AC Pool pump powered (1.5 hp) powered by solar panels?  Good idea? - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: April 13, 2018, 03:19:10 am
content: My yearly power bill when I don't use the pool pump puts me on the boarder of solar being a cost effective. I'm thinking of just installing solar panels to power the pool pump.The pool pump with a 1.5 HP AC motor. I'm thinking I would disconnect this from my mains and power it at 220 volt with solar panels and an inverter?Correct me if I am wrong or feel free to offer suggestions.A 1.5 HP more draws about 1.11 kw. Using 290 watt panels I would think I'm thiking I woudl need 4 or 5 panels.5 Panels would give me max 1,450 watts. (The extra panel would give me a little extra wattage in the morning and late afternoon.)I already have solar thermal panels so no need to power at night or cloudy/rainy days or have banks of batteries.I'm thinking this would not be grid tied. This would be device solar or a solar system dedicated to the pool pump.Should the panels be in parallel or series.Roof is in full sun from 9-5 March - October.I'm thinking it would not be cost effective to replace the AC motor with a DC one.The motor is is dual voltage 120/240. I'm thinking it would make more sence to keep it at 240, whihch means I need an inverter rated for 240 volts and around 10 amps. (Over specing to cover starting current.)Inverter - Not sure which way to go here. Micro-inverter on each pannel. Solar industry type inverter? Or an industrail type inverter like this one.https://www.amazon.com/Holdwell-AC200-240V-Power-Inverter-1500W/dp/B06ZZ38SPY/ref=sr_1_4?ie=UTF8&qid=1523588525&sr=8-4&keywords=240+volt+1500+watt+inverterThen I'm thinking I need somethigng to protect the motor from under voltage/current. Maybe a contactor? Or some other type of protective circult?I do not power the pool pump in the winter so could I'm thinkg maybe I would install a transfer switch to connect the solar panels to a solar inverter connected to the mains in the off months.Or am I over thinking this?

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 13, 2018, 03:56:30 am
content: I have seen a video of a university project VFD specifically designed to run a pump motor directly from solar, no batteries required. Using a VFD reduces power usage and makes for some very significant savings.

author: Seekonk
author_rank: Super Contributor
timestamp: April 13, 2018, 12:57:53 pm
content: There are a lot of youtube videos from India on this. Seems to be very popular for irrigation videos. You should go grid tie and schedule most pumping for middle of the day. I wouldn't use any method you are suggesting. This is very complex and expensive to do unless you buy a complete ready made system. Doubling your panel requirements is a good place to start.

author: bicycleguy
author_rank: Frequent Contributor
timestamp: April 13, 2018, 08:45:29 pm
content: I could be wrong but a 1HP permanent magnet DC motor, ~$1,248 like this:http://www.baldor.com/catalog/CDP3455could be run on 5 panels in series with no other controls. (except a HVDC cutoff switch )A pool pump has low starting torque and will just start moving as the voltage comes up, higher voltage = faster. You don't need perfection.You really want the same shaft size and motor mounting however and the same RPM and ~HP rating as the current pump. However 1.5HP is a little to much current and very pricey. A 180V 5amp 1HP motor might be good enough.Looking at the motor performance graphs and guessing on your panels and pump, 5 panels in series on a good day might get you 1600rpm. Really need to see the pump performance curves and the panels but I think it's doable.

author: james_s
author_rank: Super Contributor
timestamp: April 13, 2018, 09:04:45 pm
content: I think I would look for a used surplus DC motor, or use a brushless motor as used for RC aircraft, those are readily available up into multiple horsepower. Using an inverter to power a conventional induction motor I suspect you will have difficulty any time the light on the panels is not optimal.

author: bicycleguy
author_rank: Frequent Contributor
timestamp: April 13, 2018, 09:13:36 pm
content: Just looked at multiple listings on e-bay for under $300 used, $600 new.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 13, 2018, 09:39:03 pm
content: Thanks everyone.

