Grundfos CU301 retired

[Kent M]

I installed a new CSV1A and pressure switch today and retired the still (surprisingly) working CU301 V2 from 2003.  I bought a 60/80 switch and adjusted it to 60/75 and set the CSV1A to 70.  Everything is working as advertised.

For my own curiosity, I installed a pressure gauge upstream of the CSV1A to see what the back pressure was during pump running.  I was seeing around 155 psi.  Is that a fairly normal reading?  Kind of surprised that our 12 year old  SQE 15-250 (though I guess it's really just an SQ now) can produce that much pressure.

An interesting side note about the switch I bought:  It has a lever with labels Auto -> Start ->  Off.  Took me a while to discover that it would not run in Auto with less than 10 psi at the switch.  It's apparently a safety in case the well pipe completely ruptures.  To start from an empty pressure tank, one has to lift the switch to the Start setting to manually close the contacts until the pump builds the needed pressure for it to switch normally.

[Cary Austin]

I installed a new CSV1A and pressure switch today and retired the still (surprisingly) working CU301 V2 from 2003.  I bought a 60/80 switch and adjusted it to 60/75 and set the CSV1A to 70.  Everything is working as advertised.

For my own curiosity, I installed a pressure gauge upstream of the CSV1A to see what the back pressure was during pump running.  I was seeing around 155 psi.  Is that a fairly normal reading?  Kind of surprised that our 12 year old  SQE 15-250 (though I guess it's really just an SQ now) can produce that much pressure.

An interesting side note about the switch I bought:  It has a lever with labels Auto -> Start ->  Off.  Took me a while to discover that it would not run in Auto with less than 10 psi at the switch.  It's apparently a safety in case the well pipe completely ruptures.  To start from an empty pressure tank, one has to lift the switch to the Start setting to manually close the contacts until the pump builds the needed pressure for it to switch normally.

I am surprised the CU301 was still working as well.  Although it is a good thing you changed it out to a CSV before it left you out of water on some morning when you needed to get to work and didn't have time to be out of water.

Yes the 155 PSI is normal and a good thing.  Since you say it is a SQe15-250 and the backpressure is 155 PSI, I can tell you the water level in your well is about 62'.  If you had ask this question before and could have told me your water level was at 62', I could have looked at the pump curve and told you the backpressure would be 155 PSI.

Yeah those low pressure cut off switches need the lever held up until the pressure gets up to about 20 PSI, then they will work as any pressure switch.  They will help protect you if there is a break in the mainline or if the well is pumped dry.  But normally they are just a nuisance problem as you will have to manually start the pump like that after every power outage.

[Kent M]

I have a followup question regarding tank fill time.  When the demand has stopped, our pump only runs for about 30 seconds before shutoff pressure has been reached.  It is a 20 gallon diaphragm tank and the air pressure is ~ 56 psi.

The draw-down is 2.5 gallons, so I was expecting a 2.5 minute refill at 1 gpm.  The refill time from pump start (if I shut off the demand right away) is about 45 seconds.

Any ideas why the tank refill time is so short?  Thanks.

[Cary Austin]

2.5 gallons of drawdown with a 20 gallon tank at 60/75 sounds about right.  So with the CSV set at 70, it is only filling the last 0.8 gallons of the tank at 1 GPM.  So 45 seconds sounds about right.  That is really all the run time you need because as the CSV fills the last part of the tank at 1 GPM, the amps are reduced, the motor is cooling down, so it doesn't have to run the minimum 1 minute as it normally would if drawing full load amps.

But you can double the run time if you want by setting the CSV at 65 PSI or by upping the pressure switch cut off to 80 PSI.

[Kent M]

Thanks for the reply, Cary.  The run time of 30 seconds when demand is removed makes sense to me after thinking about it more - the tank itself is seen as demand until it, too, reaches the set-point of 70 psi on the CSV1A.  It only has to continue filling from 70-75 when the other demands stop.

The second situation is the one that has me somewhat flummoxed - tank is completely empty and no demand exists other than the tank.  The 45 second refill in that situation means an avg flow rate of 3.3 gpm.  Is the 1 gpm fill rate based on a certain pressure differential through the valve, rather than any type of metering action to maintain an absolute 1gpm flow rate?  If so, then I am assuming that our ~ 100 psi differential after pump startup must be higher than that used to estimate a 1 gpm fill rate.

I don't think it's a problem in either situation.  We might get an occasional extra cycle with the shorter fill time, but as you said, I could always back down the CSV1A set-point or bump up the cutoff setting on the switch, or both.

