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Thread: Jacuzzi Magnum Pump Replacement Recommedations -- HELP!

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    Jacuzzi Magnum Pump Replacement Recommedations -- HELP!

    Hi everyone,
    My trusty 16 year-old Jacuzzi Magnum pump has finally died when I opened the pool today. Seems like the bearings seized-up since the pump would not spin initially. I was able to free it up, but now the pump is v-e-r-y noisy.

    Here are my pool's details:
    - 20x40 - 8' deep end/3.5' shallow end with 2'x2' cut corners (approximately 32,500 gallons)
    - Suction Side: Two(2) Corner Skimmers; Main Drain in Deep End
    - Returns (three separate return lines each with valves to control flow on/off):
    - Two (2) Corner Returns & Paramount Floor Circulation (2 floor jets). These returns alternate & are not active @same time.
    - Two (2) Hydrojets in 8' Stairs
    - Four (4) Hydrojets in 2-Person Spa Seat
    - Polaris 380 Cleaner w/separate Booster Pump
    - GoldLine SWG (T-40)
    - 1-1/2" plumbing on all suction lines/returns back to the equipment pad.
    - Pump is approx 10 feet from the pool's corner -- longest pipe run would be about 70 feet (10 feet to pool + 20 feet along short side + 40 feet along long side of pool to farthest corner return.
    - Pump is approx 12-18 inches above the pool's water surface.
    - Pressure gauge reads about 12psi after backwashing the filter (last season).

    No plans to add any future water features.

    Magnum provided good flow with all returns open -- clear water & no algae blooms with 8 hours of runtime per day. When using the spa seat, I usually close-down the other 2 return lines and set the muli-port valve on 'whirlpool' which bypasses the filter media (currently sand but plan to change out the filter to a cartridge model @same time as replacing pump).

    The existing pump is a 1HP (wired for 220V/draws 7.0 amps) and has served well. I'm leaning towards a 2-speed replacement pump so that I can operate @low speeds most of the time & save some electricity.

    Looking @Pentair dual-speed models: WFDS 3/4/6 or WFDS 24/26/28. I checked 'pool school' for an explanation of uprated and full-rated pumps. The current-draw specs appear to be the same for pairs of these models (i.e., WFDS 4 and WFDS 26 have the same current draw @both high and low speeds), so is there any difference in performance?

    That question aside, which of the Pentairs listed above would be a good-fit replacement for the Jacuzzi Magnum? I used the worksheet on Hayward's site to calculate TDH and am getting 38 feet TDH, but not sure I calc'd it correctly. Unfortunately I don't know and can't find the specs on the Magnum.

    Any recommendations on a replacement pump?

    Thanks in advance,
    SteveK

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    Melt In The Sun's Avatar
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    Re: Jacuzzi Magnum Pump Replacement Recommedations -- HELP!

    The label on your pump should have both a HP (1) and a service factor. Multiply these to get the service factor HP (or Total HP). This may be 1, or it might be 1.5, 1.65, etc. If you look at the spec sheets for Pentair (or any other brand) there will be a column showing total HP. That's what you want to match.

    Keep in mind also that the new pump may have different dimensions than your current pump (dimensions are also in the spec sheet). Height is especially important, since you may have to do a lot more replumbing if you get something that is taller or shorter than the old one.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
    TF Test Kits -- PoolMath -- Pool School
    Make each day your masterpiece. - John Wooden

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    Re: Jacuzzi Magnum Pump Replacement Recommedations -- HELP!

    Unfortunately, any indication of service factor (SF) on the pump is long gone. The motor itself has SF indicated with dashes (----); no value There are 2 other sun-bleached labels -- one of which shows "SF", but alas, the actual numeric values have faded.

    But with some additional searches it appears that the motor is an 'energy saver' model with a service factor of 1.65. Even if that is not the correct SF, it is the highest I've seen for this motor (other sites show 1.4 and 1.5 as the SF). So with an SF of 1.65 @1HP, the SFHP would be 1.65.

    The Pentair WFDS4 & WFDS26 have a SFHP of 1.65, so those pumps would be the minimum to replace my current pump. As I understand SFHP, you can replace with a higher SFHP, but not a lower SFHP.

    Is there really any difference between these 2 pumps?

    In looking at the performance curves for these 2 pumps, it would seem that the low speed is too 'small' and the high speed is too 'big' for my need (38 TDH & desired flow rate of 45 GPM [12 hour run time]). The 38TDH/45PGM intersection falls in between the low speed and high speed performance curves, but not on (or even near) either curve.

    Sorry for the questions -- just trying to 'right size' the replacement pump.
    Thanks,
    SteveK

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    Melt In The Sun's Avatar
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    Re: Jacuzzi Magnum Pump Replacement Recommedations -- HELP!

    They are exactly the same pump. I'm in the process of picking a new pump right now, and I noticed that too; just FYI, prices for the -26 are a lot less than the -4. Stupid, huh? The rules for replacing with bigger but not smaller only apply when you're replacing the motor on an existing pump (have you considered that, by the way?) but not when replacing the whole pump. You're not likely to find a pump with that low a flow rate, and your popups probably wouldn't work all that well either.

    Here is what I've hashed out so far, and I'm in a similar situation.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
    TF Test Kits -- PoolMath -- Pool School
    Make each day your masterpiece. - John Wooden

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    Re: Jacuzzi Magnum Pump Replacement Recommedations -- HELP!

    Thanks for posting the link to your other thread....I think I saw that last night.

    Physical size is not an issue, since my equipment is not enclosed in any way. If I need to do a little PVC work no biggie.

    Anyone else with opinions on the Pentair WFDS26 being a suitable replacement for the Jacuzzi Magnum Plus (1HP)?

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    Re: Jacuzzi Magnum Pump Repl Recommedations -- dual speed @l

    Considering my TDH (see my original post in this thread), will running the Whisperflow WSDS26 @low speed provide sufficient flow for the SWG's flow sensor?

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