I get a call about no power to an ac unit.So I see the fused disconnect has a blown fuse.It is a 5 ton dx unit.After inspecting the unit taking voltage and amperage and ohm readings.I chalk it up to a power surge or thunderstorms.Replace fuse and go about my way.A few days later the bldg maint man tells me that the unit has been blowing fuses on a regular basis.So I return to the roof telling myself well I find it this time.After tearing it apart for a few hours and megging the compressor,fan motors etc.Still cannot find a problem.The unit is 1 year old and is made by carrier.On a side note they wire those things pretty crazy.3 phase compressor single phase blower motors.The contactors for the three phase compressor was only switching two legs and a relay was switching the other leg.I am at a loss it is not about money just the fact that this thing is beating me.There are 6 other units on the bldg with no problems.I replaced the fuses today well I should say fuse A phase and baby sat it all day.Ran with no problems for at least 12 hours now.I am tempted to take the maint man suggestion and put some copper tubing in place of the fuse.Just kidding I don't like fire.Anybody got an ideas??
