Drake,
As a normal CYA, I'll always gently let a customer know that this
(or any) particular combination of inverter and load sometimes
proves incompatible, just in case the unexpected happens. (We once
had a MS4448 that would not reliably start and run a condensing
boiler; a switch to a different boiler resolved the issue.)
Having said that note of caution, I wouldn't give it any concern.
3/4 HP and 1 HP well pumps have never been an issue; I would
expect 1.5 HP to be easy to run. At 2 HP I'd be asking these
questions here.
You might check that it's a 3-wire, capacitor-start motor, but
nowadays nearly all are. Two-wire pumps (with no control box) can
add 50% to the surge.
The Magnum has a fairly poor voltage regulation response.
Sometimes the AC voltage can drop to ~80 VAC momentarily. So you
might also caution your customer that the lights may flicker when
the pump starts. In our home we know whenever our Kenmore fridge
turns on.
Allan
Allan Sindelar
[email protected]
NABCEP Certified PV
Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy,
Inc.
505 780-2738 cell
On 7/2/2014 8:17 AM, Drake 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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