PeterFukt Posted November 1, 2016 Report Share Posted November 1, 2016 Hello, I got the task to make a control system for a air conditioning unit which I guess needs 4 PID loops. One each for heating, cooling, humidification and dehumidification. Only two loops will be active at the same time. The product overview for Samba SM35-J-TA22 say "Auto-tune PID, 2 independent loops ". Does this mean that it is not possible to have 4 loops in the program? I would appreciate a quick reply! Link to comment Share on other sites More sharing options...
MVP 2023 Joe Tauser Posted November 2, 2016 MVP 2023 Report Share Posted November 2, 2016 To answer your question - yes, the Samba only does two loops. You may want to reconsider whether you need PID at all for an HVAC system. Often people think they need PID control when on/off control will do and is much simpler. You're probably trying to control to 1% humidity, which is actually impossible because most humidity sensors are accurate to +/- 2% RH. In addition, it probably takes a while for the environment to react to the humidifier or dehumidifier being turned on, so if you turn it off when the setpoint is reached (on/off control) it probably won't overshoot. Ditto on the temperature. There are a lot of "probably"s in my comment. Let me know if I've made incorrect assumptions about what you're doing. Joe T. Link to comment Share on other sites More sharing options...
PeterFukt Posted November 7, 2016 Author Report Share Posted November 7, 2016 Thanks Joe, It will be for a system to control temperature and humidity in archives. 18 +/- 2 deg C and 35% +/- 5% RH are the requirement. after some thinking, I do believe I won't require more PID loops than two in most applications. I have earlier used Siemens PLC systems with a lot more loops which is why I asked. Heating and cooling use two AO's. I was thinking to use two PID for this, or maybe some kind of linear function instead works just as fine. For humidity I think I will use some compare blocks to trigger the DO's. Link to comment Share on other sites More sharing options...
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