Running 220v pump from solar

cummins13

I know that similar questions have already been asked, but mine is slightly different. I would like to be able to run 1.5 hp, 220v pump with batteries, an inverter and solar, to fill a tank. The pump would only need to be run about 30 minutes per day, and not necessarily all at one time. How large an inverter, how many batteries, and how much solar capacity would I need.

inetdog

How much volume are you pumping and against what head pressure?
The pump is rated at 1.5HP but may not actually be drawing that full power when pumping.

ldiorio

hi
have the same situation-have a 240volt pump down 140 feet
just installed a magnum 4400 watt(48V) inverter, 8- 415ah Fullriver 6V AGM batteries and 6-255 watt panels w/classic 150CC

have run the pump with no problem-inverter handles the initial surge ok

still a lot to learn about operating the system -setting paramneters--levels of battery discharge etc
lou
PS see if you can measure the AMP draw from the pump that will tell you how big the inverter should be

BB.

Welcome to the forum Cummins13.

Very difficult to design a "cost effective" system to run such a well pump for a short period per day. Just a really quick rule of thumb design:

• 1.5 HP pump would need about 5x running current (guess at 2,000 watts to run) to start... Near 10 kWatts.

Very roughly, you would need a minimum of:

• 5 kWatt AC inverter
• 500 AH @ 48 volt battery bank (to support starting surge current)
• 2,000 Watt minimum (5% rate of charge) Solar array based on battery bank size

If you go with some other battery chemistry--For example LiFePO4 type with very high surge current ratings... Call it a 1x Capacity (pretty high discharge rate):

• 10,000 Watt surge * 1/0.85 AC inverter eff * 1/46 volts minimum voltage * 1.0 discharge rage = 256 Amp peak surge ~ 256 AH @ ~48 volt Li battery bank minimum based on surge current
• ~2,000 Watt load * 1/0.85 inverter eff * 0.5 hour per day operation * 1/48 volt batter bank * 1/0.50 discharge of battery bank = 49 AH @ 48 volt Li battery bank minimum (based on energy used)
• ~2,000 Watt load * 1/0.52 system eff * 0.5 hours per day * 1/3.0 hours of sun minimum = 641 Watt array minimum for Li based battery bank

The above numbers are very rough... But close enough (within 20% or so) of the accurate numbers (just using rules of thumbs and minimum hours of sun per day) to give you some idea of sizing such a system.

Now, the alternative... Get a small pump and run it for 2-6 hours per day directly from solar panels... This is also known at "slow pumping". As long as you have sun, then you pump. Use a larger water tank to "store energy" for bad weather. If you need water during the deep winter (no sun, bad weather), a backup genset will usually be more cost effective than trying to do it with a battery bank (adding batteries increases the cost of power by something like 4x--Plus batteries only last 3-8 years or so--for typical batteries).

A "solar friendly pump" is not cheap (probably $2,000 to $3,000 for a ~900 Watt Grundfos pump).... But they are very good pumps and will last you many years with little in the way of maintenance (no batteries to monitor, no batteries to fill, no batteries to replace after X years, no charge controller+AC inverter that need to be replaced every 10_ years, etc.).

Grundfos Solar Submersible Well Pumps (SQF family direct from solar panels--expensive. SQ family is AC only, but much more solar AC inverter friendly).
http://www.solarpumps.com/pumpintropage.html
http://www.solar-electric.com/wind-and-water-products/sodcwapu.html (more solar pumps)

There are alternatives to use with standard induction motor well pumps (VFD--Variable Frequency Drive) which can give you soft start and variable speed (RPM) control. And if you change the pump to a 3 phase pump, VFD drives can work very nicely with those type of motors... VFDs are pretty nice and can be pretty AC inverter/Battery system friendly, but do have their issues too.

BB. wrote: »

Re: Working Thread for Solar Beginner Post/FAQ

Some discussions about VFD (Variable Frequency Drives)... Basically a variable frequency inverter with (typically) three phase output. Used to soft start motors (handy for 3 phase well pumps, or pumps with well head starting capacitor) and can also turn an AC motor into a variable speed motor (very handy for pumping applications).

