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Thread: Variable Speed pump "sizing" and how do I figure it out

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    Question Variable Speed pump "sizing" and how do I figure it out

    I'm considering replacing my single speed 2hp (1.1sf) pump with a variable speed pump. I'm struggling with trying to understand how variable speed pumps are "rated". I was looking at the Hayward EcoStar for example, and I can't find anywhere a rating for horsepower. Does the variable speed controller somehow make this information irrelevant?

    I'm sure it would be perfectly fine under normal conditions, but when I want to run the SPA my 2hp seems to "barely" get the job done, so how do I get an idea if the ecostar (or some other vs pump) would be suitable to run the spa?

    Also, I'm considering at the same time, an upgrade to a DE filter (and maybe some solar panels).. I was going to go with a very big one to increase time between cleanings... something along the lines of the hayward pro grid 72sf. Does filter size play into my pump selection?
    rectangle 11.5K gal IG concrete pool;; 125sf cartridge filter; 2hp 1 speed pump; K-2006, k-1766; PF:10

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    There's a curve in this brochurehttp://www.hayward-pool.com/pdf/lite...LITECOSB11.pdf
    A larger cartridge filter might give better flow and efficiency.
    12'x24' oval 7.7K gal AG vinyl pool; ; Hayward S270T sand filter; Hayward EcoStar SP3400VSP pump; hrs; K-2006; PF:16

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    Quote Originally Posted by kelemvor View Post
    Does the variable speed controller somehow make this information irrelevant?
    Yes, the variable speed controller allows you to virtually size the pump to the job. This is what makes a VS very flexible. However, it does have a limit to the amount of flow rate it can produce.


    Quote Originally Posted by kelemvor View Post
    I'm sure it would be perfectly fine under normal conditions, but when I want to run the SPA my 2hp seems to "barely" get the job done, so how do I get an idea if the Ecostar (or some other vs pump) would be suitable to run the spa?
    On full speed the EcoStar is the equivalent of a 2.5 HP Up Rated TriStar Pump. So the Ecostar will produce a bit more flow rate than your current pump on full speed. Most of the other VS pumps produce about the same flow rate so going with another VS probably won't help you much.

    I might be able to help you better if you can give me some more details about your set up:

    What size pipe do you have for the spa both suction and return?

    What is the distance between the spa and the pump?

    How many jets do you have and what is the orifice size of the jet (not the eyeball)?
    Mark
    Hydraulics 101; Pump Ed 101; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    Ooh I see some good reading in your signature links.. I know a fair bit about electricity, but when it comes to hydraulics... not so much.

    I went outside to verify this stuff before I got back to you and found something that was a surprise to me. Most of the pool plumbing is 2" including the "spa drain" (suction side from the spa). The spa return, however is 1.5" at least near the jandy valve. The return jets appear to be 2" and there are four! There is a strange contraption (maybe a past repair? I bought the house with the pool) that reduces the pipe from 2" to 1.5" on the spa return. The spa is about 35 feet from the center of the spa to the pump assuming the underground plumbing is roughly straight with some 90 degree bends. So 40' for the furthest return, 30 feet from the closest. There is also an "air" pipe that is connected to the spa piping underground a further 10' from the spa. I guess this is where it gets the air to make the bubbles with, the kids blocked off one of the spa jets once and water came pouring out of that pipe...

    Suction Pipe size: 2"
    Return pipe size: 1.5"
    Jets: 4 @2"ea
    Distance from pump to spa: 35' approx

    Hopefully that pipe reduction is some kind of design feature rather than a design flaw or (worse) a homeowner pipe repair. Not that it's relevant, but the "backwash" (really just a drain) and cleaner suction lines are also only 1.5" but without the strange coupler that is present on the spa pressure side pipe.

    Photos:
    exposed plumbing:
    closeup of that spa return line:
    rectangle 11.5K gal IG concrete pool;; 125sf cartridge filter; 2hp 1 speed pump; K-2006, k-1766; PF:10

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    I doubt you have 2" jets. Most spa jets are usually either 3/8" or 7/16". The jet nozzle is deep inside the pipe not near the surface.

    But unfortunately, given you have such small pipe for the jets, that is most likely the cause of your weak jets. The EcoStar will help some but there is only so much you can do with that size of pipe. If you did have 7/16" jets, you might be able to replace them with 3/8" jets and the jet would feel a lot stronger.

    But a bigger concern is with entrapment. With 2" pipe and such a big pump, you have the potential for some very serious entrapment issues. So if you do decide to go with a VS pump, please make sure you get the SVRS version of the pump.
    Mark
    Hydraulics 101; Pump Ed 101; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    The pool and the spa both have multiple drains in them, I assumed to reduce the entrapment risk. If that's not enough then I guess I'll have to put just a little more priority on this project I am considering.

    I dug up the pipe under the "strange contraption" which it turns out is a spring check valve (that must not be closing correctly). Unfortunately, it looks like the underground section of pipe for the spa is also 1.5" .

    Are the jets themselves something that can be accessed from the spa end of the pipe, or is that something that would require breaking up the decking to access?
    rectangle 11.5K gal IG concrete pool;; 125sf cartridge filter; 2hp 1 speed pump; K-2006, k-1766; PF:10

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    Multiple drains do reduce the risk somewhat but because of the pipe size and pump size, the velocity can be quite high at the drain. Many cities now require both dual drains and SVRS especially for spas because the drains are not very deep.

    The jets can be accessed from inside the spa end of the pipe. A socket wrench is used to unscrew them. Sometimes debris gets trapped behind the jets so it is a good idea to remove them and run the spa to flush out anything that may be there.
    Mark
    Hydraulics 101; Pump Ed 101; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    I am going through the same issue. It seems like the Variable Speed Pumps give you a one size fits all and then you tune it to meet your needs. The most popular is the Pentair Interlliflo but it only has a one year warranty. My issue with them is they have a lot of complaints and all they are doing is taking a 3 phase motor and mating it with a VFD. Minimally they should be giving 3 year warranty.

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    My Hayward EcoStar SVRS has a sicker on it that says: 2.0HP, 1.35 SF, 2.7 THP if this helps at all - I realize this info is not on the Hayward website so I figured I'd share.
    12'x24' oval 7.7K gal AG vinyl pool; ; Hayward S270T sand filter; Hayward EcoStar SP3400VSP pump; hrs; K-2006; PF:16

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    Default Re: Variable Speed pump "sizing" and how do I figure it out

    Quote Originally Posted by BigDave View Post
    My Hayward EcoStar SVRS has a sicker on it that says: 2.0HP, 1.35 SF, 2.7 THP if this helps at all - I realize this info is not on the Hayward website so I figured I'd share.
    Thanks very much. Sounds like the motor its-self is a little less powerful than what I've got, perhaps the impeller is better. I have no idea what my wet end is rated at, there's no markings on the pump that I can see other than the ones on the motor (which I replaced last year). I think maybe I'll try to find it local in the event it won't run the spa I could return it. My usual pool store wants $250 more than most sites online do, though.
    rectangle 11.5K gal IG concrete pool;; 125sf cartridge filter; 2hp 1 speed pump; K-2006, k-1766; PF:10

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