I have an A/B SLC 5/03 trying to tune a PID loop on a MAU. Trying to maintain 68degF DAT I have a gas burner but controling the air mixture damper instead of the gas valve. My system is laggy (slow acting) I over shoot by 8degF with the settings that I have in now. Gain 70, Ti 60, Td 6.9. What happens, since this system is slow,is when I tell the damper to close and go to low fire there is approx. betwen 10-25 sec before this occurs. In the mean time the heat exchanger heats up so I have additonal heat blowing into the space that I have no control over when in low fire. How do I take this into consideration when trying to tune this loop? Any suggestions would greatly be appreciated.