(2) 1/2hp motors on ST3 head?

[BruceM]

I wonder if I could start a 2nd 1/2 HP motor (boost pump or washing machine) with my ST-3 head with one already running?  I can do some power management so that they both don't start at the same time. 

Is this doable or am I dreaming?

Bruce M
Metro 6/1
Snowflake, AZ

[mobile_bob]

is the first motor running at rated load? or part load?

also depends on what type of motor each are, some have very heavy starting currents

so starting a 2nd with high starting amp requirment while the 1st is running at full load might cause the voltage to droop
to the point of causing the 1st to drop rpm and go into the start winding and compile the problem.

only one way to find out, try it, and monitor closely what is taking place

bob g

[BruceM]

First load 1/2HP submersible well pump, running at rated load.  Second load 1/2HP capacitor start jet pump.  I haven't picked the latter so if someone can suggest a low starting current model that would be good.  Manufacturers don't build the motors- so just say the usual 4-5x the rated current for starting current.  Not enough customers savy enough to generate start current plots, so it's a big crap shoot.

[rgroves]

First load 1/2HP submersible well pump, running at rated load.  Second load 1/2HP capacitor start jet pump.  I haven't picked the latter so if someone can suggest a low starting current model that would be good.  Manufacturers don't build the motors- so just say the usual 4-5x the rated current for starting current.  Not enough customers savy enough to generate start current plots, so it's a big crap shoot.

Bruce, are you committed to an AC jet pump for the 2nd load?   You could go DC, small battery bank, and low amp battery charger without overtaxing the ST3.  All depends on how much water and how much depth you have to work with.

Russell

[BruceM]

Long story, but until there's a brushless DC boost pump I can modify to reduce EMI on, I'm stuck with an AC boost pump.  There's an expensive "solar" rotary vane model with a permanent magnet AC motor option with allegedly lower start up current.  I may have to go that route, though it is low output and the rotary vane pump (Dankoff) doesn't have the best reputation for durability. 

A DC linear piston pump with electronic drive (piston with permanent magnets attached, external coil over non ferrous cylinder) seems obvious for high effeciency off grid boost pumps, but nothing like it is on the market. 

I could adapt a brushless DC motor to a rotary vane or other type pump if I could find a suitable motor.

[rgroves]

Long story, but until there's a brushless DC boost pump I can modify to reduce EMI on, I'm stuck with an AC boost pump.  There's an expensive "solar" rotary vane model with a permanent magnet AC motor option with allegedly lower start up current.  I may have to go that route, though it is low output and the rotary vane pump (Dankoff) doesn't have the best reputation for durability. 

A DC linear piston pump with electronic drive (piston with permanent magnets attached, external coil over non ferrous cylinder) seems obvious for high effeciency off grid boost pumps, but nothing like it is on the market. 

I could adapt a brushless DC motor to a rotary vane or other type pump if I could find a suitable motor.

Not sure if this would work for you, but Dankoff makes a piston pump called the Solar Force that is extremely durable, moves a lot of water on little power, and is available in both DC and AC. Claimed to have a lower starting surge in AC model.   It's available a lot of places, but here's one example:

http://www.scsolar.com/Piston_and_Suncentric_Pumps.html

rg

[Jim Mc]

...Not enough customers savy enough to generate start current plots, so it's a big crap shoot.

Yep, it is a crap shoot.  Why not just give it a try - nothing to lose, really.  Nobody on this board is going to be able to give you a definitive answer.  Sounds like you already know it, but capacitor-start motors have a big advantage over split phase motors (lots of washing machines use split phase motors) 

[BruceM]

Thanks RG, Jim.  I've looked at he solar force piston pump with appreciation, but over $1000 for a boost pump that would still be AC is pretty painful.  I need lots of water for grading and compacting on my building site so may just go with a cheap jet pump for now, and will see how it goes.

SquareD is now carrying some soft start controllers for small AC motors.  That might help if needed, too.

[Tom]

There is another pump. I am using using a Grundfos SQ Flex Solar jet pump. It is soft start AC 90-250V or DC 30-300V (same pump!) and it uses about 50% energy to pump the same amount of water. On my system I'm running about 300' of lift 6 GPM and using about 450W. The cost of the pump was a grand. Time will tell as to how durable it is.

[BruceM]

Tom, I didn't know Grundfos made a SQ FLex type jet pump.  Or are you talking about the submersible type SQFlex pump?  If it is a jet type (not in the well), please give me a link or a model number.  It's so new I can't find it even on the Grundfos web site.

Thanks,
Bruce

[Tom]

Oops, I meant submersible, here is a link http://store.solar-electric.com/grsqpu.html On my installation the pump is installed in a tank laying almost horizontal on the bottom. This is permissible based on their instructions. This link happens to mention its use on a diesel generator, what a coincidence!

Are you boosting from a tank or just line pressure?

[BruceM]

Hi Tom,
I'm pumping up a pressure tank from a 2000 gallon storage tank.  I didn't know you could use the SQFlex on it's side- that's helpful to know.

The SQFlex has good reliability reports here in our rural area. I agree it's a heck of a pump.
-
Grundfos needs to work on their EMI.  I checked one out at nearby home.  It radiates a lot of high frequency noise back on the power line (and out to the solar panels).  I might be able to use one in my steel tank- the tank would act as an EMI shield, I could have IMC conduit leaving the tank, and I'd just have to filter heck out of the power between it and the battery bank/solar panels.