Brennan G Today I visited for the system making a loud noise when running in the heating mode. I was able to observe the event that was causing the noise. The system would engage into defrost too frequently and the reversing valve pressure shift was loud. I adjusted the defrost timer, heat droop and compressor time delay on the thermostat. I clarified with Alphonso that the system will make this sound on occasion however should only happen when the temperatures outside are very low or when the system turns off in the heating mode. The equipment is operating normally at this time