author: james_s
author_rank: Super Contributor
timestamp: April 13, 2018, 09:51:37 pm
content: $300 seems awfully high, there are lots of surplus dealers out there, I've seen <5 horsepower electric motors for under $100 on multiple occasions. Something like a treadmill motor might work ok for this sort of thing, they are typically ~100V permanent magnet DC motors rated for around 2HP.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 14, 2018, 02:52:46 am
content: Quote from: james_s on April 13, 2018, 09:51:37 pmI have a 100v tread mill motor. 2 HP, don't think so. More like 1/10 hp. But I could be wrong. I will have to look.

author: james_s
author_rank: Super Contributor
timestamp: April 14, 2018, 02:55:53 am
content: The motor on my treadmill is 2HP, I was just looking at it recently when I did some work on the thing. Permanent magnet and universal motors are much more powerful for their size than induction motors. They have the downside of requiring a lot more maintenance though.

author: SeanB
author_rank: Super Contributor
timestamp: April 14, 2018, 03:10:43 am
content: If you are going towards an inverter I would suggest getting a 3 phase motor and retrofit the pump with it. The typical pool pump uses a standard frame size motor, and thus you can simply get the same manufacturers motor with the same frame size and mounting method and replace the motor with the 3 phase one. If it is a special shaft easy enough to simply do a change of the winding core and reuse the existing rotor and bell ends on the pump instead, as the rotor will likely be the same dimensions for the single phase 2 pole and 3 phase 2 pole motor. Then use an inverter and connect the solar panels to the DC bus, and set the inverter to run automatically on power on ( typically a jumper to start and appropriate setup), and size the panel voltage to something in the DC bus range. You might need a relay to disconnect the panels when the voltage is low so the inverter will reset correctly, and a capacitor bank to provide more ripple filtering, but most cheap inverters will work over a pretty large input voltage range, and some can be programmed as well for wide input voltage tolerance.Otherwise I second the treadmill motor and running off the panels in series with only a DC fuse of appropriate voltage and current rating, along with a DC disconnector. That speed and pump activity is variable will not worry a pool filter and pump much, though you might have issues with automatic pool cleaners as the typical pool cleaner does need a minimum flow rate to operate, and some as they age do not restart if the flow rate is rising gradually and need the pulsator tube replaced. That though is cheap, the tubes are $5 here and take 3 minutes to change. An average of 8 hours a day over the year will mean a very clean pool, and will be a big power saving as well, as the pool pump is a massive power user.

author: Seekonk
author_rank: Super Contributor
timestamp: April 14, 2018, 01:38:13 pm
content: Big change going from a standard pool pump to a DC motor. You must use a linear current booster then. It is always a waste responding to a post early on.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 15, 2018, 10:53:21 pm
content: Quote from: james_s on April 14, 2018, 02:55:53 amWhy would a treadmill have a 2hp motor? A washing machine has a 1/2 hp or a 1/3 hp motor. Something doesn't sound right to me. A 1.5 hp pool pump move several tons of water per hour. Just doesn't sound "right" to me.

author: james_s
author_rank: Super Contributor
timestamp: April 16, 2018, 01:51:05 am
content: Quote from: DougSpindler on April 15, 2018, 10:53:21 pmBecause they have to overcome a lot of mechanical resistance and inertia, you could have a 300lb person walking on the thing and it will be expected to maintain a constant speed whether flat or up hill, with speeds anywhere from a crawl up to ~10mph. A washing machine requires very little torque in comparison.https://www.surpluscenter.com/Electrical/DC-Motors/Special-Purpose-DC-Motors/2-5-HP-Icon-Health-And-Fitness-Treadmill-Motor-M-217250-10-3037.axd