WELL PUMP and Inverter QUESTION
Wind/solar for large scale pumping etc (out of my depth!)
could use knowledge - using Gould jet pump - transfering from 230vAC to ? DC (new link/thread 10/27/2012)
Help required to design off grid system (information on possibilities to connect "standard VFDs direct to solar panels) (new link 1/13/2013)

-Bill

Note, pumps like the Grundfos pumps, more or less have internal/integrated VFDs inside them.

And there are now companies beginning to offer VFD's with "solar panel" front ends--Has made a very nice solution for many parts of the world where cost of pumping (electricity, fuel, support equipment) is expensive.

LiFePO4 (or similar chemistry) batteries may work out OK for you... But Li batteries tend to be pretty expensive (2-4x the cost of lead acid) and are a bit on the "bleeding edge" of technology (you will have to do a lot of self education to design/maintain your own system). Not to scare you away--But be prepared for lots of questions and details if you choose this path.

In the end, you probably need to do a few paper designs (different choices) and see what works best for your needs.

I will stop typing here--Questions?

-Bill

CALLD

1.5hp is roughly 1250watts so my guess is you will probably need at least a 2500w inveter with a 5000w surge capability to start it. Seeing as it only needs to run 30mins a day without any other loads you can get away with a smallish AGM battery bank (24v, 200ah). You need a high-rate battery like an AGM/Gel battery to support the high surge currents. Seeing as you only need about 1kwh of power per day to run it you can probably get away with a 600w array to cover it most days. I'm basing my assumption that there are no other loads and that the pump running 30mins per day is all that the system needs to run.

waynefromnscanada

We should be careful when giving advice, not to assume the 1.5 HP refers only to power consumption, and not actual motor shaft mechanical output after all internal motor losses.
Every pump I've dealt with has or have had motors rated for mechanical output, and watts consumption is left to fall where it may.

mike95490

CALLD wrote: »

1.5hp is roughly 1250watts so my guess is you will probably need at least a 2500w inveter with a 5000w surge capability to start it......

750w / hp is only an engineering calculation. Real life readings on my 1/2 hp pump show 1.000w consumed. There are many losses involved, look for the Locked Rotor spec for your pump, and that will be close to the surge your inverter has to supply. And there is Power Factor and other losses too.

CALLD

mike95490 wrote: »

750w / hp is only an engineering calculation. Real life readings on my 1/2 hp pump show 1.000w consumed. There are many losses involved, look for the Locked Rotor spec for your pump, and that will be close to the surge your inverter has to supply. And there is Power Factor and other losses too.

We are all just guessing here - since getting my first power consumption meter I quickly realised nameplate consumption specs and actual consumption specs were hardly ever the same. The first thing I noticed was how little all my electronic appliances actually use! My 42" flatscreen TV only uses 100w on average compared to the 130w stamped on the nameplate at the back, whats more in standby mode it uses almost nothing compared to the 50% often quoted by hippies and tree-huggers.

When it comes to motors it really depends on so many things.
My 3-speed fan specified at 85w uses 80w on maximum, 70w on mid and 65w on low
My 2 refridgerators use between 70-130w each depending on the ambient temperature, much lower than the 170w stamped on the nameplates - however they can pull nearly 1000w on start-up.
My 14,000btu/hr airconditioner can pull anywhere between 600w to 1800w depending on the ambient temperature (hotter weather = more demand), the nameplate says it uses 1150w, start-up power is less than 2000w.

So motors are funny things, induction motors are the most efficient. Start-up currents can be ridiculously high as with my fridges or just a little higher as with my airconditioner. Power consumption depends largely on how much work they need to do - a stalled motor can be as bad as a short circuit. Variable speed controller's like on my fans don't really reduce power consumption significantly and I've noticed the motors just run hotter when the speed is reduced...