overflow

[joe2003]

We have had 3 geo systems that after running about 9 months to 1 year on a pressureless system all of a sudden overflow fluid from the QT center, we have flushed them with the flush cart until all the air was gone and then have to go back in a week or so because it overflows again. Does anyone have any ideas of why this is happening?

[protechplumbing]

bad expansion tank?

[crash11]

The thing about an all liquid system that is mostly water is it behaves the opposite of what you'd think. In the winter time as you slowly cool the liquid over time, the pressure rises ever so slightly. Then in the summer the pressure slowly falls. I try to keep my system at about 15 psi, but right now I've noticed it creeped up to 25 as I've been in the heating season. Then in the summer I have to watch it regularly to make sure the pressure doesn't fall to 0.

[protechplumbing]

uhhh, what? water expands when heated not cooled.

[jrbenny]

The tubing expands and your pressure drops.

[drsmith012]

Mine does this on occasion. If it has been off for over a day then it seams some disolved air comes out and collect at a high point preaking the vaccum lock. I solved this two ways. Letting the GT flow center get a little lower and hooking an external switch to the slaving inputs for the pump. After a day I go down and flip a switch let it run a few minutes and then turn it off.

Yes my water is higher in the winter than the summer. The pipe expansion and contractions more than offsets the expansion and contraction of the water.

[crash11]

uhhh, what? water expands when heated not cooled.

Is that why everyone worries about straight water in their engine blocks in the winter? Or water in driveway cracks during the winter? Last I checked solid water (ice) floats in liquid water.

I think you're thinking of gases. We're talking liquids here.

[drsmith012]

liquid water expands as the temperature increases from 0C to 100C. Water Vapor expands as temp increases as well. The funny thing about liquid water is what happens as the temp decreases past 0C (as it freezes). It begins to expand becoming less dense than liquid water. I believe there is a point where water ice will begin to contract as the temp continues to drop but never reaches the same density as liquid water.

In our geothermal systems the pipe volume is increasing (or decreasing) at a faster rate than the water is expanding (or contracting) thus the corresponding drop (or increase) in pressure or water level. Reverse is true for cooling.