author: David Hess
author_rank: Super Contributor
timestamp: April 16, 2018, 04:11:50 am
content: Quote from: DougSpindler on April 13, 2018, 03:19:10 amThis does not make any sense. If you are going to use a grid-tie inverter part of the year when the pool pump is not being used, then just leave the grid-tie inverter connected all year and leave the pool pump on its existing timer for the part of the year when you use it.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 16, 2018, 05:19:20 am
content: Quote from: David Hess on April 16, 2018, 04:11:50 amI’m slowing figuring that out. When I started looking into this all I wanted to do was offset the cost of running my pool pump. Right now I’m paying $0.47 kWhr. I think this summer it will cost around $1,200 to run the thing. My original thought was to do device solar or the pool pump. With device solar you don’t need any permits and I would not have to deal with the power company. And the other reason was I was getting quotes from solar experts form $20,000 to $40,000 for whole house solar. Some solar designe experts were telling me I needed 18 panels and others were selling me 40 to cover 100% of my electric bill. As I talk to “solar experts” I realize they don’t have a clue (I’m sure there are some exceptions), what they are doing except trying to make as much money as quick as they can. What a bunch of scammers ost of them are.One of the best lines I get told over and over is that during the day the solar panel produce electricity and store what’s not used in the solar panels. Then at night when you need to use electricity the electricy stored in the solar cells powers your home. When I ask of there are batteries in the solar cells I’m told there aren’t. They tell me the electricity is made and stored in the solar cells. And then they tell me to trust them because they are experts and know what they are talking about. Yeah right.Pumping all of that water this summer is going to be killer on the pocket book this summer. My electric bill doubles when I run the pool pump.My original thought was to spend a couple of thousand to power just the pool pump. (Device solar). If I did it would pay for itself in a few years. But then I was thinking since we don’t run the pumps in the winter I would use the panels to produce electricity for my home. But now that we are paying $0.47 kHr at times for electricity whole house solar is making a lot more sense.Problem I’m running into now with the solar companies is there software does do modeling for Time of Use customers. In making this post I’ve come to the realization I should install whole hose solar. Now the questestion is how may panels do I need? I can’t find anyone or any software that can do the modeling with Time of Use customers. Maybe this is worthy of making a new post to discuss.

author: james_s
author_rank: Super Contributor
timestamp: April 16, 2018, 04:03:35 pm
content: Holy cow! Here I thought electricity in CA was expensive when I heard $0.25/kWh. Mine is around $0.09/kWh.0.47/kWh is about the highest I've heard.

author: metrologist
author_rank: Super Contributor
timestamp: April 16, 2018, 07:59:43 pm
content: I don't see electric costing that much anywhere in the US. Hawaii industrial rates are still lower than $0.30/kWhr.Although I have heard some complain of various "green" energy and time of use plans not matching up well with use...

author: DougSpindler
author_rank: Super Contributor
timestamp: April 16, 2018, 08:17:28 pm
content: Quote from: metrologist on April 16, 2018, 07:59:43 pmTake a look at California prices for electricty. I am a Time of Use customer with PG&E and we pay up to $0.45 kWh. And customer on other rate plans pay up to $0.85 kWhr.I don’t think rates in Hawaii are this high.

author: james_s
author_rank: Super Contributor
timestamp: April 16, 2018, 08:40:51 pm
content: At $0.85/kWh you could just about come out ahead running a gasoline generator like a Honda EU2000, I bet a multifuel conversion burning natural gas would be cheaper.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 16, 2018, 09:27:17 pm
content: Quote from: james_s on April 16, 2018, 08:40:51 pmI know. But if you have solar you can sell excess electricity to the power company at $0.85 and buy it back when rates are low as in $0.12.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 22, 2018, 06:37:21 pm
content: Quote from: DougSpindler on April 16, 2018, 05:19:20 amNo one will size the system for you. You may hire someone, but what they do will not be any good. You'll have to do it by yourself.Panels are cheap and last long. It is wise to get more of them. I have 6kW array (24 panels). The array could produce 30kWh on a good day, but this never happens. In summer time, we use perhaps 8kWh per day. If we had a pool with a pump, we would have plenty of energy to run the pump. Winter, of course, is another story. For winter, I could use another array like this, or two ...Batteries are expensive. So, try to figure out the way to need less of them. Things such as turning off your pump during the night, using more power during the day time (dishwashers and alike) reduce the demand for battery capacity.Electronics, such as inverters and solar chargers, etc. are also an important part. I spent around $6,000 on them, plus lots of custom stuff which I did by myself.Generator is also needed. Can't go without it unless you keep the grid connection.

