We have an ongoing situation with a Trane heat pump in our attic where every few months it keeps failing. We've lived in this house for nearly three years and in that time it's had roughly four new motors and just failed again so we're looking at five in three years. The house is about 9 years old and the unit was new in the house when it was built. I can get the model of the unit and post if needed.
I'm trying to find out if the previous owners had any similar issues but am yet to hear back from them.
The motor tends to fail when we switch from summer to fall or fall to summer settings. i.e. heat mode or ac mode. It's nearly always preceded by a thumping/drumming sound.
When the motor is replaced (sometimes with a new fan blade) the system runs smoothly until the next season change. Once we switch over, it'll usually start drumming relatively soon and then within a couple of weeks fail completely.
Some extra history is the first two companies to replace the motor (under house buyers insurance (HMS)) just replaced the motor and possibly the fan blades. Due to being organized by the insurance company we had little control over who did the work and didn't realize there was more of a systemic problem until the second/third motor replacement.
The third motor was replaced by a company we have come to trust a little more and our technician found two things that were bad.
1) The reason he felt the motor failed (2nd one) was because some wires were not tied back and were brushing the fan blade causing a short.
2) When he came to replace the motor he didn't have one on his truck until he came to realize the one in the unit was undersized. He did have the "correct" unit on it truck so put that in. I seem to remember he replaced a 1/2 horsepower motor with a 3/4 horsepower.
It ran really well for about three weeks and then stopped again. This was all in January of 2011. Since he replaced that 3rd motor the 4th has run well until we switched the other day. Within a few days it was vibrating again and then blew two days ago.
So the reason for my post is to get ideas on what could be going wrong. Clearly the wires touching is something tangible and obvious, but the previous motors and this latest one are not so obvious. We're really lost as to what could be causing this.
The fan blade has been changed numerous times. I started by thinking it was out of alignment hence causing the motor to vibrate and fail. But why it would be getting out of alignment I don't know.
The current engineer is wondering if we're losing Amperage on getting a surge. A surge makes no sense since I have plenty of electrical devices in the house which would trip if we were getting a surge.
Trane have given no idea on why the motors failed, despite them being returned.
So, what should we be looking for? Why on earth would a failure be preceded by a heavy vibration/thumping/drumming sound?
Help!?! At a loss here.