Questions to Ask HVAC Installer Before You Sign
For homeowners getting bids on a new furnace, air conditioner or heat pump. The questions cover load calculations, ductwork and airflow, refrigerant, commissioning, permits and warranty, so you can judge the installation and not only the price.
The questions
Open any question for the note
What kind of work makes up most of your business, and how many systems like the one you are proposing did your crew install in the past year?
Why ask it
A company that mostly does commercial rooftop units or service calls may rarely commission a variable speed heat pump in a house. Recent repetitions with the exact equipment class matter more than the number of years on the truck door.
Are you licensed for mechanical work in my city or state, and can you have your insurer email me the liability and workers compensation certificates?
Why ask it
Certificates should arrive from the insurance agency with current dates rather than as a photo of a card in the glovebox. If an installer falls off your attic ladder and there is no workers comp coverage, the claim can land on your homeowners policy.
Will your own employees do this install, or is any of it subcontracted, and who is the lead installer on site?
Why ask it
Salespeople rarely install, and some firms hand the job to a rotating crew of subs. Getting a named lead tells you who owns the brazing, the duct connections and the startup numbers when something is off in August.
Can you give me two or three customers from at least three years ago whose systems I can ask about?
Why ask it
A new system feels great for the first month no matter how it was installed. Owners three or four seasons in will tell you about humidity problems, noisy returns, repeat service calls and whether anyone answered the phone.
Will you do a room by room Manual J load calculation for my house, and will you give me a copy, or are you sizing from square footage and the old unit?
Why ask it
Sizing off the outgoing equipment repeats whatever mistake was made last time, and rules of thumb like 500 square feet per ton routinely oversize by a full ton. An oversized air conditioner short cycles, never pulls out humidity, and leaves the house clammy at 72 degrees.
Why this specific equipment, and what else did you consider and rule out, including single stage versus two stage or variable speed?
Why ask it
The right answer connects your load numbers, duct capacity, humidity and budget to the model on the proposal. If the only justification is a brand relationship or a current promotion, you are being sold inventory rather than a designed system.
Is the indoor coil or air handler an AHRI certified match for that outdoor unit, and what is the rated efficiency of that exact combination?
Why ask it
Efficiency ratings apply to matched pairs, not to the condenser alone, and a mismatched coil can quietly cost you a rating point or two plus warranty coverage. Ask for the AHRI reference number on the quote so you can look it up yourself.
What refrigerant does this system use, and what does that mean for parts, service and any future repairs over the next ten years?
Why ask it
The industry has moved to lower global warming potential refrigerants, so new equipment, older equipment and your existing lineset may not share the same one. You want to hear that their techs are trained and equipped for what they are installing, not a shrug.
Have you measured the static pressure and airflow on my current system, and what numbers did you get?
Why ask it
A manometer reading takes ten minutes and reveals whether the ducts can actually move the air the new equipment expects. An installer who never puts a gauge on the system is guessing about the single most common cause of poor comfort and early compressor failure.
Do my existing ducts, returns and filter slot support the airflow this equipment needs, and exactly what duct work is included in the bid?
Why ask it
Undersized returns and crushed flex runs starve a system no matter how efficient the box is, and duct changes are the easiest line item to leave out of a low bid. Ask which runs get replaced or sealed, how many returns you will end up with, and what size filter cabinet goes in.
Are you reusing the existing refrigerant lineset, and if so how will you clean or flush it, or is a new lineset in the price?
Why ask it
A lineset carrying old oil or acid from a burned out compressor can kill a brand new one, and line sizing that suited the old unit may be wrong for this one. The answer should be either a documented flush and inspection or a replacement line, not silence.
Walk me through your evacuation and charging procedure, including nitrogen purge, micron target and how you verify the final charge.
Why ask it
Good installers braze under a nitrogen purge, pull the system down with a micron gauge to roughly 500 microns and hold it, then weigh in charge and confirm with subcooling and superheat. Someone who says they just braze it up and top it off is describing a system that will fail early.
If this is a heat pump, what is its capacity at my design temperature, where does the balance point fall, and how much backup heat are you installing?
Why ask it
Ratings published at 47 degrees say almost nothing about the coldest morning of the year, and capacity at your design temperature is the number that decides whether the house keeps up. Sizing the electric backup generously is the easy answer, and it is why some heat pump owners get a January bill three times the old one.
How is that backup heat controlled, and can it run at the same time as the compressor?
Why ask it
Strips locked out above the balance point and staged behind the compressor cost very little to run; strips that energize whenever the thermostat sees a two degree gap will dominate your winter usage. Ask what the control does on a recovery from setback, since that is when unrestricted backup usually fires.
If this is a gas furnace, will you run a combustion analysis and a carbon monoxide test at startup, and will you write down the readings?
Why ask it
Combustion numbers and a CO reading are what separate a real startup from lighting the burner and listening to it. They also give you a baseline, so a figure that has climbed at the next annual service becomes an early warning rather than a surprise in year six.
Where will the outdoor unit and indoor equipment sit, how loud is that unit, and how much service clearance will the next technician have?
Why ask it
A condenser under a bedroom window or wedged against a fence is a comfort and airflow problem, and published sound ratings vary by ten decibels or more between models. Cramped attic or closet placement raises the labor cost of every repair for the next fifteen years.
How are you handling condensate, including the drain route, a trap, a secondary pan and a float switch?
