Running AC pump with gas generator

HairfarmHairfarm Solar Expert Posts: 225 ✭✭✭
Greetings,

I plan to use an gas generator to run an AC water pump. I don't plan to leave the generator on all day, but just enough to fill my 50 gallon pressure tank a few times through out the day for 5-10 minutes at a time.

I've heard that some AC water pumps don't like direct power from gas generators, and can blow seals. My pump is a Flotech 1/2 hp.

Question: Can I run the water pump directly from the 6ooo watt generator, or should I smooth out the generator power with a surge protector in between so that my AC water pump isn't damaged? Anyone else using a gas generator to run their water pump?

Or is this a non-issue?


Thanks,

Hairfarm

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Running AC pump with gas generator

    Non-issue.

    Any good generator will supply clean enough power to run a pump; it's just a motor.
    I ran my 1/3 HP off the Honda 2000 for two years before I got the solar up to snuff.
    Never heard of any seals or anything else blowing because of the AC being supplied by a generator. Unless the gen is a piece of junk, the power will be clean enough. 6kW will certainly run a 1/2 HP pump.

    P.S.: This is a very good plan as opposed to spending mega $ on solar just to run a pump. Big storage/pressure tank; run the gen for 10 minutes a day and have 100 gallons available the rest of the day. You can co-ordinate it with any 'big' water use like baths/dishes/laundry and be way ahead on capital expenditure!
  • BB.BB. Super Moderators, Administrators Posts: 31,688 admin
    Re: Running AC pump with gas generator

    Eventually you may look at other options to increase your storage capacity (more pressure tanks, cistern, etc.)... For house/cabin use, a cistern and a 12/24 VDC pump + battery bank to pressurize the home would be nice too (and quiet, don't run the genset 3-4x per day).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Running AC pump with gas generator

    I second Bill's suggestion about adding tank capacity. Either a number of smaller pressure tanks daisy chained together, or a larger cistern or storage tank, then feeding in a pressure tank to feed the house.

    The pump will be happier to run with fewer on/off cycles as will the generator. What kills gas engines is starting and stopping. Once they are warm, the wear is very small. Consider for example, running the pump/gennie for 1 hour once a day rather than 15 minutes 4 times a day. You will use less fuel as well in all likelyhood.

    Another option is a solar "slow pump" that pumps nearly continuously albeit very slowly. What matters is, the net amount of water you need to be pumped on a daily basis. 250 gallons/day can be had by 5 gpm, for 50 minutes or ~75 gpm for 6 hours. (depends on how deep your well is however)

    http://store.solar-electric.com/dasosl.html

    http://store.solar-electric.com/grsqpu.html
  • HairfarmHairfarm Solar Expert Posts: 225 ✭✭✭
    Re: Running AC pump with gas generator

    Thanks for the input guys. I really like the idea of daisy chaining big pressure tanks. I didn't think that could be done. How does that work anyway? Which tank empties/fills first in a daisy chain arrangement?

    Btw, I have an above-ground 2600 gal water tank. And currently have my water trucked in. So doesn't this really negate the need for a cistern?

    The only reason I'm using the gas generator to run the AC water pump is because I don't have solar panels installed yet. But I still want to be able to bathe and use water in the cabin until I do switch to solar. Then I plan to add another DC water pump to the line and run that off of the PV array, roughly 600 watts. I'll still keep the AC pump in-line too, just in case I need emergency back-up water pumping.

    Btw, I've assembled a neat portable hot water shower kit to get me by until I can finish running all the copper line inside. I bought a small dc pump with pos/neg battery clips that I clip onto a deep cell marine battery. The pump then draws water from a 5 gallon bucket via standard hose fittings and pumps it through a Chinese tankless water heater (thanks ebay!) that I have connected to a 20 gal propane tank, then through a portable shower head. It's a great quick hot shower.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Running AC pump with gas generator

    Look at it this way,,, a pressure tank is nothing but a "wide spot" in the plumbing. As the pump pumps into a (or many) tank(s), it compresses the air (or the bladder in the case of a bladder tank, raising the pressure through out the entire system. So adding a second (or third or fourth) tank merely increases the volume of water under pressure. When you open the tap, the pressure in the tank forces the water out the tap, slowly dropping the pressure. If you look at a P-tank, the water doesn't flow in one side and out the other, but rather it flows into the tank and out at the same point. (a tank tee). Plumbing a number of tanks in the system just adds capacity. The pressure goes up evenly, and down evenly with pumping and draw. Tanks can be located nearly anywhere in the line. (within reason)

