cu301 with larger pressure tank?

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by shaun, Jan 25, 2009.

  1. shaun

    shaun New Member

    Jan 25, 2009
    Hi All,
    I have a 5 year old cu301 with SQE pump. It was installed when the house was built. At the time, I did not know any better regarding the long term reliability of this system vs. a "normal" well system with a large pressure tank.

    I have not yet experienced any of the problems that others on this forum have discussed regarding the CP system. So far, mine works nicely (knock on wood).

    The current problem that I have is that when the power goes out, I have very little water in that tiny little pressure tank. I do have a generator that I can hook up to the well system for longer power outages, but a typical power outage in my area is 1-4 hours, which is not really long enough to warrant dragging out the generator and plugging it in... It is really frustrating not being able to finish a shower when power goes out.

    I am wondering if I can simply buy a large pressure tank and hook it up in place of the 2 gallon unit that came with the original CP system... I would expect to have to adjust the PT pressure and possibly the CP system pressure on the cu301 (it is currently at 60psi).

    I am unsure if swapping out the 2 gallon PT for a larger PT would cause any issues when the pump is controlled by the cu301 and result in pre-mature failure...

    Since the CP system has not failed yet, I don't want to totally replace all the control parts (CSV, pressure switch, etc...).

    Has anyone else ran into this issue before? What would your advice be?

  2. speedbump

    speedbump New Member

    Jul 15, 2005
    Water well and pump tech.
    Riverview, Fl.
    If your talking about a bladder tank. The biggest one out there will only hold 40 gallons or less. That's not much of a shower should you be lucky enough to catch it when it's totally full. If you want storage, you would have to go with an atmospheric type tank and pull from it with another pump.

  3. Sponsor

    Sponsor Paid Advertisement

  4. valveman

    valveman Cary Austin Staff Member

    Mar 15, 2006
    Pump Controls Technician
    Lubbock, Texas
    Bladder tanks are worthless for water storage, and even more so with a variable speed system like the Grundfos SQE with the CU301 controller. To get any water out of a pressure tank, there needs to be a pressure bandwidth like 40/60 PSI. The SQE with the CU301 controller has very little if any pressure bandwidth like 47/53. It is basically a set pressure so you get very little if any water from a pressure tank. I also believe that the larger tank size will cause problems with the pressure transducer system, like not letting the pump shut off when it should.

    If it will work at all, you can put about 20 PSI air in a big pressure tank, which will give you "some" water when the power goes off. However, it is very likely that the water will have been sitting in that tank for so long, that it shove stale and contaminated water into your pipes when you do this.

    If the power goes off that often, you need to put the generator on a switch or a plug, so it is easy and quick to use. I am guessing that this pump is for house use only and you do not have sprinklers, heat pump, or anything that uses much water. With very light duty, I have seen these type systems last 5 to 7 years. With normal duty, they usually don't last that long.
  5. Mr.Nice_Guy

    Mr.Nice_Guy New Member

    Nov 21, 2008
    That is correct. Putting a larger pressure tank on the system will cause the SQE to not shut off as quickly [if at all]. With an SQE there really is no bandwidth to speak of... the tank merely provides enough flow to allow the pump to come up to speed. With a CSV you won't have a large enough tank either.

    Your only option is to do what Valveman said and use a switch for the generator.
  6. shaun

    shaun New Member

    Jan 25, 2009
    Thank you all for the advice. I think I will simply get the generator wired up. :)
Similar Threads: cu301 larger
Forum Title Date
Pumps and Tanks Well Forum & Blog. Water is life. Grundfos cu301 Jun 13, 2017
Pumps and Tanks Well Forum & Blog. Water is life. Fixing a Grundfos CU301 Jun 15, 2014
Pumps and Tanks Well Forum & Blog. Water is life. grundfos cu301 for irrigation--VFD? CSV? Homeowner at wit's end part 2 Sep 6, 2012
Pumps and Tanks Well Forum & Blog. Water is life. grundfos cu301 for irrigation--VFD? CSV? Homeowner at wit's end Aug 30, 2012
Pumps and Tanks Well Forum & Blog. Water is life. Replacing cu301 controller Aug 9, 2012

Share This Page