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Thread: Want to use my existing central A/C to chill water tanks

  1. #81
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    Progress is slower now, but I am nearly done installing the blower. The air-to-water heat exchanger is scheduled for delivery on Friday, but I still haven't decided whether to install it just before the blower in the large chanber, or install it after the blower in the small chamber. The documentation for my blower indicates that coils should be installed before the blower ("up stream"), but the coils in my central AC units are installed after the blowers. Is there any reason why it would matter?

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  2. #82
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    I decided to put the air to water heat exchanger after the blower. I think I'm just a few hours away from hooking up the water pump, but won't be able to work on it again until Monday. However, I did get the blower hooked up with 5 different speeds, which are selectable via dry-contact relays. I've also verified that I can use those speeds to vary delta T between the inlet and outlet. I haven't jacked with it much, but I achieved just over 30 degree F drop with a medium air flow.

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  3. #83
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    It seems that there have been some posts removed from this thread, since I know there have been a couple posts this year...

    Anyway, I wanted to give some updates, since this project has been very fruitful! Obviously, the design is very different from what I thought it would be, but my overall strategy of chilling water during the cooler / cheaper hours of the day, then using that cold water to cool and / or dehumidify during the warmer / expensive hours of the day is VERY effective.

    I do have a couple things to note about the particular problem I've been trying to solve, which I didn't realize were very significant a year ago. The first "issue" is that I am a marine aquarist, and have 2 [warm water] saltwater aquariums totaling about 300 gallons in the middle of my 3400 square foot "tight house". I knew that the aquariums were contributing greatly to my utility bill, but I had no idea how much they were contributing to my A/C load! It just never occurred to me how much those aquariums were contributing to the humidity level inside the house until I noticed in my Ecobee datalogs that my RH was NEVER below 50%, and was often in the mid-60% range! This made my house uncomfortable at just about any temperature, and I had no idea why.

    Once I realized how much of my problem was humidity related, I made that issue a primary focus in this project. To improve that issue, I decided to use a dedicated chiller located inside the house, so that I could chill water to a much colder temperature than the central A/C would be able to achieve, while also increasing the heat load in the house to extend the run-times of the central A/C. Once the water in the insulated water tank drops below 40 degrees, I start using it to dehumidify. The chiller runs 17 hours per day only during the hours when electricity is cheap.

    I need more time to do a detailed write-up, but couldn't wait to post some pictures of my "Cold-Pacitor", which I just brought back online yesterday. It's still too cool outside to put much load on the system, so I'm really looking forward to warmer days! Until then, I'll continue working on the software to improve the controls. I need to improve the algorithm that optimizes the flow rates of both air and water through the heat exchangers. I want the water to pass through the exchangers exactly once, with a 20+ degree increase in temperature, and I want that last gallon of water to pass through the exchanger to still be ~40 degrees.
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  4. #84
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    The site crashed. There is 8 months of data loss.

    Thanks for the updates. Aquariums add a huge load to an HVAC system, especially if they are open top. I have 5 myself.

    How much has your energy usage changed with this system you have developed?

  5. #85
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    So the small condenser is now used instead of the mini split to chill water?
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  6. #86
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    I split the dashboard into 2 halves, so they will appear at full resolution.
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  7. #87
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    Quote Originally Posted by HVAC_Marc View Post
    The site crashed. There is 8 months of data loss.

    Thanks for the updates. Aquariums add a huge load to an HVAC system, especially if they are open top. I have 5 myself.

    How much has your energy usage changed with this system you have developed?
    The unfortunate thing about this project is that my historical data is difficult to relate to current data, since there have been so many changes. Here's a short list of things that have changed over the course of this project:
    * All lighting has been upgraded to LED
    * Altered usage habits
    * Addition of 2nd aquarium (had a 180, added a 90)
    * Changed to "time-of-use" pricing (same electric company)
    * Switched from dumb thermostats at constant 73 deg temp to Ecobee thermostats with a smarter custom algorithm (lots to share about this)
    * Disabled [stupid] central ventilation system
    * As my data collection improved, my interest in the electric bill decreased, so I occasionally wasted LOTS of electricity on experiments

    That said, here are my monthly usage and pricing graphs. There is an intentional 3 month overlap / wrap-around ...
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  8. #88
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    Quote Originally Posted by rider77 View Post
    So the small condenser is now used instead of the mini split to chill water?
    I haven't decided about the mini-split yet. I got the chiller at the end of last summer, and planned to use the chiller AND mini-split to cool the water. The mini-split chills the water very quickly and efficiently from 65 to 55, but I wasn't able to control the mini-split well enough to manage a clean "hand-off" to the chiller. Basically, I was able to transfer almost 10K BTU per hour when the water was 65, but that would drop quickly. If I can figure out the LG control electronics, so that I can control its compressor directly, then I will probably install an efficient refrigerant->water heat exchanger in the loop of the mini-split, and sell the chiller.

