Grundfos MQ3-35

[jlapva]

Hi all, My Grundfos MQ3-35 has stopped working. Water is flowing through the pump but the pump doesn't kick on to boost. When I unplug from electricity and replug it in the pump turns on and pumps as normal for about 15 seconds and then turns off. Since the pump pumps fine for that short time I'm assuming it is fine mechanically and the problem must be with one of the sensors or the electronic brain. Does anyone have any experience with this issue? Is it the flow sensor? I am capable mechanically and electrically to repair but don't want to guess and buy the wrong parts of I can avoid it. Would appreciate any assistance. Thanks.

 

[Valveman]

It is always one of the sensors or the electronics. The pump/motor itself is no different than any other "dumb' pump, which are very reliable and long lasting. If you want something reliable and long lasting, get a regular mechanical pressure switch to control a dumb pump and water will reliably come out the faucets when needed. Even the constant pressure control can be done without any electronics by using a Cycle Stop Valve. I like electronics, but not controlling my water because it is not reliable. Put the MQ in the Dumpster where most end up much too soon.

 

[Sponsor]

 

[Valveman]

Get a regular shallow well jet pump and a PK1A to control it and you won't be wasting your time on forums trying to get your water back to working.

 

[jlapva]

Thank you Valveman for your reply. I am using the pump just to boost pressure from city water to provide enough boost to handle irrigation system an a 2 floor 4 bedroom home. Not a well situation. Using the MQ3-35 as a booster pump. Any thoughts on how to identify the electronic component?

 

[Valveman]

You just need a Shallow well jet pump as they work great as a city water booster as pictured above. I am capable of getting way off into the weeds on the electronics. That is why I know it is best to ditch the electronics and stay all mechanical, again as shown in the diagram above.

 

[jlapva]

Thank you sir!

 

[Fitter30]

https://www.google.com/url?q=https://api.grundfos.com/literature/Grundfosliterature-5271306.pdf&sa=U&ved=2ahUKEwiW2d3UkqqGAxUVmYkEHa7UBjYQFnoECAsQAg&usg=AOvVaw1amJVZdfs7ZumFeS4T_oPS

Look at fault chart

 

[jlapva]

https://www.google.com/url?q=https://api.grundfos.com/literature/Grundfosliterature-5271306.pdf&sa=U&ved=2ahUKEwiW2d3UkqqGAxUVmYkEHa7UBjYQFnoECAsQAg&usg=AOvVaw1amJVZdfs7ZumFeS4T_oPS

Look at fault chart

Thank you Fitter 30. I think I will replace the Flow Sensor and see if that corrects the problem.

 

[jlapva]

Hi all, I wanted to post an update to my original post above where I stated my problem with the Grundfos MQ3-35. I appreciate the input from everyone. Just in case anyone else has the problem I outlined, I wanted to let you all know that I made an educated guess and replaced the flow sensor and my pump is now working perfectly. I had no luck finding any posts anywhere with the problem I was having so I wanted to put this up for others to see if they are having issues. The flow sensor was a $113.00 educated guess vs diving right in with a pump replacement at $1200.00 - $1500.00. I hope this helps someone else. Thanks again all.

 

[Valveman]

Glad you got it working. There are threads from way back talking about the problems with the flow sensor. The problem is very commonly the flow sensor. Flow sensors and pump systems that use them are unreliable that way. A faulty flow switch is usually all it takes for someone to just swap out the pump. Not too many people who would/could replace a flow switch. That picture of a Dumpster full of MQ's I posted earlier could probably been fixed with a flow switch or something similar.

I am afraid it is just a temporary fix as it will happen again, or something else will go wrong. A lot of times when the flow sensor fails the water cooled motor gets hot, which shortens its life as well. But the dumb motor and pump parts are the most reliable parts. It is the flow switches and all the electronics that keep it from squirting water out of your faucet when you need it. All the best though, and thanks for the update!

 

[Fitter30]

Wonder if pulling the pump filling it with vinegar through the primer fitting. Cork both supply and return turning the pump different positions so everything gets wet turning every 30 minutes for 2 hours. Drain and flush it. Priming holds 1.2 gallons.

 

[AgentT63]

Hello all, new member here...first post. I'm trying to boost pressure in my home that is on city water. I have a 1" metered service with 40 lbs of pressure. I would like to get around 80 lbs. There is not pressure regulator on my main supply line and the pipes are clean. City provides and average of 60 lbs, but I'm 150' off the street where the city main runs and meter lays. I like Valveman's recommendation, but I'm concerned that there won't be enough flow on the supply side. How can I check this before investing in a system just to find out I don't have the volume needed? I think Valveman is recommending a J15S jet pump. Is that overkill for my system? I have a 2200 sqft home with 3.5 baths and 4 people living here. Also, there is a detached granny flat in the future that I would like to add to the equation. Thanks

 

[Valveman]

The J15S maybe a little overkill volume wise, but it is a good pressure builder and the CSV will make it work down to as little as 1 GPM. Test the city main by opening a large valve or several hydrants at the same time. Measure how much water is coming out and check the pressure while this is happening.