Dealing With Air-Bound Baseboard Heating Systems

Although the vast majority of homes throughout the U.S. rely on electric or gas-powered furnaces, there are still plenty of homes that rely on hot water heating systems, including baseboard heaters. It's not unusual for these systems to develop air pockets that create cold spots throughout the heating apparatus, especially after long periods of inactivity. As a result, portions of your baseboard heater may feel cold to the touch.

Some baseboard heaters have automatic air purging devices that can deal with blockages caused by air in the system. If you don't have one installed on your baseboard heating system, then here's a quick guide on how to successfully purge an air-bound system.

How Can Baseboard Heating Systems Become Air-Bound?

There are a couple of common reasons why baseboard heating systems often become air-bound:

  1. A minor leak somewhere within the system -- even a microscopic crack -- can cause small amounts of hot water to evaporate. This allows minute amounts of air to build up within the pipes, eventually culminating in an air pocket that's large enough to interfere with your baseboard heater.
  2. Routine maintenance can also allow small amounts of air to enter the pipes. This usually occurs when a small amount of water is lost during service, with air rushing in to fill the void.

Preparatory Tips

Since you'll be relying on the baseboard heater's own water pressure to purge trapped air from the heating system pipes, you'll need to have the heater up and running before you start working on the unit. This will also help force hot water through the vacated pipes upon purging the trapped air. Set your thermostat on "heat" and let it run for approximately 10 minutes. This way, the system will be at proper operating pressures.

Next, you'll need to locate all of the bleed valves on your baseboard heating system. The bleed valve should be located where the hot water pipe emerges from the floor. You may have to remove the valence and end-pieces to reveal this location.

When bleeding your baseboard heater units, start with the baseboard that's highest and furthest away from your boiler. If you have a multi-story home, for example, you'll want to start on the top-most floor. Place a container underneath the air bleeder to catch any water that spills out during the bleeding process.

Purging the Air Out of Your Baseboard Heater

While the heating system is in operation, use your flat-head screwdriver, radiator bleed key, or a pair of needle-nose pliers to crack open the bleed valve. Turn the valve counterclockwise until air begins to bleed out. Leave the valve open until water starts coming out instead of air. Once you start getting water instead of air, carefully close the bleed valve and move on to the next baseboard.

When bleeding your baseboard heating system, you'll want to work your way downwards from the top-most floor. Make sure all of the bleed valves are closed and that there aren't any leaks before you start using your heating system normally.

How to Purge Without Using Air Bleeder Valves

Some baseboard heating systems may not be equipped with a bleed valve or have issues that make using one problematic. Until you're able to install new bleed valves, you can always drain your baseboard heating system through the water feeder and boiler drain on your heating boiler. This time, you'll need to shut off your boiler for safety.

Start by attaching a garden hose to the boiler drain and direct the other end towards a nearby drain or suitable outdoor area.  Don't forget to open the drain valve afterwards. Next, carefully open the water feeder bypass valve and listen carefully as air and water leaves the boiler. Once there's a steady flow of water from the heating boiler, close the water feeder and the drain valve. Don't forget to remove the garden hose from the boiler drain.

Last but not least, check your baseboard heaters to see if there's adequate heat. A completely purged system should start feeling hot to the touch.

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