What inverter size would run this well pump? Please check my math and logic :)

[Davester]

I know watts is amps multiplied by volts. I'm hoping to spec my first inverter large enough to power my deep well pump.

Here is my confusion. and the label says...

115/230 volt
MaxLoad Amps 9.9 / 4.95

Why the 2 voltages? Am I assuming correctly that the MaxLoad amps are 9.9 on 115volt and 4.95 on 230volt?

I'm attaching a photo of the label and the wires entering the relay. I'm assuming 2 of the 4 wires are power in at 110/120 volt, and two wires out of the relay are 11/120 volt as well.

9.9 times 115 = 1138.5 watts

I know initial draw on startup is high so I have to over-spec. Will a 2000-watt inverter suffice? 3000-watt?

Thanks for any advice. Want to be prepared for hurricane season. When we lose power it can be down for weeks. This isn't for a permanent set-up, but rather for grid down situations.

Any advice would be appreciated.

Thank you.

 

[Mattb4]

Never assume, measure it . You could be wired for 240vAC. However with this being a 1/2hp pump you should be able to power it with a 2000w inverter if the voltage is correct. I power my 1/2hp 120vAC water pump with my 3000w (24vDC) without problems. But understand that not all 2000w inverters are equal. Many of the mobile ones out there are pretty iffy when it comes to actually reaching rated output.

It does help if you have higher battery voltage (24vDC or 48vDC) and heavy duty cables.

 

[Davester]

The fuse on my panel that is labelled 'water pump' is a single 20 amp glass fuse, so I'm pretty sure it is 110/120 volt.

I see a 4000 watt (8000 watt peak) inverter on Amazon ($500 Canadian Dollars) with 4 AC outlets. I'm worried the 4 outlets are only going be only 1000 watts each (2000 watts peak) and will it fail to drive my pump which requires 1138.5 watts. Is my math and reasoning correct?

Good idea on measuring the load. I'll borrow someone's clamp amp meter and check it.

Your 3000 watt inverter ... is it 2 plugs? Maybe 2 1500 watt outlets. I wish the Amazon listings showed the per plug information

Thank you!

 

[ampsarus]

There is only one inverter circuit inside, all of the receptacles are wired parallel.

 

[Mattb4]

The fuse on my panel that is labelled 'water pump' is a single 20 amp glass fuse, so I'm pretty sure it is 110/120 volt.

I see a 4000 watt (8000 watt peak) inverter on Amazon ($500 Canadian Dollars) with 4 AC outlets. I'm worried the 4 outlets are only going be only 1000 watts each (2000 watts peak) and will it fail to drive my pump which requires 1138.5 watts. Is my math and reasoning correct?

Good idea on measuring the load. I'll borrow someone's clamp amp meter and check it.

Your 3000 watt inverter ... is it 2 plugs? Maybe 2 1500 watt outlets. I wish the Amazon listings showed the per plug information

Thank you!

You would want to check the outlet specs from the inverter. Though not lsited at Amazon you likely can Google up the manufacturer and get the full specs for them. They could be 15a or less. Most inverters you will want to look for will have a place (terminals) to hard wire for full amperage.

My inverter is built into a Off Grid AIO (All in One) and is hard wired only.

 

[OffGridForGood]

The two voltages and Amperages for the pump are because the pump moter has internal wiring diagram allowing either voltage to be wired. The lower FLA (full load amps) is for the 240v and the higher is for 120v.
The full load amps is not the same as In-Rush, and unless you have a meter capable of catching the max in-rush amps, most meters will not be quick enough to report the max in-rush amps actually required to start the pump motor.
The breaker being single pole tells you 120v, yes
the 20 amps on that breaker does NOT mean the in-rush amps is below 20 amps.
The breaker has a trip-curve (relationship between how many amps and for what duration) and this will allow an item like a pump motor to far exceed the 20 amps, for a very short time, without tripping.
A good quality inverter may also allow exceeding it's max output for a short time, a cheap one - not so much.
A number of members here on the forum have suggested x4 FLA or x5FLA as an estimate for in-rush on start up. But the reality is 'it depends', what is the back pressure on that pump, is it a submersible or is it a jet pump, is it new or old and tired with poor bearings that sucks lots of amps to get moving. All these things can have an impact.
I have a 1/3Hp jet pump that pumps from a tank in my cabin, the MPP2724 inverter (2700 Watts, 24 volt) runs this jet pump effortlessly with a 304Ah battery and 150A BMS, on 150A DC rated breaker.
If your planning 12volt DC, you will need double the DC amperage for starting a motor than the same set up with 24vDC.
Does this mean you can start your 1/2Hp pump with a 2000W inverter?
No, it doesn't tell you that.
You noted a $500CAD inverter, - The MPP2724 is about 418USD shipped, ($543 CAD), no guarantee it will start your pump. The 2724 is not capable of parallel connection of a second inverter.
The next size up MPP3048 (which can be paralleled to another one later to expand) is $475USD plus shipping $133, I would feel confident the 3kW MPP will start your well pump, but again it may depend on the battery behind that inverter, total pump resistance and that is unknown at the moment.
My 1Hp well pump at my home was able to start with a single MPP6048 and 200Ah battery supply. You can see the MPP options on Maximumsolar.online
Someone with a high quality multimeter (with in-rush measuring capability) will be able to get you some better information,

 

[Jimmy79]

