2 pumps in series used like a 2-speed pump

[ChadH]

Hi All, Great Information that this site provides.
I am considering putting a 2nd pump in-line with my current pump. I currently have a 2hp pump that is purposely oversized because of Pop-Up heads on my pool floor. I want to put in a lower pump (1hp) in line with my current system and then would use some sort of switch box to determine which one of the pumps would be running. The reason for this is that I have solar panels and would like to run the smaller pump for longer hours to get the most sun bang for the buck. I talked with someone about this and they thought that the centrifugal impeller on the pump that was not running would severely restrict the flow to the pump that was. Any comments on this? Thanks all for your insights.

[mas985]

Yes, they are correct. You would eliminate any cost savings with the reduction of flow that would cause.

If you want the second pump, you should plumb it in parallel instead of series. If you use one way valves on the inputs or outputs of both pumps, you can prevent backflow into the pump that is off.

[tphaggerty]

I would guess that it would be cheaper to replace the motor (only the motor, not the entire pump assembly) with a 2 speed pump than it would be to buy and install an entirely separate pump. I know that you can buy the 2 speed motor for the Hayward series of pumps online at some pretty reasonable prices.

Normally, though, solar is run at high speed, not low speed. There is another discussion going on about running solar at low speed. You can run solar at low speed, but in order to do that, you normally have to prime the system at high speed to get water up to the panels and completely purge the system of air. Then you could change to running at low speed. On my solar controller, there is a relay that can be used to kick a 2 speed pump to high (or to run a separate booster pump), I used it to kick my system up to high when solar is on, then it goes back to low when solar is not running.

I think that with a more expensive controller, it would be an easy thing to program to run at high for a bit, then kick down to low, but I'm not sure. My Ikeric pump has the ability to start in high speed for a while, then kick itself back down to low (this is normally used for pressure side cleaning systems). I haven't played with that since I don't have that requirement.

[ChadH]

Thank You folks for your thoughts and insights, they are very helpful. I had previously thought that one day when my existing pump (2hp Max E Glas II - P4EA6G-188L) stops working that I would then replace it with a 2-speed option. This all started because I noticed some pumps available for cheap on our local used market and thought that maybe I could do something in the meantime. I initially thought of the 'in serial' connection because one of the used pump options did not have a strainer basket attached. So I thought that if I put it after the other pump that the 1st pump's basket would strain the input for the 2nd pump. With the restriction issue pointed out, I will be abandoning this idea in lieu of the parallel option if I go the 2 pump route. I'm currently installing a brand new Goldline GL-235 Solar controller that we purchased for this. I have not read where this model can do the High speed, then low speed kickdown. What I have determined is that the 2hp pump does a great job at cleaning the floor but it is entirely overkill when it comes to solar. Unfortunately I don't have extra plumbing into my pool to seperate the cleaning and solar as would be optimal.

[tphaggerty]

Chad,

On the GL-235, there is an option to have a 220v relay vs. a 110v relay (mine only has the 110v). I would opt for the 220v if you think you are ever going to get a 2 speed, 220v pump. That way, you should be able to use the GL-235 to DIRECTLY kick the pump up to high speed (or, possibly even to have it go to low speed from off, not sure how that would be wired though).

With the 110v relay option, you can only turn on a 110v booster pump (or use it as a non-powered switch like I am doing).