    A even simpler hot shower system is available from Zodi outback gear. It is a simple copper coil that fits on a camp (or kitchen) stove with a shower head on the one end, and a simple "D" cell pump on the other. Drop the pump in a 5 gallon bucket, hand the head over head (even into a shower enclosure) fire up the stove, and the water comes out as hot as you wish. If it can't get hot enough, you can recirculate the water until it is warmer, and then send it to the shower.

    We used one for years in our off grid cabin, drawing water from the frozen lake at -40 to get a good shower all winter. (We preheated the water on the wood stove). A pair of "D" batteries lasts about a month.

    A 2600 gallon tank is the functional equivalent of a cistern. Are you filling the tank from a deep well? If so, consider a smaller deep well pump, like the shurflo 9300 if the well is deep. If it is not too deep, consider a Dankof slow solar pump. (See the site host for examples) 600 watts is a pretty big draw off a battery based solar system. A Shurflo 9300 draws ~10 amps (12vdc) and pumps ~3-5 gpm depending on head.

    Personally, a single ~ 50 gallon conventional P-tank will provide enough water for most people, with the pump running a few minutes a day. We use a shurflo 9300, into a 50 gallon tank, and we run the pump ~ twice a day. I also wait and turn the pump on in the morning when the sun is up. A 50 gal. pressure tank set at 30-50psi, will deliver water for a good long time after the switch calls for water, so after the last evening shower is done, I turn off the pump, and there is plenty of water to use in the evening and in the morning. If not,,I just turn on the pump breaker,, just load shifting until when the sun is good.
    Tony
  • RCinFLARCinFLA Solar Expert Posts: 1,351 ✭✭✭
    Re: Running AC pump with gas generator

    If you are using bladder tanks in parallel make sure the empty tank bladder pressures are same between tanks and at least 5 psi below your pump pressure switch turn on pressure.

    Personally, I would only use bladder tanks as non-bladder tanks become water logged over time (air dissolves in water, particularly under pressure) and are a pain to drain and re-establish air in the tanks.

    A 2 to 3 kW sinewave inverter should have enough surge capability to start up and run the 1/2 hp AC pump.

    When you get battery/solar power you might keep in mind that pumping to 50 psi can takes almost twice the pump run time then a cut off set at 40 psi and you only get about 10-15% more water stored in tank for the 50 psi. I run mine at 20 psi ON, 40 psi OFF settings on pressure switch.
  • HairfarmHairfarm Solar Expert Posts: 225 ✭✭✭
    Re: Running AC pump with gas generator
    A 2 to 3 kW sinewave inverter should have enough surge capability to start up and run the 1/2 hp AC pump.

    Do I need to convert the sine wave from my generator to my pump? Is that what a sine wave inverter is for?
  • BB.BB. Super Moderators, Administrators Posts: 31,688 admin
    Re: Running AC pump with gas generator

    RCinFLA is suggesting the size of a battery powered sine wave inverter needed to supply that size of AC pump...

    You would not need an inverter between your AC genset and your AC pump (assuming voltage/current requirements match).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Running AC pump with gas generator
    Hairfarm wrote: »
    Do I need to convert the sine wave from my generator to my pump? Is that what a sine wave inverter is for?

    An inverter is for producing AC from DC (batteries). Generator output is pure sine AC. This is as opposed to MSW inverters; Modified Sine Wave or more accurately Modified Square Wave or Multiple Square Wave. AC induction motors don't run well on MSW.

    Glossary of terms: http://forum.solar-electric.com/showthread.php?t=6136
    It helps to understand the nomenclature, eh? :D
  • HairfarmHairfarm Solar Expert Posts: 225 ✭✭✭
    Re: Running AC pump with gas generator
    RCinFLA is suggesting the size of a battery powered sine wave inverter needed to supply that size of AC pump...

    You would not need an inverter between your AC genset and your AC pump (assuming voltage/current requirements match).

