View Full Version : Lennox Heat Exchanger AC unit keeps blowing the capacitor.

08-20-2012, 01:32 PM
My brother's lennox heat exchanger AC unit keeps blowing the capacitor on the pump motor. Is this because in the hot weather the unit cycles on and off too frequently and that puts too frequent a load on the capacitor? I'm not sure of the size of the unit but it's a single phase, 208/230 cube-type unit that sits on a pad outside the house. Any help will be appreciated. Thanks guys.

08-20-2012, 02:33 PM
The lennox unit is an HP29-024-1P. I believe he was charged around $90 and he's had to have this capacitor replaced 3 times in the last 2 years. I've replaced capacitors on 3/4 - 2 h.p. woodworking motors before and it was pretty easy.

Runs with bison
08-21-2012, 06:07 PM
I'm not an HVAC tech or an electrician but I wonder if it should have a larger capacitor. If the current HVAC tech hasn't figured out a solution after three tries at the same problem in two years, then its probably time to find a better technician.

Higher outdoor temps actually result in less cycling if the unit isn't vastly oversized. The unit will end up running continuously in the hottest weather. Now if it is greatly oversized it will cycle off and on frequently even at peak temperatures.

08-24-2012, 01:51 PM
Thanks Runs with Bison. Since I posted this I asked a buddy of mine who is an E.E. and also a pretty good electrician. Here's what he had to say:

- the capacitor is the wrong size

- the voltage is not correct (especially if it's too high, but could also be if it's too low)

- it's taking too long for the motor to get up to speed, or speed sensor (if there is one - sometimes a centrifugal switch) doesn't release the capacitor when the motor is up to speed.

- any kind of drag on the motor (bad bearings, fan rubbing the housing)

- a fault (partial short) in the windings of the motor

- a partial ground anywhere in the motor/capacitor circuit

- a bad connection, probably on the capacitor

There are a few other possibilities, and most of these can be checked out. It's even possible (though not likely) that the "new" one you put in was bad. But if you've replaced it more than once and it's still happening, that's VERY unlikely.