Well pumps and SWs [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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Ken,

Kurt says no problem 3/4HP pump on SW5548, but it will cause a big 
dip in the voltage every time it starts. The lights in the house will 
dip -- fluorescents especially.

And, regarding the option of using a constant-pressure pump, this 
helps in one way -- it uses a variable speed motor system with 
soft-start. That's good. But, it runs MUCH longer time periods. 
Rather than run at full speed only, then stopping, it spends lots of 
time running at reduced speeds to balance against water demand. Not 
only does this add extra running time, but the efficiency is lower at 
reduced speeds. It's a little like using light using a light dimmer 
-- less power during slow running, but at lower working efficiency. I 
have not observed a constant-pressure pump in actual use, but I 
believe it is a very poor choice for energy efficiency. If any 
wrenches have some experience, please chime in.

Windy


At 11:55 PM -0500 10/16/03, sunwise wrote:
>Ken wrote:  The well driller said it needs the 240V all the time for the
>sensor.  
>
>
>Hey Ken -- Perhaps a very small inverter (with high efficiency at low
>power levels/idle current) powering the sensing circuit, with it pulling
>in a relay connecting the pump to the inverter/transformer?
>
>I'd say you'd have no problem with running the 3/4 horse pump off the
>SW5548.  None.  Regards to pressure switches, on a pump that size, I'd
>parallel (twice the current at 120vac) the 2pole contacts in a Square D
>pressure switch and use it to power up the primary side of the
>transformer with the secondary side wire directly to the pump.
>
>One other thought.  Are you sure they need a 3/4 horse pump and if a 1/2
>horse will work (not a real deep well and no irrigation going on), a 120
>volt pump might work very well and moe efficiently.
>
>Kurt Nelson
>SOLutions
>
>
>2. A 3/4 HP - 3 wire motor and 7 gpm pump. Does anyone have experience
>STARTING a pump like this with a SW5548?
>
>Any other suggestions?
>
>
>
>Ken & Chris Hulet
>Engineering Services Co.
>P.O. Box 4
>Blanchardville, WI 53516
>
>608.523.3726

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