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An In-Depth Guide For Bleeding Baseboard Heating Systems

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Hot water baseboard heating systems aren't as common as they used to be, but they're still used in many older homes and apartments throughout the country. After a long period of dormancy, the baseboard heating system can become "air-bound" – that is, the heating zone or loop can develop air pockets that prevent the heat from circulating. Learn how you can successfully diagnose and repair this issue.

How to Tell When Your Baseboard's Air-Bound

One way you can literally get a feel for your baseboard heating system's condition is by feeling the baseboard itself. Avoid bending the delicate fins lining the baseboard, as it can be difficult to bend them back into shape without the right tools. If you can't get access to the whole baseboard, simply feel the start and end sections.

Under normal operation, the entire baseboard should be hot to the touch. If it isn't, feel your way from the section that feels cold until you've hit another section that feels hot. If portions of the baseboard or the entire baseboard itself feels cool to the touch, it's a sign that your baseboard is air-bound.  

How to Remove Air from the System

Some hot water heating systems feature automatic air bleeder valves that purge trapped air without any intervention needed. However, there are plenty of heaters that rely on manually-controlled air bleeder valves for unwanted air removal. The following shows how to properly bleed the system of its trapped air:

  1. Make sure the hot water heating system is warm and operating at normal pressures. You'll need the heating system's pressure to help force out the trapped air and subsequently force hot heating water through the baseboard.
  2. Locate the air bleeder valve at the start of the baseboard, which is usually where the hot water supply pipe enters the room. You'll want to place a small cup underneath the valve to catch spills if and when they occur.
  3. Open the air bleeder valve by grabbing the square portion of the valve and turning it counter-clockwise with a pair of needle-nose pliers. You can also use a skate key to open the valve, if you happen to have one of those lying around.
  4. Keep the valve open and allow all of the air to escape the baseboard. Keep going until you start seeing water gush out of the valve. Afterwards, you can close the valve and feel the baseboard for signs of heat.

Air Bleeding via Water Feeder & Boiler Drain

If your heating system doesn't have air bleeder valves, then you may have to bleed the system through the boiler drain. For this particular procedure, you'll need your boiler shut off at the circuit breaker or service switch and for the boiler's contents to be relatively cool:

  1. Locate the boiler drain and attach a garden hose to its end. Route the hose to a convenient drain route.
  2. Locate and open the water feeder pressure valve by lifting the bypass valve lever upwards. This allows a torrent of high pressure water to flow through the heating system, pushing air pockets out of the system.
  3. Keep an eye on pressures within the tank. Make sure these pressures don't exceed 30 psi, otherwise the pressure valve could start leaking.
  4. Once all of the water has been forced out of the system, lower the lever and quickly close the drain valve. The water feeder pressure valve should start feeding water into the radiator until it the boiler's starting pressure is reached.

Afterward, turn on the boiler and verify that all of the baseboards in your room are receiving sufficient hot water flow. Don't forget to disconnect the garden hose and set it aside.

For additional services to your baseboard heating system, contact a professional business like Lowry Services: Electric, Plumbing, Heating & Cooling.


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