Residential pump house backup

[0260n4s]

I realize this question has probably been posted before, but I am such a newbie that I cannot be confident that my understanding of the replies are accurate, and it's difficult to pull the trigger on a system without the confidence that it will work for my needs.

We are grid-tied in a rural area without city water. We have an underground well that supplies water via a 1500W motor mounted in an external pump house, which gets plenty of light in Southeastern US. Not long ago the power went out for three days after a hurricane, and we were left collecting rainwater off the roof just to flush the toilets. Not wanting a repeat of that, I'd like to have a solar-powered backup system to keep our water flowing.

Ideally, we'd stay grid-tied, but automatically switch to solar/battery backup during power outages. However, since the system pressurizes and still supplies water for a short time without power, it's perfectly acceptable to have to run out and plug it into a offline system manually. OR if we can have consistent, reliable results, we don't mind it being run entirely from solar...that might even save some money.

Is there a particular link, DIYSolar video, or other "everything you need" suggestion to accomplish this?

Thank you for your help and I apologize for being such a newb!

 

[Rednecktek]

The cheap and simple answer is to wire up a propane generator and transfer switch for use in emergencies. Propane lasts forever in the tank and a manual switch and socket to a generator are pretty simple to install and have low paperwork overheads.

The next option requires doing some math and gets pretty expensive quick. What you'll need to know is:

What is the startup surge on the well pump?
220v 3-wire or 110v 2-wire?
Does it have any kind of soft start?
How long does it need to run to top off the tanks?
How many times a day does it run for that long?
Do you want it completely separate from the grid or just an over glorified UPS with a huge battery bank?
How comfortable are you with doing the wiring?
How many days of power outage do you want to plan for?
How much sunlight do you get in an average month?
Do you have the physical space for the equipment?
Will that space ever be below freezing?
What's the budget?

All those questions will help narrow down the best solution for your needs. To answer question 1 you'll probably need an amp-clamp meter with inrush settings to see what it spikes at. After that most of it comes down to math and a basic power audit.

Prepare to have your mind stuffed to overflowing with info and welcome to the forum!

 

[0260n4s]

Thank you for your reply. I'm not really looking to buy the bare minimum I need, so having such a fine-tune calculation seems a little overkill. Let's say have a 115V/16.1Amp pump supplying a residential house of 3-4 people with average use, including watering grass, in an area with mostly direct sunlight 10 hours per day (the pump house roof angles East in Southeastern US with no blocking trees). We want more than enough to keep it running off-grid. We have a budget of $2,000-2,500. The unit would likely be mounted in the pump house which has reasonable space for the equipment and doesn't get below freezing. I'm okay with wiring; I just want to know what to buy. Is that possible?

 

[sunshine]

We have an underground well that supplies water via a 1500W motor

How deep?

 

[Rednecktek]

The runtime and surge loads are a major factor as those will determine the size of the inverter and the capacity of the battery bank. If you're on a hard budget it gets a little more difficult and there are some places you can skimp to save money you'll need for other parts that you really can't skimp on.

For the napkin math, you're looking at about a 2KW draw on the inverter which will need a Low Frequency inverter for, budgeting a 3KW so you have extra head space and surge capacity is going to run you about $800.

At 2KW of draw on a 24v inverter, with inefficiencies you're looking at about 2400Wh which would be a 100Ah 24v (or 2x 12v 100Ah in series) PER HOUR of run time. If you go the LFP route without freezing protection that's going to be about $700 of battery PER RUNNING HOUR of pump. You can save cash here by going the FLA route but it takes more space and requires maintenance, but you can get 5700Wh of FLA from WalMart for about $800 that will get you 2 hours of run time.

National average for USABLE sunlight (as in it's bright enough and direct enough to be effective) is about 4 hours, you might get 5 at best with East facing panels since they're not going to do much in the afternoon, so figuring that in you're roughly looking at 500w of panel to recharge 1 hour of run time. 2 hours of run time a day will need 1000w of panel, and so on. If you can find used panels you can get theat as low as $0.25 per watt. Double that for winter/rainy weather.

Once you figure that out you'll be able to figure out how big your charge controller needs to be but let's rough in about $600 for a 100A charge controller of decent-but-not-stupid quality.

Fuses, wires, etc will add to that, but call it $300 for rough napkin math. Remember that FUSES ARE CHEAPER THAN FIRES and don't skimp out here.

So, doing rough napkin math without a proper audit, and going cheap where you can, used panels, lead acid batteries, etc and you're looking at:

Batteries 2880Wh Usable: $400
Controller 100A Mid-Grade: $600
Inverter 3Kw/9Kw Surge Pure Sine: $800
2000w Panels used: $500
Wire & Fuses: $300

Total: $2600 rough napkin math.

