I picked up a 10 hp compressor, dual heads, 2 stage, 120 gallon tank.
The Pump has a centrifical unloader. The Motor is 3 phase 240 of which
I run on my 10hp rotary phase converter wired with 8-3 With Ground and
a 40 amp breaker.
The compressor starts fine but the breaker trips when the compressor is
near its top end around 160 psi. What are some causes for the breaker
to trip?
Thanks

When you get another breaker you might get with somebody who knows more
than usual about breaker selection. When getti nto larger sizes there
are sometimes other factors to consider.
Call the Square D rep and ask him. Perhaps their Web site will be of
some assistance.

"gtslabs" wrote in message
ups.com...
I picked up a 10 hp compressor, dual heads, 2 stage, 120 gallon tank.
The Pump has a centrifical unloader. The Motor is 3 phase 240 of which
I run on my 10hp rotary phase converter wired with 8-3 With Ground and
a 40 amp breaker.
The compressor starts fine but the breaker trips when the compressor is
near its top end around 160 psi. What are some causes for the breaker
to trip?
Thanks


I assume that you are you refering to a 40 amp single phase breaker on a
240 volt circuit that feeds the rotary converter.
The rotary converter isnt supplying perfect 3 phase.
Pumping at 160 PSI might be loading the compressor's motor to near its
max.
The 40 amp breaker is operating very close to the current where it is
designed to open.

If you want to experiment with this compressor current requirement, maybe
you can put a tachometer on the motor pulley. I suspect the motor is
turning at an RPM lower than its specified RPM at max power.

Jerry

You might need all the air that this unit is capable of delivering, but if
not, I would probably consider removing the belt(s) from one head/pump.
That way you'll have emergency belts and a backup pump, should they become
neccessary.

The earlier recommendation to lower the maximum cut-off pressure setting is
valid. The motor is under the highest load at the highest pressure.
Generally, you can also reset the low cut-in pressure a little lower too.
Lowering the high point will most likely add longevity to the pumps.

WB
...................

"gtslabs" wrote in message
ups.com...
I picked up a 10 hp compressor, dual heads, 2 stage, 120 gallon tank.
The Pump has a centrifical unloader. The Motor is 3 phase 240 of which
I run on my 10hp rotary phase converter wired with 8-3 With Ground and
a 40 amp breaker.
The compressor starts fine but the breaker trips when the compressor is
near its top end around 160 psi. What are some causes for the breaker
to trip?
Thanks





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I would think that the obvious reason the breaker is tripping is that the motor
is drawing more than 40 amps. In the absence of any contrary indicator, I don't
see that anything is necessarily wrong. Ugley's says, in its table headed
"FULL-LOAD CURRENT AND OTHER DATA : THREE PHASE A.C. MOTORS":

10hp 230V 28amps 60A breaker #2 starter 32.2A heaters #10 wire 3/4 EMT

So from that I would conclude that even though the full load amp rating is only
28 amps it can draw a bit more so if I were you, everything else being met, I
would simply replace the 40A breaker with a 60A breaker.

Grant Erwin
Kirkland, Washington

"gtslabs" wrote in message
ups.com...

I picked up a 10 hp compressor, dual heads, 2 stage, 120 gallon tank.
The Pump has a centrifical unloader. The Motor is 3 phase 240 of which
I run on my 10hp rotary phase converter wired with 8-3 With Ground and
a 40 amp breaker.
The compressor starts fine but the breaker trips when the compressor is
near its top end around 160 psi. What are some causes for the breaker
to trip?