You could problably use the Honeywell theromstat but it would be in the non-communicating mode. You will not get all the information from the furnace and condenser though the digital interface. This would include the static pressure readings and the reporting of any fault codes.

Spend the extra money and get the Infinity controller. You can probably sell the Honeywell theromstat on ebay.

You also will not qualify for the Carrier rebate unless you buy the Infinity controller. The rebate amount should be larger the the cost of the controller.

Mike, you sound like the expert. So, here is where I am:

I like the Honeywell because of several features:
1. The outdoor sensor shows me the outdoor temp and RH.
2. I have the wireless remote which I use on the 2nd floor to control the temp in the summer months. I like it reading from the remote and also seeing the outdoor temp.
3. The color display is cool.

I'm currently using it with an old single stage furnace and AC, but it has the ability to control multi-stage and humidifier. The manual says it learns from the RH and outdoor temp readings to best control the furnace.

It does appear that if I go with the Infinity, that I should also go with the Infinity controller to maximize the features.

My dealer has also proposed the Comfort series, which is a better match for the honeywell T-stat.

So, my choice is. The Infinity with modulating valve and replace the Honeywell, or get the Comfort series, which is lower cost, and keep the honeywell.

I have an older brick farm house about 3500 sq and it is not energy efficient to begin with.

I currently run a stand alone humidifier. The dealer has recommended a Honeywell TrueSteam humidifier. What do you think? Do they work?

I have a choice of electronic air cleaner, or media filter. I want clean air, but my ductwork is 130 years old. I'm going to have it cleaned, but I cannot make a new clean dust free house out of my old farm house. Is the electronic cleaner really going to help?

Hybrid system. Is it worth it getting a heat pump? Is the combo more efficient than natural gas alone for heating?

I know.. a lot of questions but before I spend a lot of money, I need to be sure I spend it in the best way.

Thank you very much.
Mike C

I own Carrier Infinity HVAC systems and the controller. I am not an expert, but I will give you my opinion.

The Carrier Infinity system is great for comfort and efficicency. In the winter you will not get blasts of cold air when the furnace comes on, and in the summer it will do a great job of reducing the humidity.

I would not down grade to the Comfort series just to keep your old thermostat.

I don't own a humidifier, so I can't advise you. I have heard good things about Aprilaire humdifiers. The humidifers do work well when properly installed. The Infinity system should allow you to run the humidifer without the furnace.

I am not a fan of electronic air cleaners. I recommend a 4 inch media filter.

For most parts of the country, you are better off getting a 95%+ efficiency furnace and not getting a heat pump hybrid system. Natural gas rates are low and will likely to remain low in the near future.