Trying to determine well pump starting and run wattage for a future backup solution

[yyzhulk]

Hi all, I'm researching information so I can setup a solar charged, battery backup solution for my well. It seems that we get hit with at least 1 power outage per year and aside from our refrigerator, water is the biggest issue. These outages seem to last anywhere from 3 - 10 hours. I was hoping someone could help me estimate the start and run wattage. I find conflicting info on the required wattage and I would appreciate any help you can provide. Here is my configuration info:

Well pump type: Submersible
Well Depth: 462 Ft
Static Water level: 367 FT
GPM: 17 (1 hour test last year)

The Well is on it's own meter. Below the meter there is a box with 30 Amp breaker. Then below that is a 3 HP Franklin Electric Water Pump Control box (2823028110).

According to the control box it is:

3 HP
230 V
Single Phase
AMP 14.5
S.F. Max. Amp 17
KW 2.2
RPM 3450

The pressure switch runs for about 1 minute intermittently based on water usage at 30-50 PSI. If start and run capacitor numbers are helpful, I can provide those also.

Thank you for any help you can provide!

 

[hwy17]

Does the controller indicate what the exact pump model is?

I find another reference to someone who measured 74 LRA on their 3HP well pump. So you're probably in the 50-100 ball park.

Genset for well pump

Looking for a genset to power my deep well pump. Pump is a 3-wire 240v 3hp at 800 feet down the hole. LRA is 76A. Measured startup current with current probe and scope. Peak current was 98A ( for 5 cycles). I believe the peak current is converted to RMS by multiplying peak current by 0.707...

www.smokstak.com

I bet a Schneider XW would start and run it ok, without requiring the addition of a soft starter. I'm not sure which other inverters might start it too. Maybe 18kPV, maybe 6000XP, maybe some of the Solarks. Maybe an SW4048.

I would guess that total daily usage from the pump is not all that great, less than 5kWh or something. That's a gut feeling, not a calculation.

So your battery selection would also be limited by starting current more than capacity, if the battery was for the well pump alone. 1 Lifepower4 would not be able to start that pump on an XW, it would trigger short circuit protection. 2 Lifepower4's maybe ok, 1 Powerpro probably ok.

 

[DIYrich]

The rule of thumb is 3x running amps for startup. 17 amp running, implies 51 amps startup. SF Max is the max continuous running amps (about 4kW). You would think the KW 2.2 is 2.2 kW running watts.

 

[yyzhulk]

Does the controller indicate what the exact pump model is?

I find another reference to someone who measured 74 LRA on their 3HP well pump. So you're probably in the 50-100 ball park.

Genset for well pump

Looking for a genset to power my deep well pump. Pump is a 3-wire 240v 3hp at 800 feet down the hole. LRA is 76A. Measured startup current with current probe and scope. Peak current was 98A ( for 5 cycles). I believe the peak current is converted to RMS by multiplying peak current by 0.707...

www.smokstak.com

I bet a Schneider XW would start and run it ok, without requiring the addition of a soft starter. I'm not sure which other inverters might start it too. Maybe 18kPV, maybe 6000XP, maybe some of the Solarks. Maybe an SW4048.

I would guess that total daily usage from the pump is not all that great, less than 5kWh or something. That's a gut feeling, not a calculation.

So your battery selection would also be limited by starting current more than capacity, if the battery was for the well pump alone. 1 Lifepower4 would not be able to start that pump on an XW, it would trigger short circuit protection. 2 Lifepower4's maybe ok, 1 Powerpro probably ok.

Thank you for all the great information! I don't know the actual pump model. The pump was installed before I purchased the property back in 2015 and the controller was a replacement back when the old one failed in 2018. The well guy replaced it at the time, though from what I have learned over the years, I probably could have just replaced some of the components a lot cheaper. I now keep backup capacitors and contactors. This would be only to power the pump.

 

[yyzhulk]

The rule of thumb is 3x running amps for startup. 17 amp running, implies 51 amps startup. SF Max is the max continuous running amps (about 4kW). You would think the KW 2.2 is 2.2 kW running watts.

