We ran the geothermal radiant cooling for the first time today

Brent_2

At 63° surface temp you will be safe to about 76° and 60%
room conditions before getting condensation. Did you figure out how many btu's you are putting into the house?
I would think about controlling the pump with a humidity sensor. When the indoor RH gets above setpoint you turn the pump off to avoid the possibility of condensation.

Brent

John Ruhnke

We ran the geothermal radiant cooling for the first time today

Hello Everyone,

Today we ran the geothermal radiant cooling system for the first time. It worked great!!

Here is what happened. The project started with well pump problems. A few years back I noticed that my 40 year old jet pump was starting to have problems. I then looked for a replacement. I spent a few years thinking about this project. I was told by my well guy that submersable pumps were more efficient cutting energy costs in half. I also liked the fact that you could get much better pressure.

It was a no brainer. Submersable pump it was to be. Well I looked at the two pipes and thought to myself. What am I going to do with the spare pipe? A friend suggested that I run the well pump wires though it. I thought no. A electrician friend of mine has a trencher and it would be easy to bury the pipe the needed foot. The well pipes were four feet under ground. A much more expensive thus valuable trench.

What am I going to do with that spare water pipe?

I thought about the radiant heating system I was installing into my home. I made a few phone calls an then designed a simple radiant cooling supplemtal system. This system works with the existing heat pump system in my attic. The radiant cooling system will handle an estimated 10% to 15% of the cooling load. I got this number from another friend who has a simular system in his house.

We cut out the jet pump and pulled up the well piping. Then we attached a submersable pump at the bottom of the well. We then cut off the return pipe about ten feet below the top of the well cap. We borrowed a trencher and burried the wire about a foot. Inside we tied in a heat exchanger to the secondary loop of the second floor radiant heating system. The well water runs through the other side of the heat exchanger. A solanoid valve opens and discharges the well water through the heat exchanger and back to the well. On the system side of the heat exchanger, an injection pump moves water from the heat exhanger through a set of close spaced tees. A system pump moves the water around the secondary loop and through the radiant floors.

This is a simple system with no compressor. The well pump is half horse. The well water entering the heat exchanger is about 56 degrees. We ran the system full out for a little bit. The well presure dropped to 25 pounds pushing the limits of the well pump. We read the return and feed temps on the system loop that leads to the radiant floors. 58 degrees feed temps and 64 degrees return temps. We ran it that way for about 20 minutes. No condensation anywhere!!

We then dropped the water flow on the well side in about half. This way the water pump pressure went up. We wanted to leave extra room too so that there was enough water pressure for the domestic load. I call this design conditions. The temps on the system side feed were 63 degrees. On the return comming back from the radiant was 67 degrees. Again no condensation on the system piping!! The well water does cause condensation on the copper pipe when it runs through in the basement though. The radiant tube runs through quickTrac. The tubes are exposed because the hardwood floors have not been installed yet. There is no condensation upstairs either.

We only have run the system for short periods so far. It needs lengthly testing. I''ll run it tonight for a few hours when I can watch things. I have wires in the wall for future humidity control. Currently there is no humidity control. My thinking is that the output of the system is not high enough to cause the floors to condense. If this is the case then I won't need the humidity controls. This is my own house so that I can keep an eye on things.

Electricity costs are very low. We are only running two taco pumps 007 and 008 plus a half horse well pump. No Compressor!! We have a traditional AC system run through ducts in the attic. I feet that the radiant cooling might handle 15% of the load and save 10% in electricity costs. For a little bit of work, the job was easy. I feel it is woth it because of the long term savings.

Below in the bottum left corner of the picture you can see the cooling heat exchanger. Sorry for the mess of wires on the board. Work on other systems aren't complete yet.

John Ruhnke



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Josh_10

Absolutly awesome.

john_27

please post more pix and commentary....you were quite inventive interms of the install....let us know more as you can....Good Work!

Glen

would you care ....

to post a schematic of the piping - along with your elect controls????? I am considering this very project - radiant heat in the winter - cooling in the summer. I figure a loop temp of 65 deg F will be OK for cooling.

hydronicsmike_2

Love it John!

Great Work. I too, would be very much interested to see more pictures.

Mike

Tim Doran

Performance expectations

Hey John,
You can reasonably expect to get 12 to 14 btu/sqft of cooling from a floor system. If there is direct solar load onto the surface it can be much higher. As a rule I don't design to surface temps any lower than 66f, this has to do with comfort as defined by ASHRAE Standard-55 and dew point issues. With a surface temp of 66f and a room set point of 78f you can have an Rh near 50%.

Tim D.

John Ruhnke

Thanks Tim

Tim,

At design conditions my water temps are 63 degrees in and 67 degrees out. Surface temps are 69 to 71 degrees. This is bare quickTrac. I am sure temps will be higher with the hardwood. I have a air system as a back up. Do you think I would need humidity controls? Or am my water temps high enough not to worry about that.

JR

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John Ruhnke

Update.....

I have now been running the system for 8 hours. The water temps on the inlet into the floors are 63 degrees and 67 degrees on the outlet. Pretty steady. The back up air system isn't running cause the electrician isn't finished. The floors are nice and cool to the touch 70 degrees. I walked barefoot and it was awesome!! Nice and cool!! The radiant cooled upstairs is cooler then the downstairs. The downstairs is being cooled by two room air conditioners for 7 rooms cause central air isn't done. The room ac units total 15,000 btu's together. It is 77 degrees downstairs and 75 degrees upstairs. Normally on a day like today without ac, it is 80 degrees downstairs and 83 degrees upstairs. 8 hours at design conditions and no sign of condensation.

Radiant Cooling ROCKS!!!!!

Drawings won't be done for a while. I have some hand drawings but they have crossed out and erased sections. We made changes as we went. They look bad. I'll post some more pictures in a few days.

10 minutes ago I cranked the system to full blast I'll run it that way for a couple of hours and check the output. At first the water temps on the inlet side dropped to 58 degrees. The outlet side was reading 66 degrees.

JR



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John Ruhnke

RE:

> At 63° surface temp you will be safe to about 76°

> and 60% room conditions before getting

> condensation. Did you figure out how many btu's

> you are putting into the house? I would think

> about controlling the pump with a humidity

> sensor. When the indoor RH gets above setpoint

> you turn the pump off to avoid the possibility of

> condensation.

>

> Brent





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John Ruhnke

RE:

Brent,

I don't ever see the floor getting down to 63 Degrees. The floor shoudn't ever be cooler then 69 degrees. I don't think humidity controls are needed. When the finished fllor is in I will calculate the btu output. I could do that by measureing the floor temps and square footage then plugging the info into my software.

JR

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