cooling slab with irrigation water?

[ryantowry_81]

So I am still in the planning phase of my shop and don't have the budget right now for a true A/C system but wanted to put in tubing for in floor radiant at some point. then I got to thinking, I have irrigation water off a irrigation canal to my property that is usually in the 45-50ºF range or cooler. what if I just did a single pass through the slab before going to watering the plants in the summer to help keep the shop cooler. I know of the condensation risk and dew point but in my area we are in a very low humidity area with very low dew points most of the summer.

Anyone else setup a system like this before? any lessons learned?

 

[nadogail]

I have never done this, but in IMHO the theory should work. As I understand thermodynamics, the heat in the slab should transfer to the water circulating through the tubing.

Somebody please correct me if I am in error.

Any advice you take from me is guaranteed to be worth exactly what you have paid me for it.

 

[Bogie1632]

Not much help here but I've seen plenty of chilled water AC setups in the past. I can tell you living in a military dormitory with one that leaked sucked. Mold and mildew everywhere. Mildew f'ed up my Service Dress in under 2 days, right before an inspection, and on E-4 pay the replacement cost hurt. Apparently it loves starch. Not a problem buried in cement.

My question would be are you filtering it or hoping it never leaves anything behind to plug up your system? I'd think a more traditional style chilled water AC setup blowing air across some sort of heat exchanger may work better than just pumping it through your floor lines and from some DIYs I've seen on the internet I don't think it would brake the bank to build your own.

Good luck. It'll be interesting to see if this works for you. Hope it does.

V/R
Bogie

 

[rattle_snake]

Can you return the water to the canal and run at any time? Or does it only have water in it at pre-determined times (that's how mine works)?

 

[HoosierBuddy]

I don't think you'll get a lot of meaningful cooling of the air in the garage by cooling the slab to 30 degrees under ambient. You'll get some cooling...I just don't know if it'll be enough to justify the project. If you go ahead with it...post back here and let us know. I'd love to be wrong on this one.

Phil

 

[Copymutt]

Understanding that cold air sinks, you may achieve a stratified cooler layer of air at floor level, but not much of a space conditioning effect. Might use an laser temp gun compare soil temp a foot down compared to the water temp. Our irrigation water here is ice cold, that certainly would be desirable.

 

[Jwallace1]

would you run into condensation problems with floor being so much cooler than the air temp? i agree i don't think you would get much of a cooling affect with the floor being cold, radiant heat works great because the warm air rises.

 

[Jackfre]

I think you would be better served with an air handler either in the ceiling or suspended. As noted cold air is heavier than hot. I think you would end up with a cold wet slab.

 

[ryantowry_81]

Not much help here but I've seen plenty of chilled water AC setups in the past. I can tell you living in a military dormitory with one that leaked sucked. Mold and mildew everywhere. Mildew f'ed up my Service Dress in under 2 days, right before an inspection, and on E-4 pay the replacement cost hurt. Apparently it loves starch. Not a problem buried in cement.

My question would be are you filtering it or hoping it never leaves anything behind to plug up your system? I'd think a more traditional style chilled water AC setup blowing air across some sort of heat exchanger may work better than just pumping it through your floor lines and from some DIYs I've seen on the internet I don't think it would brake the bank to build your own.

Good luck. It'll be interesting to see if this works for you. Hope it does.

V/R
Bogie

yeah a coarse prefilter before entering the slab to keep larger particles out s a good idea. I will add that to the list.

Can you return the water to the canal and run at any time? Or does it only have water in it at pre-determined times (that's how mine works)?

I don't think returning it to the canal is feasible as we are a ways away but seeing as I pay a flat yearly fee for 9 inches to irrigate 10 acres and currently use almost none of it I don't have a problem just running it strait into the ground either. we are in a river valley so I can dump a lot of water strait to dirt without any real issue of saturation.

I don't think you'll get a lot of meaningful cooling of the air in the garage by cooling the slab to 30 degrees under ambient. You'll get some cooling...I just don't know if it'll be enough to justify the project. If you go ahead with it...post back here and let us know. I'd love to be wrong on this one.

Phil

I was thinking about this as well. I was thinking a couple ceiling fans to de stratify could help there. most of my shop activities are fabrication or automotive so I still do spend a lot of time on the floor or near it....lol

Understanding that cold air sinks, you may achieve a stratified cooler layer of air at floor level, but not much of a space conditioning effect. Might use an laser temp gun compare soil temp a foot down compared to the water temp. Our irrigation water here is ice cold, that certainly would be desirable.

