Couple Quick Compressor Questions

[RLaCasse1]

Hi folks, couple quick questions I have for this 80 gallon Porter Cable compressor I picked up a while back. I was able to buy this thing for $200, but I had to replace the starter switch (or whatever it was called) in the motor. Still, it's a pretty cheap decent compressor. I haven't had to use it frequently, only every now and then. So usually I just kick it on and run it up to about 130 psi and then manually shut it off. But, I'm about to start some projects and wanna leave it running automatically. However, it turns on at 140 psi and shuts off at 175 psi, which is more than I really need for what I am doing. Which leads to my questions.

First, it takes a little over 5 min to build to 130 PSI. I can't imagine how long 140-170 PSI is gonna take. Also, 5 min seems like a while for it to hit 130, so maybe the pump needs a rebuild. Thoughts?

Second, any good suggestions on a different controller? Preferably an adjustable one that I can set both the turn-on and turn-off points.

Thanks!

 

[The Cobbler]

the pressure switch on it is probably already adjustable.
take the cover off & snap a picture

 

[RLaCasse1]

the pressure switch on it is probably already adjustable.
take the cover off & snap a picture

The pressure switch has a label that states ON at 140 and OFF at 175, which made me think it is not adjustable.

 

[The Cobbler]

pretty sure that security torx in the center is the pressure adjust
what is under the yellow blob near the white wire?

 

[RLaCasse1]

pretty sure that security torx in the center is the pressure adjust
what is under the yellow blob near the white wire?

Looks like some sort of adjuster. Which is which then?

 

[The Cobbler]

one is the differential between the cut in & cut out, the other adjusts the high or cutout pressure
I don't know which is which. a little foggy , sorry. I think the torx is the high setting. try to adjust it counterclockwise & see what it does. I would make 1 turn and see what it did to your pressures

 

[RLaCasse1]

one is the differential between the cut in & cut out, the other adjusts the high or cutout pressure
I don't know which is which. a little foggy , sorry. I think the torx is the high setting. try to adjust it counterclockwise & see what it does. I would make 1 turn and see what it did to your pressures

Ok, I'll try that.

 

[The Cobbler]

actually you can probably go 3 or 4 turns at first to get an idea.

 

[7635tools]

On a off note, that looks like a 7.5 hp motor or maybe a 5hp. Either way, that cord and plug is not code compliant. It should be hardwired.


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[RLaCasse1]

On a off note, that looks like a 7.5 hp motor or maybe a 5hp. Either way, that cord and plug is not code compliant. It should be hardwired.


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That's good to know. I know it was hardwired when I bought it, as it was used commercially. However, I asked that question when the electrician was putting in the circuit for it. They had said it wasn't necessary. Fingers crossed they were right.

 

[sberry]

This is a 2 stage compressor, the reason they were made was to go from 140 to 175. Run it and see what happens before messing with every screw. It's SPOSED to do this. The guys that designed it were not amateurs, it wasn't their first comp and they did post on a forum to figure out how to set the switch.
Yes, it took 5 mins to pump that far but it doesn't need to start from 0 every time. Plumb a ball valve on it first thing.
I see there is a valve. The next thing is a fil/reg, this is what is used to set working pressure. Something that IS important is the belt tension and condition.

 

[stonesfan68]

I wouldn't mess with that pressure switch. Why not just install a pressure regulator at the discharge of the tank and set it for the pressure that you want? The higher tank pressure will give you some working time between starting and stopping the compressor.

 

[American Locomotive]

Leave the switch alone! Your compressor is working perfectly! 5 minutes for 0-130 PSI on an 80 gallon tank calculates out to 20 CFM! It takes a while to fill the tank because it's such a large tank.

The compressor was designed to operate at 175 PSI. Get a large regulator, and set it to 100-120 PSI. That is how you are supposed to use these compressors. That way you get a constant 120 PSI of air while the compressor is allowed to do its thing.

You will lose a lot of storage capacity if you adjust the switch down to 130 PSI, and the compressor will run more often and may shorten the life of the motor or pump.

 

[DerekV]

On a off note, that looks like a 7.5 hp motor or maybe a 5hp. Either way, that cord and plug is not code compliant. It should be hardwired.


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[emoji106]

 

[RLaCasse1]

This is a 2 stage compressor, the reason they were made was to go from 140 to 175. Run it and see what happens before messing with every screw. It's SPOSED to do this. The guys that designed it were not amateurs, it wasn't their first comp and they did post on a forum to figure out how to set the switch.
Yes, it took 5 mins to pump that far but it doesn't need to start from 0 every time. Plumb a ball valve on it first thing.
I see there is a valve. The next thing is a fil/reg, this is what is used to set working pressure. Something that IS important is the belt tension and condition.

