What an HVAC maintenance visit should include, what to ask the technician to write down, and what to keep for the warranty

Published September 30, 2026

• Deepsel, the publisher of this page, makes software for HVAC contractors, and the trial button in the header is for them. This page is for the person paying for the visit: a homeowner, a landlord or a building board. There is nothing on it to sign up for. The technician's checklists are linked at the end.
• This is general guidance. Your equipment's instructions, local code and a licensed technician come first. Every number and quote has a numbered source.

An HVAC maintenance visit is the once-a-season appointment where a technician cleans, tests and measures your heating or cooling system. You pay for it without taking a reading yourself, so the invoice, or the report the shop emails afterward, is your only record of what was done. If the visit ends with "everything looks good" and no numbers on either document, you paid for a sales call. A visit that leaves the readings behind was maintenance, even at $19.

What the visit should include, and who does what

Your part is small. ENERGY STAR says to look at the filter once a month and change it when it's grey.² The filter change log lists the interval by filter type and includes a sheet to tape inside the filter door. Trane says to keep shrubs and plants two feet from the outdoor unit on all sides,³ and a fence should get the same clearance. Then, on a humid day, find where the condensate drain line (the small pipe that carries water away from the indoor unit) ends. In a basement house it usually ends at a floor drain or a small condensate pump beside the furnace. Where the primary drain is the only line that ends outside, it should drip. In North Texas the primary usually runs to a plumbing drain inside the house, and the pipe that comes out of an exterior wall, often near the eave or an upstairs window, is the secondary: the emergency line from the pan under the unit. A drip there means the primary is blocked and the pan is catching the water; a Dallas home inspection firm and a North Texas contractor both say to watch for it.^{38, 39} Water on the floor by the indoor unit means the same thing. Either one is a reason to call the contractor.

Everything else belongs to the technician. Federal law requires EPA certification for anyone who services equipment that could release refrigerant,⁵ and gas and electrical testing are the technician's job as well. Carrier's own guide says to change the filters yourself and leave the tune-up to a professional.⁴ The task lists below follow ANSI/ACCA 4, the maintenance standard for houses, and ENERGY STAR.^{1, 2} We read the 2013 edition of the standard, the one available free online.

Two rows in that table promise less than the marketing lists do. ENERGY STAR and Carrier both print "clean" for both coils.^{2, 4} The standard says to inspect the fins and clean them as required,¹ and a full indoor coil cleaning is a separate job: $100 to $400 in place, or $400 to $700 with the coil pulled out (HomeGuide, updated August 2025).⁴⁰ A Texas contractor with offices in Houston, Dallas and Austin says the same on its own tune-up page.⁴¹ The refrigerant charge is the second row. ACCA 4 has the technician check the temperature drop and the airflow before putting gauges on the system, and a technician on r/HVAC lists his order the same way.^{1, 24} Expect line temperatures and the temperature drop at every visit, and gauges when those readings are off.

A cooling-season visit covers cooling. Trane calls for two visits a year, with the defrost control checked in the fall only.³ In September 2025 a homeowner on r/hvacadvice wrote that a $49 heat pump tune-up in August had covered the cooling side only. The reply with 168 upvotes came from a technician: some companies do check only cooling on a summer visit, the heating visit adds three other things, and those are better tested when it isn't hot outside. Another technician in the thread wrote, "The only dishonest part is calling it a tuneup."²⁶ Ask which side the visit covers before you book, and book the fall visit at the same time.

The numbers to ask for on the invoice

Carrier's guide says many contractors "will provide a written summary of the inspections and tests completed along with results and recommendations."⁴ Not every contractor does, so ask for one. The tables below list the results worth having. The ranges are what technicians see on most houses; where your equipment's nameplate prints a number, the nameplate wins. (The nameplate is the sticker with the model, serial number and ratings. It is on the side of the outdoor unit and inside the door of the furnace.) A mini split or inverter (variable-speed) system skips the static pressure row and the subcooling number; the section "Where this page applies" explains why.

Central air conditioner

Gas furnace

Heat pump

In spring a heat pump gets the air conditioner readings, weather permitting. The charge check needs an outdoor temperature of about 55°F or warmer,⁴³ so an early-spring invoice that says "charge not checked, outdoor 48°F" is an honest one, and the reading is owed on a warmer day. The fall visit adds the four readings below. On a dual-fuel system (a heat pump with a gas furnace as its backup) the heat strip row stays empty; the number to record instead is the outdoor temperature at which the controls switch to the furnace, what Carrier calls the balance point.⁴⁵ Steam from the outdoor unit during defrost and supply air that feels cool to the hand are both normal on a heat pump. The heat pump troubleshooting chart written for technicians quotes the manufacturers on both.

These are the words to say at the door; read them from your phone. In spring: "Please write these on the invoice: the temperature drop, the static pressure, the capacitor reading and the rating printed on it, the compressor amps and the rated amps on the sticker, and the refrigerant readings." In fall: "Please write these on the invoice: the carbon monoxide readings in the flue and in the house, the flame sensor reading, the gas pressure against the nameplate number, the temperature rise, and which safety switches you tested." A heat pump gets the spring request plus the four fall readings above. The technician writes the units. If a reading was skipped, the invoice should say why: too cold for the charge check, or not included in this visit's price.

How long it takes, and what it costs

Plan on about an hour per system. Carrier and Aire Serv both say one to two hours,^{4, 18} a Utah contractor says 60 to 90 minutes,¹⁹ and a furnace contractor who runs a combustion analysis budgets 90 minutes for the fall visit.²⁰ A visit that took fifteen minutes was a filter change and a look at the outdoor unit, whatever the invoice calls it.