I should go take a temp of the canal right now. it is not the hottest time of year right now but the river the canal feeds from comes from stays pretty consistently cold. thanks for the idea

would you run into condensation problems with floor being so much cooler than the air temp? i agree i don't think you would get much of a cooling affect with the floor being cold, radiant heat works great because the warm air rises.

I looked into the historical data from the national weather service for my area and it looked like the average dew point for the last two summers was around 45ºF. I was thinking if I could control the water flow to keep the slab temp around 50 I should be able to keep it from sweating too much. luckily our relative humidity here is really low. one benefit of living near the desert.

I think you would be better served with an air handler either in the ceiling or suspended. As noted cold air is heavier than hot. I think you would end up with a cold wet slab.

that is a good point. I was thinking of the reaction speed of in floor being as slow as it is maybe having a air to water heat exchanger would help to have some more fine tuned control.

Only reason I was thinking about inslab cooling was the tubing I would have to add now and if it does not work for cooling I can always use it for heating down the road.

secondly, besides the physical cost of the tubing and a manifold, this cooling would cost me absolutely nothing to run. No need for a pump and no charge for the water ( well besides the yearly fee but I am going to pay that anyways) so why not try it. worst case I have radiant tubing in the slab I don't use? if I install some ceiling fans to de-stratify they will still help me with or without floor cooling.


Thanks everyone for the feed back keep the ideas coming. I really love throwing out ideas and seeing how others view them and help them evolve.

 

[Tduby]

Look up caleffi idronics they have some useful information you would have to keep your slab above the dew point. But you could use a heat pump or just the chilled water in an air handler to remove the latent heat and get it nice and chilly in there for not much energy.

 

[meathooker]

Ran pressurized un-metered irrigation water through a radiator backed with a $20 Home Depot box fan. Measured incoming and outgoing water temp, estimated water flow, entering and leaving air temp, and rated cfm on fan. Calc’d out to approx 9,000 - 10,000 btu. Kept a 1500 sqft insulated shop around 75deg in the summer (100-105 outside temp). It was great “free cooling”

I have a heat exchanger piped in my new shop radiant loop with the intent of doing a chilled slab. I think it will work great.

 

[PWC Repair]

Well, I don't have much to add about pumping water through the slab. But, about 40% or more of my shop slab is below grade. The cooling effect in the middle of summer is very noticeable every morning. I can also keep doors shut 'til noon or so to keep the cooler air IN. So......I think it will help.

 

[ryantowry_81]

Ran pressurized un-metered irrigation water through a radiator backed with a $20 Home Depot box fan. Measured incoming and outgoing water temp, estimated water flow, entering and leaving air temp, and rated cfm on fan. Calc’d out to approx 9,000 - 10,000 btu. Kept a 1500 sqft insulated shop around 75deg in the summer (100-105 outside temp). It was great “free cooling”

I have a heat exchanger piped in my new shop radiant loop with the intent of doing a chilled slab. I think it will work great.

this is good info. I was also thinking that the radiator option could be actually cheaper than in slab for cooling tubing. I would really love to put the tubing in the foundation for heating as well but i am on the fence if this is a want or need.

 

[nadogail]

During my High School days, 1953 to 1958, there was a radiator repair shop in Anchorage, Alaska that heated their shop by circulating the hot water from their radiator cleaning Hot Tank through a radiator from a D8 Cat with a fan behind it.

 

[Tduby]

this is good info. I was also thinking that the radiator option could be actually cheaper than in slab for cooling tubing. I would really love to put the tubing in the foundation for heating as well but i am on the fence if this is a want or need.

You definitely can do both just keep the slab above the dew point it will cool the garage some then run a fan coil to do be a dehumidifier. And same set up in the winter use the slab to keep it lower but comfortable and the fan coil to make it warm. Not saying you will save the money with just heating but the free cooling makes it a no brainer.

 

[ryantowry_81]

During my High School days, 1953 to 1958, there was a radiator repair shop in Anchorage, Alaska that heated their shop by circulating the hot water from their radiator cleaning Hot Tank through a radiator from a D8 Cat with a fan behind it.

Man, living in Alaska in the 50's, I bet you have some fun stories. I lived there in the 2000's and it was an adventure.

 

[ryantowry_81]

You definitely can do both just keep the slab above the dew point it will cool the garage some then run a fan coil to do be a dehumidifier. And same set up in the winter use the slab to keep it lower but comfortable and the fan coil to make it warm. Not saying you will save the money with just heating but the free cooling makes it a no brainer.

yeah I am leaning towards doing a closed loop system down the road with a HX for the irrigation water and a heater with a recirc pump and then I can heat or cool on the same loop of in concrete pipe and a radiator with catch basin for condensate.