Economical Heater/Chiller

[gotbluegrass]

I've been thinking about setting up several grow-out tanks in my garage (no basement). The garage contains the furnace, water heater, and well pressure pump. It's insulated, but temps can vary from 40 to 90 degrees.

My biggest concern is for winter heating expenses and secondarily for cooling on extreme days. I've come up with the idea of using my home water heater to both heat and cool a central sump. What I'm thinking of is creating loops on both the cold water inlet and hot water outlet of the water heater. Each loop would have a coil of stainless steel tubing submersed in the central sump to act as a heat exchanger. They would each have a small circulation pump. The pumps would be connected to a thermostatic controller. Hot water would circulate for heating, cold for cooling.

I'm interested to hear if anyone has tried this. Even if not, what are the drawbacks/pitfalls in this design? The following is a diagram of what I'm talking about:

 

[Dan F]

For heating this could work, depending on how you have it plumbed (for some reason the picture didn't come up).

For cooling the water would have to be running to work. Recirculating won't work - you need to have fresh cold water flowing through, otherwise the cool water will quickly warm to tank temperature and will cease to have any cooling effect. It could work if you ran cold water through the heat exchange coils and then out to your lawn sprinklers, for example. You could have a solenoid valve hooked to a chiller controller to turn on and off the flow.

I think this would only be efficient if you were going to use the water anyways. A co-worker of mine has radiant floor heat in his house and runs the irrigation water through it to cool the house. One nice thing is that typically the hotter it is, the more you need to water.

 

[Dan F]

I got the diagram to come up. For this to work as a heater you need to have the water circulate through the water heater. Flow should come off the hot side and return to the cold side.

Like I said, this won't work for cooling unless water was running through the cooling loop and out, recirculation won't result in any cooling.

 

[Dan F]

I drew a picture.

 

[Wheat]

For heating you can heat the room. Run some baseboard on a few of the walls connected to a circulator pump and it's own thermostat. For cooling, unless you're keeping some reef tanks it's not really necessary. If you are keeping some reefs, a small air conditioner will do the job. I ran a small 5000 btu ac in my fishroom and it kept the reef system at 76* and it made working in the fishroom in the summer so much more comfortable.

 

[gotbluegrass]

Thanks, Dan! Sorry about the diagram screw-up...here is what I was trying to post.

I think you are correct that the water needs to return to the cold side. That's the way the hot water circulators work to get instant hot water at the furthest location from the water heater.

Being on a well, I don't have a water bill...I just have to pay for the electricity to pump it. I think I'll consider how to hook this up to water the yard. I think I would only need this less than 30 days per year. Of course being on a well is a two-edged sword. When it's hottest, there is also a usual drought and potential for the well to dry up. When we had a severe drought a few years ago many home around me had to drill new wells. I think I'll also consider piping the heat exchager for cooling though a dorm fridge. I have one in the garage already for cold drinks in the summer. That way I could make it a completely closed loop and use no extra water. Your thoughts?

 

[gotbluegrass]

I think my main problem here is that this is a garage that is used as a garage. I have the door open & closed. It's fairly large also, so I would guess it would cost considerably more to heat the entire space 24x7 for several months each year.

I am considering making a fish "closet" out there and heating/cooling that space. Basically I would put insulated doors to close off the aquariums from the rest of the garage.

As far as cooling goes, I'm really only concerned about the hottest summer temps. If the air space heated to 90 for an extended time, wouldn't the water try to reach this equilibruim? Anyone out there have experience with the scenario of high ambiant temp and it's effect of water temp?

 

[Dan F]

A couple thoughts:

If you are on a well and worried about running it dry, you could run the outflow back into your well casing instead of to a sprinkler. That is basically a geothermal heat sink. However, if your well is very deep the energy needed to pump the water could be fairly substantial, making this inefficient. Like I said earlier, unless you take advantage of water you were already going to use, this setup will not be cost effective.

If you are going the mini-fridge route there are a number of ways to set it up. You can use a closed loop like you mentioned. You can also just pump tank water through a heat exchanger in the fridge. The main problem with this is that the biofilm that inevitably forms inside the heat exchange coil will reduce its efficiency. If you run an open loop to the tank it is better to have a storage vessel in the fridge than just a coil of tubing.

 

[Wheat]

I think my main problem here is that this is a garage that is used as a garage. I have the door open & closed. It's fairly large also, so I would guess it would cost considerably more to heat the entire space 24x7 for several months each year.

I am considering making a fish "closet" out there and heating/cooling that space. Basically I would put insulated doors to close off the aquariums from the rest of the garage.

As far as cooling goes, I'm really only concerned about the hottest summer temps. If the air space heated to 90 for an extended time, wouldn't the water try to reach this equilibruim? Anyone out there have experience with the scenario of high ambiant temp and it's effect of water temp?

The summer temps here get to over 90*. My pump added 6* to my system (1/2 hp pool pump). I noticed once that the temp in the tanks were 90*! I put the a/c in, and it took care of it. I kept it on the power saver, the room was insulated pretty well so once the temp came down, it didn't run all the time.

 

[Dan F]

I think my main problem here is that this is a garage that is used as a garage. I have the door open & closed. It's fairly large also, so I would guess it would cost considerably more to heat the entire space 24x7 for several months each year.

I am considering making a fish "closet" out there and heating/cooling that space. Basically I would put insulated doors to close off the aquariums from the rest of the garage.

As far as cooling goes, I'm really only concerned about the hottest summer temps. If the air space heated to 90 for an extended time, wouldn't the water try to reach this equilibruim? Anyone out there have experience with the scenario of high ambiant temp and it's effect of water temp?

I have two tanks in my garage, a 185 gallon fiberglass tank and a 90 glass. I use a single 250W Stealth heater in each of them and they kept temperature even when outside temps were in the twenties (probably high thirties in my insulated garage). I have both of them insulated pretty well, when it warms up I'll remove the insulation to better view my catfish.

Hot air temps will raise the water temp. You can see that I covered the window in silver insulation - that is for the summer sun more than the cold. I have managed to keep the temp down by covering the south and west windows and keeping the door closed during the hottest part of the day.