Tallahassee in NOAA's engineering weather tables
NOAA's engineering weather data lists Tallahassee at an elevation of 69 feet. For the Tallahassee station it gives a 1% summer design temperature of 93°F, paired with a mean coincident wet-bulb temperature of 76°F, and a 99% winter design temperature of 28°F. In an average year at Tallahassee, NOAA counts about 2,073 hours with the wet-bulb temperature above 73°F and about 3,899 hours above 67°F. The Tallahassee data also lists a 50-year basic wind speed of 120 mph (3-second gust at 33 feet), a 100-year rainfall rate of 4.5 inches per hour and about 26 freeze-thaw cycles in an average year.
The rest of this page turns from the station to your own house: how it feels today, what a new system has to do, and what to ask the people who bid on it.
Keep a comfort log first
A contractor can only respond to what you tell them, so write things down for a while before the first visit. Useful notes include:
- Rooms that run warmer or cooler than the thermostat setting, and the time of day it happens.
- Whether the house feels sticky or damp even when the thermostat says it has reached its setting.
- How long the system runs on a hot afternoon, and how often it starts and stops.
- Rattles, whistles or humming from the air handler, the ducts or the return grille.
- Water stains near the indoor unit, on ceilings around registers or below the attic hatch.
- Your power bills for the past year, if you have them.
Give the same notes to every bidder. A proposal that answers your specific complaints is easier to judge than one that simply quotes a box.
Sizing should come from arithmetic
The capacity of a new system ought to come out of a room-by-room load calculation, often called a Manual J, rather than from the label on the unit being replaced. That calculation adds up the heat moving through walls, glass, ceilings and duct runs. Put these to each contractor:
- Will you run a load calculation for this house and give me the printout?
- Which outdoor design conditions went into it, and where were they taken from?
- Did you measure window areas, insulation depth and duct locations on site, or estimate them?
- How does the capacity it recommends compare with what is installed now, and what explains the difference?
- Would sealing ducts or adding attic insulation first change the answer?
A bidder who adds capacity "to be safe" deserves a follow-up question. Equipment that is too large tends to cool a room quickly and shut off, which can leave the air cool but damp.
Moisture removal and run time
Air conditioning does two jobs: it lowers the air temperature, and it condenses water vapor on the indoor coil so it can drain away. The second job depends on the coil staying cold long enough. Ask:
- From the manufacturer's data, how much of the quoted pair's capacity goes to cooling the air and how much to pulling out moisture?
- Could variable-speed or two-stage equipment, or a lower fan speed, keep the coil working longer per cycle?
- Does the thermostat offer a dehumidify setting or show indoor humidity?
- Is a separate whole-house dehumidifier worth pricing, and where would it drain?
The federal efficiency floor
The Department of Energy places Florida in its hot-humid Southeast region. In that region, split-system central air conditioners installed on or after January 1, 2023 must be rated at least 14.3 SEER2 (13.8 SEER2 for 45,000 Btu/h and larger); split-system heat pumps must meet 14.3 SEER2 and 7.5 HSPF2 nationwide.
A SEER2 or HSPF2 number is earned by a tested pairing of outdoor and indoor equipment. When a bid quotes a rating, ask which condenser and which coil or air handler it was tested with, and request the AHRI reference number so you can check the pairing in the AHRI directory yourself.
Heat pump, gas furnace or dual fuel
Bids for the heating side usually fall into a few shapes: a heat pump with electric resistance backup, a gas furnace with a separate air conditioner, or a dual-fuel setup that switches between a heat pump and a furnace. For whichever is proposed, ask the contractor to explain the choice for your house. Find out the outdoor temperature at which the second heat source takes over, and how the thermostat is set up so resistance strips stay off whenever the heat pump can carry the load. A yearly running-cost comparison built on your own utility rates is fair to request, along with the working behind it.
Where the outdoor unit sits
The condenser or heat pump outside deserves its own line in the bid. Ask how it will be fastened to its pad or stand, what anchoring the manufacturer's installation manual calls for, and whether the crew will follow that manual. Ask which wind-related mounting rules, if any, apply at your address and who inspects them. Check that the unit will have the side and top clearance its maker specifies, that the pad is level, that roof runoff will not pour onto it, and that the refrigerant lines and electrical disconnect are protected from mowers and trimmers.
Ducts, returns and the condensate drain
New equipment cannot make up for a leaky or undersized duct system. Ask whether the bid includes a duct leakage test and a static pressure reading, which joints and boots would be sealed, whether any runs would be replaced or re-insulated, and whether the new blower needs more return air.
The water the coil removes has to leave the house too. Ask where the primary condensate line ends outdoors, whether there will be a secondary pan with a float switch that stops the system if the line backs up, and whether the line will have a trap and a cleanout you can reach.
Florida's contractor numbers
Florida contractors either hold a state certificate of competency, shown by a license number beginning with C, which lets them contract anywhere in the state, or a registration, beginning with R, which lets them contract only in the local jurisdictions where they met competency requirements.
Ask each bidder for that number. Then look it up on DBPR's license search and check that the license type matches the work.
Paperwork to settle before signing
- Which city or county permits does this job need, and who pulls them?
- Can you show proof of liability coverage and workers' compensation? Your own insurer can help you read it.
- Will your employees do the installation, or a subcontractor?
- What happens to the refrigerant in the system you remove?
- Once the new equipment is running, which measurements go on the start-up sheet (airflow, charge, the split between return and supply air), and will I get that sheet?
Lining up the bids
Set the proposals side by side and compare them on the same points: model numbers for both halves of the system, the matched SEER2 and HSPF2, the load calculation and the size it supports, backup heat, duct testing and repair, outdoor unit mounting, drain and float switch work, the thermostat, haul-away of the old equipment, permits, start-up readings, and written parts and labor warranty terms. Where one bid leaves an item out, ask about it before you compare prices.