Editorial policy

Last updated November 14, 2026

Sources we accept

• Manufacturer service manuals, installer guides, troubleshooting guides and owner's manuals.
• Manufacturer support pages.
• U.S. government and state agency pages (for example the Department of Energy, the Energy Information Administration, ENERGY STAR and the Washington State Department of Health).

We do not treat other websites' code lists as evidence. If a code only appears on repair blogs and forums, we do not publish it.

How a code gets onto the site

1. We find a manufacturer document that contains a code table.
2. We read the code's meaning and action in the document itself, not a summary of it.
3. We record which product line and models the document covers and state that scope on the page.
4. We link the document so you can check us.

Brand and model scope

The same code can mean different things on different brands, and even on different control boards from the same brand. Each table says which models its document covers. Your furnace's wiring-diagram label and owner's manual always take priority over this website.

Safety rules for our writing

• We never give instructions to bypass, jumper or defeat a safety device.
• We separate checks a homeowner can safely do (filters, vents, breakers, outdoor terminations) from work for licensed professionals (gas pressure, combustion, refrigerant, line voltage, internal parts).
• Where a manufacturer document is written for technicians, we say so and report it for context.

Calculators and estimates

Our heating cost calculator uses published U.S. Energy Information Administration prices and standard energy content values, shows the assumptions, and lets you change them. Results are estimates, not quotes.

Corrections

If you find an error, write to contact@heatingcodes.com with the page and the document you are comparing. We correct confirmed errors promptly and update the "last reviewed" date.

Advertising independence

Ads are provided by Google AdSense. Advertisers do not review or influence our content, and we do not accept payment for placement in our code tables or guides.