I bought a house 6 months ago with a forced air gas/CAC HVAC system.
It has three zones. Two separate furnace/CAC coils, one with two
damper zones. The equipment is clearly in need of upgrade. Furnaces
from 1965, one dead CAC compressor and one CAC compressor probably 10
years old and not working. Damper zoning motors are working, but
only after I cleaned the switches in them. Hot air ducts in attic are
poorly insulated, return duct in attic was un-insulated, crawl space
and basement ducts un-insulated. Return ducts look like they could use
some cleaning. I live on Long Island, NY. Historical energy
costs: $1500 gas heat, $300 blower electric, $500 CAC electric
(utility bills provided by former owner)
After getting 4 quotes I have decided on the following equipment:
Furnaces: 2-stage, variable speed blower gas, all S/S heat exchangers,
90%+ AFUE Kenmore/Tempstar
CAC: single stage scroll compressor, 2-speed fan, R-22 refrig.,
14+ SEER Kenmore/Tempstar
Warranty: lifetime on heat exchanger, 10 yrs parts/labor otherwise
Zoning system: Keep original for now, Trol-a-Temp brand.
Ducts to be sealed and insulated in spare time.
Questions:
1. How much value should I put on the warranty over a more typical
5 yr parts/ 1 year labor warranty? Service calls are about $100 min
in my area.
2. Should I consider a multistage CAC compressor?
3. Any hints on duct sealing and insulating?
4. Any other comments on choice of equipment?
Replies
As long as you have a scroll compressor, configure so you can run as heat pump when outdoor temp is over 50-55F and leave gas off. Way cheaper that way based on 80cent therm gas and 8 cent kwhr, probably need to refigure differential for our costs in area.
We have very high electric rates in my area.
Gas: $1.03
Electric: $0.14
Also, I been told that heat pumps compressors do not last as long as
CAC compressors.
OUCH!
Questions:
1. How much value should I put on the warranty over a more typical
5 yr parts/ 1 year labor warranty? Service calls are about $100 min
in my area.
2. Should I consider a multistage CAC compressor?
3. Any hints on duct sealing and insulating?
4. Any other comments on choice of equipment?
1. Tough to say, depends on the outfit that you will be dealing with. The equipment you mentioned is of good quality.
2. You didn't mention the size of the equipment. Residential furnace/AC combos usually go up to 5 tons of cooling and 125 mbh input for gas heat, in a single unit. At that size, I don't think multistage (cooling) is an option. Scroll compressors are not typically load variable, recips are, but not many use them on smaller equipment. See what you can find and at what price.
3. The cheapest and best way to seal low pressure, sheet metal ductwork is with mastic. Easiest is the foil tape, but at $20/roll, cost adds up quickly. For insulation in the attic, foil faced, 1-1/2" thick fiberglass wrap with the foil out and seams taped is a good, fairly standard practice. Insulte supply and return ducts. In the crawl space and basement, seal the ducts. Insulation is optional depending on whether or not the basement is a conditioned space and wether or not the crawlspace is ventilated. My basement is conditioned and crawlspce is unvented and open to the basement. I did not insulate the ductwork.
4. Depending on how you operate your home, the extra cost for the 14 SEER (over a 12 SEER) is of debateable cost effectiveness. If you have the AC running constantly from June through August, at your electric rates, probably a good choice. If you use the AC only when its unbearable, a waste of money. I suggest that you invest in 7-day programmable thermostats, and computer controlled, powered humidifiers. Both are a preference of mine and optional.