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Pressure switch for 5hp compressor?
- Thread starter rustybill
- Start date
GeorgiaHybrid
Well-known member
I used a Square D pressure switch from Northern tools. Are you going to switch the motor thru the pressure switch or just use it to trigger a mag switch? A 5 HP motor is right on the line for this from what I understand.
Mr_fixit
Well-known member
Most would use a Mag starter for 5hp and then any pressure switch would work on the coil side.
Mr_fixit
Well-known member
well if you use it to trigger the mag starter , than a lower amp one would work. I robbed one off an old junked compressor...
which scenario is better?
pressure switch connected to a mag starter.
GeorgiaHybrid
Well-known member
I used the pressure switch to activate the coil side of a Siemens mag switch. The pressure switch should last a long time without having 20+ amps running thru it.
Mr_fixit
Well-known member
A magnetic starter uses a low current magnetic coil to pull a set of contacts together that are rated for a high current, (the rating of the motor). . Most motors at 5 hp or above use that setup.
In addition to it's function as a "relay" where a low current switch controls a high current switch, it serves another purpose. Built into that magnetic starter is a fuse that will blow if for some reason the current of the motor exceeds a selected current rating. ( so the magnetic starter needs to be rated for that specific motor And so does the current limiting fuse) If it blows , the motor's power or current gets interrupted and the motor stops.
This is to protect the motor in case something goes wrong.
When you connect the pressure switch to the low current coil side, of a magnetic starter, the pressure switch could be rated much lower and should last a very long time.
If you skip the magnetic starter, the pressure swicth would need to be rated for the current of the motor, and there would be no over current protection to protect the motor. Usually 5 hp motors don't come with built in circuit protection. And the pressure switch wouldn't last very long at such high current levels. the contacts would burn, or burn up, arc, whatever you want to call it.
Some "farm duty" 5 hp motors have built in circuit protection and wouldn't necessarily need a magnetic starter.
If you running a true 5 hp motor and it has no overload protection built in, you should consider a magnetic starter mandatory. In that case, almost any pressure switch should work. Magnetic starters cost more, but, in many cases you're protecting a couple hundred dollar motor.
In addition to it's function as a "relay" where a low current switch controls a high current switch, it serves another purpose. Built into that magnetic starter is a fuse that will blow if for some reason the current of the motor exceeds a selected current rating. ( so the magnetic starter needs to be rated for that specific motor And so does the current limiting fuse) If it blows , the motor's power or current gets interrupted and the motor stops.
This is to protect the motor in case something goes wrong.
When you connect the pressure switch to the low current coil side, of a magnetic starter, the pressure switch could be rated much lower and should last a very long time.
If you skip the magnetic starter, the pressure swicth would need to be rated for the current of the motor, and there would be no over current protection to protect the motor. Usually 5 hp motors don't come with built in circuit protection. And the pressure switch wouldn't last very long at such high current levels. the contacts would burn, or burn up, arc, whatever you want to call it.
Some "farm duty" 5 hp motors have built in circuit protection and wouldn't necessarily need a magnetic starter.
If you running a true 5 hp motor and it has no overload protection built in, you should consider a magnetic starter mandatory. In that case, almost any pressure switch should work. Magnetic starters cost more, but, in many cases you're protecting a couple hundred dollar motor.