Heat and Air Handbook

How We Check

Where Heat and Air Handbook gets its HVAC rules, codes and steps, how rules are dated, why some brands say not confirmed, and how often it all gets rechecked.

Heating and cooling rules are easy to get wrong. The federal efficiency and refrigerant rules changed in 2023, 2025 and 2026, and old lines keep circulating. A furnace code means one thing on one maker’s board and something else on another’s. Some furnace work is safe for an owner and some can cause a gas leak, carbon monoxide or a fire. And DOE’s own consumer pages on furnaces and air conditioning returned “page not found” when we checked on 10 November 2026. This page sets out where our rules and figures come from, how rules in force are dated, why some brands and codes say “not confirmed”, what we will and won’t give steps for, how often everything is rechecked, and where our limits are.

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.

Where rules and figures come from

We go to the source that makes the rule or wrote the document, and link it at the claim:

  • Efficiency rules: the eCFR and the Federal Register. The minimum SEER2, EER2 and AFUE levels are in 10 CFR 430.32; who is responsible when an air conditioner is installed in the wrong region is in 10 CFR 429.102 and 429.154; the EnergyGuide label is in 16 CFR 305.20. Rule changes, proposals and petitions come from the Federal Register, read by citation.
  • Refrigerant rules: the eCFR and EPA. Section 608 of the Clean Air Act, in 40 CFR 82 subpart F (who counts as a technician, the venting ban, the sales restriction, certification); the HFC rules in 40 CFR part 84; EPA’s own pages, such as its refrigerant sales restriction page, its R-22 fact sheet and its SNAP table for home air conditioning.
  • DOE and ENERGY STAR. ENERGY STAR’s own pages, such as its maintenance checklist. DOE’s Energy Saver pages on furnaces, central air conditioning and air conditioner maintenance returned “page not found” on 10 November 2026, so we cite Internet Archive copies, each labelled with its capture date, such as the furnaces and boilers page as captured on 31 May 2026, and replace them when DOE restores the live page.
  • Safety agencies. CDC on carbon monoxide, CPSC on carbon monoxide alarms, PHMSA on what to do if you smell gas, and the US Fire Administration on heating fires.
  • Energy prices: EIA. Electricity and gas prices come from the US Energy Information Administration, with the month the price is for and the date EIA released it.
  • Makers’ documents, by number and edition. Owner’s manuals, installation instructions and service manuals, read on the maker’s own website or literature host, such as Carrier’s 59SC5A-11SI (Edition 10/18), Goodman’s RS6621301, Lennox’s 508547-01 (12/2025) and Trane’s 32-5083-1C-EN. A maker’s document tells us what that maker says about its own equipment. It is not a rule for every brand, so pages say “Lennox’s manual says”, never “furnaces need”. The documents are copyrighted, so we describe them in our own words, quote only a few words, and never copy a code table wholesale. A copy of a maker’s manual on a retailer’s or parts seller’s site is not good enough: we find the maker’s own copy.
  • Model codes and state rules. The International Residential Code and other model codes, cited by section and edition and read in the publisher’s free viewer, as model codes, never as your local law. A state’s licensing or permit rule only from that state’s official text.
  • Never a source: HVAC contractor and service-company pages, parts sellers’ code lists and how-to pages, trade blogs, forums, videos, question-and-answer sites, home-improvement media, comparison and “best” sites. Not for a rule, a figure, a code meaning or a step.

How a rule gets on the page

Each rule, code meaning and figure is sorted by how directly it was read, and that decides how we word it:

  • Read in the primary text: the regulation in the eCFR, the Federal Register notice, the agency’s own page, or the maker’s document on the maker’s site. We state it plainly, with the citation or document number and the date we read it. Before a writer uses it, the whole section is read again, not just the sentence a search turned up, because exceptions often sit further down.
  • Read only in part, or only in an archived copy. An archived copy is labelled with its capture date. A rule read only in part is not stated as a flat rule; if a page has to mention it, it says what we could and could not confirm.
  • Not read. It stays off the page, or the page says “not confirmed” and links the agency’s or maker’s own page.

Why some brands and codes say “not confirmed”

Furnace codes depend on the control board, not just the brand, and makers publish them in different places. A brand’s codes go into our furnace error code lookup only once we have read its table in a maker document on the maker’s own site. As of 10 November 2026:

  • Trane: the installer’s guide we found on Trane’s document library shows how the display works but has no full fault list in readable text, so Trane codes say “not confirmed”. We give the lockout reset printed in Trane’s owner guide instead.
  • Bryant and Payne: both are Carrier-family brands, but we have not found a Carrier-family document saying which of their boards use Carrier’s codes, so they are not in the lookup yet.
  • Thermostats: we read Lennox’s thermostat installation guide on Lennox’s site. Pages state another thermostat maker’s wire letters, delays or screen messages only where we read that maker’s own guide or support page on its own site (Resideo and Honeywell Home, Copeland’s Sensi, ecobee), name the model, and say that other models may differ.
  • New York’s HFC rule (6 NYCRR Part 494) is read in the express terms and FAQ that New York’s Department of Environmental Conservation posts, not in the official compilation, and pages say so.

