4kw-12kw pure sine wave inverter does not power up deep well pump

dougahole

The original intention was to have the Honda 7000 as a backup to the system including auto start. (see previous post re inverter not recognizing generator power) My 4kw-12kw split phase pure sine wave inverter does not power up deep well pump But when I researched the spec of the inverter it showed that it supported a 240v 1 hp pump. I now recognize that we should have installed a soft start pump but I would like to know if there are any other more cost effective alternatives.

mike95490

What is your battery voltage ?   Are the cables sufficient ?    Is the pump 3 wire or 2 wire ?

here's the generic starting specs, I use a 6kw 48V inverter & 800ah battery to power a 1/2 hp pump.  It's a quality inverter and has had no issues for 10 years.  Power Factor can eat up some of your inverter capacity, different brands of inverters deal better with poor PF.

dougahole

Thanks for your response. We are investigating  your points. 1, system battery voltage is 24 v; 2, battery to inverter may be under spec, will investigate and most probably change; 3, pump is 3 wire, 1 hp 350' down

MichaelK

This is a problem with designing based on paper specifications.  What you find in the real-world is that paper sometimes does not match reality.  What you should be doing is actually measuring the startup and running amperage of your particular pump.  I have two clamp meters that can read "inrush current", a Fluke, and a UniT.  I've found that the far cheaper UniT gives me readings within 1% of the more expensive Fluke.

https://www.ebay.com/itm/UNI-T-UT216C-600A-Digital-Clamp-Meters-NCV-LCD-Test-ACDC-Auto-Range-Multimets/333683530820?epid=710119969&hash=item4db1169c44:g:wfEAAOSwiKpfM1PL

Is your 4000W inverter the Conext 4024?  That has a maximal 100ms surge of 41amps. What I've found with my Grunfos 1hp pump is that the starting surge is 37-38amps, in line with the chart the other Mike is posting.  For my own system I have Schneider's XW+6848, which handles the surge of my pump just fine.

For now, here's what you can look at.  Get the UniT clamp meter and DETERMINE what your real-time startup surge is.  Also measure the voltage of the battery just as you try to turn on the pump.  If your battery is too small, or the battery to inverter cables too thin, the inverter is not going to get the required amps to start the pump.  Also, make sure you have at least 2000W of incoming solar at the time you switch on the pump. 

Ultimately, you may find that your system is just too small to handle the pump.  I could recommend two different options.  If you do indeed have the Conext 4024 you could either parallel it with a second 4024 powered by it's own panels and battery, or go to 48V and utilize a XW+ instead.  What I can tell you is that my 1hp pump is also 3-wire, 380' down, and my 6848 starts it without complaint every single time.  I'd say you're better off upgrading your system to power the pump, rather than changing the pump to match the system.