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Thread: Controlling a 5k BTU window Unit

  1. #1
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    Controlling a 5k BTU window Unit

    My tank is in a detached, insulated work-shop. It is starting to get hot out there. I purchased a 5k BTU window unit to help lower ambient temps. I have a few questions controlling the unit with my neptune apex.

    The unit has a 4 amp draw. I assume the Eb8 that I will be using won't have a problem running it, but the programming is where I am concerned.

    I think the temp sensor will read air temps good enough. I have been testing it with my second sensor the last week or so and it has been close to another air temp thermometer I have.

    Is it possible to have the program have min run times so it doesn't short cycle? Say I want it to turn on at 80 and cool to 78 and turn off, but a min cycle time of 10 minutes? Meaning when it turn off it won't come back on until at least 10 minutes has elapsed, or won't turn off until 10 minutes has elapsed?


    I assume the chiller program has something similar since the compressors kicking on and off rapidly would pre-maturely wear them and cause compressor problems.


    Thanks,

  2. #2
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    Quote Originally Posted by coryjac0b View Post
    My tank is in a detached, insulated work-shop. It is starting to get hot out there. I purchased a 5k BTU window unit to help lower ambient temps. I have a few questions controlling the unit with my neptune apex.

    The unit has a 4 amp draw. I assume the Eb8 that I will be using won't have a problem running it, but the programming is where I am concerned.

    I think the temp sensor will read air temps good enough. I have been testing it with my second sensor the last week or so and it has been close to another air temp thermometer I have.

    Is it possible to have the program have min run times so it doesn't short cycle? Say I want it to turn on at 80 and cool to 78 and turn off, but a min cycle time of 10 minutes? Meaning when it turn off it won't come back on until at least 10 minutes has elapsed, or won't turn off until 10 minutes has elapsed?


    I assume the chiller program has something similar since the compressors kicking on and off rapidly would pre-maturely wear them and cause compressor problems.


    Thanks,
    Yes, you can run the temp sensor in open air. My recommendation is have one in water and one in air.

    Yes, an EB4 will run a 4 amp AC with no issue.

    Yes, you can run it to prevent short cycling. I would program it for a minimum run time and a minimum off time. Cycling will ruin your compressor motor. Also, you will want the AC to dehumidify the air (since I see you are also in NOLA!) which means you need to run it for a minimum time frame. I would also run it at a lower temperature if your tank gets warm so you can be a little proactive.

    Perhaps, try this program to start with:

    [Window AC]
    Fallback Off
    If Temp_Air > 80 Then ON
    If Temp_Air < 78 Then OFF
    If Temp_Wat > 80 Then ON \\Optional - because things other than shed air temp may drive up the tank temp, but lowering the shed temp will help lower the tank
    If Temp_Air < 76 Then OFF \\Use this if you use the one before it so you don't freeze your coils - feel free to play with and adjust these numbers by the way to see what works
    If SW_Humid Closed Then ON \\Optional - but I also recommend a humidistat set to 65% in the shed so your tank does not contribute to rotting the structure - this will connect to your apex as a switch - it will also help promote evaporation, which also cools your tank.
    Min Time 10:00 Then OFF \\keeps the AC off for at least 10 minutes
    Min Time 20:00 Then ON \\keeps the AC on for at least 20 minutes

  3. #3
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    Does the AC unit not have its own thermostat? I'm not an AC guy, but even cycling the unit 20 minutes on, 10 minutes off worst case doesn't seem like a great idea, I'm pretty sure they weren't meant to do that.

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    Window units can cycle 20 minutes with no issue.

    A primary reason to run it on an Apex instead of the onboard thermostat would exactly be to control the cycling. The onboard thermostats usually do not do this and if the 5k BTU AC is installed on a small shed, it will cycle. Another reason to use the controller is you can overrun the AC past just ambient room temperature set points based on other criteria, such as tank temp and/or room humidity as per my example above. You are basically just running it like a chiller.

  5. #5
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    I will give the code a try and see how it goes. I need to get a dehumidifier and humidistat to help with humidity.


    Most thermostats only have a 5 minute delay on them between cycles.


    The unit I purchased does not have an on board thermostat.


    Thanks!

  6. #6
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    You don't need a dedicated dehumidifier, your AC already does that! The fact that it does not have an onboard thermostat is perfect for this application.

  7. #7
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    Ah ok. I will look into getting a humidistat though. Sounds like something that would help with moisture.

  8. #8
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    Quote Originally Posted by coryjac0b View Post
    Ah ok. I will look into getting a humidistat though. Sounds like something that would help with moisture.
    Yes, you set the humidistat to what humidity level you want to maintain and use the humidistat as a switch on the Apex. When the switch is closed, it is telling the Apex that the humidity is above a certain percent. I would set it to 65% to start and then lower it if the A/C can keep up. Have the programming set to advanced and program the logic so that the humidistat on program comes after your temperature on and off commands.

    The key to controlling humidity is the AC needs to run for long extended periods, not cycle on and off.


    ------------

    btw, on a side note, I came home to a 99 degree home. My thermostat decided the house was only 39, so not only was the A/C off, but the heater was on! I'm in Metairie.

  9. #9
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    I ran a 5btu window unit in my garage some years back to keep the air dehumidified and the temp around 75.
    it worked well along with good insulation for having almost 3000 gal of saltwater in multiple systems.
    tank temps averaged 79 in the dead heat of summer south east Louisiana

    dependimg mg on the conditions you may have to run it longer during the humid hot summer months.
    good luck with the apex control amd programming
    let us know how it works for you.

  10. #10
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    Seems to be working out fine. Humidity stays around 50% at the moment. I purchased a humidistat to connect to a BoB to help control if it gets to high. This is actually for a central/south american freshwater biotope type tank. The water stays between 79.7-80.2 degrees. The temp got up to 83 a week or two ago and decided I had to act. The unit seems to be able to keep up with the ambient temperature I am trying to stay around. It cools down the shed in the min time I have it running (20 minutes).

    There was once yesterday it stayed on for 30 minutes at about 5:00pm. That's usually when the shed gets the most sun.

  11. #11
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    Awesome. I will be curious how this performs in August

    And feel free to pass by LARC. There is a few of us on here now as we recently jumped on the Apex bandwagon. I've been using an AquaController Junior since 2005 and finally upgraded this year. We bounce Apex ideas around over there too.

  12. #12
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    Yeah, the tank was setup back in October so I haven't experienced august yet with it. I previously had 210g saltwater tank, but it was in need of a re-seal and we were having our house raised. I didn't go back to SW. I used to frequent LARC.

  13. #13
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    Quote Originally Posted by coryjac0b View Post
    Yeah, the tank was setup back in October so I haven't experienced august yet with it. I previously had 210g saltwater tank, but it was in need of a re-seal and we were having our house raised. I didn't go back to SW. I used to frequent LARC.
    User name seems familiar.
    dont be shy top on in and post up your system in the new fresh water forum.

    im glad to hear that the AC is helping / doing its job.
    the apex has many interesting features that I am still discovering, keep us up to date how things go when the hot months roll around.

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