Can hydronic system cool building in place of air conditioning?

[700renegade]

So this weekend as I'm pulling wires for a split AC system to put in my workshop rec room, I began thinking about cooling using the floor. After all it was about 15* cooler inside the shed than outside, thanks to the thermal mass of the concrete floor.

It seems you could get the BTU's needed pretty readily from well water at roughly 55* ( 2gpm X 500 X (70*-55*) = 15,000 BTU ). The cost to pump the water from the well is 1/12 the cost to run a traditional air conditioner using those numbers.

Has anyone done this? I suspect there are some problems that make it impractical like

a. cold air won't move away from the floor
b. anytime the dew point approaches the floor temp you will get sweating like crazy
c. no humidity is removed from the air

Just curious if anyone has tried it.

 

[stee6043]

This topic pops up about this time of year every year! I've heard varying reports of folks trying this but I've never heard of any real success. And utlimately it's the moisture that get's discussed the most. Run a 55 degree line through my basement ceiling on a 90 degree day and it will most certainly end up dripping condensation...

 

[Mark Holden]

When air is cooled, it's less able to hold water. So moisture that's suspended in the air gets closer to the condensation point; which we experience as relative humidity.
Air conditioners cool the air way down for a second, causing the moisture to condense out as water; they dehydrate the air as well as cool it. Then the dry cool air is spat out into your room. This actually uses energy, sometimes half the power of the machine.

If you gently cool the room as you propose, relative humidity will rise a lot; but if you're in an extremely dry area, it will work just fine.

 

[rkusek]

My 30x60x14 Morton building has no window except for on one of the two walk-in doors. The 18x12 overhead door is isulated, walls are R19, and ceiling is R38. The slab is not insulated. The past 3 summers it has been much cooler inside but too damp to where I had mold issues. After getting tired of scrubbing things with bleach each fall, I finally hooked up a dehumidifier. I wish I had a bigger model but it cycles normally now after running nonstop initially. The shed is very comfortable to work in and kids & dog frequently go in there to cool off. I make sure to only open the big door just long enough to get something in or out. The window on the door also has a mini-blind. The uninsulated slab must be transfering heat pretty freely to achieve this. In early winter the reverse seems to happen, where I don't need to worry about freezing in the shed until well into winter if I'm not running the boiler for some reason. Heating the shed in the dead of winter has always been easy too. Just cycling water through my homemade water-to-air HX with fan off(old residential outdoor ac condenser unit) will keep the shed in the 60's no matter how cold it is outside. The 120v fan motor I added still runs too fast even on low speed and must have a tremendous delta T since it returns ice cold water when the fan is running. This winter when I finally add storage, I think a box fan on top my W/A HX tied to a line voltage T-stat should help me keep it at a constant 70 without much effort. I know the boiler and 10+ feet of single wall probably contribute quite a bit too.

If you added a dehumidifier and a ceiling fan to your proposal I think you might achieve what you desire. My dehumidifier is only 450W and I think the larger ones would actually be more efficient for the size of my building. I think the electricity to run everything would roughly equate to less than 1/5 of an air conditioner in your case. If you need the cooling it would probably be worth a shot to see if it works. I was also told by a builder that he had seen shops like mine cooled where the farmer ran a few hundred feet of aluminum irrigation pipe buried in the ground with tractor type air cleaner/filter attached where it came out of the ground in a shaded area. The only cost was for the fan that pulled the air through to pipe into the pole barn. Because of my lack of windows and insulation, I had no reason to try it.