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Discussion Starter #1
I have a 60-gallon belt-driven compressor that has a Harbor Freight motor and head (both new). Every time the compressor gets up to the desired shut off amount it does so but also trips the reset on the motor. Additionally, I have to turn the breaker off and back on for the motor to restart. I have replaced the pressure switch and the same thing happens. I even switched tanks with the same result. Does anyone have any suggestions on what the problems maybe?
 

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a1handy,

How close are you to the Motor FLA (listed on the motor) at the shutoff pressure? a simple ammeter from Harbor freight would tell you that. Did you change the pulley size? If you replaced an american motor rated at 3HP with a Harbor freight 3HP that could be your problem. The Harbor freight 3HP is actually a 2 HP overated. It will technically produce 3HP but will overheat in the process. a 3HP motor draws 15 to 17 or so amps at 240VAC if it is efficient.

Stephen
 

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a1handy,

I just remembered the Smith + Jones motor FLA is 12.26 which translates to 2 HP basically. If you load this motor to 3HP, it will produce 3HP at 16 amps until it overheats, thus tripping the thermal overload. If you reduce the motor pulley size to a 2HP load, this motor would work, less CFM output of course
 

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a1handy,

If the house outlet breaker trips, that would be another issue. Most circuit breakers use the 80% of rating use rule. Meaning that you are only supposed to use 80% of the rated value, so on a 20 amp breaker with the correct gauge wire you could safely use a 16 amp load all day. But if you use a 19 amp load, eventually the circuit breaker will overheat and trip. This is quite normal for typical circuit breakers. If this is the case the outlet, wire and breaker will have to be upgraded to the next size up. Say 10 guage wire, 30 amp outlet and a 30 amp breaker for a steady 19 amp load all day

Stephen
 

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Discussion Starter #5
If I understand you correctly, you are saying the motor is not suitable for what I am using it for. Do I need to get another motor? A smaller or larger pulley? Also, for whatever its worth the engine does not feel hot to the touch as I have seen happen in similar instances with other motors. Thanks
 

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a1handy,
I'm not saying that your motor is no good, What I am saying is that it seems to me (no test done) that you are asking for more HP than the current motor can provide for a long period (one cycle in this case). This can be approached in different ways. You could blindly just buy a smaller motor drive pulley and try it out or do a more educated calculation. To engineer a solution you need a few more facts (none posted here) What current draw is on one wire or leg of the electric motor at top air pressure generated? What is the listed FLA posted on the motor? (that will determine the actual HP the motor can provide, the listed HP may be a fantasy) next what RPM at what HP is listed for the pump? What is the supply voltage and circuit breaker 240v @20 amps for example. With this information and a little math you can generate a viable plan and an effective solution. The windings and core can overheat before the case gets hot. If you overload an electric motor the core gets saturated drawing up to locked rotor currents which are 8 to 10 time FLA listed
at startup
 

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you are better off with a name brand motor.
and if you are doing the low cost motors use a 5 hp...
this is a 60 gallon tank...
a 5 hp setup works less to fill that tank...
just saying!!
in this case bigger is better..
the jina knock off motors are not the value they seam.
baldor and a few others are better.
I did a reliance on a LARGE drum fan...
it was a big difference on the current demand from the jina motor that was on the unit.
way lower current draw. I was able to over spin a bit and still have low current as well.
 
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