I have a question about the PSC motor versus the variable speed motor as it relates to noise. My furnace has always been located in a closet in my kitchen and is mounted on a raised platform. The return air plenum consists of the space between the concrete slab and the raised platform. The return air grills are in the room opposite the furnace. There has been some sound deadening material and baffling in the return air plenum since the old system was installed.
I just had my furnace and air conditioner replaced a couple of months ago. My old system was a Lennox 5-ton 2-speed system with a furnace that had a PSC motor that had 2 blower speeds. My new system is a Lennox 5-ton 2-stage system with a 2-stage furnace with a variable speed motor.
I understand that the variable speed motor has a number of advantages such as lower electrical costs, motor feedback to achieve a given cfm, dehumidification options, and the flexibility to change ramping and cfm with switches,. I was also told the VS motor was quieter than the PSC motor. I have found that the variable speed motor has a lot more noises than my old PSC. The only noise I remember on my old PSC motor was on start up. The stopping seemed to be quiet. On the VS motor, the stopping seems to have a lot of noises toward the end of the stopping. I have been told that this is due to braking and that the noises are normal for a VS motor. I find these noises very noticeable. I presume that if the furnace was in the attic, I would not hear these noises. I realize that you cannot hear the noises since you are not at my house
1. For those of you that install these VS motors, do you notice more noises during the stopping phase than the PSC motors?
2. Are the PSC motors the same as 15 years ago or do they also have new braking that would make them noisy on stopping?
3. Do you find some of your other customers have noticed what I am noticing?
Considering the additional noises, a part of me wishes I had stayed with the PSC motor. I really had very few complaints about it.