Pressure switch replacement

Discussion in 'Pumps and Tanks Well Forum & Blog' started by mrron, Sep 29, 2013.

  1. mrron

    mrron New Member

    Messages:
    5
    Location:
    massachusetts
    I had a well installed early this year with a tank and pressure switch. I use the system to water my lawn. After 5 months of use the Merrill MPS4060 switch failed. Seems like the contacts broke and shorted. The inside of the plastic cover and inside melted. I obviously thought I should get more than 5 months out of it. In searching for a replacement I found, based on reviews, that this is a common problem. Luckily, the pump seems OK. Does anyone have a suggestion for a replacement that is durable. I assume they are plastic since some people would locate it outside or are they cheaply made. thanks. Ron
  2. craigpump

    craigpump Member

    Messages:
    943
    Location:
    ct
    Pressure switches aren't what they used to be, but it should have lasted longer than a few months. Are you sure the pump isn't short cycling against a water logged tank and overworking the switch?
  3. mrron

    mrron New Member

    Messages:
    5
    Location:
    massachusetts
    If you mean that it comes on and off at pressures other than 40/60 all I can say I have watched the system operate (when it was operating) and it came on and went off when it was supposed to. The tank also is only 6 months old and by water logged you mean the bladder is punctured not sure but I can hear it expand and contract. When I install a new one I can do any test you suggest. Thanks for responding.
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,141
    Location:
    Houston, TX


    That is a very cheap switch, $10.00

    I would put in a better switch, May cost you $20.00

    http://www.amazon.com/Square-Schneider-Electric-FSG2J24CP-Pumptrol/dp/B000BQSERE

    What is the HP of your Pump Motor ?


    Good Luck
  5. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    If your pump is less than 2HP, as DonL is asking about, and the tank is not waterlogged as Craig is asking, then a burned pressure switch is one of the first signs of too much cycling on and off. “Coming on and off when it is supposed too” can still be too much cycling and burn up a pressure switch, starter, motor, or all of the above.

    When you are running sprinklers or anything for more than a few minutes at a time, the pump should run continuously and NOT BE CYCLING ON AND OFF AT ALL.

    Even the Square D switch now has a plastic contact holder instead of the old fiberboard. Any long term cycling will melt the switch, which is just an indicator of more problems to come.
  6. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,141
    Location:
    Houston, TX
    The problem with a lot of the cheap switches is that the contact plating is no good. Burnt contacts have resistance, and make heat.

    Melting plastic is some sign of overload or resistance in the connection.

    A loose connection on the wiring terminals can cause heat and melt the thing.


    A good properly rated switch should be able to handle a bunch of cycles before it fails. The pump may fail first, before the switch gives out.
  7. Texas Wellman

    Texas Wellman In the Trades

    Messages:
    532
    Location:
    SE Texas-Coastal
    Don I tried the Merrill switches and they melt. I have about a dozen or so left but I refuse to use them. Shame too because the on/off was spot-on wheras the Square D seems to have a lot of variation these days.
  8. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    I agree. Except the only time contacts burn is when they make or break. Just means the cheaper the pressure switch, as well as the cheaper the pump, the more important it is to limit the cycling.
  9. mrron

    mrron New Member

    Messages:
    5
    Location:
    massachusetts
    WOW! This is a great forum. Thanks for all of the suggestions. Let me offer more detail:

    Pump: sta-rite S10P4JP05121 10GPM
    Tank: Flex-Lite FL12 35gallon
    Sprinkler heads: Orbit .8 gpm no more than four on at any one time.

    So if my math is correct a full tank should empty in about 10 minutes. I assume it never really empties. Question is how long does it take for the pressure to drop from 60 psi to 40 psi. No idea! Probably dependent of friction in pipes, orifice size, atmospheric pressure, my mood. Just kidding. But I think you get the picture. I temporarily switched back to town water and the sprinkler heads don't throw the water nearly as far as the well does even though town pressure is 80psi. Go figure. I bought the Square D today on Amazon. I want to buy a backup. Keep the ideas coming.
  10. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    You have a 10 GPM pump and a 32 gallon tank holds 8 gallons of water. So using four of the .8 GPM sprinkler heads is requiring 3.2 GPM. That means your tank is draining in 2.5 minutes and refilling in 1.5 minutes. That is a complete cycle every 4 minutes, 15 cycles per hour, or 360 cycles in a 24 hour day. That can add up to 131,000 cycles per year if left running 24/7. Even a Square D switch can’t survive with that much cycling. You either need to run no less than 13 heads at the same time, or get a Cycle Stop Valve so you can run as few heads as you want without cycling the pump (and switch) to death.
  11. mrron

