"Industrial" pressure switch for air compressor ?

[Indyducati]

I'm sure if I'm asking this question, I'm not qualified to be doing this work
Other than expense, is there any reason not to use an industrial pressure switch
on an air compressor ? Properly sized, wired and adjusted.
Something like the photo below.

 

[alfredeneuman]

No

 

[Norcal]

No.

 

[4x4Pete]

That's what I have on a remote tank compressor. The switch is on the tank with 24v control wires running from the compressor starter to the switch. Has worked perfectly for 20 years

 

[TurnipTruck]

Post pic with the cover off. I’m not sure if the dead band can be adjusted, so the compressor might turn on at X, but turn back off at X+5 psi.

 

[walta]

Yes you can use it, so long as you understand the contacts are rated for pilot duty mean the they control a relay\contactor that operates the motor.

7 pounds between cut in and cut out non-adjustable would be a problem.

https://www.farnell.com/datasheets/1812000.pdf

Walta

Walta

 

[micromind]

The A300 rating of the contacts means it can handle 10 amps continuously.

It also means it can turn on an inductive load (motors, solenoids, etc.) of 7200VA. This would be 60 amps @ 120 or 30 amps @ 240.

Further, it can turn off and inductive load of 720 VA. This is 6 amps @ 120 or 3 amps @ 240.

This is roughly 1/3 HP.

Even further, the contacts are rated for a maximum of 300 volts AC.

 

[nadogail]

A properly adjusted industrial pressure switch will control the motor starter.

The Pressure switch should not be used to switch the motor, it should be the Pilot to direct the Motor Starter is that switches the motor and provides over current protection.

 

[Indyducati]

Gosh, I know I've made this harder than it needs to be...
Thank you all for the input and information.
@walta, that document is the best I've seen !

So, I'm looking for an Allen Bradley 836T, or Square D type A.
I believe I need a single set of contacts, to engage
the motor starter. It'll get 120v at the pressure switch.
120v signal at the starter to engage the 240v contacts.
I'll want the highest differential available ?
Let's say 90psi to 150psi ?
I've got a Quincy, two stage pump, so 175psi is possible.
A maximum range of 200psi or more ?

Am I on the right track ?
Thanks,
Steve

 

[alfredeneuman]

It'll get 120v at the pressure switch.

No. The pressure switch will get the full 240V when it closes.

 

[Indyducati]

@alfredeneuman , wouldn't the pressure switch control the magnetic starter ?
The starter control wouldn't be full 240V would it ?
I appreciate your interest and am trying to learn, not argue.

 

[mm08822]

@alfredeneuman , wouldn't the pressure switch control the magnetic starter ?
The starter control wouldn't be full 240V would it ?
I appreciate your interest and am trying to learn, not argue.

More likely than not, your starter coil is 240v to eliminate needing a step-down transformer in the starter enclosure or requiring the branch circuit to require a neutral.

So, as Alfred stated, the contacts will be subjected to making/breaking a 240v circuit, meaning the control circuit is 240v as well the power circuit.

 

[Indyducati]

Thanks for the clarification!

 

[TurnipTruck]

The coil of the motor starter will indicate the voltage it needs, I would not assume that it needs 240v.
The pressure switch will only need to switch at most an ampere or so.

 

[Tynee]

Gosh, I know I've made this harder than it needs to be...
Thank you all for the input and information.
@walta, that document is the best I've seen !

So, I'm looking for an Allen Bradley 836T, or Square D type A.
I believe I need a single set of contacts, to engage
the motor starter. It'll get 120v at the pressure switch.
120v signal at the starter to engage the 240v contacts.
I'll want the highest differential available ?
Let's say 90psi to 150psi ?
I've got a Quincy, two stage pump, so 175psi is possible.
A maximum range of 200psi or more ?

Am I on the right track ?
Thanks,
Steve

I know this is an old thread, but I wanted to point out for others who may find this in a search like I did…

Base your shut-off pressure on the lower of your max pump discharge pressure a d the MAWP of your tank. Some percentage below the lower of those two is wise. Maybe 10% under?

 

[wyliesdiesels]

The coil of the motor starter will indicate the voltage it needs, I would not assume that it needs 240v.
The pressure switch will only need to switch at most an ampere or so.

as said above, if there is no control transformer and the motor is rated for 240v, the starter coil will indeed be 240v. pressure switch needs to be rated for 240v or higher

 

[Norcal]

Just buy a quality SQ D, or Hubbell, (Furnas) pressure switch & all will be good, & keeps things simple & reliable.

 

[ArcReactorKC]

Just buy a quality SQ D, or Hubbell, (Furnas) pressure switch & all will be good, & keeps things simple & reliable.

It's easy to say "just buy that", there could be other factors that limit the abillity to buy that

 

[Norcal]

It's easy to say "just buy that", there could be other factors that limit the abillity to buy that

Stupidly buying cheap garbage is foolish. buy well & buy once.

 

[alfredeneuman]

It's easy to say "just buy that", there could be other factors that limit the abillity to buy that

"That" are much less expensive and simpler than even the cheapest Chicom motor starter.

 

[mm08822]

"That" are much less expensive and simpler than even the cheapest Chicom motor starter.

To add to "That", an air compressor specific ps usually has contacts rated for 5hp, unloader valve and on/off lever control.

Pretty simple and wrapped up in a small package. Also have a long life.