[RE-wrenches] Magnum and Pumps

[Larry Crutcher, Starlight Solar Power Systems]

If you have a clamp on meter that can capture inrush current (I use a Fluke 337 for this) you can get a good idea of the starting current needed.

One problem is that while backing up the house, you will likely have other loads operating when the pump starts which will decrease the available surge current. I would recommend using a stacked pair of 4448’s as a minimum if you have other house loads. 

Larry Crutcher
Starlight Solar Power Systems




On Jul 2, 2014, at 8:17 AM, Drake <drake.chamberlin at redwoodalliance.org> wrote:

Hello Wrenches,

We are hoping to use a Magnum PAE 4448 to back up a household that includes a 3/4 HP deep well pump. There is about 120 feet of vertical rise and about 1000 feet of horizontal distance. 

I have been told that there is a correlation between the locked rotor current of a pump and the predictable ability of a specified inverter to power that pump. 

The plumber who installed the pump left no paperwork and retained no records of what pump he put in the hole last year. He could only say it was a 3/4 HP pump. We are therefore unable to obtain the manufacturer's nameplate specifications.

The Magnum PAE 4448 has a 1 mS surge of 70 A (at 240 V) and a 100 MS surge of 40 A. According to the NEC Table 430.251(A), a 3/4 HP motor has a locked rotor current of 41.4 amps at 230 V. 

This inverter can surge at 35.4 A for 5 seconds. The specified battery bank will be 8 Full River  L-16 AGMs. Can anyone say if:
Is there enough information to know if this setup will handle the pump, and if so, will it?
How can an inverter's ability to power a motor or pump be calculated by knowing its locked rotor current? Which surge periods should be compared to the locked rotor current?
Does the surge current need to equal locked rotor. How long must the inverter meet its required maximum surge?
From experience with Magnums and pumps, does this seem like a good combination?

Thank you,

Drake 

Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV 
740-448-7328
http://athens-electric.com/ 
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