A/C buzzing noise

[booger]

When heat pump turns on thee is buzzing noise. You can feel vibration in wires. I have checked for voltage drop and overcurrent also checked grounding. There is equipment ground run with the feeders. Circuit is run in conduit and I have check for proper support i.e. loose straps everything checks out, any ideas or similar experiences out there.

[bphgravity]

Is there a contactor or transformer involved with the circuit?

[booger]

There is the 24 volt transformer and the contactor on the outside condensor, the circuit is fed from a 120/240 single phase system from utility.

[bphgravity]

My guess is either the transformer, contactor coil, or contactor contacts are creating the vibration. It is then being transmitted to the case of the A/C unit.

[booger]

It only does it when it first starts up. If contactor was the problem wouldn't it vibrate all the time?

[don_resqcapt19]

Sometimes this is just the wires moving in the raceway because of the magnetic fields set up by the high starting current.

[booger]

Know of any cures? This conduit happens to run thru a yoga medidation room and it is distrubing their medidation.

[booger]

Would increasing the wire size be of any real help?

[ken987]

I would have a HVAC tech check the unit it may be starting against a high head pressure, and be locked up. Is it emt or ridged up into the unit, if so maybe changing to a flexible raceway would help.

[hurk27]

A'HHHH there is life for Smurf tube.