The valve has been working great!  I don't sense any difference in functionality between it and the CU301 it replaced, though I'm confident it will prolong the life of the pump and save a lot of money by eliminating the parasitic electric load.

[Cary Austin]

As the tank drains from 75 to 60 PSI you will get about 2.5 gallons of water.  So when the pump comes on the tank fills very quickly from 60 to 70 PSI because the CSV doesn't start working until 70 PSI.  Then when you stop using water the CSV only fills the last 0.8 gallons of the tank at 1 GPM from 70 to 75 PSI, which should only take about 45 seconds.

[Kent M]

Thanks again, Cary.  Somehow I had the idea that the valve was starting out at a 1 gpm setting from pump start.  Thanks for taking the time to clear up my confusion.

[Cary Austin]

The valve has been working great!  I don't sense any difference in functionality between it and the CU301 it replaced, though I'm confident it will prolong the life of the pump and save a lot of money by eliminating the parasitic electric load.

Glad you got it working like you want.  I do expect the CSV will increase the pump life compared to the CU301.  I have been telling people to wait until their CU301 controller quit before switching to a CSV.  However, I can now see where the CSV will  save maybe 100 bucks a year on electricity over the CU301 controller.  I never realized those VFD controllers used so much power when in standby mode.  And for some reason the company that makes the SQE with the CU301 and claims they save energy never mentions the power used when in standby mode.  I guess if everybody knew these VFD controllers used more energy in standby than when running the pump, it would be much harder to sell them. 

[Kent M]

I never was able to get an amp reading on the CU301 when it was installed.  If I did it now, it would only be what the CU301 was using and not anything that the SQE was using in standby mode.

The 40w reading that I saw before might only be a default lowest value, rather than an actual reading.  I never saw it deviate from that number when the pump wasn't running.  That seems like an awful large amperage draw just to do some powerline communication.  Regardless, I'm glad to see it replaced.

[Cary Austin]

You really need an RMS meter to check for power consumption on a system like that.  But here is a quote from another guy who purchase one of the little remotes that can track all that information.  I think it is pretty obvious that the SQE/CU301 unit is using about 40 watts when in standby mode.

Being somewhat of a techno nerd, I acquired an R100 remote a few years ago to be able to read the data stored in the pump.  As of 8/10/2015, here are the numbers reported by the system, with a few estimates of my own:

Power Consumption (kWh):  1,088*
Number of Starts:  176,471
Operating Hours:  1,016
Starts Per Op. Hr.:  173.7
Starts Per Day:  41.5  (4,248 days between 12/23/2003 and 8/10/2015)
kWh Per Day:  0.26

Estimated Gallons Pumped:  609,600   
Estimated Gallons Per Start:  3.5   
Estimated Gallons Per Day:  143.5

* The R100 reports a 40W load, when the pump is off.  If that is accurate, then an additional 4,000+ kWh of electricity were used in standby mode.  I need to measure that with amp meter to verify.  Pretty sad if true.

[Kent M]

I've seen that guy's comments...I wouldn't believe a thing he says!!! 

Since I never got a standby amperage reading, the 40w number I saw on the R100 remote is still questionable to me.  Not saying it isn't right, but I'd hate to be the source of misinformation if it's wrong.

You really need an RMS meter to check for power consumption on a system like that.  But here is a quote from another guy who purchase one of the little remotes that can track all that information.  I think it is pretty obvious that the SQE/CU301 unit is using about 40 watts when in standby mode.

Being somewhat of a techno nerd, I acquired an R100 remote a few years ago to be able to read the data stored in the pump.  As of 8/10/2015, here are the numbers reported by the system, with a few estimates of my own:

Power Consumption (kWh):  1,088*
Number of Starts:  176,471
Operating Hours:  1,016
Starts Per Op. Hr.:  173.7
Starts Per Day:  41.5  (4,248 days between 12/23/2003 and 8/10/2015)
kWh Per Day:  0.26

Estimated Gallons Pumped:  609,600   
Estimated Gallons Per Start:  3.5   
Estimated Gallons Per Day:  143.5

* The R100 reports a 40W load, when the pump is off.  If that is accurate, then an additional 4,000+ kWh of electricity were used in standby mode.  I need to measure that with amp meter to verify.  Pretty sad if true.

[Cary Austin]

LOL I didn't realize I was talking to the same person.

40 Watts would only be .17 amps at 230 volt.  Might be hard to get a reading with an amp meter.