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How to Troubleshoot a Malfunctioning Heating Zone

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If you have a hydronic heating system, then you have water baseboard heat. Baseboard heating is generally efficient and consistent, but you may sometimes notice that one part of your home is not as warm as the other spaces. If this has become a constant problem in your home, then one of the heating zones is not working properly. This issue can typically be fixed with a few easy troubleshooting tasks.

Bleed the Radiators

Sometimes, a heating zone will not work properly because water cannot move through the baseboard radiators. This happens when an air bubble blocks the pipes. To help draw out air, locate the bleeder valves on all the radiators in the affected heating zone. If you are unsure about which radiators belong to each zone, touch each radiator. The ones that are cold will be the ones that you need to bleed. Use a flathead screwdriver to open up the valves a small amount. You should hear a bubbling or hissing noise as air releases. Close the valves when water starts to come out of the openings. 

Wait for hot water to start moving through the radiators and for the baseboards to start heating up. It should not take longer than an hour, so if your baseboards still feel cool to the after about 60 minutes, then an air blockage was not the issue. 

Investigate the Zone Valve

Hot water is moved through the baseboards of your heating system when your thermostats call for heat in each heating zone. To keep hot water from constantly moving through the radiators, valves close off the water pipes when the area is warm enough. The valves are called zone valves and they are wired directly to your thermostats. When the zone valve gets the message that the heating zone needs heats, a small motor will open up the valve and hot water will pass through. This motor can sometimes break or wear down, and the valve will stay closed or open. An open valve will cause hot water to run through the heating zone whenever the furnace turns on. This will cause the zone to be hotter than it should be. When the valve is stuck in the closed position, the zone will be cold.

Locate the thermostat that controls the heat in the zone that is cold. Pull the thermostat off the wall and look to see where the wires lead. For example, the wires may lead straight down into the basement. Go into your basement, locate the wall were the wires led downward, find the thermostat wires, and follow them to the zone valve. Look for a switch on the back of the valve. The switch should be in the auto position. This means that the zone valve motor controls the movement of the valve. Move the switch to the open position. This should open the valve and allow water into your radiators. 

If your radiators start working again, then you will need to replace the zone valve motor at this time. Otherwise the zone will begin to overheat. Flip the zone switch to closed. 

Change the Valve Motor

Replacing the zone valve motor is a simple job. Look on the back or side of the valve for a serial number. Also, look for a name on the valve that indicates the manufacturer. For example, Honeywell makes many different varieties of zone valves. When you have the information you need, go to your local heating supplier and ask for a new motor for the zone valve you have. 

Once you have the motor, gently remove the wires from the zone valve. There will usually be four wires connected to it. Consider taking a picture of the wires and where they connect so they can be reconnected properly. Climb on a ladder to reach the top of the zone valve. You will see a screw on the top. Loosen the screw until the motor pops out of the valve. Set the new motor in place and tighten the screw. Reconnect the wires and flip the switch to AUTO. Watch your thermostat for the next few hours to make sure the zone valve is working correctly. 

For more information on the best heading and air conditioning tactics, talk to local HVAC contractors.