Two Zone hydronic baseboard heating system. Appears to be air in system.

[Modifyit]

I recently installed a new heat exchanger in my Burnham boiler due to corroded and leaking coil mounting plate. In chasing what seems to be excess air in the system. I have found that the B & G Flow control valve could be part of the problem. With boiler at approximately 180 degree temperature and system calling for heat, temperatrure reading with a laser gage shows very close to the expected temperature on the body of the flow control valve. However, the temperature on the outfeed side reads just barely past 110 degrees. Setting the flow control to open setting or control setting, there is no change in the above results. I have no idea what is inside this valve, but I am beginning to believe there is a major breakdown of components. Perhaps junk in the valve is reducing the flow which is affecting temperature control and volume of water moving throughout the system. This flow control valve is more than 20 years old. Just wondering if a rebuild kit would make a substantial difference.

 

[Dana]

If you're measuring the temperature of bare copper with a IR thermometer it can read 10s of degrees cooler than reality due to the low emissivity of the copper. A wrap of hockey tape or a spot of spray paint (any non-metallic color) would yield more realistic measurements. If the flow balancer/or globe valve (got a picture or model number?) has a well-aged or painted iron body it should read close to true temp.

Why do you believe there is air in the system?

Does there appear to be at least some flow on that zone? (Is it able to satisfy the thermostat?)

What is the system pressure?

How many vertical feet is there between the pressure gauge and the highest radiator/baseboard on the system?

BTW: Almost no residential heating system in the US actually NEEDS 180F water. Many/most can still meet design condition heat emittance with 140-150F water, which is usually more comfortable.