“Not confirmed” says nothing about what a code means or what a rule is. It means we have not read it in a source we would stand behind. Every code result also tells you to check the label inside your furnace door, because that label is written for your board.

How rules in force are dated

A rule is right only for certain equipment and a certain period, so we give that, not just the number:

  • By manufacture date or install date. Federal efficiency standards apply by the date a unit was made, or for the regional air conditioner rules, the date it was installed. A split central air conditioner made from 1 January 2023 needs at least 13.4 SEER2; one installed from 1 January 2023 in the Southeast or Southwest needs 14.3 SEER2 if it is under 45,000 Btu/h (10 CFR 430.32(c)(5) and (c)(6), read 10 November 2026). Pages say which date applies, and that a standard does not make an existing system illegal.
  • Rules under review, with their status and the day we checked. The 95% AFUE minimum for non-weatherized gas furnaces made from 18 December 2028 is still in 10 CFR 430.32(e)(1)(iii). On 8 June 2026 the Supreme Court vacated the appeals court judgment that upheld it and sent the case back (No. 25-879), and a petition asking DOE to delay the dates (91 FR 22477, 27 April 2026) had no DOE decision in the Federal Register as of 10 November 2026. So pages say: on the books for furnaces made from 18 December 2028; under legal review; may change, with the date checked.
  • Rules with their latest amendment. EPA’s HFC rule for new home air conditioning systems was last amended by 91 FR 31284 (26 May 2026, effective 27 July 2026). Pages give the section as it reads now and say when it changed.
  • Model codes by edition. Section numbers move between editions. The 2024 International Residential Code puts carbon monoxide alarms in Section R311, where earlier editions used R315 (read in the ICC viewer, 10 November 2026). Pages give the edition with every section number.
  • Prices with their month and release. Energy prices carry the month they are for and the date EIA released them.
  • Maker documents by edition. Each step or code meaning names the document number and its edition or print date, because makers revise their manuals.

What we give steps for, and what we don’t

A wrong step on a gas furnace can cause a gas leak, carbon monoxide poisoning or a fire, and an outdoor air conditioning unit carries 240 volts and capacitors that can hold a charge after the power is off. So our steps follow these lines:

  • Safety first, on every furnace page. What to do if you smell gas (PHMSA and the makers), what to do if a carbon monoxide alarm sounds (CPSC and CDC), how to shut off power and gas, and that a furnace that has been under water is not relit. These come before any step.
  • Owner checks the makers give owners. The filter, the thermostat, the furnace switch and breaker, the gas valve, the blower door, reading a code, a reset the owner’s manual prints, keeping the outdoor unit clear, and the condensate drain.
  • Furnace repair steps only from a maker’s own document. Some pages go further, such as cleaning a flame sensor, and give steps only where we have read the maker’s procedure on the maker’s site, cited by document number and page. Where the maker says a job is for a qualified technician or service agency, the page says so at that step, with the maker’s cautions. If we have not read a maker’s procedure for a part, the page explains the part and stops at the technician. Any step that opens a gas connection carries the maker’s leak test. Some states require a permit and a licensed gas fitter for gas work: Massachusetts, for example, issues gas fitting permits only to properly licensed individuals (248 CMR 3.05, mass.gov copy, read 10 November 2026). Elsewhere, ask your building department.
  • No refrigerant steps, because of federal law. Under Section 608, anyone who attaches gauges or hoses, adds or removes refrigerant, or cuts a refrigerant line counts as a technician and must be certified, and there is no homeowner exemption (40 CFR 82.152). Venting refrigerant is illegal (82.154(a)), and “Only Section 608 certified technicians can purchase refrigerants intended for use with stationary refrigeration and air-conditioning equipment” (EPA, read 10 November 2026). So no page gives steps to recharge, top up, recover or swap refrigerant, or to read pressures. Pages explain the signs of a leak, what the law asks of the technician and what to ask them.
  • Electrical: owner checks only. Power off at the thermostat, the furnace switch, the breaker and the outdoor disconnect, resets printed in an owner’s manual, what you can see and hear with the panels closed, and low-voltage thermostat wiring with the power off, following the thermostat maker’s guide. No page tells a reader to open an outdoor unit’s electrical panel, touch a capacitor or contactor, discharge anything or test with a meter.
  • Never a bypass. No page tells a reader to jump, bypass or disable a pressure switch, limit or rollout switch, flame sensor, door switch or refrigerant leak sensor.
  • Explanation only. The heat exchanger, the burner orifices and gas pressure, gas piping beyond the furnace connector, and anything inside the refrigerant circuit: pages say what each does, the signs of trouble and what a technician checks.