The $19 visit and the $149 visit print the same checklist (the tune-up checklist page sorts the 21 advertised points into readings and padding). What differs is the time on site and the reason the company came. Ask when you book which readings the visit includes. At any price, expect the temperature drop, the amps, the capacitor reading and a flushed drain. On a full-price or plan visit, expect static pressure, the charge readings, a combustion analysis and a forced defrost as well; a furnace visit with a combustion analysis runs about 90 minutes.²⁰

Five Star explains the cheap visit on its own offer page: "Loss-leader. We offer a deep discount to new customers because we know if we do good work, you'll call us next time something breaks," and "The $19 doesn't cover our cost."¹⁹ One r/hvacadvice commenter draws the line at $100 ("Any tune up under $100 is a sales pitch"). A technician in the same thread, who sells two visits for $250 a year, disagrees: "not sure why most people here are saying they are a scam."²⁵ A cheap visit is not a scam on its own. The company hopes to earn the next call, and often what it sells you is a maintenance agreement, a yearly contract for two visits with a repair discount. That is a fair sale if the readings are on the invoice or the report, and the tables above are how you judge whatever the company recommends. The agreement runs the same checklist; the extra money buys a second visit that's owed and dated, and last year's readings on file. Before you sign, check who books the visits and when a paid visit expires. The HVAC maintenance agreement template on this site is written for shops, and it is the contract you should be handed.

Three questions before you approve a repair

In February 2026 a homeowner on r/hvacadvice booked a $125 furnace tune-up and ended the day with a condemned heat exchanger and a $13,000 replacement quote. The top reply came from a technician: "I would call 2-3 other companies and make them get you pictures of the heat exchanger."²⁷ Three questions, asked before you approve any repair, keep you out of that position.

1. What did you measure, and what should it be? Ask for the rating and the reading. "Rated 45, measured 40.1, tolerance 6 percent" is something a second company can check over the phone; "weak" is a word they cannot. One technician's rule: "I very rarely upsell anything unless it's out of spec."²⁵
2. Can I see it? Ask for a photo of the crack, or of the coil before and after cleaning. Some parts are condemned on sight rather than by a number: ACCA 4 says to replace a contactor with pitted, arced contacts, a capacitor that is bulged or split, and a flame sensor with a cracked insulator or wiring.¹ For those parts, the answer to "what did you measure" is the photo. A Texas furnace contractor's own checklist says: "Document everything in writing. Pressures, temps, amp draws, CO numbers, and a photo of the heat exchanger. You get a copy."²⁰
3. Is it safe to run tonight? If the answer is no, the equipment should be off and you should have that in writing. ACCA's standard tells the contractor to shut it off and tell the owner why, in writing.¹ The test is whether the technician shut it off at the gas valve, tagged it and wrote down the reason, or at least offered to. It is your furnace and you can refuse the shutdown. A technician who condemned the furnace and never offered to shut it off is the one to doubt. The technicians in the $13,000 thread asked that question first: "Did they lock out your furnace?"²⁷

If the answer to the third question is yes, you have time. Get the reading and the price in writing and decide tomorrow. For a capacitor or a contactor, the second opinion is a phone call: a second company can quote against the numbers on your invoice. (This page prices the visit and the plan; we have no sourced price for the small parts.) For a replacement quote, call the second company and ask for an inspection, a visit that measures and photographs without adjusting anything, so that their numbers sit next to the first company's. The HVAC inspection checklist is that sheet. Ask for their report with the numbers on it and compare it line by line. The same sheet is the one to ask for when you are buying a house.

Before you pay for a part, check whether the manufacturer's parts warranty covers it. The heat exchanger carries the longest term of any part in the furnace, and it is the part the $13,000 thread was about. On their current forms Trane, Lennox, Goodman and Carrier all cover the heat exchanger for 20 years at the least. Some models get lifetime coverage: Trane's and Carrier's when registered, Lennox's for the original owner (the model lists are in the source notes).^{30, 32, 46} Goodman goes further. If a registered furnace's heat exchanger fails in the first 10 years, Daikin replaces the whole furnace, once, with labor excluded.³⁵ A cracked exchanger on a registered Goodman under ten years old is therefore a new furnace for the cost of labor, and under any of these forms a furnace under 20 years old has a parts claim to make before anyone signs a replacement quote.

Records to keep for the warranty

Two different documents get called a warranty. The manufacturer's limited warranty came with the equipment. It covers parts that fail from a factory defect, usually for 5 years, or 10 if you registered on time, and it does not cover labor. Carrier has one exception: at registration, through a dealer in its Consumer Choice program, you can take 5 years of parts plus 3 years of labor instead of the 10-year parts term.²⁹ A home warranty plan is a service contract you buy each year from a company like American Home Shield to cover breakdowns from ordinary wear. AHS says it needs no maintenance records at all, and its New Jersey notice calls the plan separate from anything the builder or manufacturer provides.³⁴ Keep the two in separate folders.

Each brand words its maintenance requirement differently. We read the current residential warranty from the four biggest brands on September 30, 2026. They are 2022 to 2025 forms, dated in each row below, with the rest in the source notes. If your furnace went in in 2016, the certificate from its box is the one that counts; these forms show what the brands ask for today.^{28, 30, 32, 35, 46} Each is quoted below and linked in the sources.

