Temp controller help

Discussion in 'General Discussions and Advice' started by nudibranch, 3 Feb 2015.

  1. nudibranch

    nudibranch

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    Hi All

    I recently purchased STC-1000 temp controller and have connected it to my heater. The question I have is should the temp sensor be in the sump or the DT?

    Currently the temp in my sump is showing slightly higher than my DT, is this normal or just maybe a calibration issue of the two different devices?

    Thanks
    Paul
     
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  3. dallasg

    dallasg Moderator MASA Contributor

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    put it where the heater is, not to close and down stream
     
  4. Nemos Janitor

    Nemos Janitor

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    Going to disagree with Dallas here.

    The reason you want to control temp is you want the temperature in the tank to be stable. If the temperature in the tank is hot you want cooler water entering the DT, if it is cold you want hot water entering the tank.

    So the temp of the sump is irrelevant IMO. If it takes 50C water in the sump to maintain your tank at 25C then the heater should heat the water to that temp. Don't take those temps literally. Just an exaggerated analogy.
     
    4age likes this.
  5. dallasg

    dallasg Moderator MASA Contributor

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    most heaters have there own thermostat, STC-1000 is a good back up if the heater jams on.

    have you measured the 2 temps using the same thermometer?

    so NJ where do you advise to place it, since that was the Q
     
  6. 4age

    4age

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    I have mine in the tank as I figured that's the area where the temperature must be perfect for the corals.
     
  7. Nemos Janitor

    Nemos Janitor

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    Dallas the sensor is best placed in the DT.

    As you know both heaters and chillers have an hysteresis. This is why the temp fluctuates in the DT if they are set to 25C. For a heater set at 25C the temp can rise to 26C before it switches off and to 24 before it switches on. The same for chillers. Well the most common Haliea ones around.

    I have found that one can maintain a very accurate temperature with as little as a 0.2C fluctuation with proper control with the temp sensor in the DT

    I have not used the STC-1000 but i assume it is similar in operation to the profilux and aquatronica. The typical logic is.

    set for 25C
    if temp >= 25C switch on chiller. Hysteresis 0.2C
    If temp >= 25C switch off Heaters. Hysteresis 0.2C
    If temp >= 28C switch off lights
    If temp <= 25C switch on heaters. Hysteresis 0.2C
    If temp <= 25C switch off chiller. Hysteresis 0.2C
     
    Last edited: 3 Feb 2015
  8. Criggy

    Criggy

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    I think the most crucial thing here is stability surely? Therefore if the sump is being regulated to a certain temp which has the water from the dt moving through it then surely the fluctuation should be relative and therefore provide a stable DT temp should arise out of a stable sump temp - whether it be 0.2 - 0.5 off from the sump.

    I have my STC probe at the return in my sump to the DT and have never had an issue. This is also after all my heaters.
     
  9. dallasg

    dallasg Moderator MASA Contributor

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    which is all well, but i have a fuge and frag tank in my setup by sump so a higher temp there wont work.
    I have a 0.5 variance avg and max 1deg, so with my tank thermostat set at 25.5, my DT ranges arent that bad, the ocean has bigger swings
     
  10. Criggy

    Criggy

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    I suppose it comes down to your system setup at the end of the day
     
  11. Nemos Janitor

    Nemos Janitor

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    I hear what you guys are saying. From my experiance there is definately a differance between monitoring temp in the DT to the sump. I don't have the data at hand as the tests were done many years ago. I am talking from when @LikesFish first wrote the aqua stats program for the aquatronica.

    Having installed a hundred+ odd controlers in my time on various tank type setups i have found the best option to be monotored from the DT. On some installations we install two or three temp sensors to monitor various things but always control is done from the DT.

    Installations some times have sumps 20 to 30 meters away from the DT and the sump is in an out building where it is cold. So if the temp is monitored in the sump and water has to travel some 20 meters the sump temp could be 25C but by the time the water reaches the DT the temp has dropped to 15-20C and you tank runs very cold.


    Hope that give some incite as to why it is best to monitor temp from the DT.
     
    Last edited by a moderator: 26 Nov 2015
  12. zippy

    zippy

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    I've never really seen any issues with heat changes as Dallas has mentioned.

