Hot water heating system air scoops, air separators & air scoops:
What a bulk air eliminator or "air scoop"does, where they belong, how they work to prevent noise and loss of heat in hydronic heating systems.
Automatic air removal from hot water heating systems avoids air-bound boilers, baseboards, radiators, radiant heat loops. What is the function of the air scoop automatic air purger on heating systems? Common manufacturers of bulk air eliminators include American air purgers, Taco air scoops, Sparco air purgers, Bell & Gossett inline air separators
This article series answers most questions about central hot water heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.
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Hot water heating systems, whether using baseboards, convectors, radiators, or even radiant tubing, can be noisy if there is air circulating in the system. Worse, as we discuss
at AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE, if the amount of air is excessive, the circulator pump(s) may not be able to circulate hot water at all and portions of the heating system (radiators, baseboards etc) may just stay cold.
Air is dissolved in cold water in any hydronic heating system. When we heat the water, some of that air returns to a gas form as air bubbles that cause noise heard at circulator pumps, in the hot water piping, or in radiators or baseboards.
Air might also enter a hot water heating system due to a leak in piping that lets water out when the system is hot and lets air in when the heating system is cold. Of course there are other causes of noise in heating systems, but air in the piping is perhaps the most common noise complaint.
Taco™, a manufacturer of heating system components and controls, provides this clear explanation of the function of the air scoop or air separator on a hot water heating system:
The Taco Air scoop is specifically designed to provide a noiseless, air-free hydronic heating, cooling or combination system, by efficiently separating out the air from the water in any of these systems.
Air being lighter than water, it travels along the upper portion of a horizontal pipe in low velocity hydronic systems. As the air and water enter the Air Scoop their velocity decreases, permitting the air bubbles to be scooped up by the baffle and directed to the top of the chamber.
The air reaching the top of the air scoop is either immediately vented through a Hy-Vent or it moves into a conventional plain steel expansion tank, if used.
Should the air completely fill the plain steel tank and back down into the Air Scoop, the excess will be removed by the Hy-Vent without disturbing the operation of the system.
Also see AIR BLEEDER VALVES that work with air scoops to remove un-wanted air from hydronic (hot water) heating systems. Air in heating distribution piping, boilers, radiators, can prevent hot water circulation and thus stop heat from being delivered to the occupied space. If your heating system is having trouble with noise or cold baseboards or radiators,
see AIRBOUND HEAT SYSTEM REPAIRS.
For a complete list of diagnostic articles for radiators or baseboards that do not get hot when they should includes
see AIR-BOUND HEATING SYSTEMS.
Install the air scoop in the right direction: Notice the arrow cast into the body of the Taco™ air scoop (photo above, sketch at left) and on the sketch of the Sparco™ air purger below?
[Click to enlarge any image]
Make sure that your air scoop is installed in the right direction, consistent with the intended flow of hot water in the heat distribution piping. Installing the device backwards, a common error on both air scoops and flow-check valves, is likely to prevent it from working.
If a check valve is installed, make sure it too is installed in the right direction. Your system may not use a check valve if its circulator pump incorporates an internal flow check valve (IFC).
If your hot water heating system is noisy, is not automatically purging air, or is air bound, in addition to purging un-wanted air manually and finding and fixing any leaks that are letting air into the heating distribution piping or boiler, be sure that your air scoop is properly installed.
Make sure the air vent is working: Even if the air scoop is properly installed and located (see Taco's sketch, above), if the "Hy Vent" or "Float Vent" or automatic air purge valve (these are all synonyms from different manufacturers) is not working the system may not successfully purge air.
At above left we illustrate another air purger manufactured by Sparco.
At above right we include a sketch of Bell & Gosset's inline air separator (IAS). The B&G inline air separator has the same function as the air scoops discussed above, but its internal workings are a bit different. Here is B&G's explanation of how their IAS works:
"IAS stands for Inline Air Separator. It has two chambers, and it's a bit wider than the pipe it serves. We separated the two chambers with an orifice, and therein lies the secret to the IAS's great performance.
"An orifice is a hole that's a bit smaller than the chamber itself. Air-laden water flows down the pipe and enters the "wide space in the road" - the IAS. Naturally, as the water widens out in the IAS, it also slows down. That slowing motion releases the air bubbles in the same way a slowing river current releases floating debris.
"The air bubbles quickly float to the top of the first chamber and get trapped by the wall of iron that makes up the orifice and flows to the radiators. Since the IAS snatches the air out of the flow just as it leaves the boiler; the air doesn't get a chance to create problems out in the system.
"Once captured, the IAS vents the air out of the system through an automatic air vent, which you'll install in the IAS's top tapping. If you're using a plain steel compression tank, the IAS will pass the air up into the tank." - Bell & Gossett
Continue reading at AIR-BOUND HEATING SYSTEMS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see AIR BLEEDER VALVES
Or see DISSOLVED OXYGEN DAMAGE CONTROL - use of bulk air eliminators on hydronic heating systems helps avoid damage from dissolved oxygen
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(Aug 21, 2011) john said:
my 30yr old boiler is being replaced do i need to replace taco air scoop?
John I don't see any reason to replace the air scoop unless it's corroded or clogged.
(Jan 28, 2012) Don said:
I need to replace the air vent thats mounted on top of the air purger. Can I just turn off the pump to change it, or do I have too drain the system?
(Nov 15, 2012) Paul Eckerson said:
I have a process that is mixing a powder that increases the water's viscosity and also in-trains air and pumps it into an 1 1/2" pipe. I'm looking for a trap and automatic purge valve with 1 1/2 pipe female fittings to put inline to remove the air. You can call me @ 402 890 7361 to discuss appropriate solutions.
Feb 17, 2014) Joe said:
Should the air purger on top of the taco air scoop remains open or close?
Joe, unless the air purger is leaking water we leave the cap loose or unscrewed a turn or so on most models; there are a few air purge devices that have more precise outlet controls.
(Feb 18, 2014) Anonymous said:
how to change air vent on air purger
To change an air vent or purger the steps required depend on what device is being replaced and where it is located.
At the top of this page under the article title you'll see a link to a closely-related article: AIR BLEEDERS - reading there you'll find a series of details on where air bleeders are located and how they are repaired or replaced.
For an air-scoop device like the ones discussed in the article found on this page you would have to shut down the heating system, let the system cool down, drain it, and use normal plumbing procedures to remove and replace the old air scoop device from the heating system piping.
Following replacement of a device like this one that requires draining the heating system piping (it's not necessary to drain the boiler or other components that are LOWER than the air purger/air scoop) you will have an air bound heating system so it will usually be necessary to manually force air out of the systems. InspectApedia sports articles on several methods to do that - fixing AIRBOUND HEAING SYSTEMS.
For just replacing a simple air vent like the ones at AIR BLEEDERS it is often possible to work carefully, removing and installing the new unit with just a minimum of spillage, and without having to drain the system, though letting it cool is important to avoid getting scalded, and dropping system pressure can make the squirt and leak problem more manageable.
Oct 9, 2014) Anonymous said:
we need to change a zone valve. we can isolate one side of the zone valve with a valve will the air purger work as a check valve to isolate that from the other side? or do we have to drain the whole system?
Not for air purgers I've seen. That valve does not include a shut-off in the water line.
Sometimes a flow control valve at the boiler can be closed to act as the second shutoff. But
Your plumber may need to install a second shutoff, or may need to drain and re-fill the piping, purging air after that.
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