Unconventional Air Scoop Location

geno54

I find piping methods that are sometimes out of the ordinary

Have found this way of piping an air scoop on several service calls where the scoop is on the return rather than the supply.  It appears to be working.

Any ideas, good, bad. Is the installer a lunatic or a genius

Chris S

air scoop

On my own home, and on several other radiant installs,  I have installed spirovents on the return, followed by a ball valve. I put a boiler drain in the bottom port of the spirovent.  I have found that this configuration allows for fast venting of the air in the system on start up.  Of course in my case the pump is on the supply side.

If we install a spirovent on the supply side just after the pump,  we bleed the system in reverse, and then on pump start up reverse the flow.  If any air was not completely out, but was moving towards the drain, in this way it is pushed back into the system.  In the first scenario the water and air is always moving towards the spirovent.

I used to install embassy systems, and one of the only things that I really liked about their manifolds was the built in air vents on supply and return.  Their systems almost bled themselves.

In your photo, the air scoop is at the point where system pressure is the lowest, and so least desirable but... is it working?

Xray

Separator there can suck in air!

I have seen twice when float-vents located just upstream from pumps actually pulled air in when the system was under low pressure due to plugged reducing valve. Maybe a kind of venturi effect..

hot_rod

air eliminates

best at the highest temperature point in the system. But these days with low temperature boiler operation it may not be as much as an issue.



But really you want to catch and eliminate air before it can get into the piping, valves, flow setters. and high points in the system. Seem the return would be the least desireable point, considering all the above.



If you leave it there the expansion tank should be connected so you establish your PONPC and pump away from that. With the PONPC and pumped away you should not suck in air.



But I know where you can get anti-siphon caps for air vents should the need arise



hr

Xray

Freakin air

In the old days, it was common to put a float-vent at the lowest return elbow. Gnarph! I agree with Mark Eatherton: best to use a regular old air scoop, with the pump downstream, pumping away!

Coany

isn't there supposed to be 1' of horizontal pipe before...

the air scoop? Thats my only question from the picture.



I have been removing float vents from returns since forever.

Xray

Sensible man...

I hadn't heard about the 1 ft rule.....keep taking them off the return forever.

Unknown

Scoop or no scoop

Air will come out best if under lower pressure, higher temperature and low velocity.



Scoops are obsolete in modern low temperature hydronic systems. Micro-bubble air eliminators rule. They may be placed before or after the boiler but work best when the circulator is "Pumping Away" from them as this will be the point of lowest pressure. If the "diaphragm" expansion tank is connected to the air eliminator everything is Jake.