OK--

Sizing:
Manual J and Manual D may not be common in your area, but it's certainly the right thing to do. Oversized equipment is not efficient and tends to have a shorter lifespan, let alone less humidity-removal ability. Especially in your location, 3.5 tons for 1500 square feet? I don't buy it. I have 1500 sq. ft. on my first floor with an additional 1000 upstairs and 800 in the basement conditioned with 3.5 tons. 3.5 tons is probably a little undersized for me, but it does the job and I've never run into any cooling issues unless having a party with tons of people in the house.

Equipment:
Rather than using the ADP coil, which wouldn't be a bad choice provided it is an approved match by ARI, you could get Carrier's tin-plated copper coil (has ATA at the end of the model number) with a 10-year warranty. You're looking at good equipment--not top notch. They probably told you what they did about the Performance condenser upgrade because you wouldn't gain much if anything in SEER without the variable-speed blower that the Infinity furnace has to offer. The Performance condenser can interface with the Infinity system, so it can be used with the Infinity control, which is a good control. Whether or not you want to upgrade is up to you.

Controls:
If you go with the Infinity furnace and Performance condenser, go for the Infinity control. Otherwise, I'd go with the Honeywell VisionPRO TH8320. It is a great thermostat, but it doesn't have dehumidification abilities. I find it easy to program and easy to use. It will work well with the 58CTX and 24ACA4. The wire issue is probably a matter of how many wires you need versus what you would have available. Have them pull a W1 and W2 to let the thermostat control the staging. I also prefer having a C wire run to provide 24v for the continuous backlight.

Humidifier:
If you want to use a humidifier, the VisionPRO IAQ can control it without the use of more wires since it has a module mounted near the indoor equipment. The Infinity control can control the humidifier as well. Otherwise the humidifier is on its own control.

ryanhughes -- You're awesome! Thanks so much for the help. A couple more thoughts and questions...

Sizing
Based on what I've learned on this forum, it does sound like the Manual D and Manual J are the right thing to do, but no one around here sees the sense for a small house. You'll probably see the same feedback from a couple of other people who have posted from the Bay Area (doesn't make it right, just frustrating) *sigh*

Equipment
I asked Company 1 about the Carrier coil and the contact said he wouldn't even quote it because Carrier is having so many problems with them. He can't get it from either of the local distributors, and if anyone is quoting that coil they're getting it from out of state. Oh, and he felt so strongly about not using this coil, that he was "willing to lose the job over it."

There is the likelihood for a 200 sf addition in a year or two, so the estimators are trying to figure tonnage for a 1750-1800 sf house, even though I'm only at 1500 today.

Yes, I know I'm looking at good, not great equipment. The reason for that is that I'm not sure how long I'll be in the house. Plus, there are a couple of other big-ticket projects that need to be done before the winter, and only so much $$ to spread out :-). In the world of "Good, Better, Best," I'm looking at the "Better" solution.

**So, is there any reason not to pair the Performance furnace with the Performance A/C unit (and then add the Honeywell t-stat)?

BTW, asking Company 1 to quote the Infinity furnace with the Performance A/C unit got me this:
Furnace -- Infinity #58CVX090-14, 2 stage, variable speed, 80% AFUE, 4 ton
Air Conditioner -- Infinity #24ANA748A003, 4 ton
ADP Cooling Coil -- #HC-PT9648-C175
Note: Infinity A/C does not come in 3.5 tons, so upsized to 4 tons

Is it just me, or does that seem like too much tonnage?

Controls & Humidifier
Thanks for the info. I like the look of the Honeywell. Not sure about the humidifier at this point. Is that something that can installed later?

A humidifier can be installed later. If you go with the Infinity setup, go with the Infinity controller--otherwise I feel like you'd be wasting many of the system's abilities. 4 tons sounds like a lot, but on low stage it would be around 2 tons. 4 tons would be if you need extra cooling. Most of the time would be spent in low stage. I would NOT be surprised if a 3-ton unit would do it, especially in your climate where A/C I presume isn't used too much, but unfortunately no load calculation was done...

Do you know why an 80% furnace was quoted rather than a more efficient one? Do you use the heat much? Was PVC venting an issue?

The Infinity controller looks good, so yes, if I go with the Infinity system, I'll definitely go with that controller.

80% was quoted because of (1) the amount of time I'm likely to be in the house (less than 10 years and most people recommend the 80%). And (2) not sure if the PVC venting is an issue, but it would be an added install/retrofit and again more $$ and time. In my neighborhood, I'm not sure that I would recoup going with top of the line. (Where's that crystal ball when you need it?)

As for heat, I tend to be cold in temps below 65 ;-), so I use it from late October until mid-April. As for A/C, this year is strange -- heatwave weeks, followed by 75-degree weeks. In a usual year we have mid-80's and I would likely run the A/C in the afternoon to cool the house. Maybe a bit at night in hot weather.

**So, is there any reason not to pair the Performance furnace with the Performance A/C unit (and then add the Honeywell t-stat)?

The Performance setup would be fine. Again, you can use the Performance outdoor unit with the Infinity controller and furnace inside. Otherwise the Performance furnace and condenser and Honeywell VisionPRO TH8320 would be a fine setup. Only setback is the lack of a v/s blower on the Performance furnace. The Performance air handler (not furnace) does have one, though--go figure.

Thanks so much ryanhughes!
If there's interest, I'll follow up with my choices and install experience after the work is done.

alg

a properly sized Infinity 80 furnace including Infinity controller paired with a correctly sized Performance 15 AC would be a first rate system. You would enjoy better comfort, eff, and overall satisfaction with the var speed blower on the Infinity 80.

IMO

Hi alg,
I have also posted for help. I live in East Bay Area and looking for reasonable contrctor to install Furnace and A/C unit for my 1500 sq. ft. home. Not many responses received until now. I wonder which part of Bay area you are from and if it is ok with you, you can provide me the list of your contractor's so I can too get quote from them. If not no problem. thanks.

vyas

tigerdunes -- thanks for your input! Much appreciated. That is the direction I'm heading, subject to final price, warranties, etc. (The last quote from Company 2 had the Infinity furnace with the Comfort A/C.) The tendency here seems to be the "1 ton / 500 sf" approach. I've been pushing the final two dealers to really be sure about their sizing by giving them as much info as possible (the number of windows in the house, no insulation, orientation, etc, etc.)

vyasmk9 -- I'm on the Peninsula -- as are all of the contractors I've contacted. It just seems that people around here seem to service a smaller area (although I could be wrong), plus I like to support local biz whenever I can.

Just FYI, I started by selecting a couple of well-known brand names (Trane and Carrier) and looking on their websites for local dealers. Followed that up with searches for reviews of those dealers on local.yahoo.com and yelp, as well as checks on the BBB. Also asked my electrician and utility company guy for their thoughts/referrals.

Not sure what the forum rules are for recommending contractors, so I'd rather ask before naming names. Anyone want to comment?

I suggest going with the Performance A/C if you go with the Infinity furnace. It will interface with the Infinity system and control. It just makes sense to me.

vyasmk9 - I'm going thru the same process now in Oakland. Please send me an email if you obtained useful information you're willing to share. Thanks.

Eric