Purging with cold water doesn’t do it. Venting the high points of the system won’t do it either, and neither will an automatic air vent stuck somewhere in the boiler header. No, to really get rid of system air and all those nuisance call- backs, you need a good air separator.But where does the air come from in the first place? Good question! It comes into the system with the cold fill water. You can’t see it, no matter how hard you look, because it’s dissolved in solution just like sugar in hot coffee. But, unlike sugar, the air in a hydronic system comes flying out of solution as soon as you heat the water. That’s why purging with cold water can’t possibly get rid of it.
And once it’s released, system air whips through the pipes with the pumped water at a pretty good clip. That’s why a high point air vent or an automatic air vent near the boiler can’t catch it. It’s moving too fast. On most jobs, the air is out of the boiler and up into the system piping in about 1-1/2 seconds. The only way to catch it is to slow that water down.
The boiler room is the best place to get rid of that air. If it gets past you there, it will sound like marbles up in your customer’s pipes and radiators. System air also blocks the flow of heat to their rooms and acts as a terrific insulator against heat transfer which is exactly what you don’t want, because that kind of “insulation” raises fuel bills and leads to very unhappy customers.
But a good air separator can get rid of system air once and for all. And if you use one on each of your boiler installations, chances are you’ll save yourself a lot of nuisance callbacks and wind up with happy customers who are sure to recommend you to their friends.
The best part is if you plan things right, you won’t have to spend a small fortune on that air separator either. Take a look at the IAS, Inline Air Separator, for instance.
This is a very uncomplicated device that’s remarkably effective. The folks at B&G designed the IAS to work on a simple principle when you slow water down, trapped air rises to the top because it’s buoyant. Common sense, right? And once the air reaches the top of the IAS, it can’t get out because the orifice traps it.
The orifice acts like an upside-down dam against the air. The air can’t get sucked through by a whirlpool because an orifice simply won’t create a whirlpool. As you can see in our illustrations, the balloons being held by the little man represent air bubbles, the two rooms are like the chambers within the IAS, and the door is the orifice. When the balloons (air bubbles) are released, they rise to the top and are trapped by the wall of the orifice even though the water is flowing, as shown by the fan. The air stays at the top because it’s buoyant. Since it can’t get out of the IAS, it moves to the large 3/4″ outlet, where it’s either vented to the atmosphere or directed up to a plain steel compression tank.
There are no moving parts in the IAS, nothing to fail or clog with system debris. There’s a convenient 1/2″ tapping for a diaphragm-type expansion tank in addition to that 3/4″ vent tapping. That large tapping, by the way, allows you to use a high-capacity air vent such as B&G’s #87 or Hoffman’s #79. And if you ever have to replace the air vent, you can do it without having to replace the entire air separator. That’s certainly to your customer’s advantage, isn’t it?
The 3/4″ vent tapping gives you something else as well: the option to use an existing, plain steel compression tank. The IAS is the only air separator of its size that lets you do this. All you have to do is run a 3/4″ copper line from the IAS up to the existing compression tank.
To keep the steel tank from waterlogging, use a B&G Airtrol Tank Fitting. This simple fitting is the most positive and time-proven way we know of to keep the air from leaving a steel compression tank. Reduce your pipe size from 3/4″ to 1/2″ when you reach the Airtrol Tank Fitting, and you’re done.
Install your IAS in the horizontal boiler header, about 18″ downstream of the supply elbow. The hottest water in the system must pass this point, so you’ll be able to snag those troublesome bubbles before they have a chance to make it out to the radiators.
It’s easy to take charge of system air without spending a lot of money when you use the B&G IAS. It ain’t the same. Try one on your next job, and you’ll see what we mean.
Reprinted from CounterPoint October 1994, Vol. 1, Issue 4