Wiring compressor so I don't leave it on

[jblnut]

nope. a breaker is not the overload protection for a motor of this size. notice the FLA on the motor nameplate is a lot lower than 50a? the red button on the back of the motor is part of the overload assembly in the motor however some motors do not have this integral overload protection so it needs to be provided with the contactor aka starter. it would go below the contactor then the motor connections are terminated on the load side lugs of the overload

the breaker is solely for short circuit and ground fault protection. it will not protect the motor or wiring.

That makes sense. Thanks for spelling it out so nicely like you do so often

I recently purchased a 2nd dust collector that draws right at 12a when running but a staggering 57a for a moment when starting. I’m almost 100% sure that motor has no built in overload. Should every circuit I plug it into have an overload protector ?

 

[mm08822]

That makes sense. Thanks for spelling it out so nicely like you do so often

I recently purchased a 2nd dust collector that draws right at 12a when running but a staggering 57a for a moment when starting. I’m almost 100% sure that motor has no built in overload. Should every circuit I plug it into have an overload protector ?

The overload protection should be part of the dust collector.....either integral to the motor or and overload relay within a starter enclosure.

Provide pics of the motor and on/off hardware. Or the mfr and model #. It is usually very easy to confirm.

 

[wyliesdiesels]

smaller cord and plug connected motors can get by with protection from the breaker (such as garbage disposals, furnaces, vacuums, etc). but it all depends on the motor, manufacturer, etc

the startup current is typical as in-rush current can be 4x-8x FLA

 

[manwithtools]

The compressor motor also has that annoying little red button on the side that’ll pop if something gets pissy out by the compressor.

That would mean the motor has built in thermal overload protection. You would not need anything beyond what you have today - breaker, contactor, timer.

 

[Citation]

That makes sense. Thanks for spelling it out so nicely like you do so often

I recently purchased a 2nd dust collector that draws right at 12a when running but a staggering 57a for a moment when starting. I’m almost 100% sure that motor has no built in overload. Should every circuit I plug it into have an overload protector ?

The dust collector is a different type of load vs the compressor. The compressor has some compression load on the first rotation of the pump. That can be really hard on the motor and if the oil is cold etc it's not unreasonable to think the motor would stall and trip a breaker. The dust collector fan has some inertia but other than inertia it has no load as it starts turning. For that reason it it probably is fine with a non-resetable thermal/over current fuse inside the motor.

 

[Milton Shaw]

I put a normally closed 120 volt ball valve on mine, and wired it to cycle it with the light switch. I used a hydraulic line to connect the ball valve to the compressor. Air flow turns off when the lights are off. I also turn off the smoke detector off when the lights are on. As I am in the shop, welding or burning wood sanding or running gas engine and setting off the detector. I would see a fire while I was in the shop and didn't need the smoke detector going off to let me know. The ball valve slow opens to cut the shock of going to full air pressure like a solenoid valve would.

 

[AntonLargiader]

As long as I shut the ball valve on the compressor it won’t run when I’m gone. It’s now a habit.

Unless the pop-off valve goes bad. Happened to me a few years ago. Came in to find the compressor running, air roaring out of the valve, and everything in that room HOT.

So I want to control it with a low-current 120 to 240V solution. Smart switch, tied into lights, something like that. Any recommended relays or starters? Compressor just has a 240V pressure switch. Dewalt, motor says 3.7 HP.

Looks like I have two ways to accomplish it, too. Is one preferred? #1 seems simpler.

1. 120V pulls in a contactor powering the overall compressor
2. Run switched 120V through the pressure switch and then have the contactor run the compressor directly.

 

[MFortie]

Unless the pop-off valve goes bad. Happened to me a few years ago. Came in to find the compressor running, air roaring out of the valve, and everything in that room HOT.

So I want to control it with a low-current 120 to 240V solution. Smart switch, tied into lights, something like that. Any recommended relays or starters? Compressor just has a 240V pressure switch. Dewalt, motor says 3.7 HP.

Looks like I have two ways to accomplish it, too. Is one preferred? #1 seems simpler.

1. 120V pulls in a contactor powering the overall compressor
2. Run switched 120V through the pressure switch and then have the contactor run the compressor directly.

I did #1. Pulled 120V from one of the banks of lights (I have 3 banks) in the section of the shop I store the MH -- I don't turn on those lights unless I need the comp or am doing something with the coach. And I always shut off the lights when I lock up.

This is the one I used: https://www.amazon.com/dp/B008KNRTD0?tag=atomicindus08-20

 

[Milton Shaw]

I used an electric ball valve to connect the compressor to my air piping. Then the valve is operated with a feed from the light switch. I used a short stub on 3/4 hydraulic hose to connect the normally closed ball valve to my air piping. That is a slow opening valve so that the pressure is not a solenoid fast surge into the pipe. This gives an air system that is off when lights off but full compressor volume is available when I turn the lights on. The idea of emptying the compressor wastes a lot of air and just adds more water vapor to the tank.

 

[wyliesdiesels]

Unless the pop-off valve goes bad. Happened to me a few years ago. Came in to find the compressor running, air roaring out of the valve, and everything in that room HOT.

So I want to control it with a low-current 120 to 240V solution. Smart switch, tied into lights, something like that. Any recommended relays or starters? Compressor just has a 240V pressure switch. Dewalt, motor says 3.7 HP.

Looks like I have two ways to accomplish it, too. Is one preferred? #1 seems simpler.

1. 120V pulls in a contactor powering the overall compressor
2. Run switched 120V through the pressure switch and then have the contactor run the compressor directly.

make sure that the snap switch is rated for the coil voltage you are using. if its a 240v coil you will need a 240v rated switch

 

[Steve W.]

As long as I shut the ball valve on the compressor it won’t run when I’m gone. It’s now a habit.

My practice, as well. However, If I am going to be out of town for more than a weekend, I will turn off the breaker in the panel.


My compressor stays energized virtually all the time. When I want air, I want it NOW, I don't want to wait several minutes for it to build up. I have a ball valve at the compressor. Just downstream of that is a regulator with a gauge. The gauge can be mounted on either side of the regulator, there is a plug on the un-used hole. I replaced the plug with a brake switch for a Harley. If there is more than about 50 psi in the lines, the switch is closed. I have wires run from the switch to a light near the exit door. If there is air pressure (>50psi) in the lines, the light is ON. It reminds me to go to the compressor closet and turn the ball valve OFF. I then bleed the air to turn the light off.

I used to have a small 12-volt trailer marker light by the door. My kids got me something a little more noticeable.



Absolutely NO WAY to miss it now.

.

 

[AntonLargiader]

...This is the one I used: https://www.amazon.com/dp/B008KNRTD0?tag=atomicindus08-20

Thanks. I found a different version of that one that has the HP rating I need.

I used an electric ball valve to connect the compressor to my air piping. ...

Which valve did you use? I looked at them a while ago (for water, not air, but I would like one for air) and almost everything I found seemed to be a differently colored version of the same valve by US Solid.

 

[Milton Shaw]

Thanks. I found a different version of that one that has the HP rating I need.

Which valve did you use? I looked at them a while ago (for water, not air, but I would like one for air) and almost everything I found seemed to be a differently colored version of the same valve by US Solid.

Amazon has a 3/4 and 1" normally closed electric ball valve with 120 volt cord. They have gone up a bunch since I got mine. That lets it switch by just plugging it into a normal outlet switched by the light circuit. Just search for normally closed electric ball valve 120 volt.