The four forms split two ways. Lennox and Trane make maintenance by a licensed contractor a condition of coverage and can ask for the paperwork. Carrier and Goodman require "normal" maintenance and, in the documents we read, never ask you to prove it. All four warranty periods start on the installation date. If you cannot prove that date, Carrier, Trane, Goodman and Lennox start the period 90 days, 60 days, three months and six months after manufacture instead.^{28, 30, 32, 35} That makes the installer's invoice the most valuable paper in the folder. Trane's period starts on the day start-up is recorded on that invoice, with model and serial numbers included.³⁰

If the house changes hands, the warranty may or may not go with it. In Texas it does by law. Since September 1, 2021 the manufacturer's warranty on an air conditioning system that is part of the house transfers to the buyer automatically, at no charge, as if the buyer were the original purchaser,⁴⁷ and Carrier's forms carry a footnote saying so.²⁸ Elsewhere the brands differ. Carrier gives a second owner 5 years on parts with no registration.²⁸ Trane passes the balance of the term only if the transfer is made within 90 days of closing and any fee is paid.³⁰ Goodman's registered term lasts as long as the original registered owner or spouse owns and lives in the house, except in states that require transfer.³⁵ Lennox counts a later owner of the house as an owner, with the lifetime heat exchanger term dropping to 20 years for them.³² A buyer's folder needs the closing date next to the installation date.

Keep these in one folder for as long as you own the equipment:

• The installer's invoice with the model, serial number and installation date, plus the warranty certificate from the box. Lennox tells you to keep the installer's commissioning paperwork as well.³²
• The registration confirmation. Registering within 60 days (Trane, Lennox, Goodman) or 90 days (Carrier) is what turns the 5-year parts term into 10, "in most cases" in Trane's words; some Trane outdoor units get 12 years on the compressor when registered.^{29, 30, 31, 33, 36} Trane's 60 days run from the start-up date on the installer's invoice.³⁰ Some states forbid the condition. Goodman gives the registered term without registration in California, Florida, Georgia and Quebec,³⁶ Carrier does the same in California and Quebec and anywhere else that bans the condition,²⁸ and Trane in Florida from July 1, 2024.³⁰ The installation checklist has the deadlines for Daikin and Mitsubishi too, along with the close-out sheet your installer should have left you.
• Every maintenance invoice, dated, with the company's name, its license number where your state issues one, and the readings above written on it. Texas requires the license number on every invoice;⁴⁸ Minnesota has no state license for mechanical contractors, only a $25,000 bond filed with the state, and cities may license on their own.⁴⁹
• The photos the technician sends you.
• Your home warranty plan agreement and claim numbers, in a separate folder.

If you would rather type the record than file it, the equipment maintenance log template has one row per unit and one row per visit, with a column for the date the parts warranty ends. It was built for shops, but the printable page works for one house.

Where this page applies

The tables above are written for a split system (a central air conditioner or heat pump outside with a furnace or air handler indoors), a packaged unit (both halves in one cabinet outside) or a ductless mini split (wall-mounted indoor units with their own outdoor unit). Mini splits and inverter (variable-speed) systems get a shorter list. Their compressor changes speed to match the load,⁵⁰ so ACCA 4, the maintenance standard the tables follow, sends the technician to the maker's own procedure for the charge and skips its coil checklist for wall- or ceiling-mounted indoor units.¹ For those systems, ask for the charge and the electronics to be checked the maker's way, skip the static pressure row and the subcooling number, and hold the technician to the rest: filter, drain, coils, temperature drop, amps. Packaged units have their own checklist in the same standard, with the same tasks.¹ A condo or co-op apartment with its own equipment gets the same tasks too, though in a building over three stories it falls outside that standard's written scope without landing inside the commercial one.^{1, 37} The page stops at shared building equipment. VRF (one outdoor unit feeding many indoor units through shared piping), PTHPs (the through-the-wall heat pumps in hotels and some apartment buildings) and central plants (boilers, chillers or rooftop units serving a whole building) fall under a commercial standard, ASHRAE/ACCA 180, and need a service contract with its own task list. The commercial HVAC maintenance contract template shows what one looks like from the contractor's side, with that task list attached.³⁷ A board with a central plant should not judge its contractor by the tables on this page. A house heated by its own boiler has a separate list, the boiler maintenance checklist.

Where Deepsel fits

• Deepsel, the publisher of this page, makes software for HVAC contractors that tracks which maintenance-agreement visits a shop owes each customer and whether they happened. If your contractor uses it, that is where the record of visits owed and delivered lives. The readings live on the paper invoice either way.
• We wrote this page because the technician checklists on this site kept reaching homeowners, and those checklists are written for a different reader. The software mention is advertising. Everything else on the page has a source.

The sheet to hand the technician

Each sheet prints the target beside the task and leaves a blank for the reading. First ask the technician for the shop's own report with the numbers on it (Carrier says many contractors provide one⁴) and compare it line by line to the sheet. Hand the sheet over if the shop is willing to fill it in. For a house with one air conditioner, one furnace and no plan: use the tune-up report card for a promotional visit, the AC checklist for a full spring visit and the furnace checklist for a full fall visit.

• HVAC tune-up checklist and report card: two pages, 21 points per season, readings table on page two.
• AC maintenance checklist: the spring cooling visit, with the temperature drop, static, capacitor and refrigerant targets.
• Furnace maintenance checklist: the fall visit, with the carbon monoxide, gas pressure and temperature rise targets.
• Heat pump maintenance checklist: both seasons, including the reversing valve, defrost and heat-strip tests.
• HVAC maintenance checklist: the five-page sheet a shop uses under a maintenance agreement, spring and fall in one file, with a line for which agreement visit this is. If you are on a plan, ask for this one.

All of them are on the free HVAC checklists page.

Frequently asked questions

How often should HVAC maintenance be done?

Twice a year if you have a furnace and an air conditioner, or a heat pump: the cooling side in spring and the heating side in fall, before contractors get busy. That is ENERGY STAR's schedule, and ENERGY STAR also asks you to look at the filter once a month. A home with only an air conditioner needs the spring visit.

Does skipping maintenance void the manufacturer's warranty?

