temperature is 95°. What that mean is, if it is 100° outside and your inside temperature will only get to, let us say 96°, you will have no ground to argue.

Now, if you want two systems, tell the builder.

[home4us]

Thank you so much for your help! I am forwarding your message to my husband. Hopefully, this will get all settled before we HAVE to close on the home. My builder is pushing us to communicate with the contractor. They have even scheduled a meeting with all parties on Monday. I agree with you about conversations with the contractor. There should be none. Oh-well. I feel like the builder is just passing the buck, instead of handling the situation themselves. Thanks again.

[skippedover]

I'd want even more information on this system. Anytime you zone a system you have to have a 'relief strategy', unless each zone can handle 70% of the total load individually. A 2-stage furnace is only part of the equation. You would be wise to invest in a 2-stage condenser as well. If you use Trane equipment for the furnace & AC, you should also use a Trane zone control system with relief strategy. That means that the zones can be 'cracked' open if necessary to satisfy the building needs as well as the equipment needs. You can't slow the blower down below 70% of full capacity without running the very real risk of freezing the coil and other potential system damage and discomfort. I can't speak for Trane today but we used to use Trane and put in many of their residential zone control systems. Properly designed and installed, they work well. Today we know that the United Technologies, Carrier & Bryant, high end products can handle their relief strategies without a log of engineering. In fact, those systems will, on a daily basis, ramp up, self calculate the capacity of each zone, then close all the zone dampers and calculate the duct loss, all done with a 4-wire thermostat.

pctrooper said it well. Deal with the builder, get the calculated loads in print, get the equipment specifications in print and get the temeprature guarantees in print. I can't speak for Texas but up here in the northeast, if you want to get really taken to the cleaners, just let the GC pick the HVAC company. You'll lose every single time. No one wants to be disappointed in the outcome of the new home so you're right on target asking questions and getting answers. Now you need to be just as determined with the GC to get what you want, be it a zoned system or multiple systems.