SW2512 and pump problems [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

<x-flowed>Jack,

Kurt said:
>...it is my understanding that sub-pumps can actually draw
>more current when pumping at zero PSI to an open pipe than when
>"finishing up" at high PSI and not moving much water.

Yes. This is true for ALL centrifugal impeller-type pumps, regardless 
of sub or surface, AC, DC whatever. Also, motor start initial inrush 
current is due to the first instant of power being applied to a 
"locked" (stopped) rotor -- regardless of the load. The load will 
effect only the duration of the surge -- probably longer duration 
with open discharge!

>    I think inexpensive two wire
>pumps have a starter winding that should come on to get things going and
>if the starter winding is toast, the primary winding could be drawing
>lots more current on pump start-up.

The starter winding never cuts out, or else there is no separate 
starter winding at all (not sure) but I think that if there was 
winding damage, then it would not start at all. If the pump has not 
apparently changed since first installation, then I would assume pump 
is fine. Again, this surge problem is to be expected under your 
conditions.

Frank said:
>My experience with well pumps powered by inverters say not to use 2-wire and
>always use a pump controller. The controller softens up the start of the pump.

He's right about avoiding 2-wire pumps. To clarify, you cannot add a 
controller to a 2-wire. The controller is a part of a 3-wire system, 
it applies power to the start winding which draws too much current to 
stay in the circuit once the pump gets up to speed -- at that point, 
it switches it out.

I don't think there is anything trick you can apply to the 2-wire 
pump circuit that will make any significant difference, but ... 
anybody?

Windy

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