Why ask it
Attic and closet air handlers eventually plug their drains, and the ceiling below is where you find out. A float switch that shuts the system off costs very little and prevents a repair that insurance may argue about.
Does my electrical panel and circuit support this equipment, who does any electrical work, and is that in the quote?
Why ask it
Heat pumps with backup heat and larger air handlers often need a bigger breaker, new whip and disconnect, or panel capacity you do not have. This is a classic mid job change order, so settle who is responsible before demolition starts.
Who pulls the mechanical permit, who meets the inspector, and is the permit fee in the price?
Why ask it
Skipping the permit saves the contractor a fee and an inspection and leaves you with unpermitted work to disclose when you sell. An installer who calls permits unnecessary for a swap is telling you they would rather not have the job looked at.
At the end of the job, what measured numbers will you document for me, and who walks me through the thermostat settings?
Why ask it
A real commissioning sheet lists total airflow, static pressure, refrigerant charge with subcooling and superheat, temperature split, and combustion readings on gas equipment. Written numbers give you a baseline to compare against when performance drifts in year three.
What are the exact warranty terms: parts coverage length, the registration deadline, how long labor is covered, and what maintenance is required to keep it valid?
Why ask it
Most manufacturers require registration within roughly 60 to 90 days to extend parts coverage to ten years, and that step is often forgotten. Labor is a separate promise from the contractor, and its length is one of the biggest real differences between two similar bids.
Line by line, what does this bid include and exclude, how do change orders work, and what is the payment schedule?
Why ask it
Old equipment removal, refrigerant recovery, duct sealing, electrical, drywall patching, thermostat, filter cabinet, pad, permit and rebate paperwork are the items that turn a low bid into a surprise. A modest deposit with the balance at completed startup is normal, and a demand for most of the money up front is not.
Hiring an HVAC Installer Without Regret
Practical guidance for the conversation itself
How to Get Bids You Can Actually Compare
Make the Load Calculation the Entry Fee
Tell every bidder you want a room by room Manual J and a copy of the output. Contractors who size from the old nameplate will often disqualify themselves on the phone, which saves you two hours in your living room and the humidity problems that follow an oversized system.
Ask for the Same Three Numbers From Everyone
Request the AHRI matched pair reference number, the design airflow in CFM, and the measured static pressure on your existing ducts. When one bid is thousands cheaper, those numbers usually show it is a different system, not a better price.
Price the Ducts Separately From the Box
Have each proposal split equipment from duct, return, filter and electrical work. Otherwise the cheapest quote is simply the one that assumed your existing ductwork is fine, and you will pay for that assumption in comfort or in a second job later.
Put Commissioning in the Contract
Write in that final payment follows a startup report with measured airflow, static pressure, charge, temperature split and combustion readings where applicable. Installers who commission properly are happy to sign that. The rest will tell you why it is not necessary.
Handle Rebates and Registration Yourself if Needed
Ask which utility rebates or tax incentives apply to the exact model and who files the paperwork, then confirm the equipment is registered with the manufacturer once it is running. Both have deadlines, and both are worth real money you cannot recover later.
Numbers Worth Knowing Before the Sales Visit
- Sizing: from a Manual J load calculation, not the square footage per ton rules of thumb that commonly oversize by a full ton
- Airflow: roughly 350 to 400 CFM per ton of cooling, lower end in humid climates for better moisture removal
- Static pressure: most residential equipment is rated near 0.5 inches of water column total external, and readings well above that mean a duct problem
- Evacuation: pulled to about 500 microns and holding, verified with a micron gauge rather than a needle on a manifold
- Temperature split: commonly about 16 to 22 degrees between return and supply air on a properly charged cooling system
- Filter: a 4 inch media cabinet adds far less resistance than a 1 inch high MERV filter squeezed into a return grille
- Heat pump backup: staged and locked out above the balance point, since unrestricted electric strips are what create shocking winter bills
- Warranty registration: usually 60 to 90 days from installation to unlock the full 10 year parts coverage
- Labor warranty: often 1 year as standard, with 2 to 10 years available and a genuine differentiator between bids
- Deposit: a modest percentage up front, with the balance due after startup numbers are documented
Warning Signs Worth Walking Away From
A Quote Given Without Entering the House
Bids produced from a phone call, a satellite photo or a five minute look at the outdoor unit skip the load, the ducts and the returns entirely. Whatever is wrong with your current comfort will be reinstalled with a newer badge on it.
Sizing Up for Safety
Phrases like we will go up half a ton so you are covered are the most common expensive mistake in this trade. Oversized cooling short cycles, leaves humidity behind, wears out the compressor faster and makes the house feel worse at the same thermostat setting.
Today Only Pricing and Same Day Signatures
Manufactured urgency, a discount that expires when the salesperson leaves, or financing paperwork pushed before the scope is written are sales tactics, not engineering. Good installers are typically booked out and will still be there next week.
No Permit and No Inspection
An installer who says a changeout does not need a permit in your jurisdiction is usually avoiding scrutiny of gas venting, electrical and condensate work. That decision becomes your disclosure problem when you sell the house.
Vagueness About Startup
If nobody can tell you what gets measured on the last day, nothing will be. Charge by guesswork, unmeasured airflow and skipped combustion tests are how a properly specified system delivers mediocre comfort and a call back within two summers.