air compressor pressure switch - need a replacement

[stickshift]

Need to replace the pressure switch on my air compressor. Old switch, pictured below, has 4 ports + unloader valve, so I guess getting the same is easiest.

How do people use 1 port pressure switches? Do they have another port on the tank, or do they use a tee off the tank so they can connect tank gauge, safety valve, regulator?

Some of the switches refer to a 2-way release valve? Is that the unloader valve or something else?

If I want to install a regulator like this, I guess I need to use a 90* elbow on either side to orient the regulator similar to how the regulator and gauge are oriented on existing setup?

 

[joe_padavano]

Your current switch appears to be proprietary to that compressor manufacturer. Just use a generic pressure switch with a tee fitting under it. Run the regulator off of the tee. There's nothing magic about this plumbing.

 

[redmondjp]

Get a Square-D replacement switch (can get on Amazon) - there are many options - this link shows some of the more common switches and the options:

http://www.hfwinc.com/uploads/specs/Square_D_Pressure_Switches.pdf

 

[csp]

Lots of options on Amazon. Watch the pressures so that the cut in/out are close to your existing one. You don't want one that's off at 150 psi if you have one now that's off at 125 for example.

 

[stickshift]

Get a Square-D replacement switch (can get on Amazon) - there are many options - this link shows some of the more common switches and the options:

http://www.hfwinc.com/uploads/specs/Square_D_Pressure_Switches.pdf

Thanks, that helps narrow it down.

They show models for smaller (1.5HP on single phase) and larger (2HP on single phase) HP motors. Table below. I have one of those old 20-gal 5HP horizontal tank compressors. It's certainly not a 5HP motor. Pic of motor label attached. Any idea if I should get a switch for "smaller" or "larger" HP motor?

 

[Citation]

Just about any 4 port pressure switch will do. The pressure range isn't critical as that can be adjusted. You shouldn't have to spend more than about $20 for the switch.

 

[Citation]

Here is a better one
https://www.homedepot.com/p/Powermate-105-135-psi-Pressure-Switch-034-0226RP/202592803
And a cheap one (same type as my CAT compressor)
https://www.ebay.com/i/264558372422

 

[The Cobbler]

pretty much any 4 port pressure switch with on /off/unloader can be easily installed and or plumbed to fit . that compressor I would get a 95/125 switch. yes, most of them are adjustable, some aren't
stay away from the el cheapos . I had one that lasted all of 1 week

 

[redmondjp]

Thanks, that helps narrow it down.

They show models for smaller (1.5HP on single phase) and larger (2HP on single phase) HP motors. Table below. I have one of those old 20-gal 5HP horizontal tank compressors. It's certainly not a 5HP motor. Pic of motor label attached. Any idea if I should get a switch for "smaller" or "larger" HP motor?

Your motor is around 2HP so I would go with the bigger one.

 

[stickshift]

Your motor is around 2HP so I would go with the bigger one.

Thanks. That's what I was thinking since the motor is 15A at 115V, so ~1.5kW, which is what the higher HP switch is rated for.

These are a bit more pricey and not as readily available as the lower HP version. Kinda running up how much I'm sinking into this old compressor.

 

[Citation]

I wouldn't worry about the HP claims. If the switch is rated for 15A, 120V you are fine. All of these are meant to switch a motor so just check the amperage.

 

[Citation]

Thanks. That's what I was thinking since the motor is 15A at 115V, so ~1.5kW, which is what the higher HP switch is rated for.

These are a bit more pricey and not as readily available as the lower HP version. Kinda running up how much I'm sinking into this old compressor.

Get the Condor one I linked from Amazon. Condor is a good switch and all of $25.

 

[redmondjp]

I wouldn't worry about the HP claims. If the switch is rated for 15A, 120V you are fine. All of these are meant to switch a motor so just check the amperage.

Um, no. The big deal here is not running current, but starting current, which can be as high as eight times as much as the full-load current.

Plus, a motor is an inductive load, not a resistive one, so interrupting current to such a load can cause a large arc at the contacts, depending upon exactly where you are on the AC voltage waveform when the current is interrupted.

So for a motor, you can't just use the current - that's why electrical switching devices have separate ratings (typically in motor HP) besides the resistive load ratings listed on them.

Yes, you can get away with using an under-rated switching device - for awhile. But in this case, spending a few more dollars for the pressure switch with the larger contacts is money well spent and the correct thing to do.

 

[stickshift]

Get the Condor one I linked from Amazon. Condor is a good switch and all of $25.

Thanks, but the Condor one isn't for the range I need (I need 95-125psi) and in the Q&A, the distributor said it's not adjustable and provided a model # for the 95-125 version, which isn't readily available.

I think I may go with this one: https://www.amazon.com/gp/product/B06XVJTY2M/?tag=atomicindus08-20

Supposedly made in Taiwan. Good reviews. 25A rating. Only $18, so about the same as the Lefoo. Hard to justify spending as much on the Square D as I paid for the whole compressor.

