NOAA's station named Columbia
NOAA's engineering weather data lists a station named Columbia, at an elevation of 899 feet. It gives a 1% summer design temperature of 92°F, paired with a mean coincident wet-bulb temperature of 76°F. On the heating side, the 99% winter design temperature listed for Columbia is 5°F.
A drinking-water note
Columbia's water is pumped from wells tapping a water-filled bed of sand and gravel beneath the bottomland along the Missouri River just southwest of the city, deposits left long ago by glacial meltwater.
A replacement, stage by stage
Swapping out a furnace, air conditioner or heat pump is less a single purchase than a small project with stages: the first call, the visit, the written proposal, the install day, the start-up, and the first heating or cooling season afterward, when anything left unsettled may show itself. Each stage offers a moment to ask something specific, and the notes below follow that order so you can keep them beside the phone.
Before anyone comes out
The first call sets the terms of the visit. Tell the scheduler what you want priced: a like-for-like swap, a whole new system, or a repair figure next to a replacement figure. Ask whether the person coming out will also write the proposal, or whether someone else prices it from their notes.
Then pull together what an estimator can use:
- a year of gas and electric bills, if you keep them;
- old service tickets and any warranty papers;
- photos of the nameplates on the indoor and outdoor equipment;
- a short list of complaints, by room and by season;
- anything changed since the present system went in, such as a finished basement, an addition, new windows or added attic insulation.
Hand every company the same packet. Proposals built from the same information are far easier to compare later.
What the estimator can look at
You learn a good deal from where the estimator goes in the house. It is reasonable to hope they will:
- open the furnace or air handler cabinet and look at the blower and coil, not only the label;
- go up into the attic, or down into the basement or crawlspace, wherever duct runs can be reached;
- measure rooms and windows, or ask whether you have a floor plan;
- ask who is home during the day and where people feel too warm or too cool;
- look at the electrical panel, the circuit feeding the outdoor unit and, with gas heat, the gas piping and the vent.
Ask whether a static pressure reading was taken on the existing blower and what it showed. If the visit never leaves the furnace closet, ask how the rest of the proposal was built.
What a sizing answer should settle
The capacity printed on a proposal deserves a reason behind it. Put these to each bidder:
- Was a room-by-room heating and cooling load calculation run, and does a copy come with the bid?
- Which outdoor design conditions went into it, and from what source?
- Which inputs were measured here, and which were assumed?
- How far is the proposed equipment from the calculated load, and why that margin?
- How does the equipment you propose handle moisture removal on days when it runs at part load?
Equipment arrangements to price
Ask every company to quote each setup it is willing to install, on separate lines:
- Gas furnace with an air conditioner. Request the furnace's AFUE rating, whether the burner fires at one rate, in stages or modulates, and what kind of blower motor it uses.
- Heat pump with electric backup. Ask for the maker's published heating output at low outdoor temperatures for the exact model, how much backup heat is included, and what brings it on.
- Heat pump paired with a gas furnace. Ask at what outdoor temperature the system changes over, who sets that point, and whether it can be changed later.
For each option, ask for a yearly operating estimate worked from your own utility rates, with the arithmetic shown on the page.
Ducts and airflow
A new unit pushes air through the same ducts the old one did unless the proposal says otherwise. Ask each bidder to describe in writing what they found on the runs they could reach: disconnected joints, crushed flex duct, uninsulated sections crossing an attic or crawlspace, and rooms with no return path. Ask whether duct sealing or a duct leakage test is offered, and get it as its own priced line. If one room has always lagged behind the rest, ask what change to supply or return ductwork would address it.
Questions for install day
Ask ahead of time:
- How long will the house be without heat or cooling, and who will be on site?
- How will floors and finished areas be protected along the path to the equipment?
- Will the refrigerant lines be replaced or reused, and if reused, how will they be cleaned and tested?
- Will the new refrigerant circuit be pressure-tested and evacuated before it is charged?
- Where will the condensate drain run, and is a safety float switch included?
- What will the outdoor unit sit on, and where will its electrical disconnect be mounted?
- How will the old equipment and its refrigerant be handled?
Start-up readings worth keeping
Ask the installer to write down the start-up numbers and leave a copy: the refrigerant readings used to set the charge, total external static pressure, the temperature difference across the coil, and, for a gas furnace, gas pressure, combustion and carbon monoxide readings. Ask what the thermostat was set up to do, including staging and any heat pump changeover point. Ask for the AHRI reference number for the matched indoor and outdoor pair.
License, permit and coverage questions
- What state license or registration, if any, covers this work, and what is the number?
- Which city permits does the installation call for, who files them, and when would an inspector come?
- Can you send proof of liability coverage and workers' compensation before the start date? Your insurer can help you read it.
- Will your own employees do the install, or a subcontractor?
- Who registers the equipment warranty, and what labor coverage do you put in writing?
The first season afterward
Ask what follow-up comes with the job: a return visit after the first heating or cooling season, a number to call, and what you should be watching for. Keep a short log of anything odd, such as a room that runs warm, frequent starts and stops, a new noise or water near the indoor unit, and raise it while the labor warranty is still fresh.
Holding the bids against each other
Lay the proposals out on one sheet with matching rows: equipment model numbers, AHRI reference, load calculation result, fuel arrangement and controls, duct work, line set plan, condensate plan, thermostat, haul-away, permit, start-up readings, warranty terms and payment schedule. Wherever a row stays blank, send that company a question before looking at its total.