How to refill a closed baseboard heating system?

Answer 1

You need to purge air from the system and in the process fill it with water.
There should be a drain valve and water tap near the circulating pump. Connect a garden hose and run to a sink or outdoors. Manually open the zone valve for the basement heaters and open the drain valve. Water should flow through the system and force out any air. While you are at it, you may want to purge the entire system. Open each zone valve and let the water flow through. When done there will inevitably still be some air in the system and you may hear gurgling for a short time after the heaters come on. Make sure the purge valve above the expansion tank is open to allow the air to escape.

I have some pictures on my web page, maybe they could help as well.
http://members.rennlist.org/warren/furnace.html

Answer 2

You should have a pressure reducing valve feeding the closed loop. Usually set at 12 PSI unless someone adjusted it for a taller house. If it is working OK, it should auto-feed the system until it reaches setpoint.
If it is not working properly, there should be a bypass valve you can open and feed the system until pressure is about 10 PSI at boiler. You'll have to bleed the air from the baseboards (hopefully you have air bleed fittings on the baseboards.)
Fire the boiler only after you have bled the air out and have positive pressure on the highest baseboard.

Answer 3

A closed baseboard heating system must be with water, with a boiler in use and a circulating pump, should be filled on the supply side of the heater and pump, look for a connection, also if you can flush the system and add needed corrosion chemicals, i like electric base board heaters but they use more energy, good luck

Answer 4

there should be a valve on the left or the right of the basebored heater . just turn it until there is no more air than close it. It would be a good idea to check all of them.