Heat and Air Handbook is an independent, plain-English guide to the central air conditioner and gas furnace a US household already has. It explains why a system stopped cooling or heating, what a blinking light or a code means, what the maker gives owners to check and where that stops, how to keep the system going, what the refrigerant and efficiency rules mean for the equipment you have now, and when repair stops making sense. We cover furnace problems, AC problems, maintenance and filters, thermostats and parts, refrigerant and efficiency rules, and repair or replace.
General information, not professional advice. Your system’s maker, your manual and a qualified technician decide what’s safe for your equipment, and local codes decide what needs a permit or a licensed installer. If you smell gas, leave the house now and call 911 or your gas utility from outside.
What we do
Much of what is written about home heating and cooling is a seller’s page, and the sources that matter often disagree. Take the furnace filter. ENERGY STAR tells owners to inspect, clean or change it once a month (maintenance checklist). Goodman’s service manual for its 80% single-stage furnaces says every two months or as required (RS6621301). Carrier’s owner’s manual for its 80% furnaces says to check the filter every 4 weeks (80GSFRN-B-03OM, Edition 08/22). The EPA says manufacturers typically recommend replacement every 60 to 90 days (Guide to Air Cleaners in the Home). All four were read on 10 November 2026. Each is right for what it covers, and none is an average of the others.
So every step, code meaning, interval, rule and figure on this site carries its source: the maker’s document by number and edition, the federal rule by section, or the model code by section and edition, with the day we read it. Where sources disagree, we show them side by side. The makers we have read draw the same line: filters and the checks before a service call are the owner’s, and most other work is for trained service people. Carrier’s installation manual for its 59SC5 furnace puts it plainly: untrained people can clean and replace air filters, and “all other operations must be performed by trained service personnel” (59SC5A-11SI, Edition 10/18). Our pages show that line, explain what lies past it, and say at each step where the maker reserves a job for a technician. Our how we check page explains where each kind of fact comes from. Pages are published under the Heat and Air Handbook name.
What we are not
Heat and Air Handbook is not an HVAC contractor, a technician, an equipment maker, a parts seller, a retailer, a gas or electric utility, or a government agency. We give general information, not professional advice. We have not seen your furnace, your air conditioner, your venting, your gas piping or your wiring, and we never diagnose a reader’s system, by email or any other way. We never say that your system is safe, that it is fine to keep running, that a repair is within your skills, or that an installation meets your local code. Pages explain what the parts do, what the maker’s label and documents say, what the federal rules and model codes say, and who decides. For your own unit, the maker, its manual and a qualified technician decide what is safe.
How we are funded
Heat and Air Handbook is free to read and is funded by display advertising. Ads may not appear yet while the site is new. Once they run, some may come from equipment makers, HVAC contractors, parts sellers, retailers or other companies that sell to homeowners. An ad is not an endorsement, a referral or a recommendation, and advertisers have no say over what we publish. Nobody pays us anything to read a page or use a tool.
How we stay independent
- No affiliate links. We earn nothing if you buy a furnace, an air conditioner, a part, a filter or a tool, or hire anyone, after reading a page.
- No paid placements. Nobody can pay for coverage, a mention or a better position.
- No sold leads. We collect no details about you, your home or your system to pass on to contractors, makers, parts sellers or anyone else.
- No contractor referrals. We don’t name, recommend or rank HVAC contractors, technicians, gas fitters or electricians, and we offer no “free quote” or “find a pro” service.
- No product rankings. We publish no “best furnace”, “best air conditioner”, “best filter” or “best thermostat” lists and no model-by-model picks.
- No maker sponsorship. No maker pays for or reviews our pages. Makers are named only as the source of their own manual, label or code list, or where a page is about their equipment.
That is why our pages can say things a seller might not. R-410A is not banned: EPA’s rule still lets a new R-410A split system be installed where all its specified components were made or imported before 1 January 2025 (40 CFR 84.54(c)(1), as amended by 91 FR 31284, read 10 November 2026). The federal tax credit for a new air conditioner or furnace covers improvements made through 31 December 2025, not 2026 installs (IRS, read 10 November 2026). And the regional efficiency rules for air conditioners in the South bind the installer and the distributor, not the homeowner (10 CFR 429.102(c)).
How pages are checked
Every page gets a fact-check against its sources, separate from the writing. Each page ends with the date its sources were checked. Our editorial policy sets out each step.
Where to start
If you smell gas or a carbon monoxide alarm sounds, don’t read on: get everyone outside and call 911, or your gas utility for a gas smell, from there. Carbon monoxide and your furnace explains what CPSC, CDC and the makers say, for afterwards. If the heat won’t come on, start with furnace not turning on. If the house isn’t cooling, AC not cooling goes through the checks in order. If your furnace is flashing a light or showing a code, the furnace error code lookup gives the maker’s meaning for the boards we have confirmed, with the maker’s document. For the routine jobs, see furnace maintenance and AC maintenance. If you are weighing a big repair against a new system, the repair or replace check sets out the points to weigh, using your own quotes.
Mistakes and questions
Our corrections page logs what we have fixed, and our contact page says how to reach us. Please read our disclaimer too.