Doable? Probably if you only need 1-2 hours of runtime per day. You can see where doing the proper power audit and getting the info really makes a difference in the system.

 

[0260n4s]

Wow. I really thought solar was better than that. If all I can get is 2 hours, I might as well just buy a 55-gallon drum and a few drops of bleach to keep me flushing toilets, sponge bathing, and washing dishes for days.

I really thought a 200 AHr battery attached to 1000W of solar panels for at minimum 5 hours/day would do me just fine. At 16.1 Amps, the grid-charged 200 AHr battery would give me over 12 hours, which I'm not realistically using each day. The solar panels would provide 5,000 Watts/day to recharge 2.5 hours of usage per day, so it would be days or even weeks before I fully depleted the battery bank. That was just my inexperienced understanding, which is why I posted.

The YouTube channel "DIY Solar Power with Will Prowse" shows several all-in-one, complete packages. I thought someone might point me to one of his videos and just say, "buy this and you're golden." Wishful thinking, I guess.

 

[Rednecktek]

Wishful thinking, I guess.

It's all wishful thinking until you learn about math and weather.

Check your local CraigsList for 255gal food grade totes, they're usually pretty cheap and a LOT more capacity than a drum.

Watts are like grams, it takes a LOT to accomplish much and most people only see the 5000 and don't grasp how small a Watt really is. When you realize that a cheap LED light bulb running for a day is 225w it really clicks.

 

[tomy2]

if you have or can install a storage tank (1k gallons $800.) to pump into. you can use an Aquatec 24volt pump $100. that will pump to your house at 60 psi. it can run off a 200 watt panel and one 25 volt 50 AH battery for night use.,and an inline fuse. Then pump into a 50 gallon pressure tank ($300 to $500 ) then to the house. If you don't use your sprinklers, you should have enough water for four or 5 days without using the other pump.

 

[tomy2]

Wow. I really thought solar was better than that. If all I can get is 2 hours, I might as well just buy a 55-gallon drum and a few drops of bleach to keep me flushing toilets, sponge bathing, and washing dishes for days.

I really thought a 200 AHr battery attached to 1000W of solar panels for at minimum 5 hours/day would do me just fine. At 16.1 Amps, the grid-charged 200 AHr battery would give me over 12 hours, which I'm not realistically using each day. The solar panels would provide 5,000 Watts/day to recharge 2.5 hours of usage per day, so it would be days or even weeks before I fully depleted the battery bank. That was just my inexperienced understanding, which is why I posted.

The YouTube channel "DIY Solar Power with Will Prowse" shows several all-in-one, complete packages. I thought someone might point me to one of his videos and just say, "buy this and you're golden." Wishful thinking, I guess.

your math is wrong, a 200 AH 12volt lithium battery will only supply less than 1800 watts for an hour. a lead acid battery much less. If your pump is drawing 16 amps off 110v, it will require about 1800 watts per hour. so your one battery will only run that pump for one hour at night. Remember that your battery is 12volt and your pump is probably 110-120 volt.

 

[0260n4s]

Yeah, totally didn't factor in the battery being 12V.

 

[0260n4s]

Aren't there people out there powering their whole house with solar?!? Like, central A/C, refrigerator, hair dryers, water heaters, etc. I'm just wanting to power one pump that works intermittently. It just seems this shouldn't be so impractical. Do the guys powering their houses have an entire solar farm in their backyard and roofs with massive arrays of batteries?

 

[pvdude]

We have a submersible 240 volt 1hp well pump that fills a pre-charged pressure tank.
It takes about 60-90 seconds of "pump on" to fill the tank. Pump cycles about 4-6 times in 24 hours.

Hurricanes and drunk drivers take down power here, and we have no other
easy source for water.

I put in 16 solar panels, a 6.8kw inverter, breaker panels, switchgear, charge controller, FLA batteries.

To start the well pump requires about 10kw (inrush current) and to run the pump requires 1800 watts.

Batteries are just enough for overnight, and will run some other loads (lights, refrigerators, etc)

No sell-back to the utility.

I think it was around $11k for all the components for the version 1.0 of this system.

(I have since expanded the system, so as to run more things - heat pump, pool pumps, etc.)

 

[camelCase]

Another option is a few hundred gallon poly cistern tank buried in the back yard that is fed from your well. If the power is out, a cheap, low amp 12v pump would be plenty to pump water from it.

 

[0260n4s]

Thanks, everyone, for the suggestions.

 

[Rednecktek]

Aren't there people out there powering their whole house with solar?!? Like, central A/C, refrigerator, hair dryers, water heaters, etc. I'm just wanting to power one pump that works intermittently. It just seems this shouldn't be so impractical. Do the guys powering their houses have an entire solar farm in their backyard and roofs with massive arrays of batteries?

