Home irrigation pump start relay intermittent shut off issues

Discussion in 'Irrigation / Sprinkler Forum' started by kurtze, Jul 25, 2013.

  1. kurtze

    kurtze Reporter

    Messages:
    4
    Location:
    West Michigan
    I have a AEG SH07 pump start relay for my irrigation system. The rainbird SST -900i controller was having some problems with a zone wiring issue. I have since fixed that but at times the pump will run without any zones running. The pump is 2hp and I don't want to ruin the pump or impeller system let alone the electricity. What check can I do to see if there is a problem so I can replace the faulty component.
  2. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    The pump should possess protection on a stand-alone basis, and not depend on everything else being just right. Relay controlled pumps are about the worst possible situation. One system component can fail, and the pump won't know about it. The simplest form of protection is a pressure relief valve, but sometimes it's too simple. A lot of pumps chosen for lawn sprinkler use don't operate all that far from their maximum possible pressure (when trying to pump into a closed system, aka "deadheading") and that provides very little range to have a relief valve operate in.

    More applicable to low-pressure pumps might be a thermal cutoff. These mount in a pump's drain connection, and react to a dangerous rise in the pump's water temperature, and cut off pump power completely, until the temperature falls back to a safe range.
  3. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,435
    Location:
    Houston, TX

    Did You reset the controller ?
  4. Murphy625

    Murphy625 Member

    Messages:
    150
    Location:
    Michigan
    Yup.. I agree.. Monitoring the temperature of the volute is an excellent way of determining if the pump discharged is completely closed. A simple snap action thermostat with a manual reset would work great.. if the thermostat tripped, it would cut power to a relay coil and shut the pump down. It would then require someone to push the little red button to reset the thermostat.

    Another option is to run a bleeder line out a few feet so that it always passes a gallon every five minutes or so... the would prevent the pump from ever heating up in the first place.
  5. kurtze

    kurtze Reporter

    Messages:
    4
    Location:
    West Michigan
    My system is lake fed and runs about 50psi. where would I get a thermal cutoff. I looked around the internet and didn't see anything.
  6. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,435
    Location:
    Houston, TX
    Why not just use a pump pressure switch and set it at 60 or so, then if it pumps into a closed output the switch will cut it off ?

    Most pumps have a thermal cut off built in.


    Good Luck.
  7. Murphy625

    Murphy625 Member

    Messages:
    150
    Location:
    Michigan
    Yup.. he could do that, but he'd have to wire the pressure switch to a latching circuit.. Otherwise, once the pump shut off and the pressure dropped, the switch would kick back in and start it back up again.
    A simple push-button, relay latching circuit could prevent this but most folks have no idea how to wire something like that.
  8. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    To elaborate on an earlier post, an existing thermal cutoff would be part of the motor protection, and not a device that reacts directly to water temperature in the pump. Those devices are expensive ($100 +) and not applicable to all pumps, due to how they attach to a pump.

    Strictly for the money, you would do better with a pressure switch, preferably in connection with a small pressure tank. Such a setup might require the use of an electric valve to protect the system mainline from 24/7 water pressure (aka a "master valve")
  9. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,435
    Location:
    Houston, TX

    I Agree with that, a tank would help a bunch.

    If it was me and I had a Piss Poor Controller, I would fix that first.


    Redundant is nice but should not be required in most applications, If everything is working properly.
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