Thank you for the formula! This is very helpful Maybe the 2.2 is based simply on the HP? 750 x 3 = 2.250

 

[hwy17]

Thank you for all the great information! I don't know the actual pump model. The pump was installed before I purchased the property back in 2015 and the controller was a replacement back when the old one failed in 2018. The well guy replaced it at the time, though from what I have learned over the years, I probably could have just replaced some of the components a lot cheaper. I now keep backup capacitors and contactors. This would be only to power the pump.

I'm a bit of a one track mind, so these are the only two inverters I think of in any case: The Schneider XW and the Midnite Rosie.

Both I think have a very good chance of successfully serving your well pump's surge, but both might be a bit overkill too just for that purpose, they could probably serve the well pump and most of your house loads too.

 

[yyzhulk]

Thank you, I'm definitely going to consider on of those. I like the setup of the battery recommendation using Lifepower4 as well. The server rack seems ideal for adding/removing batteries. In the hypothetical situation of running both home and well, I'm curious as to how I would wire the inverter for two transfer switches. Home and well are on two different meters on a power pole adjacent to each other; separate weather heads. I have a few power stations for backup in the house which are more than adequate for things we commonly use in an outage, which isn't really much.

 

[MichaelK]

I think it might be appropriate at this point to suggest a course change. Yes, you can build a solar system that can power your well-pump, but at this point I'd question instead as to whether you should power it with a solar system? This is for outages that might occur once or twice a year? It might be more economical and straightforward to have a standby generator ready to start rather than the solar system just sitting there 363 days out of the year.

At my own homestead, I've been powering my 1hp pump for years now, solely on solar. I'm using Schneider's XW+ 6848, which has performed flawlessly. I'm not quite sure though that a single 6848 is enough to power your pump though. Look at this chart....

Assuming a starting surge of ~18500W, I think two 6848s in parallel would work. But, a dual 6848 system is going to be REALLY BIG. I think you could put it together at a DIY cost of ~15,000$, but do you really want to invest 15k into something that sits there 363 days of the year.

If you think you want to go off-grid completely, then I think that's fine, and very doable, but as a blackout only system, I'd say that's a bit of an over-investment. I think it would be money better spent investing in a stand-alone generator if it's fired up only a few times per year.

 

[yyzhulk]

Thank you for all the info. This is where I get back to conflicting information. In previous replies it was determined that the running amps are approximately 2.2 kW which I believe is based on horse power being about 746w x 3(HP) = approx 2.2kW as it states on the sticker of the control box. From previous responses it was determined that a Midnite Rosie could handle the starting watts. I'm going to run some tests with a multimeter to see if I can get more accurate numbers. Can you help me understand the discrepancies between the calculations? Assuming the cost of the the inverter, batteries and other components from other replies, it seems it would be significantly less. I get what you are saying about costs but I'm still weighing what it's worth it to me for convenience and I won't know the definitive costs until I get the numbers right.

 

[42OhmsPA]

You could use a clamp meter capable of reading inrush current to determine the starting surge.

Have you considered adding a holding tank and booster pump? You could use a much smaller inverter to power the booster pump and get you through outages.

Welcome to the forum.

 

[MichaelK]

In previous replies it was determined that the running amps are approximately 2.2 kW which I believe is based on horse power being about 746w x 3(HP) = approx 2.2kW as it states on the sticker of the control box.

NO!!! These numbers are absolutely NOT correct. The 3hp value is the power OUTPUT of the pump motor, NOT the power input. Please go back up to post #8 and look carefully at the numbers posted for a 3hp pump.

My recommendation at this point is stop asking for people's opinions, and start making real measurements of your own pump yourself. Having hard data on what your actual pump needs is where you should start.

You need a clamp meter that can read AC starting amps, or commonly what is referred to as inrush amps. A regular AC clamp is not fast enough to catch the starting surge, that lasts maybe 500 milliseconds or so. An inrush meter will. The one I've been using recently and recommend to others is the UniT216C. It can measure DC amps, AC amps, and ACinrush. You can find this meter on Ebay for ~80$. Get it. I compared it side by side to a much more expensive Fluke inrush meter, and they match each other to less than 1%.

Once you have real numbers to base decisions on, you can weed out the lesser inverters. Schneider's 6848 is a VERY robust low-frequency inverter, and it has a VERY long surge capacity of 60 seconds. But, it's rated at 12,000W for 60 seconds, not 18,500W. Don't buy anything else until after you've completed your pump measurements. Then we can help you design a system that is not going to choke, and let you down.

