If my old AC motor rpm was 850, what damage will a 1050 rpm motor cause?
Context? It depends on what it's driving. But we don't know that, do we? Tell us more and we can tell you more.
Do not replace the motor with anything else other than a motor with very similar specs. If the old motor was an 850, put an 850 on there. The big issue here is amp draw. An 1150 RPM motor may very well pull more amperage than the system is designed to handle, which can damage other electrical components in the system. Also, they don't just slap any RPM motor on these systems and expect them to work. The RPM is selected in the design process with a specific amount of air being moved to attain the correct amount of heat transfer in the coil. If you change the amount of air being moved, you change the dynamics of the system which can change the efficiency of the system (and probably not in a good way). This can even eventually lead to failure of other components in the system. If a system doesn't cool as well, it runs longer, if it runs longer, all the electrical components and motors run hotter. Running hotter equals a shorter life span. Your motor that you need to replace has an RPM rating, a horsepower rating, an amp draw rating and a direction of rotation (many are reversible). The RPM and HP and rotation of the new motor have to match exactly to the old one. The amp draw needs to be as close as you can get it. OEM replacements will be exact but if you buy a universal replacement, the amp draw may be a bit off. Just don't go more than a few tenths of an amp off. Another thing is to make sure that you have the right sized run capacitor for the new motor. Its cap rating may very well be different than the old motor. I would recommend replacing the old cap either way, even if it is the same rating. Caps wear out over time and this can lead to motor failure.
I usually go right along with JFS on most things,.... but on this one I'm going to go the other way. If this is a condenser fan motor, there's not a damn thing wrong with pulling more air through and rejecting more heat.... I did this the other day on an older 10 SEER unit. I could not get the guy to replace the thing and it was clearly on its last leg, but he just wanted the condenser fan motor replaced. The older 825 RPM motor, was for some reason fairly expensive, but a 1075 RPM motor was $75 cheaper.... hmm go figure. But installing this thing actually made this old dog perform a little better.... its running right now and the system is apparently happy, so the owner is happy. Hope thais works out for you.
