problem with geotherm system

zepfan

does anyone know how to find out if you have a leak in the well of a closed loop geotherm system? we have a building with several geotherm heat pumps and one of them last january devoloped a leak in the refrigerant to glycol heat exchanger.we replaced it and when we did lost about two gallons of fluid.we started the system back up after the repair and it ran without any problems the rest of the winter.the owner then called in june and noticed the sound of the fluid running through the lines.i went out and put  much more fluid in then was lost during the heat exchanger replacement.the noise seemed to go away for sometime and then it returned along with the circulator making a noise like it was running dry.this setup has two circulators per unit one supplies water from the loop and one returns water to the loop.the one that is making the noise is the one that is supplying water from the loop.if fluid is mannually added the noise goes away,as soon as you stop adding fluid the sound returns.i have traced the piping (all done is schedule 40 pvc) as far as i can above ground, and found no leaking.i am now down to having to test the loop in the ground, and am not quite sure how this is done.there is definitly glycol in the loop so i am assuming it is a closed loop.we did not installed this system,but have worked on it for the last three years and have never had to add fluid or had this problem. thank you

zacmobile

air?

After you replaced the heat exchanger did you re-flush the ground loop? It sounds like you may just have a few slugs of air moving around in the system that are getting caught in the circulators. Are there any P/T ports (Pete's plugs) anywhere in the system? You could pressure up the system there using a pete's plug probe and temporarily insert a pressure gauge there as well to monitor the pressure over a period of time with a minimal amount of disturbance.



http://www.bricebarclay.com/Petes_Plugs_Pressure_Temperature_Test_Plugs_P-T_Plugs.html

Ironman

Leaking Somewhere?

It's like freon: if you have to keep putting it in, then it's going out somewhere.



I would recommend what Zac said: pressurize it and see if it holds. Can the loop be isolated to check it separately? If not, can you install isolation valves?



I would not overlook the possibility that the new heat ex. could be leaking if the last one failed from freezing and the cause wasn't corrected. Is it a plate or co-axial heat ex.? A plate is more susceptible to failure from fouling on the water side.



You mentioned that the building has several geo units. Are they on a common or separate loop?



Is there a strainer on the loop? Have you checked to see if it's clear?



Just a few suggestions.

zepfan

geotherm problem

thank you for your help.when we replaced the heat exchanger we did not re-flush the ground loop because i thought you needed a "flush cart" to do that which i do not have.yes there are pete plugs at each unit that i unscrewed and put in boiler drains on the unit we are having the problem with.one i hooked a garden hose to and the one above it i opened to vent the air.i turned on the hose and let it fill,vented the air, closed the top boiler drain,turned off the hose and started the circulator.i cannot be doing this right.when you say use the pete plugs are you talking about pressurizing through one and venting through the other,or pressurizing through one and using the screw on the back of the circulator to vent the air?i would expect it is only air due to the air showed up after the heat exchanger was replaced.getting rid of it is proving to be a problem.is the only way to get rid of the air in one of these systems is with a "flush cart"? thanks again for you help

zacmobile

flush

Yes, the only way to get the air out of a geo loop is to flush with a high head pump, unless the system has some kind of air removal device like an air separator which is definitely not the norm in the geo industry. If you don't have a flush cart you can rig something up with a jet pump and a trash can, I have a 1.5HP pump on my cart that can do 30gpm @ 80 ft head, that's good for pretty much any residential loop. Pipe the pump discharge into the geo loop and the suction side of the pump should pull from the bottom of the bucket, (it helps to have a screen to keep out the nasties) then the return from the system should be about within the top 1/3 of the bucket. Run it for a good 2-3 hours or until all the microbubbles are gone (it helps to have an old t-shirt or something over the end of the system return to break up the bubbles). I would probably start here before leak testing so you're starting from a clean slate, it's quite possible that's all it is anyway, I have seen many systems that appeared to have a leak but it was just a lot of air in the loop.

zepfan

thank you

thank you so much for your help.i'll give it a shot