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Thread: Bigger Filter, Variable Frequency, create head

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    Bigger Filter, Variable Frequency, create head

    I have been trying to get this figured out. I have a 15x30 soft sided pool 13,500 gallons, new 1/2 hp whisper flo (110), waterway fc100 cartridge filter. This was here before I got the house with the exception of the new pump. I over heats in about 1 hour or so and is over amping at 12 amps. The suction line is 1 1/2" along with the 1 return line also at 1 1/2" (eyeball 3/4"). The skimmer is 10' from the pump with 3 90 degree elbows. The return is 17' with 4 90 degree elbows. My filter pressure is at 16 it was at 6-7 before the new pump. I dont want to spend anymore money on this if I dont have to. Should I create more head instead by adding more 90 degree elbows? Would getting a bigger filter solve my problem or a variable frequency drive? I have checked all my wiring and connections. If a filter is needed recommendations are appreciated.
    17k (430 Sq Ft) Salt Water In Ground Pool, 3.5'-7' depth, MDX2 Infloor system, Grotto/Tile Slide/Rock Waterfall Features, Wet-Edge Chilean Beach Tahoe Pebble surface, Intellichlor IC40, Easytouch Control w/remote, Pentair Clean & Clear Plus Cartridge Filter, Intelliflo VS-3050 Variable Speed Pump, 2 x intellibrite LED Color Lights

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    Guest

    Re: Bigger Filter, Variable Frequency, create head

    I have never considered a 1/2 HP pump anything more than a water feature pump. For that small of a pump, your filter is fine. Since I have never used that small of a pump before, it could be that it is not rated for your application (running through a filter) and that is causing the problem.

    I'm just guessing, and I'll be interested to see how this plays out.

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    JasonLion's Avatar
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    Re: Bigger Filter, Variable Frequency, create head

    Nothing you mentioned should cause the pump to overheat. The filter pressure alone is providing enough dynamic head to keep it from being a low dynamic head problem. Likewise you couldn't have the filter pressure that high if you had a significant suction side blockage.

    The only thing that comes to mind is if the pump is configured for a different voltage than the one you are providing, which would cause the problem you describe.

    simicrintz, the 1/2 HP WhisperFlo is not your average 1/2 HP pump. The SF is 1.9 and it is super efficient, so it has as much power and water movement ability as most other 3/4 HP pumps (and even a few 1 HP pumps).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Guest

    Re: Bigger Filter, Variable Frequency, create head

    Do you have a spec sheet on that, Jason? I'd be interested to learn more about that!

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    Re: Bigger Filter, Variable Frequency, create head

    Well it originally was a 3/4 hp which was amping at 15 amps. I downsized the impeller to a 1/2 hp which brought down the amping to 12. I have also played with the return eyeball sizes. I have removed it completely leaving the 1 1/2" exit no change in amps, 1" eyeball amps go up to 13, 3/4" eyeball 12 amps. I have also experimented with a friends brand new 1 hp whisper flo. This shot up my psi to 23 and amped up to 17. I was beginning to think that all that back pressure is causing the pump to over heat.
    17k (430 Sq Ft) Salt Water In Ground Pool, 3.5'-7' depth, MDX2 Infloor system, Grotto/Tile Slide/Rock Waterfall Features, Wet-Edge Chilean Beach Tahoe Pebble surface, Intellichlor IC40, Easytouch Control w/remote, Pentair Clean & Clear Plus Cartridge Filter, Intelliflo VS-3050 Variable Speed Pump, 2 x intellibrite LED Color Lights

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    JasonLion's Avatar
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    Re: Bigger Filter, Variable Frequency, create head

    16 psi on the filter is not an unusual amount of back pressure, and should be well within what any of the pumps you mentioned can do.

    Have you measured the voltage at the pump while it is on? If you have too much voltage drop on the line it could cause the amps used to go up and eventually cause overheating. Also, which specific WhisperFlo did you start with? Pentair makes quite a few different models.

    simicrintz, the WhisperFlo 1/2 HP WFE-2 moves 40/55/68 GPM at 60/50/40 feet of dynamic head. For comparison a Pentair SuperFlo 3/4 HP SF-NI-3/4FE moves 15/38/43 GPM, a Hayward TriStar 1/2 HP SP3205EE moves 14/44/62 GPM, and a Hayward MaxFlo II 1 HP SP2707X10 moves 18/43/59 GPM. All from the manufacturers specs.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    mas985's Avatar
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    Re: Bigger Filter, Variable Frequency, create head

    First off, the reason the Whisperlfo 1/2 HP uses a service factor of 1.9 is not because it needs 0.95 SFHP motor but because it is difficult to find a low SFHP high efficiency motor to match the impeller so manufactures tend to use a larger motor than required. You can always use a larger motor than necessary but not the other way around. This is also why you can take any pump and reduce only the impeller to get a smaller pump without having to replace the motor. Replacing the motor doesn't really buy you much.

    Second, rolexguy, you mentioned you replaced the impeller but did you also replace the motor? Did you also replace the seals? If the seals were not replaced or where replaced incorrectly, then the motor could overheat. If you replaced the motor with one that was not rated high enough, which is probably unlikely, that could also cause the motor to overheat.

    Third, for residential pool pumps, amp draw is proportional to flow rate. So the more backpressure or head loss on a pump, the LOWER the amp draw.