It depends on the brand. Lennox's current residential warranty says failure to maintain the equipment voids it, and that proof of prior maintenance may be required. Trane makes maintenance by a licensed contractor a condition of coverage and may ask for written documentation. Carrier and Goodman require normal maintenance and, in the documents we read on September 30, 2026, never ask you to prove it. A home warranty plan is a separate contract, and American Home Shield says it needs no maintenance records at all.

What should be on the invoice after a maintenance visit?

The date, the company's name and its license number where your state issues one, the model and serial number of each unit, the filter size, the readings from the tables on this page, any part replaced along with the reading that justified it, and anything recommended with a price next to it. The signed invoice is the document a manufacturer can ask for later, so keep it.

Is a $19 or $49 tune-up worth booking?

Yes, if the numbers get written down. The company loses money on the visit and hopes to earn the next call; some say so on their own offer pages. Often what it sells you is a maintenance agreement, which is a fair sale if the readings are on the invoice or the report. Ask for the readings and the photos before the technician leaves. A visit that ends with 'everything looks good' and no numbers on the invoice or the report was a sales call.

Sources

1. Air Conditioning Contractors of America, ANSI/ACCA 4 QM-2013, "Maintenance of Residential HVAC Systems" - scope 2.1: "minimum requirements for the inspection, by appropriately licensed HVAC contractors, of residential HVAC equipment found in one- or two-family dwellings of three or fewer stories"; Checklists 5.4 (gas furnace), 5.7 (evaporator coil), 5.8 (condensing unit) and 5.8-HP ("Test reversing valve operation," "Test defrost cycle controls"); 5.9 ("Test electric heater's capacity and sequence of operation"); 5.13 (package units); motor amps against nameplate; 5.4 item w: "Inspect ceramic insulator, flame probe, and associated wiring for any cracks or abnormalities"; 5.4 item x: "Record micro-amps for comparison with OEM specifications"; 5.7 item i: "Inspect coil fins. Ensure fins are visibly clean, straight, and open. Clean and straighten as required"; 5.7 note: "Does not apply to wall- or ceiling mounted evaporator units matched with a ductless mini split" and "a good diagnostic field practice is to measure superheat or subcooling to ensure proper refrigerant charge. See OEM instructions for inverter-driven equipment"; 5.8 item f: "Replace contactors and relays demonstrating evidence of excessive contact arcing and pitting"; 5.8 item h: "Inspect motor capacitors. Replace those that are bulged, split, incorrectly sized, or do not meet OEM specifications"; 5.8 item l: "If indoor airflow is within OEM specifications but TD is not (see Checklist 5.7 #h), check refrigerant charge using manufacturer recommended procedure"; 5.8 item o: "Inspect coil fins. Clean, straighten, and repair as required"; section 3.3.7: "the contractor shall shut off the equipment and advise the occupant and/or owner, in writing, of the unsafe condition." transductiontechnologies.com (PDF mirror of the 2013 edition), read September 5, 2026. The current edition is ANSI/ACCA 4 QM-2019 (R2024), sold by ACCA.
2. ENERGY STAR, "Maintenance Checklist" - "Inspect, clean, or change air filters once a month in your central air conditioner, furnace, and/or heat pump"; "check the cooling system in the spring and the heating system in the fall"; contractor tasks including "Check and inspect the condensate drain," "Clean evaporator and condenser air conditioning coils," "Tighten all electrical connections" and "Check all gas (or oil) connections, gas pressure, burner combustion and heat exchanger." energystar.gov, read September 5, 2026.
3. Trane, "Home Heat Pump Maintenance" - "Schedule a preventative maintenance checkup with your local dealer twice a year"; dealer list includes "Inspect the reversing valve" and "Check the defrost control operation (in the fall only)"; "keep shrubs and plants at least 2 ft. away from the heat pump on all sides"; check for snow or ice build-up in winter. trane.com, read September 5, 2026.
4. Carrier, "AC Tune-Up Service: Costs, Checklist & Benefits" (Ryan Mayes, expert review by Michelle Notaro) - "typically costing $75–$200 and taking 1–2 hours"; "Inspecting and cleaning the condensate drain line: The drain line is cleared to prevent clogs that can cause water damage or humidity issues"; "many contractors will provide a written summary of the inspections and tests completed along with results and recommendations"; task list includes "Cleaning the evaporator coils and condenser coils"; "You can perform some basic AC maintenance tasks yourself, like changing filters, but a full AC tune-up is best handled by a professional." carrier.com, read September 30, 2026.
5. U.S. EPA, "Section 608 Technician Certification Requirements" - "Technicians who maintain, service, repair, or dispose of equipment that could release refrigerants into the atmosphere must be certified." epa.gov, updated July 15, 2026, read September 5, 2026.
6. Centers for Disease Control and Prevention, "Carbon Monoxide Poisoning Basics" - "Install battery-operated or battery back-up CO detectors near every sleeping area in your home"; "Have your heating system, water heater, and any other gas, oil, or coal burning appliances serviced by a qualified technician every year." cdc.gov, read September 30, 2026.
7. Bryan Orr, HVAC School, "The '5 Pillars' of Residential A/C Refrigerant Circuit Diagnosis" - "The air temperature split during typical conditions will be between 16 and 22 degrees' difference from the return to the supply"; "Typical ranges for subcooling are between 8 and 14 degrees on a TXV system." hvacrschool.com, July 24, 2019, read September 5, 2026. On humidity lowering the split: Genry Garcia, HVAC School, "20° ΔT (Delta T), A Lazy Rule of Thumb," hvacrschool.com, April 5, 2019, read September 5, 2026.