    mrron New Member

    Messages:
    5
    Location:
    massachusetts
    I learn something new every day. Didn't realize a 32 gallon tank held only 8 gallons. I installed the Square D switch and it works fine as expected.
    For the first time I examined the pressure during a watering cycle. When the system with 4 sprinkler heads came on the pressure held steady at 58 psi. No recycle. The output of the 4 sprinklers must be more than I expected or the pump is not delivering what I thought. I then ran two systems at once ( 8 sprinklers) and the pressure dropped to 30psi and held steady. The flow pattern of the 8 sprinklers seemed adequate. So I don't see the need to change anything except buy another switch as a backup. Thanks again for the suggestions.
  12. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,141
    Location:
    Houston, TX

    That sounds like the best way to run your system if you get the water distance that you need.

    Please post if you have the same problem using the SD switch.

    They are all getting cheap, but the SD is still made in USA, as near as I can tell.


    Enjoy.
  13. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,987
    Location:
    NW Ontario, Canada
    If your range is set to 40/60, that is cutting it a tad close. I would up the range to 45/65 or 50/70 so long as the pump cannot deadhead at 70 PSI.
  14. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,141
    Location:
    Houston, TX

    I think it was said that it dropped to 30 and held.

    I could be wrong.

    A CSV may be needed.

    Watering 2 zones at once will save water and power.


    Have Fun.
    Last edited: Oct 4, 2013
  15. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,987
    Location:
    NW Ontario, Canada
    Ja, with 8 heads but he said with 4 heads it hovered around 58. I'm guessing he has at least one zone with 4 heads and another with 8.
  16. mrron

    mrron New Member

    Messages:
    5
    Location:
    massachusetts
    No need to guess. I will share the details that I should have from the start. I have two lawn irrigation systems , a system for the front yard and one for the back yard. Each system has two zones covering half of the lawn. I can't run both zones in the front yard at the same time since the piping is separated for each zone. Same is true for the back yard. However I can run both systems (front and back) at the same time since the electrical wiring for the shut off valves for the front yard is different than the back yard. So what I have done in the past is: start time 7:00 am first zone front yard waters, 7:15 second zone front yard starts, 7:30 first zone back yard starts, 7:45 back yard second zone starts. This all happens twice a day. Now for my test. I ran the front first zone (half of yard) and pressure stayed at 58 psi. These are big sprinkler heads and man they throw the water! My friends don't call me Ronbo for nothing! I then decided to start the front and back system at the same time so now I have 8 sprinkler heads running, 4 front and 4 back. That's when the pressure dropped and stayed at 30lbs. The spray pattern when both front and back yard running at the same time is what most people would say as adequate but again my nickname is Ronbo. So their are more details. Would be interesting to calculate the energy saving if I ran the front and back yard at the same time. So you guys have been so good to me I will share a Ronbo story Sunday night. I would tell it now but I fear that all of you will say, as my neighbors said, YOUR CRAZY!
  17. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    If you only have four of those .8 GPM heads running at the same time, and the pressure just hovers at 58 PSI, then I doubt you have enough pump to run the pressure switch up to 50/70. Also if the pressure is hovering at 58 while running the smallest zone, then I doubt cycling was the cause of the pressure switch melt down. Maybe you did just have a bad switch.

    To run all your sprinklers at once operating at 30 PSI will nearly cut your electric bill in half compared to running half that many at 58 PSI. You get more water per KW of electricity when running at the lower pressure.
  18. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,987
    Location:
    NW Ontario, Canada
    IMHO, 2 PSI is cutting it way too close. If the old pressure switch had ±2 PSI of accuracy, it could well have caused cycling. I would not take a one-time reading to the bank and set-and-forget it. The pump curve can vary with the static water level.

    Also, the trip point of a mechanical switch is supposed to be clean and swift, but in real life, it can take some of the contact force off briefly before it flips open.
  19. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,141
    Location:
    Houston, TX
    Even if the pressure switch has ±2 PSI of accuracy, add that to the meter error then the error becomes greater.

    It will also depend how the differential is set.


    If the pump does not cycle then it is close enough, and will work just fine.
  20. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
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