 

[Stephen InGeorgia]

I have a 1.5hp well pump with a 3hp controller that I run on a 6kw 24v low frequency inverter. My pump used 43% of the inverter load so it looks like 2600w running. I think you need to find out what the power requirements are for the pump to make the correct assessment. Reach out to me if you want specifics on my system. You could probably get rid of the meter and same the cost with the right system.

 

[wpns]

Yeah, measure first, and then (re)design for what you really want/need. A generator that sits for 363 days probably won't start, a special purpose solar power (or even battery backup) inverter will cost a fortune, there are unanswered questions (why separate meters, can you consolidate to one meter and put an AIO in the house to reduce your power bill and backup the entire house during power failures, what's your timeline and budget, etc).

 

[yyzhulk]

NO!!! These numbers are absolutely NOT correct. The 3hp value is the power OUTPUT of the pump motor, NOT the power input. Please go back up to post #8 and look carefully at the numbers posted for a 3hp pump.

My recommendation at this point is stop asking for people's opinions, and start making real measurements of your own pump yourself. Having hard data on what your actual pump needs is where you should start.

You need a clamp meter that can read AC starting amps, or commonly what is referred to as inrush amps. A regular AC clamp is not fast enough to catch the starting surge, that lasts maybe 500 milliseconds or so. An inrush meter will. The one I've been using recently and recommend to others is the UniT216C. It can measure DC amps, AC amps, and ACinrush. You can find this meter on Ebay for ~80$. Get it. I compared it side by side to a much more expensive Fluke inrush meter, and they match each other to less than 1%.

Once you have real numbers to base decisions on, you can weed out the lesser inverters. Schneider's 6848 is a VERY robust low-frequency inverter, and it has a VERY long surge capacity of 60 seconds. But, it's rated at 12,000W for 60 seconds, not 18,500W. Don't buy anything else until after you've completed your pump measurements. Then we can help you design a system that is not going to choke, and let you down.

No worries. I'm not running out buy a bunch of stuff and commit to anything yet. I haven't bought a thing. I'm just gathering information. I'm looking at a variety of options, superficially battery backup looked like a good option. Asking for opinions such as yours has been helpful so I will continue to do so. I fully intend to get actual measurements. Seeing how people arrive at certain numbers gives me better context to what those numbers may mean rather than just recording measurements and then going shopping. Thanks again

 

[yyzhulk]

I have a 1.5hp well pump with a 3hp controller that I run on a 6kw 24v low frequency inverter. My pump used 43% of the inverter load so it looks like 2600w running. I think you need to find out what the power requirements are for the pump to make the correct assessment. Reach out to me if you want specifics on my system. You could probably get rid of the meter and same the cost with the right system.

Thank you for the offer! I will likely want to pick your brain for more info.

 

[yyzhulk]

You could use a clamp meter capable of reading inrush current to determine the starting surge.

Have you considered adding a holding tank and booster pump? You could use a much smaller inverter to power the booster pump and get you through outages.

Welcome to the forum.

Thank you. My current meter doesn't record inrush so I'm definitely going to grab one of those. I have been researching a holding tank option and how I would integrate that into my existing system.

 

[yyzhulk]

Yeah, measure first, and then (re)design for what you really want/need. A generator that sits for 363 days probably won't start, a special purpose solar power (or even battery backup) inverter will cost a fortune, there are unanswered questions (why separate meters, can you consolidate to one meter and put an AIO in the house to reduce your power bill and backup the entire house during power failures, what's your timeline and budget, etc).

Thank you, will do.

When the well was established (long before I bought the property) the original intention was to have it be shared among 3 houses. There are a lot of properties like that around here (3 to 1 well). I have a unique case where the other two neighbors never connected to the system.

Now the price for the infrastructure to deliver water to their properties (we are all on 5-7 acres out here) costs more than just having your own well drilled. Long story, short, I bought out their water rights very cheaply and they drilled wells.

The separate meter was so we could all split the bill easily and have an account that all parties could access. I don't know the cost of having the power company come out and integrate into one meter so that would be another area of research.

My timeline is not set in stone. I'm just researching all options. A backup system for water is the most critical and then keeping my two refrigerators running. In past power outages a couple power stations run most things I actually need.