Backup power for a community well

Hi Everyone,

My house is one of about 70 on a community water system. There are 3 wells, but 95% of the time, one well pump is operating to supply all the water. We tend to have 1-3 power outages that last from 1-8 hours each year. When that happens, we lose water fairly quickly. I’d like to come up with a solution that doesn’t break the bank.

Without looking at anything, I came up with the following options last year:

Option 0: Do nothing $0, but comes with outages

Option 1: Just a manual transfer switch (MTS) or interlock kit

Option 2: ~15 kW propane generator with automatic transfer switch (ATS)

Option 3: Replumb and put in a smaller emergency pump

Today, I toured the pump house with the Water Master (Sue) and saw the following (in probably too much detail):

There’s a 5hp, 60 GPM submersible pump, though it was flowing 71 GPM when it kicked on. It fills 3 pressure tanks in this pump house and ~20 in total (Sue thinks there are 2-3 pressure tanks in a second pump house and another ~15 in a third). If they’re each ~100 gallons that’s 2000 gallons or ~15 minutes to fill them all from half full to full. I was in there for ~20 minutes and it only kicked on after ~10 minutes for 3-5 minutes. Those number mostly make sense, though I’d like the ~15 minutes I calculated to be more equal to the 3-5 minutes I observed.

Anyway, the electrical box is 1 double pole 50A breaker for the pump and 2 20A breakers (for the light and the outlet they use for a heater to keep the tanks from freezing). The pumphouse is a cinder block , ~6’ by 6’ building with an insulated roof.PXL_20210408_221726774

From the electrical box it goes into the motor contactor and from there into the well.PXL_20210408_221537084 When I took the covering off that contactor box, this is what I saw, which I don’t totally understand:
PXL_20210408_221957582 PXL_20210408_222005203 PXL_20210408_222017035 PXL_20210408_222425278 PXL_20210408_222438549 PXL_20210408_222520396 PXL_20210408_222523213 PXL_20210408_222535306

My guess is that 240V comes in, with the help of a pressure switch, is sent to the pump. From reading online, I think there’s 240V between Yellow and Red and 120V between each and Black. So it’s a single phase motor. The 3 circular things on top are starting and/or running capacitors, and maybe the little round things under the wiring block are resettable overload fuses?

The pump is Franklin Electric FPS 4400 Model 60FA5S4-PE. From this pdf, it looks like the pump is discontinued/depricated/obsolete: (see page 3/12 to find the model number listed and pages 8 and 9 for pump curves). Unfortunately, that pdf doesn’t list motor characteristics like FLA.

I had thought of upgrading the motor starter to a VFD would allow me to buy a smaller generator (because I don’t have to worry about the 6-7x inrush current as compared to Full Load Amperage). But if I can’t find out if the motor on the pump is inverter rated, etc, maybe that’s not a great idea. Besides, a generator at 15 kW isn’t that much more expensive than a 5kW, and the difference won’t pay for a VFD.

So, what would you guys do to give yourselves and your community a bit more reliable water supply? Thanks for any suggestions.

My uncurrated photos/video are visible here in case the upload feature doesn’t work:

I believe a ‘soft starter’ is what you’re looking for. While VFD’s do technically exist for single-phase motors, they are not common and are not compatible with capacitor start motors or motors with separate starter windings or centrifugal switches.

A soft-starter should do what you’re looking for as far as damping startup loads, and they work well on motors with high starting loads, such as air compressors and water pumps. Having said that, talk to a well driller who knows exactly what kind of motor you’ve got down there and can help you choose and wire in a system that will take care of the pump properly.

I believe a 5hp pump should be pulling somewhere around 23 amps under load. The data plate on your Franklin Electric contactor box says Service Factor Max Amps 27.5, which is more a ‘brief overload’ number than a typical running current, so ~23amps is probably pretty close. Soft starter or no, a 30 amp generator input should be decent headroom for running the pump.

Personally, I think you’d be better off with an adequate generator (30 amps + whatever surge current it’s capable of) and appropriate wiring/disconnects. Like you say there’s not likely much savings to be had installing a soft-starter just to be able to buy a slightly smaller generator.

I believe a ‘soft starter’ is what you’re looking for. While VFD’s do technically exist for single-phase motors, they are not common and are not compatible with capacitor start motors or motors with separate starter windings or centrifugal switches.

Thanks for this, my further reading brought me to this post which made me aware: Wait? There are Single-Phase VFDs? | Wolf Automation

I found the following soft starter rated at 40A:
Would that replace most of what’s in the contactor box now? I think maybe that one’s too small since the 40A is for class 2 operation, and it’s only rated to 22A for standard class 10 starting. I think the class 10 limitation applies here.