    I have measured rock pools with life in at around 39 Degrees at low tide with the ocean at 23 Degrees C.

    Best advice imo is to have your sensor where your heater is. I seriously doubt Nudibranch has his sump 20m away from his DT... Even if he does he can calculate the difference between the two and set his temp sensor kick in or kick out times at 2 degrees above or below, his required temp in the DT
     
  13. Nemos Janitor

    Nemos Janitor

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    Lets get a few things straight.

    First point.
    I am not here to continually debate issues. Just to pass on many years of experience and information. Help others with advice, pass on time and tested methods.

    Quite frankly I do not have the time nor see the reason to continually justify every post I make. If you ( not specifically referring to you, anybody) disagree with any reason I give, then do what a responsible learnerd reefers woud do. They come back and say ' Hay NJ I disagree because of XYZ these are the reasons'.

    Having said that I disagree with your statement that a simple "set variance" ( you indicated 2C in your post) can compensate for a stable DT temperature. Can you please explain.

    Second point
    1) The sensor "measures" and "controls" the temperature at point of measurement.
    2) Two separate bodies of water cannot be in consistent "temperature" equilibrium if any one changes in temperature for whatever reason.


    Should I find the time and inclination I will do a write up on my experiences and recomdations on temp control.

    Not picking on you bud. It just seams to be the norm ......
     
    Last edited: 4 Feb 2015
  14. weezle

    weezle

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    Howzit
    Iv recently installed a STC1000 on my system and the way I did mine is I
    Put the sensor in the sump as the fan that is cooling the water is
    Blowing in the sump, the sensor is in the first compartment, the heater is in the
    2nd compartment along with the skimmer, and the fan is blowing into the
    3rd compartment along with the return pump.
    My tank holds 250L and my sump is only a 100L tank I leave my heater
    Set to maximum so the stc has controll over the heater totaly the temp
    On the stc is set to 24.7 with a 0.3 degree swing.
    My fan is potent the room temp on a hot day is 30 and my tank never goes
    To more than 25.8
    I also have a digital thermomiter in the display and it shows the same reading
    As the stc
    On a system of similar size to mine I don't think sensor placement reely matters
    But I would recomend to put it in the sump for the simple reason of that is what a sump
    Is there fore (to hide hardware such as skimmers, pumps or in this case sensors)
    Also it makes sense to me to put the sensor close to the fan and away from
    The lights.
    Cheers wes
     
  15. RiaanP

    RiaanP Moderator

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    Yeah, but that is over a very short time period. Before the next high tide moves in and cools everything down again Cannot compare a rock / tidal pool that is temporary warmer than the ocean against your system that runs at a high temperature 24 / 7
    Big difference.
     
  16. RiaanP

    RiaanP Moderator

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    Rather set the heater to 25.5.
    In case something goes wrong with the STC controller.
     
  17. Nemos Janitor

    Nemos Janitor

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    Weezle the key word is "Recently". Monitor over a few different seasons. You might change you point of view.
     
  18. RiaanP

    RiaanP Moderator

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    My STC probe is also in the first chamber. Got 4 * 300W heaters also in first chamber, 1 * 300W in the second chamber and 1 * 300W in the remote DSB.

    I did move the probe around as a test right now, with no marked difference. Well, might if the heaters were on, currently running on the fans. But temperature the same, between display and sump. Need to move STC to last chamber to really confirm, but that means a lot of cables to untangle.
     
    Last edited: 4 Feb 2015
  19. Nemos Janitor

    Nemos Janitor

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    Riaan I disagree. The controller has a far better control "mechanism" than a heater (bi-metal). The controler should be the bit of kit that you want to control your temp.

    The heaters bimetal controler should be a secendory safety. IMO same for chillers.

    Edit: We always set the heater or chiller about 2C higher or lower than the controler.
     
    Last edited: 4 Feb 2015
    weezle likes this.
  20. RiaanP

    RiaanP Moderator

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    ok, moved the probe to end of second chamber, so that the effect of the fans over second chamber could be seen.
    No difference.

    But then again, running a 12000 DC return pump will hardly have an effect in my case. Each setup is different.
     
  21. Nemos Janitor

    Nemos Janitor

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    LOL Riaan. :lol:

    What did you experiment look like in June ?
     
    Last edited: 4 Feb 2015
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