No Heat in the House? What to Check First on an Oil or Gas Boiler

When the heat goes out, five minutes of checks sometimes fix it: the thermostat, the emergency switch, the fuel and one press of the reset button. Here’s what to check on an oil or gas boiler, what the common symptoms mean, and when to stop and call.

What should you check first when the heat goes out?

Start with the controls and the fuel, because a switch, a breaker or an empty tank costs nothing to rule out. Boisvert answers these calls all winter, and the first questions our office asks are whether you heat with oil or gas and whether it’s a boiler or a furnace. Work through the list in order and stop at the first thing you find:

1. Thermostat. Make sure it’s set to Heat and a few degrees above the room temperature. A blank screen usually means dead batteries.
2. Emergency switch. Most oil and gas boilers have a shut-off switch, often a red plate at the top of the basement stairs or by the boiler room door. It looks like a light switch and gets flipped off by accident; in October 2025 a customer’s heat was out for exactly that reason.
3. Breaker. Check the panel for a tripped breaker labeled boiler, burner or heat. Reset it once.
4. Fuel. On oil, read the gauge on top of the tank. On gas, check whether the stove lights; if it does, gas is reaching the house.
5. Reset button or display. Press the oil burner’s reset button once, or write down the code on the boiler’s display.

If the heat still won’t come on, call.

How many times should you press the oil burner reset button?

Press the red reset button on an oil burner once. If the burner doesn’t light and keep running, leave it alone and call for service. A burner locks out because something went wrong, often a fuel, ignition or flame problem, and each new attempt can spray more oil into a chamber that didn’t light. Many burner controls also stop accepting resets after repeated failures: Beckett’s GeniSys control goes into a hard lockout after three in a row, shown by a solid red light. Do not press reset at all if you smell oil, see smoke or hear the burner rumble. If the tank ran dry, have it filled first. The oil line then usually needs bleeding before the burner will start, a job for a technician or your oil company.

What do common no-heat symptoms point to?

Most no-heat problems fall into a few patterns, and each one tells you whether the trouble is the burner itself or getting heat to the rooms.

A January 2026 caller described the first row exactly: half a tank of oil, a burner that ran about 30 seconds and shut off, and hot water but no heat. The boiler hadn’t been cleaned since 2023. It needed a service visit, not another reset.

Why is the boiler’s relief valve dripping?

A dripping relief valve usually means the boiler’s pressure is climbing too high, most often because the expansion tank has filled with water. A home hot-water boiler normally reads about 12 to 15 psi cold and under about 25 psi hot on its pressure gauge, and the relief valve opens near 30 psi to protect the boiler. A steady drip, or a gauge near 30, needs a service call. In the meantime, put a bucket under the discharge pipe. Never cap or plug a relief valve. It is the boiler’s last protection against too much pressure.

When should you stop troubleshooting and call right away?

Stop and get help right away for any sign of a gas leak, carbon monoxide, an oil leak or fire. Do not reset anything in these cases.

• You smell gas (a rotten-egg smell). Leave the house without using light switches, phones or appliances, then call the gas company from outside. Most of Greater Hartford is on Connecticut Natural Gas, emergency line (866) 924-5325. Parts of Windsor are on Eversource gas, (877) 944-5325. If you can’t reach them, call 911.
• A carbon monoxide alarm goes off. Get everyone outside and call 911.
• You see oil on the floor, smoke or soot around the boiler, or hear a loud bang when it fires. Turn off the emergency switch and call.
• The house is falling toward 50°F with no fix in sight. Pipes and baseboard loops can freeze while you wait. Here’s what to do about frozen pipes.

What happens when you call Boisvert for no heat?

Boisvert Plumbing & Mechanical Services repairs oil and gas boilers and furnaces across Greater Hartford and does oil burner tune-ups. When you call, tell us your fuel, whether you have a boiler or a furnace, and any code on the display, so the technician arrives with the right parts. We give an arrival window, often the next day in winter and sooner when the schedule opens up. A visit carries our standard service charge, quoted when you book, even when the fix turns out to be a switch, so the five-minute checks are worth doing first. After hours, the same number reaches our on-call staff for emergencies, billed at overtime rates.

A customer who lost heat and hot water wrote in a June 2026 Google review: “They immediately sent out someone who evaluated the situation and explained it to me. They came back the next morning, on time, had ordered everything needed overnight to repair the heat and hot water system.”

No heat? Call Boisvert

We’ve served Hartford, West Hartford, Bloomfield, Avon, Simsbury, Farmington, Windsor and nearby towns for more than 30 years and are rated A+ by the Better Business Bureau. Office hours are Monday to Friday, 8 AM to 5 PM, and we’re available 24/7 for emergencies. Call (860) 216-9104 or request heating repair online. If repairs on an old boiler keep adding up, we also replace boilers and convert oil heat to gas; here’s what a new furnace or boiler costs in Greater Hartford.