Radiant Cooling in Operation

[Hunderliggur]

I finally have my radiant floor heating system integrated with my well water. First off, my radiant floor system was design and installed to allow potable water to be run through the floor (stainless steel & bronze pumps versus cast iron, etc.). The heat is added by a water to water HX in a 1000 gallon storage tank and/or from in-line instant water heater (if storage is not adequate).

I added a bypass that routes all of my domestic water use (personal and irrigation) through one of the floor zones. When running a sprinkler for irrigating small paddocks I run about 3 GPM. This is irrigation I have to do anyway for our goats and chickens. The head loss to run it though 7x300 7/8" radiant loop is negligible.

Running the 55F well water through the floor at approximately 3 GPM has lowered the floor temperature by 1 to 2 F. It is a 1500 SF zone so the BTU potential is around 8 to 10,000 BTU. This is equivalent to a basic window air conditioner. The basement below the radiant is dehumidified anyway so condensation is not a problem (one of my biggest concerns, but proper humidity management makes it a non problem). I'll be adding some temperature monitors to measure the delta-T in the floor but as of right now it is working as planned for just the cost of some plumbing fittings.

It costs me about 0.08/hour to pump and distribute 3 GPM. This is about the same cost as a 10,000 BTU window unit. Since I am irrigating anyway this is free cooling. Now to figure out if adding a 300-600 LF ground loop and a circulator would have any reasonable payback period.

 

[jimbom]

I love this idea. Water in at 55 °F. What is the temperature of water out of the floor?

On the ground loop. I looked at my circulator and decided it would run the ground loop and the zones. Therefore, no new circulator. However, my soil conditions are so rocky that I have yet to find a way to make a ground loop pay. I need a maximum of 5,000 BTUh(15 °F delta To - Ti) of air conditioning for my on grade 1800 ft ² . I think 1000 lnft of direct ground loop would work here, but just can't get the loop into the ground.

 

[nate379]

Do you have problems with the floor sweating? We rarely have need for cooling up here (might have 3-4 days a summer that is over 75*) but I figured it would cool the floor down below the dew point and do like a glass of ice water.

 

[Duetech]

I didn't do the radiant thing but, out of curiosity, years ago, I tried a car radiatior as a source to cool the home while I was watering the garden. Using a 20" box fan to force air across the radiator you could feel the coldest temperature where the water enered the radiator and by the time the water exited the radiator the air was back to about room temp. At the time my well would deliver around 11 gpm max the sprinkler allowed around 4-5 gpm. I think a heater core from a car and a 500-1100cfm blower would work real well. (As long as the rigging could be held to the back yard I don't think the redness of the neck would be as evident.) Going radiant is scientific. Bravo!

 

[Hunderliggur]

We dehumidify the basement to below 60%, which make condensation a non-issue with our water temps. The radiant pipes are on the first floor so I can check them in the basement for sweating, they don't even at the coolest temperatures. I was going to go the car radiator route for dehumidifcation but I don't run enough water to make the reliable. My well pumps to a 1500 gallon underground cistern at about 5 to 10 GPM. I then gravity feed to the basement where a Grundfos constant pressure pump delivers 40PSI up to 15 GPM. Total power for 3 GPM is 700 watts/hours for the well and pressure [pressure is 400 watts/hour, well is 800 watts peak but averages 300 watts/hour; both are 120 VAC]

I haven't moved by heating sensors to the cooling [yet] but I'll post the deltas when I do.

 

[nate379]

Makes sense. I know when I was watering my lawn early this summer my water pipes were sweating bad. The water comes out the tap around 40-45* though. It's cold enough that I had to add a hot water feed so I could wash my dog outside.