Got a 100% MAU for kitchen hoods, starts when any hood is turned on.
Has an outside air damper then, HW coil, CW coil, discharge air sensor about 4' down the duct.
Johnson FEC controller, in unocc HW valve opens all the way
controller looks at DAT to maintain temp delivered to space
upon startup, oa opens, HW coil starts to modulate closed (hw @180 deg.).
well , control loop has HW valve all the way closed and DAT is still reading about 100 deg., With recent OA temps around 10 deg., this trips the freezestat mounted after the HW coil and before CW coil.
Obviously the CW coil has absorbed alot of the heat and is still giving off its heat, messing up the DA sensor.
Avoiding a freezeup is everybodies biggest concern so slowing down the control loop isn't very desireable as we need the HW valve to be able to respond quick enough to avoid this from happening.
Johnson guy is working on it but I was wondering what you guys would do?
I'll let you know how things work out.