I had a Carrier Infinity. It was the worst mistake I have ever made... (in HVAC).

The parts are expensive and not terribly reliable. I fought hard and got some parts free after missing a recall by a few months. My repair bills exceeded my electric bills....

Part of the ecosystem is their stats. Which aren't great and there are far better and cheaper modern replacements - Ecobee for example. But once you go Infinity, you can't really go to something else.

What is the motivation for the upgrade? Efficiency? - in Park City? I would say likely wasted but maybe you have large west facing glass and can't open the windows.

These codes are for a/c only - correct?

I would at least consider a heat pump. Usually a small upcharge and allows for some efficiency improvements even if you use a fuel as primary.

Hi, Laura,

I don't know where you are in the construction of your townhome, but an investment in improved air sealing and insulation will pay back both in terms of comfort and reduced energy use year 'round. Ditto for upgrading to higher performance windows.

According to weatherspark.com , your air conditioning season is 3.1 months long; the hottest month is July with an average high temperature of 79F and an average low of 52F. Indoor design temperature for air conditioning, per the 2018 International Residential Code, is 75F so there's not much sensible cooling load nor is there much latent (dehumidification) cooling load expected. There could be considerable solar heat gain depending on the orientation and the particular windows installed. Where the multi-stage and variable speed air conditioning systems shine is humidity control, and yes, you'll get some energy savings, too. However, given your mild climate and short air conditioning season, I wouldn't spend money upgrading to a more sophisticated system than what the builder suggests.

Sitting between the Comfort 14 Central Air Conditioner 24SCA4 and theInfinity 19VS Central Air Conditioner 24VNA9 is the Performance 17 2-Stage Air Conditioner 24TPA7. The Performance 17 may be only slightly more expensive than the Comfort 14 but it is a two-stage unit* that supports a common two-stage thermostat and is slightly more energy efficient than the Comfort 14.

I installed the Honeywell T10 Pro wifi thermostat that supports multiple, remote sensors. The thermostat is on first floor hallway and a sensor is in a second floor bedroom. I programmed the thermostat to heat/cool based on the thermostat's built-in sensor during the day and the bedroom sensor at night.

*My two-stage heat pump's blower (fan) runs slower in stage one than in stage two. The result is that heating and cooling are virtually silent most of the time as the air "whoosh" from the registers is nearly inaudible.

My one stage heat pump blower is virtually inaudible because of proper duct design (and maybe overdoing it a bit).

I have had 2 stage and 1 stage. All things being equal 1 stage is quieter. But that doesn't mean you should compare to some poorly designed loud system that someone might have in their current house. Or similarly short cycling - because my 1 stage does not short cycle .... because it is not oversized.

I agree a Carrier Performance 2-stage model would be a value. It is a good compromise between with the Carrier line up. The Comfort series is the basic equipment that gets the job done. It is Carrier's least expensive equipment. The Infinity 19VS has many features and is very expensive. It might be appropriate if you were installing multiple zones. This type of equipment needs to be installed by someone who knows it well and will do it properly.

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