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Pump temperature?

Discussion in 'Irrigation' started by mx315, Sep 23, 2009.

  1. mx315

    mx315 LawnSite Senior Member
    Posts: 394

    I had a call Friday from a guy that wanted some heads moved. I went by to take a look and he gives me the rundown of what he wants done... no big deal, except his front yard has 14 heads (7 rotors & 7 sprays) running on a 1hp pump. The last guy to work on it has the pressure switch cranked down so the system is operating at 78 lbs and cutting out at about 85. The pump is so hot that you could fry an egg on it. I told him that I would make some changes and see if I could get the pressure down, so the pump wasn't working as hard. I got it down to a operating pressure of about 62 and cutting out around 70. That's all I could get it to down to without cycling. I went by this morning to check it out and the pump still seems to be running really hot. I told him the best option would be to split front zone and add some of it to a small zone from the side of the house. But my main question is, How Hot is too hot? What temp range should it be running in, so it doesn't damage the pump?
    thanks
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,442

    I sure hope this isn't a single-stage pump.
     
  3. mx315

    mx315 LawnSite Senior Member
    Posts: 394

    Yep, 1hp Sta-rite jet
     
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,442

    I would want a 1 hp jet to be running in the 40-50 psi range, give or take. Thing is, if the outflow increases to lower the output pressure, the pump is working harder to lift more water. What happens if you manually open two zones? Can the pump run without cavitation if it delivers more water?
     
  5. mx315

    mx315 LawnSite Senior Member
    Posts: 394

    He has one zone in the back with 4 rotors, but somebody wired it to run with one drip zone in the front to keep it from cycling. He has another back zone with 8 sprays and has it wired to run with a different drip zone. They are running fine together, but you can tell that it's running high pressure. The drip line is doing alot more than dripping! I've listened to the pump and don't hear any cavitation, only short cycling issues because of the big difference in zone sizes.
     
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,442

    I'm talking about cavitation with two zones running. I wonder if this pump was a replacement for a smaller one, with the kind of imbalance you describe.
     
  7. hamham

    hamham LawnSite Member
    Posts: 62

    Is it the motor or the volute that is hot?
     
  8. mx315

    mx315 LawnSite Senior Member
    Posts: 394

    Boots, It's just a really bad install job... he's had problems since day one. I didn't run two of the main zones by themselves, I will when I go by this afternoon.
    It looks like he's been trying to work on it too. I saw alot of irrigation parts in the garage when I was checking out the controller.

    Ham, The motor is getting hot. It's so hot you can't lay your hand on it for more than a second or two.
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,442

    Sounds like there would be some point in considering a smaller pump. Or a complete re-nozzling.
     
  10. mx315

    mx315 LawnSite Senior Member
    Posts: 394

    I think I'm going to work on splitting that front zone and tying it into the smaller one, then see if I can get the pressure down to normal.
    Thanks for the input
     

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