Need help finding a pressure switch for a 4hp compressor
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 23
  1. #1
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default Need help finding a pressure switch for a 4hp compressor

    The contacts in my Square D Pumptrol switch are fried after 6 months. Upon further investigation, I see it is only good for a 2hp motor. After looking all afternoon, between part changes, I can't find what I am looking for so here I am.

    I am looking for a pressure switch with an unloader for a single-phase 230V 4hp compressor. Max pressure of 175psi with as large a differential as possible. I would like to keep it as simple and reliable as possible.

    Sorry if it is a dumb question but I can't seem to find anything that will work and isn't cheap import.

  2. #2
    Join Date
    Jun 2006
    Location
    PA
    Posts
    590
    Post Thanks / Like
    Likes (Given)
    18
    Likes (Received)
    32

    Default

    Did you try Mcmaster?
    Are you looking for something like this:

    McMaster-Carr


    btm

  3. #3
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default

    For $190 one of those would work.

  4. #4
    Join Date
    Feb 2006
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    13,189
    Post Thanks / Like
    Likes (Given)
    727
    Likes (Received)
    4117

    Default

    On my compressor, I wired it with a pressure switch to operate a motor starter (relay). The motor starter is rated for my (real) 5 HP Baldor motor. The pressure switch only sees the tiny load of the starter coil.

    Some compressors have fishy HP ratings.

    Larry

  5. #5
    Join Date
    Mar 2009
    Country
    UNITED STATES
    State/Province
    California
    Posts
    5,602
    Post Thanks / Like
    Likes (Given)
    103
    Likes (Received)
    1084

    Default

    My last mechanical pressure switch was upgraded. To say the least.

    SMC Products

    dsc_0996.jpg

    A little modification needs to be done to the electrics. The device runs on 12-24Vdc. It will switch a higher voltage relay. It's worth the trouble.

  6. #6
    Join Date
    Nov 2003
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    5,406
    Post Thanks / Like
    Likes (Given)
    188
    Likes (Received)
    1803

    Default

    Or Grainger?

    I would add a solid state contactor that is rated for about twice the load your motor's rating. Then the pressure switch would last longer than you will.



    Quote Originally Posted by btm View Post
    Did you try Mcmaster?
    Are you looking for something like this:

    McMaster-Carr


    btm

  7. #7
    Join Date
    Jan 2005
    Location
    Houston
    Posts
    6,244
    Post Thanks / Like
    Likes (Given)
    787
    Likes (Received)
    3007

    Default

    Good question as my I-R 5HP POS compressor's just failed..I think it's the 3rd one. I replaced it with a Grainger-vended Square D but I think it's similarly under-rated.

    I also will note the extra pressure relief valve I added years ago worked as it popped off when the switch fused together and the motor kept running. When I replaced the switch, I deleted the extra valve and sure enough, the pressure relief valve that came with the compressor failed and let the unit run to 300PSI at which point I luckily heard it and shut it down. I heard it because it was popping loud as hell and hardly rotating.

    Why the new switch failed to shut off...I don't know. I haven't been able to get it to do it again.

    I'm adding the extra valve back though!

    But I do want to get a good switch on it. $190 is pretty dear but if that's what it takes...

    The quality of pressure switches sure has gone to crap...another product invaded by the Chinese low dollar effect.

  8. #8
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default

    rons, more info please! I did look for one of your posts on this but never figured out the right keywords. What model and what else did you get to make it all work?

    $190 is pretty steep for a simple pressure switch. I did check Grainger before buying my last switch but shy away from them because of their prices.

    I have done the relay thing on another small coolant pump because the motor kept frying the float switch that I like. That looks like a viable direction at the moment, I just have to figure out how to make it look good with the wires hidden and safe from the elements as it is outside. For $80 that pressure switch that rons has is pretty interesting. A wide open pressure differential but max pressure of 145 psi.

  9. #9
    Join Date
    Nov 2008
    Location
    Madera county california usa
    Posts
    2,533
    Post Thanks / Like
    Likes (Given)
    21
    Likes (Received)
    642

    Default

    Use a mag starter controlled by pressure switch.

    Use 120 vac as control voltage.

    Can then interlock with shop lights easily.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  10. #10
    Join Date
    Oct 2019
    Country
    NICARAGUA
    Posts
    106
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    41

    Default

    Walmart.com has one for $14, use it to control a magnetic starter ($50 used on ebay) with 120 volt coil as Tony said. Lights on, compressor on, lights off, compressor off. Easy, and it will last. Manufacturers are busy taking the metal out of everything, because metal costs money. The problem comes when there is not enough metal left to do the job.

  11. #11
    Join Date
    Dec 2011
    Location
    Denver
    Posts
    260
    Post Thanks / Like
    Likes (Given)
    70
    Likes (Received)
    11

    Default

    Condor USA - Replacement Pressure Switches & Pressure Control Systems

    This is the pressure switch that came on my Quincy 5hp/80g compressor

  12. #12
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default

    Quote Originally Posted by PT Doc View Post
    Condor USA - Replacement Pressure Switches & Pressure Control Systems

    This is the pressure switch that came on my Quincy 5hp/80g compressor
    As I read it the single-phase switches only go to 3 hp.