8. Bryan Orr, HVAC School, "Static Pressure, Manometers, and Magnehelics" - "Total external static pressure is return plus supply, positive plus negative, and in general, you would like to see it be 0.5″ or less"; 0.8″ or higher points to a problem on most newer residential systems. hvacrschool.com, April 12, 2024, read September 5, 2026.
9. Bryan Orr, HVAC School, "Testing Run Capacitors the Smart (and Easy) Way" - "Most capacitors allow for a 6%+/- tolerance. If it's outside of that range, then replacement of the capacitor may be necessary." hvacrschool.com, March 4, 2017, read September 5, 2026. Genteq capacitor catalog GTC-02/10, "Capacitance Tolerance: ±6%," pdf.product.network, read September 24, 2026.
10. Bryan Orr, HVAC School, "Gas Furnaces - What a Tech Needs to Know" - "Below 100 PPM is the recommended CO air free target"; "If you have 400 PPM or above, you are required to shut down the furnace"; flame sensor "between 1 and 10 microamps, preferably between 2 and 6"; manifold pressure "usually between 3.2 and 3.8″ WC," LP "10.5-11.5″ WC." hvacrschool.com, March 3, 2023, read September 5, 2026.
11. National Comfort Institute, Jim Davis, "Carbon Monoxide Test Numbers: What Do They Mean?" - "1-9 PPM - Maximum allowable short-term exposure in a living area"; "If CO readings begin to rise, even slowly, there's an indication of a problem." nationalcomfortinstitute.com, read September 5, 2026.
12. U.S. Consumer Product Safety Commission, "Furnace CO Emissions Under Normal and Compromised Vent Conditions" - "ANSI Z21.47 standard (1998) requires that an air-free flue gas sample of CO not exceed a maximum of 400 ppm." cpsc.gov (PDF), read September 24, 2026.
13. Bryan Orr, HVAC School, "Furnace Air Temperature Rise" - "Every gas furnace data plate/tag has a specification for the temperature rise through that furnace. It is shown in a range like 50-80° or 45-75°"; a rise near the top of the range means low airflow and "the furnace may begin cycling on the limit control." hvacrschool.com, December 26, 2022, read September 5, 2026.
14. Matthew Bruner, HVAC School, "Diagnosing a Reversing Valve" - "The generally accepted temperature differential for a properly functioning valve from hot line to hot line or cold to cold is 3-5 degrees Fahrenheit." hvacrschool.com, March 17, 2023, read September 5, 2026.
15. Bryan Orr, HVAC School, "Electric Heat Troubleshooting, Service, and Math Class" - "you can usually (but not always) expect 5kW heaters to draw 20 amps and 10kW to draw 40 amps but still 20 amps per strip." hvacrschool.com, November 1, 2021, read September 5, 2026.
16. HVAC School, "Heat Pump Defrost Troubleshooting Tips" - forced defrost through the board's test pins; "Watch the system come out of defrost and verify that the condenser fan comes back on"; maximum defrost about 10 minutes on Carrier boards. hvacrschool.com, November 30, 2024, read September 5, 2026.
17. Bonneville Power Administration (the federal power marketer for the Pacific Northwest), "PTCS Lockouts and Balance Points: Reference Guide" - "PTCS Spec: Set auxiliary heat lockout to 35°F or lower"; "Incorrect lockout settings result in the majority of inspection failures"; the lockout is "Controlled through" a thermostat with a Wi-Fi weather station, a thermostat with an outdoor temperature sensor, or the "Outdoor unit control board or mechanical lockout." bpa.gov (PDF), read September 5, 2026.
18. Aire Serv, "HVAC Tune-up Checklist: What Does It Include?" - "seasonal HVAC maintenance appointments take 1 to 2 hours." aireserv.com, July 30, 2026, read September 5, 2026.
19. Five Star Heating & Air, "$19 AC Tune-Up St. George" - "$19 (normally $49) for first-time customers"; "Loss-leader. We offer a deep discount to new customers because we know if we do good work, you'll call us next time something breaks"; "The $19 doesn't cover our cost"; "60-90 minutes for most homes." fivestarut.com, read September 5, 2026.
20. Jason Stom, Clear the Air, "Furnace Tune-Up Checklist" - "A real fall furnace tune-up takes about 90 minutes"; "Document everything in writing. Pressures, temps, amp draws, CO numbers, and a photo of the heat exchanger. You get a copy." cleartheairac.com, October 15, 2024, updated May 9, 2026, read September 5, 2026.
21. Alexis Carthan, This Old House, "How Much Does an AC Tune-Up Cost? (2026 Guide)" - "Air conditioning (AC) tune-ups typically cost $65-$200," average $133. thisoldhouse.com, updated March 27, 2026, read September 5, 2026.
22. Dan Simms, Fixr, "How Much Does HVAC Maintenance Cost in 2026?" - "An annual tune-up costs an average of $275," range $150 to $350; "An HVAC service contract costs between $150 and $500 per year." fixr.com, updated January 30, 2026, read September 5, 2026.
23. Service Champions, "Air Conditioner Maintenance and Tune-Up" - "21-Point 'WOW!' Air Conditioner Tune-Up including a FREE Water Heater Safety Inspection for Only $88 (reg $149)." servicechampions.net, read September 5, 2026.
24. r/HVAC, "What is your AC tune up checklist?" - AustinHVAC419 (17 upvotes): "delta across indoor coil, blower amps + blower capacitor (if applicable), compressor and OD fan amps + dual capacitor under load, refrigerant line temperatures (check pressures if temp drop and line temps aren't normal)"; OkFail3716's full strip-and-clean list priced at "204 for a year membership 2 tune ups" (2 upvotes, April 14, 2023). reddit.com, April 13, 2023, read September 5, 2026.
25. r/hvacadvice, "HVAC tune up versus Preventative maintenance contracts?" - BuzzyScruggs94 (2 upvotes): "Any tune up under $100 is a sales pitch"; ALonelyWelcomeMat (4 upvotes): "I very rarely upsell anything unless it's out of spec," and in the same thread "the two tune ups for $250 a year. Not too bad and worth it for a lot of people, not sure why most people here are saying they are a scam." reddit.com, September 15, 2024, read September 5, 2026.
26. r/hvacadvice, "AITA? Should a tune-up include both sides of a heat pump?" - $49 tune-up on August 15, 2025 covered cooling only; tomat916 (168 upvotes): "Some places only check the cooling operation during a summer visit but there's only three other things they will check that's different during the heating visit and it's better tested when it's not hot outside"; 1991gts (36 upvotes): "The only dishonest part is calling it a tuneup. Just call it routine maintenance and inspection." reddit.com, September 22, 2025, read September 5, 2026.
27. r/hvacadvice, "Called for a Tune Up, got a $13,000 quote" - $125 tune-up; top reply, 159 upvotes: "I would call 2-3 other companies and make them get you pictures of the heat exchanger"; FormerAircraftMech (30 upvotes): "Did they lock out your furnace? If there were really worried about it even though it's cold they would lock it out so you don't die"; a second reply noted that a company that believed the heat exchanger was cracked would have locked the furnace out. reddit.com, February 2, 2026, read September 5, 2026.
28. Carrier Corporation, "Limited Warranty for Air Conditioner & Heat Pump Condensing Units with Puron (R-410A) Refrigerant," form ACHPVS-C-02WAR, 07/2023 - "warrants this product against failure due to defect in materials or workmanship under normal use and maintenance"; "RESIDENTIAL APPLICATIONS"; warranty table for "Air Conditioner or Heat Pump Condensing Unit Models 24VNA6, 25VNA4": original owner parts and compressor "10 (or 5)," subsequent owners 5; table footnotes: "In Texas and other jurisdictions where applicable, subsequent owner's warranty duration shall match that of original owner (10 or 5 years, based on registration), as described in applicable law" and "If properly registered within 90 days of original installation, otherwise 5 years (except in California and Quebec and other jurisdictions that prohibit warranty benefits conditioned on registration)"; Condition 4: "The limited parts warranty periods as shown in the table under Subsequent Owners do not require registration"; Warranty Condition 1: registered "within ninety (90) days of original installation" for the longer term; Condition 3: if the installation date "cannot be verified, then the warranty period begins ninety (90) days from the date of product manufacture... Proof of purchase may be required at time of service"; Condition 7: "Installation, use, care, and maintenance must be normal and in accordance with instructions contained in the Installation Instructions, Owner's Manual and Company's service information"; not covered: "Normal maintenance as outlined in the installation and servicing instructions or Owner's Manual, including filter cleaning and/or replacement and lubrication." shareddocs.com (Carrier's document server, PDF), read September 30, 2026.
29. Carrier, "Carrier Warranty Registration and Information" - "you must register your eligible equipment within 90 days of installation"; "If you register after 90 days, the standard 5-year parts warranty applies with no labor coverage"; Consumer Choice Warranty: "Upon timely registration of eligible new Carrier equipment, you can select either a 10-year parts-only limited warranty or a 5-year parts plus 3-year labor limited warranty," and "the 5-year parts plus 3-year labor warranty option is available only if your installing dealer or contractor has officially elected to participate in the Consumer Choice program." carrier.com, read September 30, 2026.
30. Trane U.S., Inc., "Base Limited Warranty" for outdoor products, form GW-OTDR-2401B, and for furnaces, form GW-FURN-2401A, both © 2024 - products "installed in residential/multi-family application (personal, family, or household use) and subject to normal use and maintenance"; Commencement Date is when start-up "has been properly completed and recorded on the installer's invoice, which includes all model and serial numbers of the installed Product(s)," otherwise "sixty (60) days after the factory manufacture date"; "Company may request proof of Product purchase and/or installation, including installation address"; Eligibility Requirements: "The Product(s) must be properly installed, operated, and maintained by a licensed HVAC service provider in accordance with the Product specifications or installation, operation, and maintenance instructions provided by Company with each Product. Failure to conform to such specification and/or installation, operation, and maintenance instructions shall void this limited warranty"; "Company may request written documentation showing the proper preventative maintenance"; "This limited warranty applies to Products manufactured on or after March 1, 2024"; "All claims under this limited warranty must be filed within 90 days of failure date"; registration "within sixty (60) days of the Commencement Date"; transfer to a subsequent owner "provided the transfer is made within ninety (90) days from the date of closing on the sale of the residence and the applicable transfer fee, if any, has been paid in full"; "Florida Residents Only: Beginning July 1, 2024, Failure to complete product registration does not diminish any warranty rights or decrease the limited warranty length"; GW-OTDR-2401B Table 1, for 4TTV, 4TWV and related models: "Registered Limited Warranty Period: Compressor – twelve (12) years, Outdoor Coil, Parts – ten (10) years"; GW-FURN-2401A Table 1: L8X1, L9X1, S8X1, S8X2, S8B1 "Base Limited Warranty Period: Parts – five (5) years, Heat Exchanger – twenty (20) years" and registered "Parts – ten (10) years, Heat Exchanger – twenty (20) years"; L8V1, S8V2C, S9B1, S9V2, S9X2, S9X1 and others registered "Heat Exchanger – Lifetime." trane.com, GW-OTDR-2401B and trane.com, GW-FURN-2401A (PDFs), both read September 30, 2026.
31. Trane, "Warranty and Registration" - Base Limited Warranty "goes into effect for units that aren't registered or were registered more than 60 days after installation... In most cases, this warranty lasts five years"; Registered Limited Warranty "if your product is registered within 60 days of installation... In most cases, this warranty lasts for 10 years." trane.com, read September 30, 2026.
