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Baseboard Heater Not Getting Warm? Here’s Why (+ How to Fix)

A baseboard heater not getting warm may be due to a simple or serious problem. The probable causes also depend on the type of baseboard heater you have, i.e., electric or hydronic. Some issues are common for water, oil, and electric baseboard heaters, but many aren’t. 

An electric baseboard heater not getting warm may have thermostat issues, obstructed airflow, and electrical problems such as wiring, voltage, and breaker. Oil-filled or water baseboard heaters may have trapped air, blocked valves, failing pumps, or faulty relays.  

You have to shortlist the typical problems based on your situation. For instance, an electric baseboard heater in one room is an isolated installation, so you have fewer potential issues to inspect. Read on as I explain the causes and fixes of a baseboard heater not getting warm. 

1. The Baseboard Heater’s Thermostat Isn’t Working Perfectly

Many baseboard heaters have line-voltage thermostats mounted on the unit. These onboard thermostats directly control the power supply to the baseboard heater. Line-voltage thermostats aren’t practical because they sense the heat in the unit’s housing and immediate surroundings. 

The air in and around a baseboard heater will be hotter than the rest of the room. Thus, the thermostat may turn off the baseboard heater even when your room isn’t as warm as it should be.  

Additionally, the thermostat may be faulty. Furthermore, old thermostats with frayed wiring or corroded connections may not work flawlessly. 

How To Fix

Here are the standard solutions based on the problem you detect:

  • Check if the thermostat has power and test its main heat settings.
  • Toggle the modes and test a higher temperature to see if the room gets warm.
  • Use a low-voltage thermostat mounted on a wall away from the baseboard heater. 

Electric baseboard heaters have a safety feature known as ‘linear high limit temperature control.’ This safety device is a switch that turns off the power supply to the heater if it overheats. Hence, you may not be able to raise the thermostat’s heat setting to an unusually high temperature. 

If a line-voltage thermostat is broken, you need to consult a certified technician. Don’t attempt to replace the hot wire running inside the baseboard heater unless you are an electrician. 

2. The Baseboard Heater Is Unclean, and Airflow Is Blocked

Unlike forced air handler units, baseboard heaters can’t regulate the airflow in your room. All baseboard heaters rely on convection heating, using the air that naturally circulates around the fins and coils or tubes. 

Therefore, an unclean unit will have limited airflow. Make sure you don’t have any obstructions around a baseboard heater, such as furniture or drapes.

All hydronic and electric baseboard heaters need sufficient clearance for optimum airflow. This unobstructed space around the unit depends on its size.  

How To Fix

Clean the baseboard heater thoroughly. Remove all the dust and debris from in and around the unit, especially the heating element and fins. 

You can also check the orientation of the fins of your baseboard heater. In rare instances, the fins of a baseboard heater may be wrongly oriented, thus restricting the natural airflow. This problem is less likely in electric baseboards, since the units are factory-sealed. 

A hydronic baseboard heater’s fins may have clear channels designed to serve as vertical slots. These clear gaps maximize the airflow from the ground and upward, so the fins shouldn’t have these slots aligned or oriented horizontally. 

Check this YouTube video at ~1:07 to note the difference between the two orientations:

3. An Electric Baseboard Heater Has Electrical Problems

Electric baseboard heaters have three typical electrical problems:

  • The wiring is worn-out, thus failing.
  • The voltage is inaccurate for the unit.
  • The circuit breaker is faulty or incompatible. 

Poor wiring, inaccurate voltage, and an incompatible circuit breaker will prevent electric baseboard heaters from getting warm, even if your unit has power.

For instance, a 240V electric baseboard heater can’t operate flawlessly on a 120V circuit. You will have less heating because the unit can draw only about half the power it actually needs. 

Likewise, a 240V unit requires a double-pole circuit breaker. A single-pole circuit breaker is what you have for most appliances, like power tools or vacuums. Electric baseboard heaters need a double-pole circuit breaker rated 30 amps to 60 amps. Otherwise, the breaker may trip frequently. 

How To Fix

The standard solutions for these electrical problems are:

  • Replace old or worn-out wiring.
  • Use a 120V or 240V circuit, as required by the unit.
  • Install a compatible circuit breaker. 

4. The Heating Element and Fins Are Not Working Effectively

If none of the problems discussed until now applies to your electric baseboard heater, you are probably looking at an ineffective heating element, including the fins. 

An electric baseboard heater may last up to 20 years, but if it hasn’t been maintained, its lifespan will be much shorter.

An old heating element can be much less effective and efficient. Hence, the baseboard heater may not warm the air in your room to the extent you want. 

How To Fix

It isn’t practical to continue using a very old electric baseboard heater. It will consume a lot of electricity, despite poor performance. 

Hydronic baseboard heaters may have a solution. If the water or oil-filled tube is working fine, you can get new fins for the hydronic system. So, consider consulting a technician to weigh your options. 

5. A Hydronic Baseboard Heater Has Malfunctioning Components

Hydronic baseboard heaters have more components than their electric variants, whether water or oil-filled. This means that any significant part failing or malfunctioning may prevent such heaters from warming sufficiently. 

Investigate these common issues with hydronic baseboard heaters: 

  • The zone valve is partially stuck or completely blocked. If this is the case, the hot water or oil won’t flow through the tube in the zone that isn’t getting warm. 
  • The baseboard heater’s tube in your room may have trapped air inside, causing uneven and insufficient heating.  
  • The circulator pump isn’t working effectively. In this instance, the hot water or oil won’t circulate properly through the zone’s tube. 
  • The low-voltage thermostat’s relay switch may be faulty or broken. This problem will result in the thermostat not signaling the unit to heat. 

Oil-filled and water baseboard heaters aren’t identical. However, both variants work on the same fundamentals, so check out these common solutions and see if they fix the problem.

How To Fix

Here are the standard remedies, subject to the problem you detect:

  • Replace the dedicated zone valve if it fails.
  • Remove any trapped air using the bleed valve. 
  • Fix or replace the circulator pump.
  • Install a new relay switch for the thermostat.

Like electric baseboard heaters, the hydronic systems may also have a faulty thermostat. A low-voltage thermostat used for a hydronic baseboard heater may have wiring, sensor, and other issues. You can test these elements to know the causal problem. 

Additionally, a hydronic baseboard heater may have boiler problems, such as excessive trapped air or mineral deposits. In this instance, you may need to consult a technician if you can’t detect why your baseboard heater isn’t getting warm. 

Final Thoughts

Always begin your inspection with the simpler elements when a baseboard heater isn’t getting warm. 

  • Check if the baseboard heater is clean and without obstructions.
  • Ensure the circuit breaker, wiring, and voltage are alright.
  • Confirm the thermostat has power and toggle the settings.
  • Inspect the parts discussed here. Fix or replace the failed component.

Author

  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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