Capacitor for jet pump?

PhilSPhilS Solar Expert Posts: 370 ✭✭✭
I power a 115V above ground jet pump (that pumps from an above ground storage tank) with an antique Heart Interface inverter (2000W).  Because it's a square or barely modified square wave inverter, the pump motor doesn't like it very much.  Been doing the job for at least five years tho.

When the pump first tries to start, it hums and buzzes for 2 to 10 seconds (trying to rotate), the inverter tries to send enough juice to start it but the overload led glows dim, and then either 1) the pump starts and all is well or 2) the inverter shuts down with an overload indication or 3) the breaker on the inverter opens.  2 and 3 happen rarely, once or twice per month.

Would a capacitor installed across the pump L1 & L2 leads help the situation?  I know there are "soft-start" and "run" capacitors, so I assume I'd need a "run" capacitor.  Any idea of size?

Phil

Comments

  • mike95490mike95490 Solar Expert Posts: 8,653 ✭✭✭✭✭
    Re: Capacitor for jet pump?

    What does the pump mfg suggest ?
    My guess would be it needs a START cap, since once it starts, you don't indicate anything is bad.

    However, a start cap needs a speed switch in the pump, to switch the start circuit off, after the pump hits some RPM.
    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 ,

  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Capacitor for jet pump?

    "However, a start cap needs a speed switch in the pump, to switch the start circuit off, after the pump hits some RPM."

    That's why I'm guessing a "run" cap, since there is no provision to change circuits after it starts. I'm sure there's a formula for the proper size IF this is a good idea.

    Phil
  • System2System2 Posts: 6,290 admin
    Re: Capacitor for jet pump?

    What HP is the motor and what is the rated current draw??
    Do you hear a "click" from the motor as it comes up to speed when started?
    Do you hear another click as it slows down when shut off?
    Answers to these questions will tell me a lot about the motor.
    Thanks
    Wayne
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Capacitor for jet pump?

    HP and current draw I'll have to check when I get home and post tomorrow. I could guess 1/2 hp but it would just be a guess. I'll look tonight. Current draw is less than 15A since that's the size of the breaker that has tripped (once).

    There's a 'click' from the pressure switch when the pressure goes low, then a 'click' when the pressure is reached and the pump turns off. No other clicks, no fancy circuits. Centrifugal pump housing on one end of a motor, pressure switch mounted on the motor side.

    So as it is now: "click".... "rrrrrrrrrrrr" (the sound of power applied to pump but no pumping action....1...2...3...4...5........"rrrrmmmmmmmmmmmmmm" (the sound of the pump starting and pumping............"click" and the pump stops.

    I'll add details in the morning.

    Phil

  • mike95490mike95490 Solar Expert Posts: 8,653 ✭✭✭✭✭
    Re: Capacitor for jet pump?

    maybe it's time to think about a DC replacement pump? Replace the inverter ? One or the other is getting "soft" after being abused for 5 + years.

    Whats the cost of an AC pump vs a DC (24, 48V ?) vs a new 2K sine inverter Seems a waste of a nice sine inverter, just to run a pump, but maybe thats' what its going to take. Simply adding a capacitor will not greatly improve the waveform. Some motors need a Run capacitor, and some need a Start capacitor.

    Mail order from Mc Master Carr is fast and reliable:
    http://www.mcmaster.com/nav/framework.asp?ReqTyp=CATALOG&CtlgPgNbr=907&term=Motor+Capacitors
    ( just search in the box for capacitor and look for Motor Capacitors )
    start caps are less than $10, and run caps are about the same Some extra voltage rating never hurts with caps.
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 30,174 admin
    Re: Capacitor for jet pump?

    Some folks have theorized that placing a smallish capacitor in parallel with the motor will help--Typically, this is done by the power utilities to bring the current back into phase with the voltage (you can see capacitor banks in the Central Valley because of the huge amount of water pumping). This is different capacitor than a start or run capacitor for an induction motor (which is permanently connected to the motor--and the motor will not run correctly if the run or start capacitor has failed).

    However, in this case, I doubt that this would help. Inverter usually can power reactive/inductive loads pretty well (see the Watt rating verses the Volt*Amp or VA rating--typically the VA rating is much larger). The killer with modified square wave inverters is that the edges of the waves are much sharper than a normal sine wave--created with content of higher frequency components. These high frequency components don't add to the ability of the motor to produce power--these components just become wasted heat.

    Hence the recommendation for a "pure sine wave" inverter (less than 5% harmonic distortion is the figure I have seen as the cut-off point for a sine wave inverter).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Capacitor for jet pump?

    Thanks all.

    Somehow reading threads about A/C units and start capacitors (RV forum) lead me to my query here.   :-(

    For the record: 1/2hp; 9.4a; 3450rpm; "SF 1.30" [what the heck is that?] made by A O Smith.  I doubt I paid $100 for it, so if it's replace the pump every 5 years or buy a 2K sinewave inverter .... well...... 

    On the other hand I've been longing for a nice Outback inverter to replace my Xantrex.... which I could then use for the water pump..... and then I can use that Heart Interface for.....? It's a dang good inverter. Been in daily use for almost 20 years! Too heavy for my RV.

    Phil
  • BB.BB. Super Moderators, Administrators Posts: 30,174 admin
    Re: Capacitor for jet pump?

    SF=Service Factor

    http://www.engineeringtoolbox.com/service-factor-d_735.html
    The service factor - SF - is a measure of periodically overload capacity at which a motor can operate without overload or damage. The NEMA (National Electrical Manufacturers Association) standard service factor for totally enclosed motors is 1.0.