32. Lennox Industries Inc., "Lennox Equipment Basic Limited Warranty," form W900001-01, 3/1/2025 (supersedes 10/1/2024) - "Failure to maintain equipment will void this Basic Limited Warranty"; "(Residential Applications only)"; if the installation date "cannot be verified, the Warranty Period begins six (6) months after the date of manufacture"; "All warranty claims must be submitted within forty-five (45) days of the applicable product failure date"; claim requirements followed by "NOTE - Proof of prior maintenance and purchase may also be required"; Exclusion 1: "Replacement components will not be provided under this Basic Limited Warranty unless the Equipment containing the defective component is properly installed and maintained by a licensed professional HVAC installer or licensed HVAC contractor in accordance with Lennox' installation, operation, and maintenance instructions"; "retain this warranty for records and future reference. As well, retain proof of commissioning documentation from the installer"; heat exchanger table: EL180E, EL180NE, EL280, EL280E "Twenty (20) years -- Residential Applications"; EL195E, EL195NE, EL196E, EL296E, EL296V, EL297E, EL297V, ELO183 "Limited Lifetime -- Original Owner in Residential Applications; Twenty (20) years -- Subsequent Owners in Residential Applications"; definition 5: "Owner" includes "the owner(s) and subsequent owner(s) of the premises where the Equipment is originally installed." lennox.com (PDF), read September 30, 2026.
33. Lennox, "What is the Lennox 10-Year Extended Limited Warranty Program?" - "In order to receive the extended limited warranty, qualifying products must be registered within 60 days of installation. All terms and conditions of the basic Limited Warranty apply to the Extended Limited Warranty." lennox.com, read September 30, 2026.
34. American Home Shield, "HVAC Warranty: What to Expect from AHS Warranty Coverage" - "Some home warranty providers require proof of regular maintenance before approving a service request. With American Home Shield AC coverage, that's not the case. You do not need to provide maintenance records for your system to qualify for repair or replacement"; "New Jersey Residents: The product being offered is a service contract and is separate and distinct from any product or service warranty which may be provided by the home builder or manufacturer." ahs.com, read September 30, 2026.
35. Goodman (Daikin Comfort Technologies Manufacturing, L.P.), "Limited Warranty" for gas furnace models CCVS80 through CDVS96, part no. PWCFURNUQNTE, 04/2025 - "This warranty applies to heating and air conditioning units installed in owner-occupied residences" (a second section covers residences not occupied by the owner); "This warranty covers parts of this heating or air conditioning unit that fail under normal use and maintenance"; not covered: "Normal maintenance as described in the installation and operating manual, such as cleaning of the coils, filter cleaning and/or replacement, and lubrication" and "Damage or the need for repairs resulting from any improper use, maintenance, operation, or servicing"; if the installation date "cannot be verified, the installation date is three months after the manufacture date"; unregistered, "5 YEARS after the installation date for all other parts"; "If the unit is properly registered online within 60 days after the installation date, an additional warranty (the 'Registered Additional Term Warranty') is provided"; unregistered, "20 YEARS after the installation date for the heat exchanger"; "The Registered Additional Term Warranty lasts for as long as the original registered owner or his or her spouse ('registered owner') owns and resides in the residence in which the unit was originally installed," a limit that "does not apply to any owner of a unit installed in any state that requires that the warranty of a heating or air conditioning unit be transferred if the property containing that unit is conveyed to a new owner"; "If the heat exchanger in any properly registered unit fails during the first 10 YEARS after the installation date, Daikin will, except as set forth below, furnish a new, equivalent unit to replace the entire unit, once only, without charge"; "If the heat exchanger in any unit that is properly registered fails within the first 20 YEARS after the installation date, Daikin will furnish a replacement heat exchanger without charge"; "Daikin will not pay for: Labor, freight, or any other cost associated with the service, repair, or operation of the unit." Copy hosted by Alpine Home Air, a Goodman dealer: documents.alpinehomeair.com (PDF), read September 30, 2026. Goodman serves the certificate for a specific unit through its warranty lookup by model and serial number.
36. Goodman, "Gas Furnace Limited Warranty: The Why, When, How" - "If the unit is not registered within the 60-day window of the installation date, the gas furnace's applicable warranty period is 5 YEARS"; registered within 60 days, "up to 10 YEARS"; "Residents of California, Florida, Georgia and Quebec do not need to register the product in order to get all the rights and remedies of registered owners under the limited warranty." goodmanmfg.com, read September 30, 2026.
37. ANSI/ASHRAE/ACCA Standard 180-2012, "Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems" - section 2.2.1 scope excludes "single-family houses or multi-family structures of three or fewer stories above grade." Public copy of the 2012 edition: philcoaircontrol.com (PDF), read September 5, 2026. The current edition is 180-2018, sold by ASHRAE.
38. Green Scene Home Inspections for CandysDirt.com, "Inspection Tip: Don't be a Drip, Get Your A/C Drain Fixed" - "a very common problem in North Texas homes: clogged air conditioner drains"; "The primary condensate line runs from the evaporator to a plumbing 'trap' in the house, usually in a bathroom sink"; "When the primary condensate line is clogged, the water drips into the pan under the air conditioning unit, which drains through another plumbing line," the secondary, "to the exterior of the house"; "locate that secondary condensate drain line on the outside of your house, and check it now and then to see if it's dripping." candysdirt.com, September 23, 2020, read September 30, 2026.