And one more question: Water Master Sue said that only certain qualified electricians are allowed to work on electrical stuff for water supply. I assume this means, I can’t do this myself. Have any of you come across this? It probably doesn’t apply to homeowners, but this is (kinda) a public utility, so there may be laws preventing me from doing this for our community. That’s probably not all a bad thing, since I’m obviously inexperienced in large well pumps, but wire sizes and other stuff should be straightforward enough to just do…

I don’t believe so, no. My experience is more in industrial 3-phase motors, so I’m not super confident in how the starting of a 3-wire single-phase well pump works, but I believe the soft starters go ahead of the motor control/starters and don’t replace it.

I don’t know how the laws work in this state in regards to ‘shared’ private wells, but I’m guessing the answer is no, you can’t work on it yourself. DBS [Department of Building Safety] would be the office to ask for sure.

IMO, you should talk to a qualified well driller about all of this. Well pumps are expensive, difficult to replace, and the risk of off-lining 70+ people from the water supply means this is not a place to YOLO anything. Find somebody who knows exactly what sort of motor you’re dealing with and can choose the appropriate soft-starter.

Tell them what you’d like to do in regards to backup power inlets and such, they’ll know what’s required per DBS/NEC for such systems; especially if there’s special requirements regarding water-supply pumps and circuits.

With regards to pressure tank size and fill time, remember that they’re likely not cycling over that wide a pressure range. You’d have to look at the gauges, but our house system cycles from about 40psi to 60psi - and I’m not sure how many gallons in the tank that is between the two. Not many, empirically.

You might consider getting a current transformer and doing some datalogging for a few weeks of operation - this will get you far more concrete information about current consumption and energy use. Without that, you’re guessing, though paying attention to the meter will at least get you average energy consumption.

50A/240V is within the range of modern inverters, though it’s a pretty hefty inverter to run it.

Obviously the default option. For 1-8 hour outages… almost certainly the cheapest option. Store 10-20 gallons in jugs in your house and cycle them occasionally.

This should be fairly easy, since it’s just electrical side wiring - a 100A transfer switch and 50A inlet plug should be more than enough to cover your needs.

However, you don’t mention details of the other well houses. Do any of them have smaller pumps in them? If the system is operating as a single unit (which it sounds like from your description), then it would be cheaper, easier, and would accomplish your goals to run the smallest possible pump. If there’s something like a 1hp 120V pump in one of those, power that instead on a lower pressure switch for the backup.

That’s going to be expensive, annoying, and did I mention expensive? Plus the regular testing of the system.

Far more trouble than it’s worth, I’m sure.

In general, if you’re not a certified electrician of some level, the only thing you can work on is a house you both own and occupy. I was able to do my solar myself because we own and occupy this place, but I can’t legally touch anyone else’s house wiring. I can stand over their shoulder and offer advice, but I can’t do the job for them, and the responsibility is entirely on them. So, I would guess the same applies - the only person who can touch a community well wiring would be an appropriately certified electrician.


I think an important question to answer before you go about any of this is, “How much do the people in your neighborhood care - in dollars?” If two people think it’s worth maybe $5/yr to have water through outages, and nobody else wants to pay a penny for it, you might have an uphill battle for the project. If most people care about it, great, have fun!


One option I don’t see discussed is a “Big UPS” setup.

You could use something like this: 8000 watt inverter charger - 8kw 48 volt inverter | AIMS Power

Mains power comes in one side, the inverter is configured for grid priority, and it charges a battery bank. When the power goes off, it runs off battery until the battery bank is dried. If you wanted, you could hook a 120VAC->48VDC charger up and run that from a small generator during prolonged outages - there’s now no need for the generator to supply the instant power requirements, only the long term average power.

But it really comes down to how much money the water organization wants to spend on the project.

Isn’t the standard solution to something like this to just convert to a water tower?

We kinda sorta have a water tower in the form of ~20 pressure tanks. I’m not sure a classic water tower is feasible for 70 suburban houses. It would need to be 115 feet tall to get 50 psi, which is crazy in a small neighborhood where the tallest house is 30’ and the tallest tree is 90’. No nearby hills either, river floodplain…

Syonyk, I agree that the difference between my calculated run time and observed is due to how much hysteresis there is in the pressure switch (delta between set pressure [50psi] and when it turns on [49 vs 47 vs 45psi]).

I should at the very least go back now and see how many gallons we’ve used in a week (irrigation has started, but not everyone has unmothballed their systems).

Re: the other wellhouses, the second one has a 20hp pump that runs when a lot of people are watering their lawns. It shares a street and therefore Idaho Power circuit with the 5hp pump in the first wellhouse.

The third has another 5hp pump that almost never runs, but is on a different Idaho Power circuit. This means only a wider area outage affects my neighborhood’s water supply.

My reading of the pump curves tells me a 3hp motor with the same pump head would easily provide ~ the same flow rate and pressure. My guess is they’ve been replacing 5hp motors with 5 hp motors for decades, and motors and pump impellers have gotten more efficient in that time.