I wouldn't mess with that pressure switch. Why not just install a pressure regulator at the discharge of the tank and set it for the pressure that you want? The higher tank pressure will give you some working time between starting and stopping the compressor.

Leave the switch alone! Your compressor is working perfectly! 5 minutes for 0-130 PSI on an 80 gallon tank calculates out to 20 CFM! It takes a while to fill the tank because it's such a large tank.

The compressor was designed to operate at 175 PSI. Get a large regulator, and set it to 100-120 PSI. That is how you are supposed to use these compressors. That way you get a constant 120 PSI of air while the compressor is allowed to do its thing.

You will lose a lot of storage capacity if you adjust the switch down to 130 PSI, and the compressor will run more often and may shorten the life of the motor or pump.

These are all good points. I guess I had intended to run it more in the 110-130 range or so, and regulate it down to around 100 PSI.

Regardless, I did throw the times into a CFM calculator last night. Up to 100 PSI the pump is averaging 18.42 CFM, and at 130 PSI it is averagin 17.85 CFM. The label on the pump states 25.0 CFM at 100 PSI and 23.5 CFM at 175 PSI. At which point do you say it clearly isn't performing as designed? I feel as though it's hit that point already.

Guess I'll clarify something hear real quick, I get those pressures and CFM are the "Air Delivery" per the label. But hey, the compressor can't deliver it if it can't even pump it.

So I don't see any way this thing will provide 23.5 CFM at 175 PSI when it's averaging 17.85 CFM at 130 PSI.

 

[56Mark]

That's good to know. I know it was hardwired when I bought it, as it was used commercially. However, I asked that question when the electrician was putting in the circuit for it. They had said it wasn't necessary. Fingers crossed they were right.

I have mine wired that way too, knowing it wasn't compliant. My receptacle and cord are way over-rated. The main thing is never ever unplug it running. Might be a good idea to put a label on it to trip the breaker before unplugging. I need to label mine; I know not to unplug mine unless it is off but someone else might not know after I get hit by a bread truck or something.

I know some on here won't like that and are strictly by the book and I usually am too on electrical stuff, but oh well, my decision.

 

[American Locomotive]

So I don't see any way this thing will provide 23.5 CFM at 175 PSI when it's averaging 17.85 CFM at 130 PSI.

Those calculators are just making estimates. Elevation (feet above sea level), atmospheric pressure, humidity, temperature and a billion other things will all factor in. You're getting 20 CFM-ish, which is close enough to the sticker IMO.

Put a new air filter on it, change the oil and let it do its thing. If it hasn't had an air filter in a while, it's possible there might be some build up on the valves and carefully cleaning them may bring back some performance.

Running the compressor at 110-130 PSI will give up a lot of tank storage capacity and cause the compressor to cycle more than needed - putting more wear on the motor and pump. Regulators also typically need a minimum pressure differential to work correctly. For example, if you set your line pressure to 100 PSI, there is a chance the output pressure will drop well below 100 PSI when the tank pressure is down to 110 when using a large air tool.

As far as the plug goes - it's not to code because a NEMA 6-50 isn't rated for an electric motor that large. The outlet and plug are perfectly capable of handling that motor's starting and running current. The main issue is the plug could arc if you try to disconnect it with the motor running. So many thousands of people plug their big compressors in without issue. Just make sure the compressor is off and stopped before unplugging it.

 

[dkmc]

Running the unit at the higher pressure puts the motor and pump under additional load, and generates more heat and wear as opposed to running a lower pressure. That's my side of this Mexican standoff.....

You will lose a lot of storage capacity if you adjust the switch down to 130 PSI, and the compressor will run more often and may shorten the life of the motor or pump.

 

[sberry]

This would be different if he was trying to soup it up but this machine is designed to do it. Someone with minds greater than our own figured it out.

 

[The Cobbler]

of course the manufacturer & engineers have designed this to go up to, and be safe with the max pressure, but if one doesn't need that pressure or volume,I see no reason to not adjust it down to a reasonable level .

 

[srr]

I have my 80 Gallon turned down to 140PSI. Trust me your electric bill will thank you.

 

[skulldrinker]

If you're afraid of it ill trade you. You can have my little non intimidating compressor.

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