Question about Grundfos JPS4 1 HP Pressure Booster Pump

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Grundfos water pump is humming with no turning, if I take pump cover off and turn the shaft it starts?

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Sounds like it could be a blown capacitor in the motor. Disconnect from the power supply and remove the capacitor - it is usually situated undet the terminal box cover- examine it for leakage or distortion and replace it if necessary.

Posted on Jan 04, 2011

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Pressure pump sometimes stays on. If you turn the power off and back on the pump reaches pressure and turns off

Posted on May 11, 2013


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Posted on Jan 02, 2017

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1 Answer

My house pump is just making a humming noise when I turn it on?

replace the start/run capacitor on the pump
any electric motor repair shop will have a suitable replacement

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No water

Does the motor turn it self off after a couple of minutes of no pumping?= ran out of water. If there is water up to the pump and still no water, check filter/s ( if there is any). Undo V band and check pump internals, impeller may be broken from shaft? When putting back together tap V band with block off wood or back of screw driver evenly as you do up the clamp to stop it distorting

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Grundfos MQ3-35 hums loudly and does not pump. Alarm light does not go on. Pump seems "happy" but when a tap opens and the pump turns on, there is no boost in pressure and the pump just hums loudly......

Pump probably runs dry, try to fill up the pump with water a few times and see what it gives. If the pump heats up then the rotor is turning but no water moves, pressure is not building up. Pressure switch is maybe faulty. If you have the possibility to connect a pressure gauge after the dicharge you can see if the pressure is building up or not.

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Check the capacitor or the centrifugal switch.

Aug 26, 2013 | Grundfos MQ3-35 3/4 HP Pressure Booster...

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Grungfos JPF4 not pumping believe impeller stuck

Normally I disconnect the power and try to spin the shaft, I do not know this pump well enough to tell you how to get to the shaft. I would listen closely to the motor then turn it on, if it hums it probably has a bad start capacitor. These tend to fail quickly when the pump cycles a lot.

Aug 24, 2013 | Grundfos Pumps Grundfos JPF-4 3 4 Hp 230V...

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Just bought a house and it has a grundfos timer/pump attached at the hot water tank. I have no hot water and the timer doesn't turn (as I've seen other timers do). Is it supposed to turn so that the...

Grundfos is a sealed unit and not a repairable item.
The timer dial should turn.
And pins located around dial control ON-OFF functions as timer dial rotates.

Does the receptacle have power?
If receptacle has power, and Grundfos is not working, then it is broken.
Grundfos manuals for UP series pumps do not show breakdown or parts list of any kind.

Bigger question:
Why don't you have hot water?
Is water heater functioning?
Water heater is a separate appliance from Grundfos pump.
Grundfos pump circulates hot water from tank into the lines so there is no waiting for hot water ... but hot water heater should still make hot water.

Add a comment about water heater if that is also a problem.
You could have 2 problems, and water heater is main issue.

For do-it-yourself electric water heater repairs:

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1 Answer

My Grundfos MQ pump won't start after it has been idle for 4 to 5 weeks. It is installed at my weekend place in the country. This has happened several times. Pump was replaced once but problem...

There should be a small cap on the motor end of the pump, take that off and you will see the stainless steel shaft with a **** in it for a flat bladed screw driver. You should not need to turn the water off. A few drops might come out, but it's safe to do it that way. Turn the shaft with the screw driver and that should loosen up the pump.

Hope this helps.

Nov 04, 2010 | Grundfos Plumbing

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