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?
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.
Re: Variable Speed pump "sizing" and how do I figure it out
Quote:
Originally Posted by
kelemvor
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
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)?
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: http://i28.photobucket.com/albums/c2...h_DSC_1490.jpg
closeup of that spa return line: http://i28.photobucket.com/albums/c2...h_DSC_1491.jpg
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.
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?
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.
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.
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.
Re: Variable Speed pump "sizing" and how do I figure it out
Quote:
Originally Posted by
BigDave
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.
Re: Variable Speed pump "sizing" and how do I figure it out
How do you figure? 2HP @ 1.1 SF vs 2HP @ 1.35 SF?
Re: Variable Speed pump "sizing" and how do I figure it out
My understanding was that lower sf was better with 1.0 being ideal, am I wrong? e.g 2hp@1.1sf = 1.8hp@1sf or 2hp@1.35 = 1.3hp@1sf
Do I have it backwards?
Re: Variable Speed pump "sizing" and how do I figure it out
As I understand it, Service Factor is an expression of the relationship between design HP and Total HP. Meaning that a 2 HP motor with a Service Factor of 1.1 can (when pressed) deliver 2.2 HP but is designed to run at 2 HP. A 2 HP motor with a SF of 1.35 can (when pressed) deliver 2.7 HP but is designed to run at 2HP. The higher SF motor has more headroom than one that's closer to 1.0 SF. I could be wrong but I'm pretty sure. Either way, the pump curve will be different for different wet-end combinations and when comparing, the pump curves are more important than motor HP.
In your case, I'd bet that the EcoStar would be able to deliver the same spa action as you've seen to date but also allow you to tailor the flow for other operations. As far as comparing the EcoStar to the Intelliflow, I can't help at all. I bought the EcoStar because I can easily integrate it's onboard control system to my Solar heating controller.
Re: Variable Speed pump "sizing" and how do I figure it out
All pool pumps are designed to run close to the rated TOTAL HP (label HP * service factor). So a 2 HP motor with a 1.35 SF will run close to 2.7 THP at the best efficiency point of the head curve. Manufactures usually leave a little bit of head room so the motor may never reach the full THP but it will get close. They can do this because a pump on a pool plumbing system has fairly constant load and torque requirements do not vary much.
Also, most pump lines come in an up rated vs full rated version. So an up rated 2 HP pump (1.23 SF), will have exactly the same performance as a 1.5 HP (1.65 SF) full rated pump in the same pump line. It is simply a relabeling of the motor but the wet ends have identical parts and so the head curves are identical.
So when comparing motors and/or pumps, you need to compare the THP, not just the label HP and not just the SF but both combined. But even that does give you a good representation of the pump. The head curve is a much better indicator of the power of the pump.
Re: Variable Speed pump "sizing" and how do I figure it out
I guess that's why hayward publishes only the head curve in their documentation and withholds information about horsepower and service factor entirely. Thanks for the lesson!
Re: Variable Speed pump "sizing" and how do I figure it out
If you look as some of the manuals and brochures, Hayward lists the label HP and service factor. For example:
http://www.hayward-pool.com/pdf/lite...RateSS11_5.pdf
Re: Variable Speed pump "sizing" and how do I figure it out
I forgot that I'd emailed hayward and asked about the motor last week. Daly from Hayward Technical Services just got back to me today with:
Quote:
The EcoStar pump has a Rated HP of 2.7, SF of 1.00 and a Total Rated HP of 2.7.
Although given what BigDave's label says I would guess this guy is wrong.. or maybe they switched motors.
Re: Variable Speed pump "sizing" and how do I figure it out
The CEC database lists the motor as a label HP of 2.7 with a service factor of 1.0. They might have relabeled the motor, but either way it is the same motor. The only thing that matters is THP.
Re: Variable Speed pump "sizing" and how do I figure it out
The label I read is actually attached to the wet end not the motor - FWIW.
Re: Variable Speed pump "sizing" and how do I figure it out
So I think this is the right pump for me, and I'm still reading docs from "pump ed 101". If I understand Mark's Hydraulics 101, I should get ~78gpm with this pump on maximum given the 2" suction and 1.5" return in the spa. ~86GPM on high when running the pool (2" pipe both ways).. The Filter I'm looking at is Hayward DE7220 which lists a max flow rate of 150GPM so I should be good there as well, right?
I think my only concern is the Hydraulics 101 post mentions "Cartridge Filters: Most energy efficient and don't require backwashing. Best suited for areas with water restriction, high electrical rates and/or pools that use a SWG."
I use a SWG, how does that play into filter selection? Is it just a matter of the additional head loss created by the SWG or is there something else to consider?
Re: Variable Speed pump "sizing" and how do I figure it out
With a SWG, you need to maintain salt and CYA levels in the water. Backwashing will remove both of these elements which will need to be replaced. A large DE filter is not as bad so you won't be replacing salt and CYA as much as you would a sand filter. Also, when you are backwashing, keep in mind that the salt level of the water is higher than normal so you may not want to backwash on to your lawn or landscaping. But if you have a backwash drain to the sewer system, this will not be a problem.
