I didn't see an exact answer to what I was looking for, so here it goes.*
Right now a chilled water control valve is in PID auto the majority of the time (using a PLC5). When a button on the HMI is pressed, the valve should close until a heating cycle completes. At this point, it should revert back to PID control.
As it is, the valve closes correctly for the duration of the cycle, but when it switches back to auto, it's going to full open instantly (the current PID CV). What is the best way to implement a bumpless transfer, without having to receive the value from an HMI? I just want to hard-code the 100% closed value (4095). The main issue is that if the valve snaps back, it causes a rapid drain on the system and faults a chiller. I considered a second PID that's less reactive for the transfer, but bumpless seems like the correct, more elegant way?
Something else that was strange to me - with the current code, the CV of the PID is set to 4095 during the heating cycle (closed). However, our historian values show a moving CV, which gradually goes from 4095 to 0. How exactly is this happening, as the valve remains closed?
Right now a chilled water control valve is in PID auto the majority of the time (using a PLC5). When a button on the HMI is pressed, the valve should close until a heating cycle completes. At this point, it should revert back to PID control.
As it is, the valve closes correctly for the duration of the cycle, but when it switches back to auto, it's going to full open instantly (the current PID CV). What is the best way to implement a bumpless transfer, without having to receive the value from an HMI? I just want to hard-code the 100% closed value (4095). The main issue is that if the valve snaps back, it causes a rapid drain on the system and faults a chiller. I considered a second PID that's less reactive for the transfer, but bumpless seems like the correct, more elegant way?
Something else that was strange to me - with the current code, the CV of the PID is set to 4095 during the heating cycle (closed). However, our historian values show a moving CV, which gradually goes from 4095 to 0. How exactly is this happening, as the valve remains closed?