 

[redmondjp]

Thanks, but the Condor one isn't for the range I need (I need 95-125psi) and in the Q&A, the distributor said it's not adjustable and provided a model # for the 95-125 version, which isn't readily available.

I think I may go with this one: https://www.amazon.com/gp/product/B06XVJTY2M/?tag=atomicindus08-20

Supposedly made in Taiwan. Good reviews. 25A rating. Only $18, so about the same as the Lefoo. Hard to justify spending as much on the Square D as I paid for the whole compressor.

For that price, buy two and keep one for a spare!

 

[stickshift]

For that price, buy two and keep one for a spare!

LOL. Lemme see how it goes with just one first. Will report back.

 

[strutaeng]

I just added a pressure switch to an older Emglo with a GE 2.0 HP motor. Nameplate amps listed is 19A @ 120V. This is the unit I replaced it with:

https://www.northerntool.com/shop/tools/product_22938_22938

My compressor had a pilot valve and was set for constant-run, and I removed the pilot valve, plugged the head under outlet on the pump, and added the pressure switch to convert it to run-stop mode. Works well for my intermittent use.

Should be okay for OP's 15A @ 120V motor. It is rated at 2HP @ 120V and 3HP @ 240V.

 

[stickshift]

Um, no. The big deal here is not running current, but starting current, which can be as high as eight times as much as the full-load current.

Plus, a motor is an inductive load, not a resistive one, so interrupting current to such a load can cause a large arc at the contacts, depending upon exactly where you are on the AC voltage waveform when the current is interrupted.

So for a motor, you can't just use the current - that's why electrical switching devices have separate ratings (typically in motor HP) besides the resistive load ratings listed on them.

Yes, you can get away with using an under-rated switching device - for awhile. But in this case, spending a few more dollars for the pressure switch with the larger contacts is money well spent and the correct thing to do.

Thanks for the explanation. I was wondering how an undersized switch would manifest problems.

 

[Citation]

Um, no. The big deal here is not running current, but starting current, which can be as high as eight times as much as the full-load current.

Plus, a motor is an inductive load, not a resistive one, so interrupting current to such a load can cause a large arc at the contacts, depending upon exactly where you are on the AC voltage waveform when the current is interrupted.

So for a motor, you can't just use the current - that's why electrical switching devices have separate ratings (typically in motor HP) besides the resistive load ratings listed on them.

Yes, you can get away with using an under-rated switching device - for awhile. But in this case, spending a few more dollars for the pressure switch with the larger contacts is money well spent and the correct thing to do.

I'm well aware of the issues associated with inrush current and back emf. Look back at what I was saying. These switches are designed to switch motors. A switch that is rated to switch a 15A, 120V compressor motor is fine. This isn't under rating. The 2hp switch is likely rated at 20A, 120V. Since this is a 15A motor pairing it with a 15A electric motor switch is fine.

Also, note that the motor has no HP rating. It's a compressor "special". A 15A compressor switch should be fine.

 

[Citation]

Thanks for the explanation. I was wondering how an undersized switch would manifest problems.

Do note that most pressure switches are rated for the same 15A as your motor. While your compressor might call itself 2hp, the motor plate has no rating so use the 15A as your guide.

 

[Citation]

Thanks, but the Condor one isn't for the range I need (I need 95-125psi) and in the Q&A, the distributor said it's not adjustable and provided a model # for the 95-125 version, which isn't readily available.

I think I may go with this one: https://www.amazon.com/gp/product/B06XVJTY2M/?tag=atomicindus08-20

Supposedly made in Taiwan. Good reviews. 25A rating. Only $18, so about the same as the Lefoo. Hard to justify spending as much on the Square D as I paid for the whole compressor.

Condor makes a lot of different ranges. Also, the range is the preset range. It's easy to adjust the range via two screws under the cover.

Here is basically the same thing with the pressure range I think you want.
https://www.amazon.com/dp/B07J2WRN7Z/?tag=atomicindus08-20

 

[stickshift]

Pressure switch received. Looks reasonably stout. I prefer the screw terminals over the spade terminals on the old switch.

It comes with what must be grommets to protect the line and motor cables from the metal enclosure. I guess the cone part of these grommets are supposed to be a dirt/weather shield? No instructions of course. Are these meant to be oriented with cone pointing outside the enclosure, then cut a slit to pass cable through, which will drag cone inward as cable is pushed through?

 

[Citation]

Cut the cone off at a height that is correct for the diameter of the wire (lower for larger diameter. It both keeps dirt out and helps hold the wire in place. The direction of the cone should be into the switch since that will help resist pulling the wire out. I think that is what you were describing.

 

[stickshift]

Cut the cone off at a height that is correct for the diameter of the wire (lower for larger diameter. It both keeps dirt out and helps hold the wire in place. The direction of the cone should be into the switch since that will help resist pulling the wire out. I think that is what you were describing.

That makes sense, thanks.

 

[csp]

Just about any 4 port pressure switch will do. The pressure range isn't critical as that can be adjusted.

Not all are adjustable and for those that do, some have a limit to their range they can be adjusted. Been there, done that and have an extra pressure switch I can't currently use as a result.