Call a pro: heat is out in the whole home or a zone

Why this happens

Slant/Fin says troubleshooting a boiler takes technical knowledge and specialized tools and should not be done by the homeowner, no matter how handy. Its boiler manual says there are no user serviceable parts. Weil-McLain's steam boiler manual says a homeowner should contact a qualified service technician with any question about how the boiler or system operates, and that its service procedures are only for a technician. This Old House lists air in the system, closed valves, low water pressure and a malfunctioning circulator pump among the common reasons for too little heat.

What to do right now

1. If you smell gas, see smoke or flames, a carbon monoxide alarm sounds, or anyone feels dizzy or sick, leave now and call 911 from outside. Do not touch switches on the way out.
2. Check the thermostat. Family Handyman says to make sure it is set to Heat, to compare the setting with the room temperature, to set it about five degrees above the room temperature to see if the heat comes on, and to replace its battery if it takes one.
3. Do not adjust, open or repair the boiler. That includes its pressure, its fill or feed valve, its pressure relief valve, the burner, the controls, the pilot, the flue, the combustion air and the gas valve. Do not add water to the system and do not drain it. Weil-McLain's manual warns that adding cold water to a hot boiler can crack it.
4. Look at the boiler from where you stand, without touching it. If you see water on the floor, or its relief valve is spilling water, say so when you call. Slant/Fin's manual tells owners to call their service company if the pressure is off or the relief valve spills water.
5. If water is standing on the floor around the boiler or its electrical parts, do not walk into it and do not touch the boiler or any switch near it. CDC says never to turn power on or off while standing in water, and Slant/Fin's manual says not to use a boiler if any part has been underwater and to call a qualified service technician right away. Call an HVAC technician or licensed heating contractor from a dry spot.
6. Plan for the cold. Weil-McLain says that in severely cold weather, a boiler failure or power outage in a building left unattended could result in frozen plumbing and water damage in a matter of hours. Boston's city site suggests leaving cabinet doors open where pipes run along cold spaces, and keeping the heat at a normal level or leaving a faucet open with a slight drip.
7. Do not heat the home with an oven or a grill. USFA says never to use an oven to heat your home, and Boston's city site says never to bring a grill indoors because of carbon monoxide. If you use an electric space heater, USFA says to keep anything that can burn at least 3 feet from it and to turn it off when you leave the room or go to bed.
8. Call an HVAC technician or licensed heating contractor. If you rent, tell your landlord or property manager right away. NYCHA tells its residents to report heat problems, Boston's city site says a building's owner is responsible for servicing its heating system, and New York City's housing department says tenants can call 311 if an owner does not fix a radiator. Rules differ by place, so check your lease and local rules.

When to stop. If you smell gas, see smoke or flames, a carbon monoxide alarm sounds, or anyone feels dizzy or sick, leave and call 911 from outside. If a pipe has frozen, cracked or is leaking, use the frozen pipe page linked below.

Start this troubleshooter over

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