# Air Scoop..



## Lifer (Nov 23, 2010)

The new system i am installing this week has an air scoop built in to the boiler ( slant fin , electric wall hung ) and it got me thinking about how much better i like Micro bubble resorbers. just wondering what you thoughts on the whole thing are ..

The Co. I am working for does not put auto air vents or manual bleeders on the wall rads at all , there solution to air is to power purge it . ** I said there answer not mine , if it were up to me they would all have a minimum of a manual bleeder at the highest point..


----------



## Scott K (Oct 12, 2008)

First off, there are some key differences between air removal devices.

Air Purgers such as auto air vents, coin vents, and units such as Spirotops by Spirotherm (higher capacity) are utilized at high points to remove accumulated air that could cause an air blockage of flow. I would not personally rely on them as the sole air removal devices in a system. While they can do a decent job if the system is set up properly, you're better off with something that interacts with the flow, so to speak. 

An Air Scoop and an Air Seperator are designed to "interact" (or maybe more correctly, interfere) with the flow of water caused by the circulator to remove air as water is circulated. An Air Scoop has a 2-3 curved metal baffles inside a "hump" where the water can slow and these baffles can "scoop" the air and push it to an air purger (auto air vent). The only problem with these is in theory, to function properly, they require some stratification of air/water which means you need some straight pipe upstream of them. This doesn't mean they won't work with a fitting right near their inlet, but they will work MUCH better with some straight pipe upstream of them.

An Air Seperator, as you already know, is designed with media coupled with a larger low pressure zone to cause turbulence to seperate the air bubbles and push them to an internal air vent. They do not have any provisions or requirements for straight piping and so are more versatile; the only practice you might want to watch is if/when you put your circulator downstream of them, I would give at least 6 pipe diameters worth of pipe between your air seperator and circulator as the turbulent water flow downstream of the air seperator could cause cavitation of the pump impellar overtime. 

In my opinion, if you follow proper hydronics practices, and have drain downs that can also function as power purge points in your Mechanical room, you will seldom, if ever, require air purgers at high points; a good air seperator or air scoop is all you will need. Start with a good power purge of the system putting your water feed PRV in the open/full flow position (make sure you've piped your pressure relief valve to a drain or safe place in case it goes off while you do this if you're not paying attention to the pressure for a second or two) or if you have a bypass on your water feed, using that. Then power purge most if the air out. Then fire up your circulators and leave your feed valve on and this will take out the rest of the air quite quickly. I have had systems that I spent about 1-2 hours power purging (each individual radiant loop - 2-5 minutes each loop say) on top of the indirect loop, and then fired them up and the air was gone in 20 minutes, literally. On a zoned baseboard system, even better/faster. 

The only time I will consider air purgers at high points is if you have some elegant cast iron radiator that was converted to hot water from steam or along those lines, or in a multi story building with a bunch of big heating mains coming off of risers. In this case, a good high capacity air purger will work with your air seperator to prevent blockages in flow.

As far as models - I'm a big fan of Spirotherm products. I've installed dozens of Spirovent Air Seperators without any issues, and for a good Air purger their Spirotops are tough to beat. Most 1/8" tapping air purgers like the no.67's 66's, etc. start pissing water and fail overtime (the float gets gummed up). The only dedicated air purgers with 1/8" tappings that I've had luck with are the Watts Auto Air Vents (blue/white box). 

A lot of people are pushing Low Loss Headers as if they are a god send replacement for air seperators. The truth is, most low loss headers, while they may function as a combination low loss header (hydraulic seperator), air seperator, and dirt seperator, they don't do each of these functions particularly well. On a small system they'll be ok, but because they often lack the media to properly seperate air and dirt, they won't do as good or as fast of a job as a proper dedicated air and dirt seperator. Having said that, Spirotherm, which I believe is a European based company, DOES make low loss headers with full media from top to bottom so they will function as a true air seperator and dirt seperator as well much like their dedicated air & dirt seperators, on top of a proper low loss headers. I really hope they can bring something like this to the North American market. 

I'm also personally a much larger fan of Air Seperators over Air Scoops; I'll spent the extra $$$ for a proper Air Seperator, which, isn't much in the grand scheme of things.


----------



## Lifer (Nov 23, 2010)

Thx Scott, 
loads of good info there for those who are not familiar with the inner workings of air separation, I would prefer to see at least one manual air bleeder on the upper floors of houses or buildings because not everyone is properly installing there hydronic systems. I am only into boilers for 3 yrs and learning every time i put a new one in.. 

Thx Lifer..


----------



## Scott K (Oct 12, 2008)

Just remember that every air purger you install outside of the mechanical room could become a liability, and I really hope you are not concealing any of them either? It's not a bad idea with an air purger to allow the capability to isolate it with a valve and when the system is up to snuff and you're confident most of the air is out, shut the valve off and only use it when it is needed. 

If you're really looking for good resources to improve your installations try buying some of Dan Holohan's books off of heating help. If you read his books a few times, they will really help you understand the relationships between the equipment in a hydronic system and how it works together to help the system perform better and last longer as well as require less down time should service be required. You might have to read his books a few times, but they're not hard to read, and he writes in laymans terms. Some books of his I recommend are Pumping Away, Primary Secondary Pumping made easy, and his Radiant Heating book. 

Best of luck.


----------

