Simple PID adjustment that saves energy

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[@AmiranBokhua]

Very simple and easily justifiable suggestion the switch away from PID when controlling terminal/zone devices.

[@TheUnojoe2]

I’ve seen SO many of these sensor issues!

[@johntlu420]

I agree with you on the energy savings, the problem i have is the people who want it an exact temperature that will scream bloody murder over it being a degree off of setpoint. Some businesses will get HR involved to make that employee happy even though they might have a temperature policy in use. Have you looked at the Johnson Controls PRAC feature in their software? It is designed to minimize the energy use by looking for a pattern and adjusting the PID parameters for steady comfort control. One of my things I teach is to stage equipment on so not make the central plant run full capacity when going occupied.

[@bryceanderson17]

PRAC, you are talking about JCI's automatic PI adjustment thing? I actually have a little problem with it. It works well until something upstream is misbehaving. E.g., the VAV box damper is hunting becuase the AHU supplying it is hunting. So the VAV PRAC starts to widen the P band to stop the hunting. And then you have a P band of 200°C. My personal opinion, with no proof, is that the PRAC should run for a week while all systems are properly working. Allow all the PID loops to self tune and then I think we turn the PRAC off. But, no one at JCI agrees with this.

[@johntlu420]

@@bryceanderson17 there are times to disable PRAC. On large sequenced loads and humidification/dehumidification it is recommended to turn it off. The one thing with JCI is that the default PID parameters are usually bad and need to be changed. I have a cheat sheet that I got and it gets me close with minimal tuning required. I want to take the equipment at the union school I teach at and try what you are recommending

[@TheUnojoe2]

This raises the need for improved flexibility from improved legal agreement conditionals, to improve the framing by giving flexible boundary conditions. Well placed effort.

[@hubert187]

@8:00 it took me a while to figure out why my thermostat was showing 72F, but the room was 79F. Turned out, the negative pressure room was sucking all of its air through a hole in the plasterboard wall.

[@arsalanzahid6434]

That was awesome Bryce!

[@bryceanderson17]

Thanks, mate :-)

[@alanjones3875]

Another simple solution to save energy. I use a wider P band for fan coils as uk offices have winter and summer design values that range from 19C to 26C. The set points allow cooler temp in the winter and warmer in the summer that helps prevent thermal shock. The problem I always encounter is with the FM team and often office staff who say the set point should be 22/23C. Trying to explain dead bands and heating cooling set points but reminding them of the employers requirements is often so hard I have to get the BMS team to add text to the graphic to explain why the apparent set point is not being achieved.

[@bryceanderson17]

That is a good point. My PB is determined around meeting lease conditions. But it is still a bit too tight, for energy efficiency. If you can stretch the temperature out another degree either way, as you suggest, a PB of 2°C would be much better. Mmm, maybe a PB of 1 for heating and a PB of 2 for cooling? I have found people will tolerate warmer temperatures in summer but won't tolerate cooler temperatures in Winter. Thanks for the comment, Alan.

[@marimuthum7936]

Hi About Supply air duct pressure reset ,do you have flow chart for creating logic for energy saving .

[@CJGorrell]

That first half of the argument doesn't really stand as a good reason to have or not have integral action. Some locations will error in favor of energy savings while others will error against energy savings. It's a valid point that more attention needs to be placed on sensor placement because it often matters as much if not more than proper tuning. The slower your variable responds to an input the smaller your integral constant should be anyway. In the case of zone temp it's very slow and I agree most all cases there, integral should be set so small that it's probably negligible to begin with. There's much more energy saving opportunities with higher order PID functions but it's rare to find people proficient in their use.

[@bryceanderson17]

I can't think of a situation where a zone temperature sensor installed in a poor location, with integral enabled will save energy? Let us know your thoughts. Thanks.

[@CJGorrell]

@@bryceanderson17 place a thermostat near a sunny window and it will read warmer than the space thus running heat calls less in the winter. Integral has nothing to do with it. Result? Not what the customer wanted. Space comfort is sacrificed but there is technically energy saved. My point was the argument of sensor placement has no influence for or against using integral in a control loop. It's a separate issue.