author: james_s
author_rank: Super Contributor
timestamp: April 22, 2018, 07:08:06 pm
content: On those grid tied solar installations, does it work to use a very small generator to keep the system online during a grid outage? That's something I hadn't really thought about, but it annoys me that most of them shut down if you lose power, when it seems like it wouldn't take much to have clean dependable standby power without a lot more hardware.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 23, 2018, 01:39:06 am
content: Quote from: james_s on April 22, 2018, 07:08:06 pmIt has been done before. The off grid inverter must be capable of accepting as much power as the grid tie inverters can output, which most cannot do. It would be easier to just open the junction box and clip on some wires.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 26, 2018, 03:19:22 pm
content: Quote from: james_s on April 22, 2018, 07:08:06 pmSome of the inverters have on 15a outlet. When the grid crashes you have one outlet tha’s slar powered.I don’t think a small generator makes sense unless you have grid outages on a regular bases. I’m in California in th SF Bay Are can’t remember the last time we were without grid power.

author: james_s
author_rank: Super Contributor
timestamp: April 26, 2018, 04:55:11 pm
content: I typically lose power about once a year, usually for a few hours or less but sometimes for a couple days. About 10 years ago a big storm came through and knocked down multiple high tension transmission lines, I was without power for 10 days. People who live in more rural areas typically have much more frequent outages.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 26, 2018, 05:28:36 pm
content: Quote from: james_s on April 14, 2018, 02:55:53 amI just look at a treadmill motor I have. You are correct it is 2.5 hp, hard to believe a motor that small is 2.5 HP.

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 26, 2018, 05:50:00 pm
content: It also helps that the motors are rated for intermittent duty and used in a protected environment.The designer for that motor can be significantly more lenient than that of a motor running 24/7 on a pump that its exposed to the elements.

author: bicycleguy
author_rank: Frequent Contributor
timestamp: April 28, 2018, 11:58:59 pm
content: Quote from: DougSpindler on April 26, 2018, 05:28:36 pmWhat's the current and voltage? You need something like 4.5A @ 180V to go without DC-DC conversion.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 29, 2018, 03:55:37 pm
content: It’s 130 vdc at 18 amps.I have to ask. Why a DC motor and not AC? I’m guessing that’s because they can control the speed? With an AC motor the speed would be much harder to control?And this one puzzles me. How do they get 18 amps? The original plug on the treadmill was a 15a.With an AC voltage of 120 (RMS) can one get 130VDC? And how does one get 18 from 15 amps?Thanks

author: james_s
author_rank: Super Contributor
timestamp: April 29, 2018, 05:06:56 pm
content: Cost, also size and weight. If they used an AC induction motor it would be much larger, heavier and more expensive as well as the electronics would have to be much more complex as it would require a 3 phase VFD.I suspect marketing BS is how they get 18A, it's not uncommon for unusual rating systems to be used with special purpose motors. For example my air compressor claims "5 horsepower" but it plugs into a 120V 15A receptacle.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 30, 2018, 06:35:02 pm
content: Quote from: james_s on April 29, 2018, 05:06:56 pmGot it. Thanks.I have 3 atitic fans. I have consdiered replacing them with a solar powered fran. Each of the 3 fans I have right now draw draw 2.3 amps at 120vac (285 watts published) and move 1500 cfm of air. But the solar paowered fans which also move 1500 cfm of air are only powered by a 30 watt solar panel.Hard to beleive solar is so efficient that 30 watts of solar power can move the same amount of air as 285 watts of AC current. There's got to be a lot of marketing BS in this.

author: DougSpindler
author_rank: Super Contributor
timestamp: April 30, 2018, 06:36:39 pm
content: One other question.....If I want to power that 130 VDC treadmill motor with AC what's the best way? Just a bridge rectifier?

author: james_s
author_rank: Super Contributor
timestamp: March 14, 2021, 10:28:00 pm
content: Nonsense, pool pump motors haven't significantly changed in 40 years. I bet there will be a followup spam hawking poop pumps.

author: daniel444
author_rank: Regular Contributor
timestamp: April 02, 2021, 06:31:19 am
content: treadmill motor would only last a year or two