Grundfos Float Switch

SystemSystem Posts: 2,511 admin
I recently used a Grundfos float switch in a storage tank being filled by a SQ Flex subpump. I installed a CU200 smart box as well through which the float switch shuts off power to the pump when the tank is full. It's a 5,000 gallon tank and at the time of the installation the shallow well was producing only 1/2 gal/min. I verified everything was working and went on my merry way. Several months later I got a call from the contractor that will be building a home at this remote site and was told that water was coming out of the CU200. Long story short, the pump did not shut off when the float switch went into a vertical position and the tank eventually filled to the point water was entering the float switch wire conduit and going into the CU200. It's a helical rotor pump and apparently they don't let water flow back into the well, so the water had continued to rise pass the fill pipe and into the conduit. Has anyone heard of these float switches sticking? The CU200 is still operational, but the display on the front cover no longer works and the whole thing will have to be replaced.

Comments

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,029 ✭✭✭✭✭
    Re: Grundfos Float Switch

    If it is a mercury float switch they are hard to get failures from. I would ask the person who designed it (was it you?) why they did not design for future failures?

    One of the hard parts of building in remote sites is having enough time to sit back and think out failure modes. All the planning and just getting things to the site can leave you short for the big picture. When it gets really busy, slow down or get help!

    Good Luck!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • sneauysneauy Registered Users Posts: 1
    Re: Grundfos Float Switch

    This comment is late considering how far back your post was originally made, but I experienced a similar problem with the SQ Flex continuing to pump even though the tank was full. I didn't experience the flooding of the CU 200 so I was lucky but I guess such a thing could have happened if I didn't have a junction box outside my tank where water could spill out of when such overproduction occurred. I was able to isolate the real problem as not being the float switch but actually the CU200 not reading the circuit as closed when the tank float was in the full position. My understanding is that a closed float switch tells the pump to turn off and open position tells it to pump. The retailer took my CU 200 back under warranty, verified that I was correct and replaced it. I had originally thought the float mechanism was the culprit but it was actually the CU200. Again, too late to help you at this point but if it happens again, you might remember my experience and get a new CU out of it.


    Pete&Sun wrote: »
    I recently used a Grundfos float switch in a storage tank being filled by a SQ Flex subpump. I installed a CU200 smart box as well through which the float switch shuts off power to the pump when the tank is full. It's a 5,000 gallon tank and at the time of the installation the shallow well was producing only 1/2 gal/min. I verified everything was working and went on my merry way. Several months later I got a call from the contractor that will be building a home at this remote site and was told that water was coming out of the CU200. Long story short, the pump did not shut off when the float switch went into a vertical position and the tank eventually filled to the point water was entering the float switch wire conduit and going into the CU200. It's a helical rotor pump and apparently they don't let water flow back into the well, so the water had continued to rise pass the fill pipe and into the conduit. Has anyone heard of these float switches sticking? The CU200 is still operational, but the display on the front cover no longer works and the whole thing will have to be replaced.
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