    A motor operating continuously at a service factor greater than 1 will have a reduced life expectancy compared to operating at at its rated nameplate horsepower.
    ...
    Example - Service Factor

    A 1 HP motor with a 1.15 SF can operate at

    1 HP x 1.15 = 1.15 HP

    without overheating or otherwise damaging the motor if rated voltage and frequency are supplied to the motor.

    Insulation life and bearings life are reduced by the service factor load

    -Bill

    PS: A "modified square wave inverter may operate around 25-30% harmonics--I would guess that motor sized for the load would either need to be SF=1.3 or should be (worst case) ~1.3 times the rated horsepower to drive the load (and not overheat).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Capacitor for jet pump?

    "For the record: 1/2hp; 9.4a; 3450rpm"
    This suggests to me, that the motor is a standard, split phase start motor and that if you listen very closely, there will be two clicks on start and two on stop. The first click will be the pressure switch, followed, as soon as the motor gets up to speed, by a second, possibly softer click of the centrifugal toggle on the motor shaft, opening the starter contacts. Likewise, on stop, you will hear the pressure switch click off, followed once again, by the motor starter contacts closing. 9.4 amps and 120 volts is typical for these type of motors. Listen again and I believe you will hear those second clicks. Now, if the motor does not have a "hump" on its top or side, (which would contain the starter capacitor), then you can add a starter capacitor, with a value of about 900 mfd,and a voltage rating of at least 110 volts AC, IN SERIES WITH the wire, or wires that go to one side (doesn't matter which side) of the internal starter switch contacts. You will have to open the motor to access the switch and it will be at the rear of the motor. You will have to bring wires out of the motor to the start capacitor, as there won't be room inside the motor. You may not be able to get a 900 MFD capacitor, so you can use two 450 MFD capacitors in parallel, to do the same thing. You will see a BIG change in how the motor starts. I've done this kind of thing many times on many different size motors, including fridge and freezer compressors with awesome results. Smaller motors will use smaller value capacitors, example, a 1/4 HP motor will work best with a 450 MFD cap, while a 1/8 HP fridge compressor works great with a 200, or 225 MFD cap. If however, the motor is designed for capacitor start, it will have the "lump" on it's top or side, be wound a bit differently and use a much smaller value cap.
    You will find it will start much faster and with much less current draw on sine wave, so you should also see a huge difference on Modifies square wave.
    Good luck
    Wayne
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Capacitor for jet pump?

    Thanks, Wayne!

    I've copied/pasted/printed your post. This weekend I'll explore further. There is NO hump anywhere on the motor. I'd be comfortable adding this modification.

    A memory is a terrible thing to waste. Upon reflection I realize this inverter/pump setup has been in continous operation for more than 5 years.... at least 12, maybe 15. The inverter 'overloaded' again last night. Becoming a 2 - 4 times weekly incident now. I put the standby 12V pump "online" as a backup so we don't draw down the tanks to zero, like while the washer is going or in the middle of a shower.

    I think your post is the one I was looking for.

    Phil
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Capacitor for jet pump?

    My first guess would be the motor is starting to go and requiring more start up amps. There is also a hard start unit, a Supco SPP6. I added one to our 3 ton AC motor, it would sometimes start and sometimes overload the inverters. After adding it is so much better. I don't really understand how it does it, but it works. Here is one from eBay, I have no idea who is selling this and have no affiliation with them.

    http://cgi.ebay.com/SUPCO-RELAY-CAPACITOR-COMBINATION-SPP6-NEW_W0QQitemZ180076045463QQihZ008QQcategoryZ42911QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    I might be off, but how old are your batteries. Maybe they are starting to drop under heavy load and the inverter is in turn dropping the output voltage as well? Or likely a combination of all this.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Capacitor for jet pump?

    Thanks, Brock.

    Your eBay tip led me to the Supco company. That particular part at eBay says it's supposed to be connected to the existing capacitor, which I don't have. They seem to specialize in solutions to problems like mine tho. Between your help and Wayne's maybe I can fix this little problem.

    Yeah, the batteries are old but in good shape (a dozen T105s) and the charge state doesn't seem to make a difference as it happened again yesterday afternoon after a full day of charging. Probably the pump is showing the effects of many years powered by a square wave.

    Phil
  • mike95490mike95490 Solar Expert Posts: 8,653 ✭✭✭✭✭
    Re: Capacitor for jet pump?

    When was the last time the bearings in the pump were lubed, and spider webs cleaned out ? Use some nice synthetic lo temp grease, or mobile 1 oil, that won't gum up. I had a motor just size up in my dryer - 25 years old, and the "self oiling" bearing were so gummed up with varnish.....
    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 ,

  • System2System2 Posts: 6,290 admin
    Re: Capacitor for jet pump?
    mike90045 wrote:
    When was the last time the bearings in the pump were lubed, and spider webs cleaned out ? Use some nice synthetic lo temp grease, or mobile 1 oil, that won't gum up. I had a motor just size up in my dryer - 25 years old, and the "self oiling" bearing were so gummed up with varnish.....
    =========================================================
    This is a more common thing than one may guess. I was wondering if there may be tight bearings, but you beat me to it. :-D
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Capacitor for jet pump?

    Guess I'll be checking the bearings and relubing if possible this weekend. Figgered to take off the end plate to inspect for the starting/run circuits anyway. The only lubrication I've used for anything since the seventies is synthetic so I'm prepared.

    Phil
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