I also think I’ve found the motor Franklin Electric puts on these pumps:

Page 13 (motor model prefix 224303) 23A under load, max load amps of 27.5A, and an LRA of 129A

Page 5 shows a helpful table of how big a generator I need:

15kW for a 5hp pump

I’m starting to lean toward replacing the 5hp pump in the 3rd wellhouse with a small (1hp? 2hp?) VFD driven pump (or may just on a soft starter?). That way, it can be powered by a small generator, or even a battery bank+ inverter like Syonyk linked.

Using the one you linked on the existing 5hp pump could work, but it’s $500 for a soft starter, $3500 for the inverter ~1000 for batteries, and another ~1000 for the generator+ 48V charger?
It’s not crazy, but the batteries will last 8-10 years and probably barely be used.

For even deeper diving, I found this wiring diagram that matches well to the photos I took:

It’s possible to pull the pump and replace the 1ph 3-wire motor with a 3ph motor to enable the use of a VFD, but it might be simpler to install a package like this one:

It does seem a shame to pull out a perfectly working pump that’s only 5 years old…

Huh, interesting. it is 1 start and 2 run capacitors. I was wondering about that.

Oh nice, that’s one of the constant pressure systems. Might be nice with multiple houses involved, keep a constant pressure instead of the swing between ~40-60psi.

FWIW you’d then have a backup on the shelf for the other 5hp pump.

It might also be worth running the backup system at a lower pressure - 30 pounds instead of 50. Less energy used to compress the water in what is by definition an energy limited situation.

I like the idea of refitting the backup pumphouse, though it still comes back to “A transfer switch, external plug, and open frame generator with some propane” as the cheapest and most reasonable option. I really don’t think batteries are required.

I data-entried the handwritten well log and ran some calculations on it. It seems the non-irrigation water demand is 11,000-15,000 gallons per day or 15% duty cycle. Energy is ~20 kWh/day until it ramps up to 60-100kWh April-October. If we build this out, I’ll definitely request a bill insert to the neighbors to conserve water during an outage.

Maybe we should be encouraging conservation now and spare all this generator crap :/. I mean, 2000 gallons (maybe 3k) is enough to run us 3-5 hours of typical usage if the tanks are full. Radical conservation may stretch that to a day (mellow yellow, no showers/laundry, etc.)…

It makes sense to have a lower pressure switch (25-30 psi) to turn on the ATS (if we go with an ATS), but unless we install a low power pump, a low psi setting will only short cycle the pump, right?

If we don’t want to pull any pumps, would this soft starter get us down to a 7500 W generator?:
I couldn’t find how much it reduces startup surge current. I have learned that the soft starting ramp must be completed in less than 3 seconds to protect the thrust bearing in the pump.

Anyway, here’s the well log data:

date PSI Flow GPM water meter million Gal Power meter kWh used million gallons pumped days elapsed kWh/day gallons /day elec duty % water duty %
1/23/2020 61 68 23.13 88517 5hp pump motor
1/28/2020 48 72 23.197 88614 97 0.067 5 19.4 13,400 15% 13% 240 V
2/13/2020 56 0 23.391 88894 280 0.194 16 17.5 12,125 13% 12% 23 A
3/20/2020 60 70 23.845 89551 657 0.454 36 18.3 12,611 14% 13% 5.52 kW running
4/16/2020 56 0 24.263 90158 607 0.418 27 22.5 15,481 17% 15% 70 gpm
5/12/2020 58 0 25.301 91671 1513 1.038 26 58.2 39,923 44% 40% 24 hours/day
6/18/2020 55 70 26.882 93967 2296 1.581 37 62.1 42,730 47% 42% 60 min/hour
8/14/2020 63 69 30.881 99761 5794 3.999 57 101.6 70,158 77% 70%
9/24/2020 58 0 33.288 3249 3488 2.407 41 85.1 58,707 64% 58%
11/12/2020 66 0 34.438 4915 1666 1.15 49 34.0 23,469 26% 23%
12/30/2020 60 0 34.972 5688 773 0.534 48 16.1 11,125 12% 11%
1/7/2021 54 0 35.061 5815 127 0.089 8 15.9 11,125 12% 11%
4/8/2021 70 36.175 1.114 91 12,242 12%

google docs: well log calcs - Google Sheets

If it’s low enough, it simply won’t run the pump at all unless the others are offline. If your normal cycling range is 50-60 psi, a 30 psi switch shouldn’t cycle unless the main pumps are offline entirely.

Though, yeah, with that much water storage, I don’t see a real reason to have an ATS at all. Wire in a manual transfer switch, a generator plug, and then buy a big generator. A 9kW open frame beast is $750. Either toss a propane carb on it or just maintain it sanely, drain fuel when not in use, run the carb dry, Stabil, etc. And toss a can of ether in where you store it.