  13. Likes GregSY liked this post
  14. #13
    Join Date
    Dec 2012
    Country
    AUSTRALIA
    Posts
    2,880
    Post Thanks / Like
    Likes (Given)
    12
    Likes (Received)
    936

    Default

    I gave up with the electric ones,and replaced it all with a Westinghouse truck compressor governor,which is just air,and a air cylinder with spring return that works a spring loaded DOL 20hp contactor...Previously had a mercury tilt switch working a relay....problem was the relay used to stick ,apparently from the vibration of the compressor.......and as mentioned ,the thing would chug away at 150psi blowing thru the safety valve ,and chewing up costly power.

  15. #14
    Join Date
    Mar 2009
    Country
    UNITED STATES
    State/Province
    California
    Posts
    5,602
    Post Thanks / Like
    Likes (Given)
    103
    Likes (Received)
    1084

    Default

    Quote Originally Posted by DavidScott View Post
    rons, more info please! I did look for one of your posts on this but never figured out the right keywords. What model and what else did you get to make it all work?

    $190 is pretty steep for a simple pressure switch. I did check Grainger before buying my last switch but shy away from them because of their prices.

    I have done the relay thing on another small coolant pump because the motor kept frying the float switch that I like. That looks like a viable direction at the moment, I just have to figure out how to make it look good with the wires hidden and safe from the elements as it is outside. For $80 that pressure switch that rons has is pretty interesting. A wide open pressure differential but max pressure of 145 psi.
    I am using the part number:
    ISE30A-NO1-P

    I have another one in a SMC box. It is the ISE30-T1-65-L. Somebody wrote down the McMaster part number on the box: 3167K14.

    McMaster-Carr

    The slightly different numbers for the part are for different connections and internal switching transistor. The important things for me was to
    get a 1/8NPT connection on the back and a internal PNP transistor. The McMaster picture shows a push-lock connector for a PVC hose connection.
    I wouldn't trust that with my compressor tank pressure going up to 150psi.

    The manual has a selection guide. I have to admit that I had to read the manual more than once.

    https://www.smcpneumatics.com/pdfs_s...-OML0003-C.pdf

    I have a couple of new old stock Festo's:
    SPAB-P10R-N18-2N-K1 (1/8 NPT)
    SPAB-P10R-G18-2P-M8 (metric M8 straight thread)

    I bought them all from surplus stock at HSC Electronics. They closed operations Jan 2019.
    The SMC's cost $15 each and the Festo's were reduced from $25 to $10 each.

    -----------------------------------------------------------------------------------------------
    To connect:
    The switch has 3 wires, 12-24V, 12-24V return, and switch output.
    If I was using a motor starter then I would connect the switch output to something like a octal relay in a socket to control the motor starter coil.
    The switch can be programmed to have any hysteresis, I'm using 125-150psi. The display can be programmed for green color when off and red when on, or reversed.
    -----------------------------------------------------------------------------------------------

    The original Square-D switch was rated for 3Hp, the starter was rated at 3Hp, and the single phase motor was 5Hp.

  16. Likes DavidScott liked this post
  17. #15
    Join Date
    Dec 2003
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    4,862
    Post Thanks / Like
    Likes (Given)
    2403
    Likes (Received)
    4417

    Default

    Seems like this was just discussed recently . . . I am with the crowd that uses a pressure switch to control a starter/contactor. Easy to interlock, pressure switch never wears out, and you can spend your time doing productive things instead of repairing it every few years.

  18. Likes WHHJR liked this post
  19. #16
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default

    rons, thank you for all of the information. I think that SMC pressure switch is $78 direct but it doesn't look like it would like being outside, minimum of 35 degrees. I wonder if it would handle colder temps? A 70 psi differential would certainly reduce cycling.

    I think I will just get two sets of contacts for my current switch, which will just get me over $25 for free shipping. One to use and fry and a second set for when I get a starter or relay that will handle the amperage.

  20. #17
    Join Date
    Mar 2006
    Location
    Auburn CA
    Posts
    435
    Post Thanks / Like
    Likes (Given)
    5
    Likes (Received)
    39

    Default

    I agree with motion guru. If your motor has internal overtemp protection then all you need is a contactor as opposed to a starter. If it was operated by a pressure switch from the factory it should have the internal overtemp protection.

    Of course if you add a contactor/starter you will need an enclosure. In the name of creeping feature ism, since you now have an enclosure, add a timer and asco type valve to the tank drain. My drain activates with each power up of the compressor. Now you can ignore that compressor and spend more time making chips.

    In my case, I hate noise, so the compressor sits in the pump house. I have a timer and switch in the shop that enables the compressor and sets the time for the number of hours I plan to be in the shop. Between that and the auto drain the compressor gets no attention. Put the used compressor into service about 20 years ago and I have never had to do any service other than clean the compressor and change oil.

  21. #18
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default

    The new motor does have over-temp protection and I installed a float activated auto drain bowl right after the intercooler last spring, what a time saver!!!! One of the best $30 I ever spent. The enclosure will probably be the biggest part of installing a relay.

  22. #19
    Join Date
    Nov 2004
    Location
    WI
    Posts
    4,749
    Post Thanks / Like
    Likes (Given)
    518
    Likes (Received)
    1105

  23. #20
    Join Date
    Jul 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    3,074
    Post Thanks / Like
    Likes (Given)
    1232
    Likes (Received)
    1294

    Default

    Quote Originally Posted by 3t3d View Post
    Thank you for that, it looks like I am going to get a Lefoo 26 amp switch with my contacts. I saw it on Amazon but shied away because it looked like cheap Chinese but upon further investigation, it looks like it might be decent Chinese. Worth a try for $14.48 and up to a 55 psi differential.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •