Types of Air Venting Devices in Boilers
There are several techniques and components designed to remove air from hot water boilers. We'll break this down into two categories: whole system air removal parts and component-specific air removal parts.
Whole-System-wise Boilers Automatic Air Removal
These air vents are installed near the boiler, ideally immediately after the pressure reducer and in a location where recirculated water must flow. Two popular choices are the air separator (scoop)/air vent combo or the Spirovent. Based on our experience, the Spirovent or an equivalent is the better choice.
Boilers Air Separator, Purger (Scoop)
As the name implies, the scoop separates air from the water. As water circulates and flows inside the scoop, it comes into contact with the baffles. Upon contact, the baffles divert the water and help air bubbles rise to the top of the scoop. It’s important to note that the air separator doesn’t remove air itself, but simply helps it rise to the top. The air vent is responsible for evacuating the air. Popular air scoop manufacturers include Watts, Amtrol, Bell and Gossett, TACO, and Honeywell.
Automatic Air Vents
There are many types of air vents available on the market, all serving the same purpose, though some designs are better than others. These air vents evacuate air from the system without requiring manual intervention. A float mechanism opens when excess air is present. These vents must be installed at the highest point in the system.
The market offers various models such as the Model 77, 78, and 79, which are one-time-use and need to be replaced in case of clogging or failure.
We strongly prefer and install the Model 97 from Bell and Gossett, or caleffi which can be opened and serviced in case of mulfuction.
Microbubble Air Eliminators – SpiroVent
To automatically remove air from boiler systems, Microbubble air eliminators are proven to work exceptionally well and may be the best option. With excellent engineering and design, they consist of woven copper wire soldered to a copper tube, creating a low-velocity area that scrubs the bubbles from the water. The air bubbles rise and collect in the air chamber before being vented from the system via an integral automatic float valve system. Following we show an good example of the SpiroVent
Note: SpiroVent claims in their marketing literature that it completely eliminates 100% of the free air, 100% of the entrained air, and up to 99.6% of the dissolved air in the system. Other companies, such as Bell and Gossett, have their own versions of Microbubble Air Eliminators. We prefer the SpiroVent, as it is made of brass, a lighter material compared to BG.
Engineering Ingenuity: It seems SpiroVent hit a home run by slowing down the water velocity. We’d like to emphasize that fluid velocity is an art, and savvy HVAC experts use fluid velocities to improve system performance. A case in point is reducing air velocity in air filters.
Terminal-Wise Air Removal Baseboard and Radiators
In this section, we’ll address terminal-wise air removal. The most common hot water heating terminals are baseboards and radiators. To remove air from these terminals, the boiler must be turned off, and the water should be cold. Air removal from these terminals is a manual process.
The common terms to remove air from these system are venting, purging, bleeding among others.
Air Removal from Baseboards
To remove air from baseboards, the terminal must be equipped with a vent valve, also called a bleeder tee. While this is a simple task for DIYers, over the years, we've noticed many units that are not equipped with a vent valve. Bleeding a baseboard is straightforward—simply slowly open the valve and allow the excess air to escape until water starts flowing. It’s essential to have a cloth on the floor and a cup to collect any water.
The most commonly overlooked step in baseboard bleeding is checking the water pressure at the boiler once all baseboards have been maintained.
Additionally, we must emphasize the importance of using the proper valve keys to vent the radiator. Using a screwdriver or any improvised device can damage the valve, leading to costly repairs.
Air Removal from Radiators
Similarly, to remove air from radiators, the terminal should also be equipped with a bleeder tee. This procedure is also suitable for DIYers. Most radiators are equipped with bleeder valves. Be sure to have the correct valve key, place a cloth on the floor, use a cup to collect any water, and check the pressure at the boiler after bleeding all radiators.
