Question about Grundfos JPS4 1 HP Pressure Booster Pump

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Grundfos pump Pump sometimes dose not turn off. If you turn the power off and on it pumps up to pressure and turns off

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It sounds like you have a bad pressure switch. I would also check the pre-charge pressure in the expansion tank. This needs to be 2lbs less then the "cut-in" pressure of the switch IE: 30-50 switch 28lbs air in pressure tank.

Posted on May 14, 2013


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Posted on Jan 02, 2017

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SOURCE: My Grundfos JPS4 1 HP Pressure Booster Pump keeps coming on for a

Definately sounds like a leak in the pipes from the pressure side of the pump onwards, even the smallest leak will cause it to turn on to regain adequate pressure.

Posted on Jul 09, 2009

  • 1 Answer

SOURCE: Grundfos UPS 25-50 180 - start up

These days it happened to me but it was an electrical problem, but mechanical..When you loosen the center screw, you should try to turn the pump house with the help of a screwdriver (to the right and left) in turn means that the water was blocked by limestone, which is unlocked after you do water to pass through screw without to see if it turns on its own. The water that comes out is very little if it works then closes the screw .. good luck

Posted on Nov 06, 2009

  • 16 Answers

SOURCE: my grundfos pump auto-reset light

check air press in built in tank.

Posted on Dec 08, 2009

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SOURCE: New grundig pump is now making a kind of clicking

I was ready to pass your question and go to the next person because you said it was making a clicking, and I could not relate or diagnose that type of sound for that kind of pump. Thank God I decided to read to the end where you said rattling sound. that is what you should have said in the beginning.
1st, did you replace the pump cartridge or the whole pump unit? 2nd, is the pump in a different oriented position than the original pump position? The inner cartridge floats inside the pump as it rotates and if it is in an oriented position that allows it to bounce (to & frow) it will make this rattle sound; not serious but can be annoying. It is was a replacement cartridge, perhaps the new gasket and the old gasket are in place, thus allowing too much space for the cartridge and it therfore moves too much and rattles. Or, if it was replaced as a whole new unit. there is a problem with it that you should not be responsible for, except for the positioning orientation. Finally, if there is still too much air in the system, the air bubbles will jossle the cartridge untill you get rid (bleed ou ) the remaining air. Goodluck<Macgivor

Posted on Jan 02, 2010

  • 1 Answer

SOURCE: Grundfos Pump Wont Stop Running

Close the outlet valve then turn electrical switch on manual for a few seconds until any air is pushed out then open the valve and return electrical switch to automatic.

Posted on Aug 01, 2010

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2 Answers

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.

Nov 02, 2013 | Grundfos MQ3-35 3/4 HP Pressure Booster...

1 Answer

Grundfos runs intermittently and needs power cycle to get going again

What type of pressure switch or pump controller on pump? Could be capacitor check. with power on try spinning fan at rear if starts probably cap. Have it checked. Could be controller faulty.

Jan 27, 2013 | Grundfos Pumps Grundfos MQ 3-45 1 HP...

1 Answer

I have a grundfos in house circulation pump that does not work. in a new home and do not have manual. is there a reset swicth

We all call those little jobs pumps but they are actually just circulaters. Sometimes older pumps that have been turned off for a while get stuck. Sometimes even new ones need a little help because the motors are so low power (Energy Efficient). "Grundfos" pumps have a screw on the back. Its about 1/2 inch in diameter and usually silver color. Remove the screw counter clockwise. A little water may drip out so be prepared. You will see a screw driver slot in the opening. That slot is in the stator of the motor that drives the impeller of the pump. Turn that screw in the direction the pump is suppose to turn while it is powered and if it is not bad, it will start. Let me know if it fails to start and we can move on to testing. Please vote. Roger

Apr 13, 2011 | Heating & Cooling

1 Answer

My water heater needed to be restarted and my comfort recirculation system isn't working now.I"m hoping it is just the timer. I need to reset the timer and I don't know how. I can't find my manual....

Grundfos timer and pump operate by plugging into ordinary 120V outlet.

1) If outlet has power, then dial on timer should rotate.
If dial is not rotating, then check power to outlet.

2) If outlet has power, but timer is not rotating then timer has gone bad > if grundfos pump is working but timer is not working, you can buy cheap plug-in timer and use that as the timer.

3) If outlet has power and pump is not working, then manually rotate timer dial to see if pump will start.
If pump will not start, then you need a new grundfos.
There are no repair parts for these pumps, and nobody at Fixya has reported taking Grundfos apart and repairing it.
My Grundfos pump will not come apart.

4) Following link has links to Grundfos installation manual, website, product manuals, and contact.

5) To set timer: Grundfos timer dial has movable pins that are used to set on-off times.
When pins are pushed out, timer turns pump ON.

6) Rotate timer dial clockwise until current time lines up with arrowhead located on inner dial.
Dial rotates as time passes, and pins move a lever that turns pump on-off.

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Feb 09, 2011 | Grundfos Comfort System Recirculator ...

2 Answers

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

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.

Jan 04, 2011 | Grundfos JPS4 1 HP Pressure Booster Pump

1 Answer

I have a grundfos mq 35 pump to boost pressure in my hot and cold system. due to loss of water recently pump ran dry and shut down. when water returned the system was restarted and pump reset. we now get...

There was possibly some damage done to the pump while it was operating dry and it in now not able to deliver the required flow of water. Pumps wear very quickly when allowed to run dry, even for a short time.

Jan 02, 2011 | Grundfos JPS4 1 HP Pressure Booster Pump

1 Answer

House pressure water pump has to be reset to

it sounds like a relay for the auto shut off ....

Jan 16, 2010 | Grundfos MQ3-35 3/4 HP Pressure Booster...

2 Answers

My Grundfos JPS4 1 HP Pressure Booster Pump keeps coming on for a


Apr 27, 2009 | Grundfos JPS4 1 HP Pressure Booster Pump

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