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Thread: Will 2 sp pump work if THD is too high?

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    Will 2 sp pump work if THD is too high?

    I just bought my home and am renovating it to be energy efficient (which my pool equip is NOT).
    I'd like to remedy this with a new pool pump and I'd like to request assistance with my logic.

    From what I've researched, I should size my pump at (30Kgal/8hr)=3750g/hr or 62.5g/min flow to exchange pool once per 8 hrs.
    My conservative estimate of THD is >50'. This is based upon 2 skimmers, too many 1.5" non-street elbows, many couplings from prior repairs, not to not to mention my pump & filter rig located ~25' from the pool.

    My current 1.5HP AO is killing me ($$$) at 230V/9.3A SF 1.0.
    A specs on a 2 speed 1.5 Haywood MAXFLO XL SP2310X152 looks good at high speed but the GPM curve is non-existent at low speed assuming >50'THD. I know lower flow rate will automatically reduce the pressure but the Haywood specs show that the THD needs to be <20' to get any flow rate at all.

    To me, that means that it would be a waste of $ to purchase unless I was able to get my THD <20'. Correct?

    One more thing. How can I tell if these advertised pumps are PMM or inductive? My assumption is an EE motor would have to be PMM but this type of info is not readily found in the pump mfg literature.
    Thank you for any assistance.
    v/r
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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    Texas Splash's Avatar
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    Re: Will 2 sp pump work if THD is too high?

    Hello and welcome to TFP! I see you haven't received a reply yet on your post about pump sizing. I just wanted to let you know we haven't forgotten about you. This reply should get your posting updated back to the top of the queue where hopefully someone experienced with your specific question can provide some constructive answers. Thanks for checking-in with TFP, and have a great day.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Re: Will 2 sp pump work if THD is too high?

    I'm assuming the acronyms in your post THD, and PMM should be TDH, and PWM?

    Variable speed motors are 3phase motors controlled by PWM inverter. Yes, they are more Energy Efficient.
    Most residential variable speed pump motors are constant torque, which function much the same as standard psc, or cap start induction run motors. With respect to increased TDH decreasing flow.

    I believe the Intelliflo variable flow pump is a true variable speed with the ability to increase torque to maintain constant volume.

    Yes, the lower the TDH, the more flow you will achieve.
    24k gallon inground vinyl liner pool, 8'-3' depth, 2 skimmers, 3 returns, basic 5 chem kit.
    Hayward: DE-60 filter, Superpump VS, AquaRite salt chlorinator w/T-Cell 15, TigerShark QC robot. Jacuzzi hot tub ~350gal. Air blower type, w/8 jets.

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    mas985's Avatar
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    Re: Will 2 sp pump work if THD is too high?

    THD is not fixed and varies with the square of the flow rate. For example, low speed on a two speed pump has 1/2 flow rate but only 1/4th the head loss as high speed on exactly the same plumbing.

    But please forgot everything you have learned about turnover. There is no magic turnover number and many pools can get by with much less than a turnover per day. It really has no meaning for residential pools. There is a pool school article on pump run time as well as a study in my sig.

    Also, all motors are induction except for most VS/VF pump motors. Those are usually PMM.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Will 2 sp pump work if THD is too high?

    Thank you very much. I've been on a steep learning curve with my first pool and I appreciate all of your advice.

    I'm plumbed w/ 1.5" pvc throughout; 2 skimmers, 2 eyeball returns, 1 polaris jet from booster pump.
    I've decided that it would be best to use gauges to determine my THD to determine the best size VS pump for my pool.
    @mas985, your Pool Pump Tools spreadsheet is amazing and has been invaluable. I've spent hours comparing each VS pump and initial/lifetime costs. Thank you so much! Do you have any specs on the new Century (AO SMITH) VGreen 165? It's low upfront motor cost appears to be a great candidate for consideration too.

    Will update as I progress.
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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    morzh's Avatar
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    Re: Will 2 sp pump work if THD is too high?

    If PMM means perm magnet, most pumps use asynchronous AC motors which have no permanent magnets in them. Any AC motor can be controlled by a var freq drive to regulate speed. PWM (pulse width mod) is used to control DC motors that do use PM in them but: they use brushes and are inherently less reliable.

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    Re: Will 2 sp pump work if THD is too high?

    My current 1.5HP AO is killing me ($$$) at 230V/9.3A SF 1.0.
    I certainly defer to the pump guys here but I am decent at practical math.

    Let's say you run you pump 8 hours daily. Multiply that times your usage rate and see how much it costs to run the pump monthly.......I'll bet you come out under $30.00. My only point being it will take a long, long time to get your money back.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Will 2 sp pump work if THD is too high?

    @morzh: Yes, I was referring to permanent magnet motors. I knew a 2 speed motor would offer a certain level of energy efficiency, a PMM would offer even greater power savings.
    My research on this site shows that "typically", only a Variable Speed motors will be equipped with PMM so I've opted to narrow my pool (pun intended) of pumps to only VS.
    I've been using mas985's spreadsheets to figure out what would be best.
    I found this gem: Pumps | Pool Spa Pumps | Speck Pumps Badu EcoM3 1.25 HP Variable Speed Pump | M1876943 - GlobalIndustrial.com
    which is a 1.25 THP variable speed pump for $350!!!!

    I believe its too small for my pool but I'm ordering the gauges now to verify my actual TDH. According to mas985 spreadsheet, this pump would cost me $5/month to operate or $700 in 5 years (initial + monthly operation).
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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    Re: Will 2 sp pump work if THD is too high?

    Quote Originally Posted by duraleigh View Post
    I certainly defer to the pump guys here but I am decent at practical math.