Basically? Yes. Many people also have to come to the realization that they're asking too much of a system when they want to have all electric appliances AND run off-grid. Somewhere there has to be some give and take and they have to be willing to pay through the nose for a system that can do it.

Huge panels covering entire roofs and back yards, multiple inverters in parallel, running as much as possible on propane/wood heat/wind/etc, and stacks and stacks of batteries.

It helps to think of Watts like Grams. It takes a LOT to do a little work and nobody is going to get ripped and totally swol with 5000 gram weights.

 

[tomy2]

We have a submersible 240 volt 1hp well pump that fills a pre-charged pressure tank.
It takes about 60-90 seconds of "pump on" to fill the tank. Pump cycles about 4-6 times in 24 hours.

Hurricanes and drunk drivers take down power here, and we have no other
easy source for water.

I put in 16 solar panels, a 6.8kw inverter, breaker panels, switchgear, charge controller, FLA batteries.

To start the well pump requires about 10kw (inrush current) and to run the pump requires 1800 watts.

Batteries are just enough for overnight, and will run some other loads (lights, refrigerators, etc)

No sell-back to the utility.

I think it was around $11k for all the components for the version 1.0 of this system.

(I have since expanded the system, so as to run more things - heat pump, pool pumps, etc.)

that set up would be enough to run my whole house and well pumps. When changing to solar on a well, the first thing to look at is your pumps and how they store and move the water. Pumping straight into a pressure tank creates a lot of unnecessary head. pumping into a storage tank and then a booster pump to your pressure tank would require a lot less power. and a grundfos slow start pump would really help. I run mine off 2 200 watt panels and 2 100AH lifepo batteries for the booster pump at night. and I still have abundant power in my shop in the day. The system cost under 3k including new pumps.

 

[tomy2]

Aren't there people out there powering their whole house with solar?!? Like, central A/C, refrigerator, hair dryers, water heaters, etc. I'm just wanting to power one pump that works intermittently. It just seems this shouldn't be so impractical. Do the guys powering their houses have an entire solar farm in their backyard and roofs with massive arrays of batteries?

I hear you, when I started looking into going solar on my well, I got designs and estimates from two suppliers. They both called for $4k-$5k systems. The ticket is to change your pump to a slow start, 6 or 7 amp 120v pump. Then you can run it off 400 watts of panels and 2 12v 100AH batteries for night. A storage tank would be a big plus also.

 

[camelCase]

The typical American house is wired with 200 amp service from the grid in order to be able to run ovens, ranges, microwaves, dryers, well pumps, furnaces, etc. concurrently. That's 24 to 48kw depending on the mix of 120 and 240 volt power used. The typical residential solar installation is a small fraction of that, even at peak sun. If you don't have a gigantic system or are not backed up by grid power, large compromises in terms of peak load have to be be made and large electric motors are a significant load, both static and peak.

 

[luckielab]

I'm just wanting to power one pump that works intermittently. It just seems this shouldn't be so impractical.

It may not be so impractical, but with only "rough napkin math" done because the answers to questions below aren't known, nobody knows for sure.

What is the startup surge on the well pump?
220v 3-wire or 110v 2-wire?
Does it have any kind of soft start?
How long does it need to run to top off the tanks?
How many times a day does it run for that long?

@pvdude's reply was interesting to me. Looks like his pump runs for about 10 minutes total a day and if I was guessing, the startup surge (inrush current) was probably one of the biggest challenges for the design. If your pump works with a soft start, that may not be as big of a challenge for you.

 

[Phantom]

I don't know if this helps , I have a well pump I run 24/7 on solar , 300 foot down in the hole.
I have

6 100 watt solar panels ( 140 foot run from panels to charge controller) $ 100.00 each
1 epever 60 amp solar charge controller 150 max input voltage ( this is more then what I needed ) $ 221.00
2 sok 12 volt 100ah lifepo batteries set up in series to give me 24 volts $ 560.00 each
1 aims 4kw split phase 24 volt inverter $ 1,200.00
electric panel box with 60 amp breaker and assorted wires and bus bars aprox. $ 300.00 - $ 400.00

the well pump is 240 volt 3 wire
I put the well pump wire as a 240 - 3 wire plug , made 2 receptacles for the pump plug , one is wired grid one is wire solar
I have had it in the solar plug for about 2 months and have had NO problem with it keeping the water pressurized and the
batteries have never run down to fully discharge yet , and that's with 3-4 days of rain off and on here in Northern New England.
grant you its still a lot of learning , what size wires , what kind of buss bars , what kind of lugs for the wire , circuit breakers , fuses
etc. Mostly I learned from you tube , Will , and still learning here on this forum . I hope this helps you decide.
Here is a pic of my stuff just not the solar panels or the electric panel box.