1. There is a loud click and what sounds like a "thump". The click sounds like it is coming from the thermostat (Honeywell) - I am not sure what, if anything, can be done about that. The "thump" comes from the compressors themselves - they seem to start in a very "hard" way. Is there anything that can be done about that?

2. The real concern I have is that every time the compressors start the lights dim momentarily. We have a brand new 200 amp service (main panel and 100 amp subpanel). Two different electricians looked at the set up and seem to think that the panels are sized and balanced properly. What could be the reason for dimming? And is there anything that can be done to remedy it?

Thank you for all your input and suggestions.

Have you called your installing dealer?

Could be a variety of reasons. Wire size may be undersized. May need hard start kits on both units.

I would call your installing dealer and discuss over the phone. I assume both units are heating and cooling satisfactorily.

IMO