air compressor tripping breaker

[deadeye123]

checking out a friends campbell hausfeld 10 gallon comp. started tripping the breaker after starting and running about 3 seconds. I am thinking it may be the start capacitor. if so how do I check to see if it is good. it has a run capacitor also, how do I tell which one is which. any other ideas what would cause this? Thanks,Deadeye.

 

[JMOR]

using extension cord? if yes, remove and plug directly to outlet

 

[DoubleO7]

Go to breaker panel and rearrange the breakers of same amperage.
That will tell you if the breaker is getting weak.

 

[guido]

Hello deadeye123,

If it starts it is not the starting capacitor. More likely the start switch stays in after it starts.
Take a look at the switch contacts. Another way to know if that is the issue is measuring the amp draw,

Guido.

 

[deadeye123]

plugged direct to outlet, ran 3 sec, tripped 20A breaker.

 

[deadeye123]

Guido, checked switch, it is not sticking and contacts are clean. could it be the run capacitor?

 

[deadeye123]

tried different 20A circuit, tripped that one too.

 

[guido]

Hello deadeye123

Yep, that is the next step. Check it with an ohm meter, also make sure it does not have a bad connection.
Heat over time make the spade terminal loose. That is more likely the problem, that's my guess

Guido

 

[Dusty MI]

Whats is the amp rating on the motor label?

 

[wore out]

Is the "unloader" working properly so the motor can quickly start and get on the way to full speed before the load hits?

If one of the capacitors is "bad" the odds are GREATLY in favor of it being the "start" capacitor.

 

[buickanddeere]

Start switch could be welded or stuck closed.
Start capacitor could be shorted.
Need to use your clip on ammeter and measure both the start current and the run current .

 

[deadeye123]

checked both with ohm meter, both analog and digital. small cap.,which I assume is the start cap. did nothing on the analog meter and read 8.60 on digital. large cap. on analog needle moves all the way to the right and stays there. on digital reads 1.1.I think the large cap. is bad. comments?

 

[guido]

Hello deadeye123,

First thing you do, take a screwdriver and go across the cap leads, this takes any charge left in it.
Set the volt meter to the ohms of the lowest range, and touch the leads to the cap. If no reading reverse the leads.
Keep going to the next resistance range, and do the same thing. Eventually you will find a range that make the scale have a reading.

Once you find the range, assuming is a good cap, the meter will react, and by reversing the leads, it will react again. This means that is a good cap. No reading in any range? its a bad cap.

Some digital meters do not have a full range to test all caps, so use the analog too!

Guido.

 

[Steve@Advance]

Take the belt off, feel for slop in the motor bearings.

If the bearings are bad the rotor will drag the field windings, increase the amp draw.

If it feels good, see if it will run without the belt. It should be practically silent and draw way below FLA's.

If it's buzzing and drawing high amps the start switch may be welded.

Feel the compressor pulley. It should turn fairly easy.

 

[rlp in Co.]

The cap is bad.

 

[deadeye123]

testing shows the run cap. is bad. I will get new one and get back with results. thanks all for the great help.

 

[buickanddeere]

A cap with a higher rated voltage and higher MFD is a worthwhile upgrade.

 

[rlp in Co.]

Not true. Higher voltage may be better but
changing the capacitance is bad. A motor is
designed to work with a certain
capacitance! Changing it can cause the
motor to run hot or have less power or not
work at all!

 

[guido]

Hello buickanddeere,

I disagree, I don't know what you mean by higher. I was thought that a replacement capacitor should not be more then 10% its original value. Granted that a much higher value may start or run a motor, that is faulting, but that could mask another problem. In this case could be tight bearings-bushings, or a non functioning unloader,

Guido.

 

[Texasmark1]

My utility company requires motors to have a 0.87 PF or greater (VxI Cosine phase angle where 1.0 is unity....resistive, not reactive load....to the power
source....them. They get paid for Watts, not VI). Too much L or C can tip the ELI the ICE man equation.

 

[Stephen Newell]

It could be any number of things. Sometimes a breaker just gets soft and trips at a lower amperage than it's rated for. It might be the wire is too small or too far from the main box to carry the amperage. It could also be like you say an issue with the motor itself. I would start with the simpler fixes first and go from there. Breakers are cheap and if that wasn't it, it's good to have a spare on hand.

 

[buickanddeere]

Do tell us how the motor is going to burn out ? RLP and others, Bull Feathers. How much lab time have you spent changing XL and CL on single and three phase motors. Then charting the start current, run current , phase angles, VARs and watts? Do tell us how a higher MFD start or run capacitor is going to burn out a motor ? What do you think a "Hard Start Kit" is ? Single phase motors start due to a phase shift between the start winding and the run winding. The larger the phase shift , the higher the starting torque. The higher mfd cap is changing the phase angle , not doubling or tripling the current through the start windings. Now tell us how increasing run cap XC which will move the phase angle closer to 1.0 is going to damage anything? Room under the capacitor cover and $$$ is going to prevent anyone from going over board and have an 0.6 leading PF. Which by the way still will not burn out the motor. At most a reduction of the thermal OL protection by one step is the most compensation that could be required. I suggest that you fellows not speculate on something that you know little about.

 

[Dusty MI]

The direct drive fan motor on our son's furnace quit. It had a remote mounted capacitor. He put a new capacitor on it first, that didn't fix it, so he got a new motor, it wasn't the same make but stated to be a replacement for the original.
He bench tested it and it ran, but he didn't ground it. It stated that it needed a capacitor and the size, which he didn't check.
After he installed the new motor and tried to run it, it burst into flames.
He put the fire out without any real damage. Then he found out that the capacitor for the old motor was the wrong size, for the new one and that is why the new motor burst into flames.
He now has a another new motor and capacitor, and everything works.

 

[buickanddeere]

(quoted from post at 14:49:56 06/12/20) The direct drive fan motor on our son's furnace quit. It had a remote mounted capacitor. He put a new capacitor on it first, that didn't fix it, so he got a new motor, it wasn't the same make but stated to be a replacement for the original.
He bench tested it and it ran, but he didn't ground it. It stated that it needed a capacitor and the size, which he didn't check.
After he installed the new motor and tried to run it, it burst into flames.
He put the fire out without any real damage. Then he found out that the capacitor for the old motor was the wrong size, for the new one and that is why the new motor burst into flames.
He now has a another new motor and capacitor, and everything works.

Capacitor start and capacitor run that leaves the start cap energized at all times ? That is all altogether different motor and application.
We are talking about single phase aircompressors with a start cap, run cap and a start switch.