    Let's say you run you pump 8 hours daily. Multiply that times your usage rate and see how much it costs to run the pump monthly.......I'll bet you come out under $30.00. My only point being it will take a long, long time to get your money back.
    Hi duraleigh. Thank you. Unfortunately, my MSEE is trumpted by the fact my wife had a pool when she was a kid. She wants to run it for atleast 12 hrs daily AND for 24 hours after we add any shock or chems.... (sigh).
    My initial plan was to slowly reduce pump time and tell her "yes dear, the pump was on all day..." but given the age of my system, I'm amicable with just footing the bill for a new pump and letting her run it as long as she wants. Happy wife, happy pool boy.
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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    Will 2 sp pump work if THD is too high?

    Quote Originally Posted by duraleigh View Post
    I certainly defer to the pump guys here but I am decent at practical math.

    Let's say you run you pump 8 hours daily. Multiply that times your usage rate and see how much it costs to run the pump monthly.......I'll bet you come out under $30.00. My only point being it will take a long, long time to get your money back.
    When I did be math on my pump last year, which is almost identical to the OP's, I came up with $50/mo at 8hrs a day at ~$.10kWh.


    30K gallon IG vinyl. 1.5HP 2-speed Waterway Mustang pump. 600 lb sand filter. Polaris 280. Circupool SI-60+. TF-100

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    Re: Will 2 sp pump work if THD is too high?

    Quote Originally Posted by wberzett View Post
    Hi duraleigh. Thank you. Unfortunately, my MSEE is trumpted by the fact my wife had a pool when she was a kid. She wants to run it for atleast 12 hrs daily AND for 24 hours after we add any shock or chems.... (sigh).
    My initial plan was to slowly reduce pump time and tell her "yes dear, the pump was on all day..." but given the age of my system, I'm amicable with just footing the bill for a new pump and letting her run it as long as she wants. Happy wife, happy pool boy.
    Show her the pump run time study that is in my signature.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Will 2 sp pump work if THD is too high?

    Quote Originally Posted by n240sxguy View Post
    When I did be math on my pump last year, which is almost identical to the OP's, I came up with $50/mo at 8hrs a day at ~$.10kWh.
    Sent from my iPhone using Tapatalk
    After duraleigh's "long, long time for ROI" comment, I went back into mas985's pump spreadsheet and plugged $0 into the Equipment Cost to compare my current pump to the one I considered ordering for $350. At $0.11/kwh, it will take me ~6months to see an ROI and reap the benefits of a new pump at that cost.

    Given that I only have 1 month's worth of GA nuclear power into my pump pad thus far, the longer I prolong the upgrade, the more $$ I've wasted.
    Thank you!
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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    Re: Will 2 sp pump work if THD is too high?

    Depending on your cost of electricity in your area and how long you plan on staying in your home, check out solar PV direct pumps - I use the Lorentz PS 600 controller with a C17.1 pump. It will move 60gpm and has a DC - DC brushless 3ph motor, good for salt water pools. LORENTZ | Solar Pumps, Solar Trackers, PV Modules, Solar Parks


    90,000litre, IG vinyl, 1/2 HP Tristar pump, Sandfilter, Aquarite T-15 ASG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Will 2 sp pump work if THD is too high?

    Quote Originally Posted by morzh View Post
    If PMM means perm magnet, most pumps use asynchronous AC motors which have no permanent magnets in them. Any AC motor can be controlled by a var freq drive to regulate speed. PWM (pulse width mod) is used to control DC motors that do use PM in them but: they use brushes and are inherently less reliable.
    Yes, it dawned on me PMM after writing my last post, acronym permanent magnet motor.
    Yes, though the variable speed pool pumps receive a single phase AC power source, they are actually 3phase DC inverted motors with a permanent magnet rotor.

    And THD stands for total harmonic distortion. Lol!
    Which leads to a whole nother discussion.
    The nice thing about vs motors is, you can dial out the harmonic resonant speeds. Unlike a single or two speed. This will inherently add life to the bearings.
    24k gallon inground vinyl liner pool, 8'-3' depth, 2 skimmers, 3 returns, basic 5 chem kit.
    Hayward: DE-60 filter, Superpump VS, AquaRite salt chlorinator w/T-Cell 15, TigerShark QC robot. Jacuzzi hot tub ~350gal. Air blower type, w/8 jets.

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    Re: Will 2 sp pump work if THD is too high?

    My guages came in and I have 12-13 mmHg at the pump and 10psi at the filter (fully backwashed).
    I would not have thought that my TDH was so low (~36') but lucky me. My PB must have used parallel 1.5" throughout given my pump is so far from my pool.
    Using some online tools to size a pump for my pool, I could easily downsize to a .75-1HP pump. It looks like that $350 EcoM3 might work but further research shows that is a non-adjustable 3 speed pump.
    The EcoM3V (V=vsp) is $400. Still a 3 speed pump but I can customize each setting from 1000 rpm to 3450rpm.
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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    mas985's Avatar
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    Re: Will 2 sp pump work if THD is too high?

    There are a couple adjustments that you need to make when calculating TDH from filter pressure. You have to add 3' for the height of the filter gauge above the pump. Also, you have to add the TDH of the plumbing between the pump and filter. You can use the spreadsheet PSIVac2GPM to do the adjustments. So total head is probably a little over 40'.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Will 2 sp pump work if THD is too high?

    Thank you Mark!
    18x40 IG liner ~30Kgal, 1.5HP SS AO Smith/Haywood pump, 1.125THP booster pump for polaris 280, Tagelus TA60D sand filter, 2 skimmers, 2 returns, 1 discharge for polaris

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