    Ok. Thanks Bill. When I actually do get the PV system installed, then I'll switch to a DC pump that is more efficient than converting from DC batteries to an AC pump. I thought maybe RCinFLA was suggesting a device I had never heard of that would convert my AC generator's modified sine wave into a pure sine wave. I waayy over thinking.
  • BB.BB. Super Moderators, Administrators Posts: 31,688 admin
    Re: Running AC pump with gas generator

    In the old'en days... It was simple. An AC generator generated Sine Wave power (rotating fields and coils). Of course, some designs are better than others (as current goes up, sometimes the alternators saturate and don't give a clean sine wave).

    Now, you have the "inverter generators". Some, like the Honda (and probably Yamaha and others) family take AC power (variable voltage and frequency) and convert that into 120/240 VAC 60 Hz power through the use of an inverter internal to the genset.

    And there are others, like the 2kW Honeywell brand inverter generator---does similar stuff but its inverter is a MSW output (as I understand--the manuals seem to studiously ignore the whole issue).

    The nice thing about inverter generators is that the generators can throttle way back ("ECO Mode" for the Honda) and still give a nice clean and stable 120 VAC 60Hz power output. Can save lots of fuel and noise (the Honda eu2000i can be very fuel efficient down to 25% electrical load--the average genset uses, roughly, the same fuel flow from 0-50% electrical load, and are much less fuel efficient at low output loads).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Running AC pump with gas generator

    "When you get battery/solar power you might keep in mind that pumping to 50 psi can takes almost twice the pump run time then a cut off set at 40 psi and you only get about 10-15% more water stored in tank for the 50 psi. I run mine at 20 psi ON, 40 psi OFF settings on pressure switch."

    Interesting,, I never thought about it that way, and more correctly, I never did the calc. I have mine set 30-50 with the idea that I can run longer without running the pump. Is it really only ~15% more water? 20 gallons, 15% is 3 gallons, for twice the run time,,,hmmm.

    Tony
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,912 ✭✭✭✭✭
    Re: Running AC pump with gas generator
    icarus wrote: »
    "When you get battery/solar power you might keep in mind that pumping to 50 psi can takes almost twice the pump run time then a cut off set at 40 psi and you only get about 10-15% more water stored in tank for the 50 psi. I run mine at 20 psi ON, 40 psi OFF settings on pressure switch."

    Interesting,, I never thought about it that way, and more correctly, I never did the calc. I have mine set 30-50 with the idea that I can run longer without running the pump. Is it really only ~15% more water? 20 gallons, 15% is 3 gallons, for twice the run time,,,hmmm.

    Tony

    The other factor is pump/seal/appliance wear. More pressure = more wear
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Running AC pump with gas generator

    Looking at the Shurflo specs it seems that at ~120' of head ~50 pst the 9300 will pump ~96 gph, while at 100' ~ 40 psi it will pump 100 gph. About a 4% difference, so pump wear issues not withstanding,,I think I will keep it at 30-50psi. (2.9 amps vs 3.2 amps)

    All ll in all, not a terribly significant difference, for ~ 100 gallons or less per day. The advantage gained by being able to time shift pumping makes up for the loss of the extra pressure IMHO.
  • jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: Running AC pump with gas generator
    Non-issue.
    Any good generator will supply clean enough power to run a pump; it's just a motor.
    I ran my 1/3 HP off the Honda 2000 for two years before I got the solar up to snuff.
    Never heard of any seals or anything else blowing because of the AC being supplied by a generator. Unless the gen is a piece of junk, the power will be clean enough. 6kW will certainly run a 1/2 HP pump.

    Can you please tell me what 1/3HP pump that was? My new Honda EU2000i wont run my current no name 1/2 water pump. My pump is connected to the bottom of my cistern which sits about 5' below the house. There is a small water/pressure tank attached to the system.
  • mike95490mike95490 Solar Expert Posts: 9,276 ✭✭✭✭✭
    Re: Running AC pump with gas generator

    My 1/2 hp pump, pulls about 1,000 watts running. It's starting surge is lots larger - maybe 6-8Kw, at 240VAC. If you don't have beefy enough power lines all the way from the AC source, to pump controller, to the motor, you could be starving it for voltage, and thus causing it to fail to start on the high amp starter windings.

    Inverter style generators don't have any high surge capacity, which is likely killing you.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

Sign In or Register to comment.