    One more thing to add, if you just downsized the impeller, then 12 amps is reasonable since it was drawing 15 amps so the motor should not overheat. Is it tripping the internal thermal switch or a breaker?
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Bigger Filter, Variable Frequency, create head

    Jason: I know 16psi isnt much on most filters but, the labels reads "working condition 6-12 psi, max psi 25". The voltage at both panel reads 120 and at the pump 117 with + or - 1v.

    Finally I think I owe some clarification on my pumps, motors, impellers. I was able to get a hold of 2 whisper flo WFE-3 (motor still attached but dead), WFE-4 wet ends in very good shape (free). I also have access to quite a few A.O. motors at no cost. I had my bud bring me a 3/4 motor which ends up being a low service factor model 1.30 SF (10.20 amps/5.10). This set up overamped me with 15 amps and shutting off in about 10 minutes. I double checked my wiring connection and everything was intact. I am or was under the assumption that any hp x sf = sfhp in either sequence. I found out the motor (.95 SFHP)was undersized for the impeller (1.25 SFHP - WFE-3). Went to my local pool shop and purchased a 1/2 hp WFE-2 impeller and seal. The WFE-2 SF is 1.90 and .50 HP = .95 this was a perfect match for this motor. Wrong while my amps did drop to 12 and it would now take longer to over heat ( 45 mins or so). At this point im trying anything and decided to fiddle with the original dead motor for the WFE-3. I find out the capacitor was bad and replaced it. Voila it works! Since it worked now I put it all back together to match the origianl factory specs with the 3/4 hp WFE-3 impeller. PSI gauge on filter shoots up to 23 but still amping at 12. This is pretty close now since its max is 11.2 amps at 110v. This morning after reading your guys replies I get the bright idea of putting the WFE-2 1/2 hp impeller on original motor WFE-3 motor (smaller impeller on bigger motor). My new amp reading is 10, below the max amps for the WFE-3 and my filter psi is 16. I dont really wont it that high and have a choice of 1 more motor. The specs are a little off (1/2 HP, SF 1.90, amps 11.8/5.9). Is this ok or will it cause me to over amp again? My assumption is since it has the orginal SF and HP it wont? I always thought and have read that HP x SF in any sequence would give you motor size. Why didnt this rule apply in my scenario?
    17k (430 Sq Ft) Salt Water In Ground Pool, 3.5'-7' depth, MDX2 Infloor system, Grotto/Tile Slide/Rock Waterfall Features, Wet-Edge Chilean Beach Tahoe Pebble surface, Intellichlor IC40, Easytouch Control w/remote, Pentair Clean & Clear Plus Cartridge Filter, Intelliflo VS-3050 Variable Speed Pump, 2 x intellibrite LED Color Lights

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    mas985's Avatar
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    Re: Bigger Filter, Variable Frequency, create head

    The actual amps drawn by a pump motor is related to the impeller and the motor efficiency only and has nothing to do with the rating of the motor. Motor ratings are to ensure that you do not overdrive the motor so if you load a motor to the SFHP, it should draw less than the max amps although it does depend on the drive voltage. However, if you drive the motor to more than the SFHP, then the motor will draw more amps than the maximum and overheat.

    When replacing a motor, you need to make sure that both the max amps and the SFHP are equal to or larger than the original motor otherwise you risk overdriving the motor. In addition, if you replace a high efficiency motor with a low efficiency motor, the amp draw will increase so that needs to be taken into account as well. If you reduce the impeller size but keep the motor, everything will be fine. But if you reduce the impeller size but use a smaller rated motor than the motor the pump orginally comes with, then there could be an issue. So even though you may have a 0.95 SFHP motor for the 1/2 HP impeller, if the amp draw is more than the rating of the motor, it will overheat.

    You would be better off using the WFE-3 motor because the efficiency of the motor is probably higher which is why you are drawing only 10 amps vs 12 amps for the less efficient motor. Also, an induction motor will have higher efficiency for a higher the SFHP. So again, you are better off putting a larger SFHP motor on a low HP impeller. The only reason manufactures don't typically do this, except for 1/2 HP pumps, is because high SFHP motors cost more to build.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    JasonLion's Avatar
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    Re: Bigger Filter, Variable Frequency, create head

    I can't help but wonder if the reason you "have access to quite a few A.O. motors at no cost" is because someone thinks they are defective. Having a motor that runs, but overheats under a perfectly normal load, is a known way for motors to fail.

    The SFHP should tell you if the motor is suitable for use with the impeller, but it won't tell you how many amps the motor will draw. The high efficiency WFE-3 is rated for 11.2 amps, while the regular efficiency WF-3 is rated for 14.2 amps. Both are 3/4 HP, SF of 1.67. You also need to keep in mind that the rated amps the amps you measure with a amp meter, and the amps measured and then calculated with a power meter are all going to be different, and the second two will vary depending on the plumbing and temperature.

    Are you just measuring the amps and then assuming that the motor will overheat, or does the thermal cutout in the motor actually trigger in each of the different configurations you have tried? There are quite a few things that can cause the amps to read higher than you were expecting, but only a couple of things that can cause the motor to actually over heat. Putting on an oversized impeller will cause the motor to over heat, as will supplying too low a voltage, as will a partial short in the windings.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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