Hey all, usually I hang out in the radiant forum but I have what is most likely a dead simple question. why would you need to purge a geo loop field? everything I know about hydronics says that air removal in a situation where all your water is BELOW you should be dead simple. fill with water, pressurize to desired pressure, and provide for air removal. we purge in hydronics, but we do that because usually we are doing horizontal loops, or loops going UP, and so air can get stuck and need to be forced out after the initial fill. but it sure seems like with geo loop fields, if air comes out of solution... it should come to you, no? maybe not if you're doing slinky loops, but in any well application.... thanks in advance. suddenly this is driving me nuts.

Some slinky loops are laid in vertically in a trench, or partially so.

On my 5 acre lot, the only clear spot I had for loop field was 200 feet down the driveway. At that point, the elevation is definitely a few feet higher than grade at the house. From there, through the length of the 300 foot trenches, the ground swells and ebbs enough where I want to ensure my loops are 100% filled with heat transfer fluid

There are tons of similarities between geo fields and radiation systems but a few big differences. Picture a radiant floor off a common trunk with multiple paralell loops with no isolation and no purging system...... are skome loops designed for purging like a radiant floor? Yes there are some manifolds by Caleffi and others that would let you flush without a cart, most of us long-in-the-tooth types prefer just 2 wall penetrations with the manifold outside.
Hope this'll let ya sleep at night.
Not

holy cow. people do a common trunk without isolation for their loops? I guess I can see why you'd need huge purging capabilities in that case.

Posted By NRT.Rob on 12 Mar 2013 12:23 PM
holy cow. people do a common trunk without isolation for their loops? I guess I can see why you'd need huge purging capabilities in that case.

I think that is pretty common practice to manifold outdoors underground without valves, except for DIY installs. The only time I've seen valves in my area is on horizontal loop fields done DIY style and use unpressurized flow centers.

well, actually, I still can't quite see this. are you actually purging for air, or is this primarily for debris?

seems like air would naturally rise and be removed at whatever you have for air removal naturally without the need for purging, in any vertical well arrangement anyway... no?

thanks for taking the time!

My 2 geo unit / 1 common water loop (diagram at http://www.welserver.com/WEL0043 ) implementation has a SpiroTech manufactured SpiroTop automatic air vent at the highest point of each HDPE pipe run (my 2 units are in the attic, and thus the automatic air vents are installed in the HDPE pipe right at the geo units).

See http://www.spirotech.com/en/product...vents.html for details.  These units are supposed to remove air very efficiently from the line, with no maintenance ever required.

Just FYI.

Best regards,

Bill

Geo loops often do not have make-up water so air purgers are not common place. It is the beauty of the nonpressurized flow center.

Joe's note above reminds me to comment that indeed in my case I do have a city water service connection to my loop, via a pressure regulator, to keep the geo water loop pressure constant regardless of HDPE pipe contraction/expansion due to changing earth temperature.  It's illustrated in the connection diagram noted above in my earlier post.

Best regards,

Bill

You are urging of debris from install, and air as well. Air can not and will be able simply rise in a vertical loop system. The water is forced to go down first before it can come back up. Just picture a 200' loop installed vertically, now you would have to force that pocket of air down 200' into the ground before it can make its way back up and exit the system ( there is no exit on a pressurized closed loop). You need Alot more flow and pressure to purge than what the flow center can produce. Purge carts are needed to move this volume of water and release air, and debris too.

Remember in my area design temps for loops are sub freezing so un checked make up water can risk serious equipment damage.

...in my case I do have a city water service connection to my loop, via a pressure regulator to
keep the geo water loop pressure constant regardless of HDPE pipe contraction/expansion ...

Hmm... 'zactly how does that work? To maintain constant (static) pressure, the "regulator"
can't just add water when the loop pressure falls, it must also bleed off ...uhh, whatever's
in the loop, when pressure rises. Be it antifreeze or "pre-owned" water, where does it go?

Looby

Calladrilling: when you're not pumping, why can't the air just rise up the "supply" pipe? you don't have check valves installed.

seems like if you had air, whenever you stopped pump, it would rise up whatever pipe is available to the high point... the header, probably the geo units themselves. I can't see why a power purge would be necessary for air removal. I could see it for dirt though

The air will rise up and if your pump is the high point cause cavitation. Remember many of these systems are not vented and do not have make up water. We can also have a loop airlocked and system will under perform

Posted By Looby on 12 Mar 2013 11:36 PM

...in my case I do have a city water service connection to my loop, via a pressure regulator to
keep the geo water loop pressure constant regardless of HDPE pipe contraction/expansion ...

Hmm... 'zactly how does that work? To maintain constant (static) pressure, the "regulator"
can't just add water when the loop pressure falls, it must also bleed off ...uhh, whatever's
in the loop, when pressure rises. Be it antifreeze or "pre-owned" water, where does it go?

Looby

Go to http://www.welserver.com/WEL0043 to see a layout of the connection.  Domestic water supply to check valve to control solenoid (on for a small amount of time each day) to regulator to water loop.

Best regards,

Bill

Domestic water supply to check valve to control solenoid (on for a
small amount of time each day) to regulator to water loop.

OK, it's obvious how water enters when the loop piping volume expands,
but what happens when the loop volume contracts? Your pretty diagram
doesn't show any relief valve or other exit path from the loop.

OTOH, if there is an exit path, wouldn't seasonal variations in volume
result in a systemic pumping action, i.e., in through the check valve,
out through the exit path? Does the loop use antifreeze, or just water?

Posted By Looby on 15 Mar 2013 06:35 AM

OK, it's obvious how water enters when the loop piping volume expands,
but what happens when the loop volume contracts? Your pretty diagram
doesn't show any relief valve or other exit path from the loop.

OTOH, if there is an exit path, wouldn't seasonal variations in volume
result in a systemic pumping action, i.e., in through the check valve,
out through the exit path? Does the loop use antifreeze, or just water?

I'm not a hydraulics expert, so I don't think I know the answer to your question.

The design is done standard with all geo installations done by the particular geo HVAC professional that installed my system.  It's not something custom that I asked for.

There's both a pressure regulator and a check valve in line - I assume these two devices prevent back flow.

The geo loop fluid is water only.  (This system is in the Dallas area, where water only is used for geo loops, and no aux electric heaters are installed.  The performance challenge down here is on the cooling side, keeping EWTs down to a reasonable level).

Best regards,

Bill

Would not the simple addition of a pressure tank solve everyones concerns? I look at systems like that as " mini commercial ". Just the doseing tank and pressure tank are misssing.
Eric