How tools work

Our tools show information and arithmetic, not decisions. The furnace error code lookup gives the maker’s meaning for a code in our own words, whether the maker gives the owner an action or sends it to a technician, and the maker’s document with its edition and the date we read it. The cooling cost by SEER2 tool works out yearly cooling energy and cost from your own usage and electricity price, with an EIA price you can change; it gives no install prices and promises no payback. The repair or replace check sets your system’s age, refrigerant and efficiency beside ENERGY STAR’s replacement prompts, and your repair quote beside your replacement quote; it gives points to weigh, never a verdict. We found no federal source for how long a furnace or air conditioner lasts, and the tools say so.

Each formula is tested against answers worked by hand before the tool goes live. Every default that is a rate or a rule says where it comes from and when we read it, or that it is our assumption, and you can change it. Results say “estimate”.

How pages are checked

After a page is written, a separate fact-check compares each rule, date, minimum, code meaning, step, figure and document number with its source, and reworks every sum on the page. A final review looks for errors, gaps and anything that could mislead a reader about their safety, their system or the law. A page with a serious problem still open does not go out.

How often rules are rechecked

  • The 95% furnace rule: monthly, in the Federal Register, the Supreme Court docket and news of the appeals court case, until its status settles.
  • Refrigerant and efficiency rules (40 CFR 82 and 84, 10 CFR 429 and 430, EPA’s Section 608 and SNAP pages): each quarter, and when a new rule is published.
  • Energy prices: with each EIA release.
  • Makers’ documents: when a new edition appears, and whenever a page relies on one we have not checked for a newer edition in six months.
  • DOE’s archived pages: at each recheck, to see whether the live page is back.
  • Everything else: at least every six months, and sooner when we learn a source has changed.

A page shows an updated date only when its content really changed. Between rechecks a rule or a manual can change without our knowing, which is why each rule and document shows the day we read it.

What is an assumption

Where we work something out ourselves, we say so. Arithmetic is shown step by step. A conclusion a source does not state is labelled as ours. We give no repair or replacement prices, no lifespan figure and no typical result, because we found no primary source for them. Where money matters, pages use your own quote.

How we treat claims seen elsewhere

Claims from sellers are reported as claims, never as fact, and we don’t name a seller when we question one. Some lines you may see, checked as of 10 November 2026:

  • “R-410A is banned.” Not what the rule says. A new R-410A split system may still be installed where all its specified components were made or imported before 1 January 2025 (40 CFR 84.54(c)(1)), and replacement components for existing systems are exempt from the bans (84.56(b)). See R-410A after 2025.
  • “R-22 is illegal to use.” No. Production and import ended on 1 January 2020, but EPA says an existing R-22 system can be used “for as long as necessary” (EPA-430-FR-20001). See R-22 refrigerant.
  • “You can top up your own AC with a can from the store.” Not for home air conditioning. The small-can exemption is for car air conditioning, and refrigerant for home systems is sold only to certified technicians (EPA). See AC refrigerant leak.
  • “95% furnaces are required in 2028” and “your 80% furnace becomes illegal.” The first is half true and the second is false: the minimum is on the books for furnaces made from 18 December 2028, it is under legal review, and it does not apply to furnaces already installed. See AFUE and the 2028 furnace rule.
  • “There’s a federal tax credit for a new AC or furnace this year.” Not for 2026. The IRS says the energy efficient home improvement credit can be claimed for improvements made through 31 December 2025 (IRS).
  • “Change your filter every 30 days.” Sources range from once a month to every two months to 60 to 90 days, depending on who is speaking and about what. See how often to change a furnace filter.

Our limits

Some sources can’t be read in full, because they block automated access, need a login, sit behind a bot check or have not been published. As of 10 November 2026 we have not read the appeals court’s action on the 95% furnace rule since the case was sent back, the National Electrical Code or the NFPA gas and alarm codes (free access needs a login), state licensing rules beyond Massachusetts, or a federal source for how long furnaces and air conditioners last, so none of these is stated on our pages. We read the regulations, agency pages and maker documents a page depends on, not every maker’s manual for every model. Your model’s documents may differ from the ones we cite. No check catches everything, so please tell us if you find a mistake. Fixes are logged on our corrections page, and our editorial policy covers the rest of how pages are made.

Before you rely on a step or a rule here, check it against the label and manual for your own unit, and ask a qualified technician or your building department where it matters.

Sources on this page checked on 10 November 2026.