Hi Pat, I can't help with your situation, but this site helped me a great deal when seeking hvac advice, hopefully someone will reply quickly for you. If not are you aware there is also another site hvac-talk.com and they have many expects as well. PS, on that site they don't allow prices to be posted. Good luck

"If you are not aware" it's early and I'm still sleepin'

The part that I can help you with is that you should not keep the existing inside coil or lines. You had a compressor burnout and doing a good job of cleanup is difficult. In addition, this board has numerous tales of "leaking indoor coils"

The decision about replacing the furnace is yours. How old is it? If it is as old as the AC, I would say don't do it. It should last 15 - 18 years.

Thanks for the input golfer1512 and jake2007.

The natural gas furnance is also 6-yrs old. Since it only heats the 2nd floor, it probably doesn't make sense to replace it.

Replacing coil, condenser and lineset (flush is an option) is running between $4K and $5K based on three quotes. 10-yrs parts and 1-yr labor warranty.

2nd quote came in with American Standard at $4,250
...A/C condensing unit model 4A7A4030 (14 SEER 2.5-ton)
...Coil with expansion valve model 4TCCB036
...no mention of flushing lineset though

The 3rd vendor will do a site inspection tomorrow to confirm his phone quote and to spec the system. Over the phone we discussed a few options:

A/C:
...Carrier Comfort 13 SEER ~$4.5K
...Carrier Performance 24APA530 15 SEER ~$4.9K

Heat pump:
...Carrier Performance 25HPA530 ~$5.7K (I think, as he said +$600 for heat pump and +$200 for thermostat)

My thought on the heat pump is that since it will run longer and at a lower BTU, it would probably reduce some of the cold rush of air that we're experiencing with the natural gas FAU. Vendor said not to expect that, to view its benefit as improved efficiency only.

BTW, I'm not pursuing an option that brings the $1,500 tax credit into play as that will be consumed with a planned Triangle Tube Prestige install that is replacing a 1950-vintage boiler.

Pat:

You're crazy if you replace a 6 year-old gas furnace. You shouldn't have a "cold rush of air" with a gas furnace. Something isn't right. You should have a blast of hot air (120 - 140F). Heat pumps have a complaint of warm air output, gas furnaces usually never do. You may have ductwork issues.

The decision of heat pump condenser or straight a/c condenser is based on your utility rates and climate.

What is your delivered price of electricity (in cents per-kw-hr?) Delivered = generation + transmission + distribution.

What is your gas rate ($ per therm, or $ per ccf)?

What State and climate?

For a second story, if you have a whole-house boiler already, I would probably just stick to straight a/c with an air handler. I say this because heat naturally rises, and having a secondary heat source, economically, doesn't sound like it would have a great payback on the second story. Do you have a thermostat for heat upstairs already, or just downstairs? If downstairs, upstairs should always naturally be warmer.

The Carrier quote does not give you many options. The first option is a bare replacement, not even including a new indoor portion (just the coil inside). The second option is a complete Infinity system. The Infinity is a nice system, but by personal preference I tend to stay to the more simple systems (i.e., 13-15 SEER with variable speed indoor portion). The variable speed indoor unit can sometimes improve airflow to some rooms depending on present ductwork condition, and as you noted it also has a low fan-on setting (I think it comes from the factory like this but nevertheless it is an option for the installers to set). Depending on the thermostat you use, it has the ability to be configured to control (de)humidity (again, that's getting more fancy with controls).

I like the American Standard quote (the equipment, that is) However it looks like this dealer too is just proposing a coil and not an actual air handler inside. Perhaps I'm confused as to what you have in the attic now (I'm assuming a fan coil/air handler - just a blower and a coil for a/c). When going to R-410A it is a good idea to flush the lineset/purge it with nitrogen. Surprisingly, some don't do this, and many times there won't be problems, but it is very good practice and any good company would know to do it or replace the lineset itself (which isn't necessary if proper size and in good condition).

The second Carrier quote (most recent post) lists two good, reasonably priced options for a/c. With Carrier, those are the two units I'd look at (Comfort 24ACB330, Performance 24APA530). The Performance series unit is physically larger outside, if that makes a difference, since it's more efficient. Either of these units can be used with a variable speed indoor fan coil (model FV4BNF003/5).

Let us know if you have any more questions.

garyg, thanks for the input. Here are the answers:

Arlington, Virginia. Hot and humid in summer and it can dip below freezing in winter.

In general I feel the gas rates are high and are only going to get higher.

Gas = $1.50 - $2.45/therm based on last several bills with higher average rate during periods of low usage

Electric = 12.1 cents/kWh

The electric rate was from the last bill. I divided the billed amount by kWh. This is more than what they list on the bill, which is shown as cents/kWh at:
9.04 Jun-Sep
7.76 Oct-May
8.24 Annual Average

Initial rush of cold air is because the flexible air ducts are in an uninsulated attic, so they're cooling off between cycles. That cold air is purged before the hot air comes out.

Thanks ryanhughes.

Baseboard heating is in the basement and on the 1st floor only. The 2nd story addition has its own A/C and natural gas furnace.

Even though heat rises, the wife's blood runs cold and the upstair's FAU gets quite a bit of use.

I'm going to rule out the Infinity due to cost and having a fairly new furnace (6-yrs old).

If the heat pump is an option, then I want to consider it. With the majority of the cost being the new condensing unit, coil and labor, adding 20% more to get a HP seems palatable.

Unfortunately, the cost payback calculation isn't straight forward as I can't tell how much gas went to the boiler vs. FAU and I only have one winter spent in the house. Payback could be as quick as 4-yrs if I save a couple hundred dollars a season. I plan to be in the house a long time.

Thanks for clarifying what you have in the attic. Now, the quotes make more sense to me as far as what equipment was quoted. The heat pump is certainly an option, and may require a new thermostat as well. The decision will be up to you, since you can make your current system a dual fuel system with the heat pump and indoor coil with furnace.

If you continue looking at Carrier, I recommend researching the following systems:

straight a/c: 24ACB330/CNPHP3017ATA* (13 SEER)
*as I assume this is a horizontal install, the CNPHP is a horizontal coil)

heat pump: 25HCB330/CNPHP3017ATA (13 SEER/8 HSPF)

Thanks for the additional input.

I'm going with the Performance line and have decided to do the heat pump upgrade. I believe I can recapture the upgrade cost in as little as 4 to 5 years.

System selected is Carrier 25HPA530, CNPHP3617ATA and Edge programmable thermostat. 10-yr warranty on the system and 1-yr on labor. Existing lineset will be flushed for re-use.

My thanks to all for their input as I feel more confident in the final selection.

Good choice, hope all works out with the new system.