    I'm also still considering installing a heat exchanger on my downstairs central unit, since int would chill that tank of water so friggin' fast that I could probably consume the whole tank worth of BTU's several times per day.

  9. #89
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    I think you will spend a lot of time by-passing controls, tweaking things, maybe get it to work for a few hours, then ambient and load conditions will change and it will all go out of balance again, adding glycol will inhibit the thermal heat exchange also, you can only add glycol to systems that are designed to do the lift/mass flow that you are thinking of, so you may end up overloading the compressor due to lift ratio, but it sounds like your going to do it anyway. In-built safety devices that have fixed design operating conditions (for a reason) may prevent you from doing any of what you want to try.

  10. #90
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    Quote Originally Posted by raptyr View Post
    I think you will spend a lot of time by-passing controls, tweaking things, maybe get it to work for a few hours, then ambient and load conditions will change and it will all go out of balance again, adding glycol will inhibit the thermal heat exchange also, you can only add glycol to systems that are designed to do the lift/mass flow that you are thinking of, so you may end up overloading the compressor due to lift ratio, but it sounds like your going to do it anyway. In-built safety devices that have fixed design operating conditions (for a reason) may prevent you from doing any of what you want to try.
    I think you're missing the fact that both of these systems have already been built and are running?

  11. #91
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    I'm also considering a refrigerant->water heat exchanger on the hot side of my chiller or A/C unit to heat my aquariums. I almost killed my reef tank during this project, since I didn't realize how cold it was getting (below 70 deg F). I recently learned (after 20+ years in the hobby) that corals don't like being below ~77 deg F, which is very hard to achieve in a <72 deg house. I briefly installed electric heaters in the aquariums, but they were consuming about 7 kWh per day!

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  13. #92
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    Quote Originally Posted by Gernby View Post
    I'm also considering a refrigerant->water heat exchanger on the hot side of my chiller or A/C unit to heat my aquariums. I almost killed my reef tank during this project, since I didn't realize how cold it was getting (below 70 deg F). I recently learned (after 20+ years in the hobby) that corals don't like being below ~77 deg F, which is very hard to achieve in a <72 deg house. I briefly installed electric heaters in the aquariums, but they were consuming about 7 kWh per day!
    I run my tanks at 80-82. Most corals dont like temps above 90. I have an internal short in a UV sterilizer that acted like a heater. I had 94 for 2 days that caused green algae bailout. Most things recovered, some died, some came back with different colors. I let my pumps and lights bring the water temp up. My house runs at 70-72 all the time.

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  15. #93
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    Quote Originally Posted by HVAC_Marc View Post
    I run my tanks at 80-82. Most corals dont like temps above 90. I have an internal short in a UV sterilizer that acted like a heater. I had 94 for 2 days that caused green algae bailout. Most things recovered, some died, some came back with different colors. I let my pumps and lights bring the water temp up. My house runs at 70-72 all the time.
    Damn ... My prior aquarium in my last house ran in the lower 80's, even with a chiller on it. However, my new systems have DC pumps and LED lighting that don't put out much heat at all.

  16. #94
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    I also have Tunze DC pumps and LED lighting, plus the return pump and a sterilizer. I took out my heaters. They never run.

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  18. #95
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    Quote Originally Posted by HVAC_Marc View Post
    I also have Tunze DC pumps and LED lighting, plus the return pump and a sterilizer. I took out my heaters. They never run.
    Wow... I'm surprised you would be getting so much heat out of those. Do you run a lot of head pressure? My pumps are smaller in size, and run at part throttle, since I only have a couple feet of head pressure. The sumps are located in a stairway closet (elevated), so that the overflows can run at full siphon without noise.

  19. #96
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    I have about a foot of head, but I run everything except the wave maker wide open. The wave maker is pulsed 5 on/5 off.

  20. #97
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    Quote Originally Posted by HVAC_Marc View Post
    I have about a foot of head, but I run everything except the wave maker wide open. The wave maker is pulsed 5 on/5 off.
    Going way off-topic, but this is also an interesting topic...

    Where are your sumps that would allow just a foot of head pressure?

    I use a custom / non-conventional wave maker (no pumps), but do have a couple Gyre pumps for programmable linear flow. I don't know how much heat they contribute.

  21. #98
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    How do you think a compressor hat runs above freezing work below freezing. I hate nonsense. I'm not smart but recoconize dumbass. Sorry stupid should be told

  22. #99
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    Try heating water for a pool

  23. #100
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    Quote Originally Posted by Gernby View Post

    Where are your sumps that would allow just a foot of head pressure?
    In the back of the main tank

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