Your boiler is running (or should be), but the house is still cold. A boiler not heating is the most common heating call we get in Union County once the temperature drops, and it doesn’t always mean an expensive repair. Sometimes it’s a dead thermostat battery. Sometimes it’s a tripped switch. Sometimes it really is a failed part that needs a professional.
Continental Plumbers has repaired hot water and steam boilers across Union County since 1985. Here are the 6 problems we find most often, what you can safely check yourself, and when it’s time to call.
Safety first: If you smell gas, leave the house and call your gas utility or 911 from outside. If a carbon monoxide alarm goes off, get everyone out and call 911. Don’t try to troubleshoot either one.
6 Reasons Your Boiler Is Not Heating
1. The Thermostat Isn’t Calling for Heat
Start here, because it’s the easiest fix. Make sure the thermostat is set to “Heat” (not “Cool” or “Off”), the temperature is set a few degrees above room temperature, and the batteries aren’t dead. A blank screen almost always means new batteries. If you have a programmable or smart thermostat, check that a schedule or “away” mode isn’t holding the temperature down.
2. No Power to the Boiler
Your boiler needs electricity even if it burns gas. Check the red emergency switch at the top of the basement stairs or near the boiler (it’s easy to bump it off by mistake), and look for a tripped breaker in your electrical panel. If the breaker trips again right after you reset it, stop and call a technician. That points to an electrical problem inside the boiler.
3. Low Pressure or Low Water Level
This is one of the most common reasons a boiler shuts down.
- Hot water boilers: With the system cold, the gauge should read about 12 to 15 PSI. If it’s much lower, there may be a leak or a problem with the fill valve, and the boiler may shut itself off to protect itself.
- Steam boilers: The water in the sight glass should be about halfway up. If the water is too low, the low-water cutoff shuts the burner off. If you can’t see any water in the glass, don’t add water to a hot boiler. Turn it off and call a professional.
If you keep having to add water, you have a leak somewhere in the system, and that needs hot water boiler repair or steam boiler repair.
4. Air in the Radiators or Stuck Steam Vents
If the boiler runs but some rooms stay cold, the problem may be in the radiators, not the boiler. In hot water systems, trapped air blocks the flow. Bleed each radiator with a radiator key until water comes out with no air. In steam systems, which are common in Elizabeth and Union homes built between the 1920s and 1960s, a radiator air vent that is stuck shut keeps steam out of that radiator. If the same rooms are cold every winter, our radiator repair team can find out why.
5. A Failed Circulator Pump or Zone Valve
Hot water boilers use a circulator pump to push hot water through the pipes, and many homes have zone valves that open for each thermostat. If the boiler is hot but the radiators are cold, the pump or valve may have failed. This is especially common after a boiler sits idle all summer and the pump seizes. You may hear a hum with no water moving. This repair needs a licensed technician.
6. The Burner Won’t Light or the Boiler Is Locked Out
Modern boilers have safety controls that shut the burner down if something is wrong: a dirty flame sensor, a failed igniter, a blocked vent, or a gas supply problem. Many boilers will show an error code or a flashing light. You can press the reset button once. If the boiler locks out again, don’t keep resetting it. Repeated resets can flood the burner or hide a dangerous venting problem. Call for service.
When to Stop Troubleshooting and Call
You’ve done your part if you checked the thermostat, the power switch and breaker, and the pressure or water level. Call a professional if:
- The boiler locks out again after one reset
- You see water leaking, rust, or a pressure reading near 30 PSI
- You hear banging, rumbling or a loud hum
- The flame looks yellow or lazy instead of blue
- The house is losing heat on a freezing night
No heat in winter can freeze pipes in just a few hours. Our emergency boiler service covers Union County, including Elizabeth, Union, Hillside, Kenilworth and Roselle Park. If your boiler is more than 20 years old and keeps breaking down, ask us about boiler replacement and financing options.
Boiler Not Heating: Quick FAQ
Why is my boiler on but not heating the radiators?
The most common causes are air trapped in the radiators, low system pressure, or a failed circulator pump or zone valve. Bleeding the radiators and checking the pressure gauge are safe first steps. If that doesn’t fix it, the pump or valve likely needs repair.
Is it safe to keep resetting my boiler?
No. Press the reset button once. If the boiler locks out again, there’s a reason, and repeated resets can make the problem worse or unsafe. Call a licensed technician.
Can annual maintenance prevent a boiler from not heating?
Yes, in most cases. A yearly tune-up catches weak pumps, dirty flame sensors and low-water cutoff problems before they leave you without heat. See our fall boiler startup checklist and our boiler maintenance service.
Boiler Still Not Heating? We Can Help Today
Continental Plumbers has provided trusted boiler repair in Union County since 1985 (NJ License #9142). We work on hot water and steam boilers of every age, including the older systems common in local homes.
📞 Call (973) 900-0430 or schedule boiler repair online.
