On 7/17/2024 11:25 AM, Steve London wrote: > I have a 20 year old forced hot air, gas furnace. Still working fine, but > it will need to be replaced in the next few years. I would also like to add > A/C to the mix. Hi Steve, Controllers for variable speed motors are notoriously noisy, and should be avoided. Yes, they are more efficient. 73, Jim K9YC