The two voltages and Amperages for the pump are because the pump moter has internal wiring diagram allowing either voltage to be wired. The lower FLA (full load amps) is for the 240v and the higher is for 120v.
The full load amps is not the same as In-Rush, and unless you have a meter capable of catching the max in-rush amps, most meters will not be quick enough to report the max in-rush amps actually required to start the pump motor.
The breaker being single pole tells you 120v, yes
the 20 amps on that breaker does NOT mean the in-rush amps is below 20 amps.
The breaker has a trip-curve (relationship between how many amps and for what duration) and this will allow an item like a pump motor to far exceed the 20 amps, for a very short time, without tripping.
A good quality inverter may also allow exceeding it's max output for a short time, a cheap one - not so much.
A number of members here on the forum have suggested x4 FLA or x5FLA as an estimate for in-rush on start up. But the reality is 'it depends', what is the back pressure on that pump, is it a submersible or is it a jet pump, is it new or old and tired with poor bearings that sucks lots of amps to get moving. All these things can have an impact.
I have a 1/3Hp jet pump that pumps from a tank in my cabin, the MPP2724 inverter (2700 Watts, 24 volt) runs this jet pump effortlessly with a 304Ah battery and 150A BMS, on 150A DC rated breaker.
If your planning 12volt DC, you will need double the DC amperage for starting a motor than the same set up with 24vDC.
Does this mean you can start your 1/2Hp pump with a 2000W inverter?
No, it doesn't tell you that.
You noted a $500CAD inverter, - The MPP2724 is about 418USD shipped, ($543 CAD), no guarantee it will start your pump. The 2724 is not capable of parallel connection of a second inverter.
The next size up MPP3048 (which can be paralleled to another one later to expand) is $475USD plus shipping $133, I would feel confident the 3kW MPP will start your well pump, but again it may depend on the battery behind that inverter, total pump resistance and that is unknown at the moment.
My 1Hp well pump at my home was able to start with a single MPP6048 and 200Ah battery supply. You can see the MPP options on Maximumsolar.online
Someone with a high quality multimeter (with in-rush measuring capability) will be able to get you some better information,

I’ve been looking for a 1/3hp pump, can you please share the model? Thanks

 

[OffGridForGood]

My cabin jet pump is a Dayton stainless case shallow jet pump - since it just pumps from a tank to the cabin it doesn't have a lot of back pressure to contend with, I am pretty sure that helps the inverter during startup.

 

[McKravitts]

Someone in one of the above post may have already mentioned this but a Low frequency inverter can deliver a much higher starting current (inrush) and for a much longer time than the less expensive high frequency inverters.
I've also been looking for an inverter to handle a 3/4 hp deep well pump and many of the cheap inverters are getting very poor reviews.

 

[42OhmsPA]

Someone in one of the above post may have already mentioned this but a Low frequency inverter can deliver a much higher starting current (inrush) and for a much longer time than the less expensive high frequency inverters.
I've also been looking for an inverter to handle a 3/4 hp deep well pump and many of the cheap inverters are getting very poor reviews.

Not sure what cheap is to you but I switched from a 'cheap' LF to a 'cheap' HF, I had no issues with my 1hp well pump on either of them but the cheap LF caused a noticeable light flicker.
Lots of info here if you're bored.

4 MWh SRNE ASF48100U200-H 10kw.

Edit 4-12-24 4,000 kWh Edit 3-23 Current Settings. Edit 3-4-24 3MWh https://diysolarforum.com/threads/2-mwh-srne-asf48100u200-h-10kw.67809/post-1027777 Edit 1-2-24 2MWh AC output, close to 2MWh solar. https://diysolarforum.com/threads/1mwh-srne-asf48100u200-h-10kw.67809/post-966398 Edit...

diysolarforum.com

 

[ChrisG]

Measure your inrush. The numbers on the side of the pump is a small part of the equation. My old 1/2hp well pump ran at 1400 watts but needed 8600 watts to start it. I’ve since installed a Grundfos SQ deep well pump that is amazing with its slow ramp up.

 

[42OhmsPA]

Measure your inrush. The numbers on the side of the pump is a small part of the equation. My old 1/2hp well pump ran at 1400 watts but needed 8600 watts to start it. I’ve since installed a Grundfos SQ deep well pump that is amazing with its slow ramp up.

You definitely need to measure inrush. I was shocked and impressed to see ~40a per leg when I clamped mine.
My next pump will absolutely be a Grundfos.

 

[Jimmy79]

My cabin jet pump is a Dayton stainless case shallow jet pump - since it just pumps from a tank to the cabin it doesn't have a lot of back pressure to contend with, I am pretty sure that helps the inverter during startup.

I’m running a 1/2 hp now much like you do. Surprising how much juice they use. I’m along way from running my 2hp submersible…. Still dreaming though!

 

[McKravitts]

Not sure what cheap is to you but I switched from a 'cheap' LF to a 'cheap' HF, I had no issues with my 1hp well pump on either of them but the cheap LF caused a noticeable light flicker.
Lots of info here if you're bored.

4 MWh SRNE ASF48100U200-H 10kw.

Edit 4-12-24 4,000 kWh Edit 3-23 Current Settings. Edit 3-4-24 3MWh https://diysolarforum.com/threads/2-mwh-srne-asf48100u200-h-10kw.67809/post-1027777 Edit 1-2-24 2MWh AC output, close to 2MWh solar. https://diysolarforum.com/threads/1mwh-srne-asf48100u200-h-10kw.67809/post-966398 Edit...

diysolarforum.com

I should have used the word inexpensive.
Most of the inexpensive HF inverters that I've seen are single phase. The cost of one plus an autotransformer exceeds the cost of a SP HF inverter.
I already have a off grid inverter and just want an 220 SP inverter dedicated to the well pump and I don't want to pay more than I have to.
I'm open to any sugestions.