39. Texas AC Services, "Water Leaking from Your AC's Secondary Drain Line? Here's Why You Should Call a Pro" - "your secondary AC drain line is likely active. This isn't normal"; "it's often a sign that your primary drain line is clogged"; the primary "connects to your home's plumbing"; "In most North Texas homes, the secondary AC drain line is located: Near an upstairs window, On the side of the house below the attic, At the roof eave or soffit, Above a garage or exterior door." txac.pro, May 21, 2025, updated April 22, 2026, read September 30, 2026.
40. Tamatha Hazen, HomeGuide, "How Much Does It Cost to Clean AC Coils? (2026)" - "Evaporator coil cleaning costs $100 to $400 to clean the coil in-place or $400 to $700 to remove and clean the coil. Condenser coil cleaning costs $75 to $230." homeguide.com, updated August 22, 2025, read September 30, 2026.
41. Trilogy AC (Houston, Dallas and Austin), "How Much Should an AC Tune-Up Cost?" - "a tune-up doesn't typically include cleaning the evaporator coil, recharging refrigerant, or leak detection." trilogyac.com, June 28, 2024, read September 30, 2026.
42. Bryan Orr, HVAC School, "Refrigerant Charging Basics for Air Conditioners and Heat Pumps" - "The piston/fixed orifice type system primarily uses the superheat method, and the TXV/EEV primarily uses the subcooling method"; on some Lennox heat pumps the subcool chart "is only valid when the outdoor temperature is below 65˚" and "requires that you block sections of the coil." hvacrschool.com, February 24, 2025, updated July 29, 2026, read September 30, 2026.
43. Trane and American Standard, "Service Facts" for the RunTru A4HP4017 split system heat pump, A4HP4017-SF-1C-EN, October 2020 - section "Subcooling Charging in Cooling between 55° F and 120° OD Ambient"; "Subcooling (in the cooling mode) is the only recommended method of charging above 55° ambient temperatures"; "the indoor temperature should be kept between 70° to 80° F"; "Always verify proper system charge via subcooling (TXV/EEV) or superheat (fixed orifice) per the unit nameplate." Copy hosted at wbmemphis.com (PDF), read September 30, 2026.
44. Carrier, "58MVP Series 170 & 180, 58MVB, 58UVB Troubleshooting Guide," form 58-06T, 6-08 - "Proper flame sense micro amps (.5 micro amps DC min., 4.0 – 6.0 nominal)"; flame current "near typical value (4.0 to 6.0 microamps)"; for a two-stage furnace, "Reference installation instructions for proper low-heat manifold pressure." shareddocs.com (Carrier's document server, PDF), read September 30, 2026.
45. Travis Baugh, Carrier, "What is a Dual Fuel Heating System?" (expert review by Seth Faber) - "combines an electric heat pump with a gas furnace"; "When outdoor temperatures fall below the system's selected balance point, the controls can switch to the gas furnace"; "there is not one universal temperature at which every" dual fuel system switches. carrier.com, read September 30, 2026.
46. Carrier Corporation, "Limited Warranty for Condensing Gas Furnace with Tube and Fin Secondary Heat Exchanger," catalog no. 90GSFRN-C-01WAR, edition date 09/22 - table: "Infinity, Performance, Comfort (59SC6) Gas Furnace" parts "10 (or 5)," heat exchanger "Life (or 20)": "If properly registered within 90 days of original installation, otherwise 20 years (except in California and Quebec and other jurisdictions that prohibit warranty benefits conditioned on registration)"; "Comfort (59SC2, 59SU5) Gas Furnace" heat exchanger 20 years for original and subsequent owners; same Texas footnote and Warranty Condition 7 as the condensing unit form. shareddocs.com (PDF; the same edition is the "Warranty Card" linked from Carrier's 59TP6 product page). Non-condensing furnaces: "Limited Warranty for Non-Condensing Gas Furnace," catalog no. 80GSFRN-C-01WAR, edition date 09/22, heat exchanger "20" for original and subsequent owners, shareddocs.com (PDF). Both read September 30, 2026.
47. Texas Business and Commerce Code § 608.002, "Transfer of Manufacturer's Warranty" - a manufacturer's warranty on an air conditioning system that is a fixture of conveyed residential real property "(1) is automatically transferred to the new owner; and (2) continues in effect as if the new owner was the original purchaser"; the warrantor "may not charge a fee for the transfer of the warranty"; the transfer "does not extend the original term"; "Added by Acts 2021, 87th Leg., R.S., Ch. 815 (H.B. 2110), Sec. 1, eff. September 1, 2021." law.justia.com, 2022 code, read September 30, 2026.
48. 16 Texas Administrative Code § 75.71, "Responsibilities of the Contracting Company," subsection (i) - "An invoice must be provided to the consumer for all air conditioning and refrigeration work performed. The company name, address, and phone number must appear on all proposals and invoices. The affiliated licensee's number must appear on all proposals and invoices for air conditioning and refrigeration work." law.cornell.edu, read September 30, 2026.
49. Minnesota Department of Labor and Industry, "Mechanical contractor bond requirements" - "While there is no state license required for mechanical contractors, businesses must file a $25,000 mechanical contractor bond with DLI in order to contract to perform gas, heating, ventilation, cooling, air conditioning, fuel burning or refrigeration work"; "mechanical contractors must comply with local licensing requirements"; "cities may require licensure or a competency card for workers performing mechanical work." dli.mn.gov, read September 30, 2026.
50. Emily Gutowski, HVAC School, "Mini-Splits for New HVAC Techs" - "these systems use an inverter-driven compressor to control capacity (some have an AC compressor, others have a DC compressor; refer to the manufacturer's literature or data plate)." hvacrschool.com, February 3, 2021, updated July 19, 2026, read September 30, 2026.