Pump replacement questions. Single or variable?

[sonoman]

Time to replace the pump on my pool; the old one is screeching at me.

I have a 28k gal pool with solar heater (panels are on a shed, 5-8 ft above water level) and suction side vacuum (Hayward pool vac ultra). Filter is Hayward DE 60ft2 and I have a salt water chlorine generator. 2" plumbing and no spa or water features.

I don't know the total dynamic head because I don't have a vacuum gage. Pressure on the filter runs about 20 psi with new media.

I live in Northern California where power is very expensive (36c kwh peak!!) and I need the solar all summer because of the cool nights.

Existing pump is Hayward Super2 3020 with 2 HP pump wired to 230v. I have no reason to believe it was sized correctly at 2 HP; it was there when I bought the house.

I would like to save on energy costs. I am considering dropping the pump to a single speed 1.5hp or a variable speed. I worry about driving the vacuum effectively (we get a lot of leaves and I fight algae) and the solar heater. New CA code requires variable speed pumps, but retros are grandfathered in (for now) and I plan to do the work myself, so I can go single speed.

Some shops told me the 2 speed is a waste of money because it won't drive the filter and it isn't compatible with the solar. They said I won't see any savings. For my application, is 2 speed all hype? Of course, that brings the question of what good is a code that requires variable speed pumps when so many pools have solar heaters...other than a regulation gone wrong??

What should I be looking at? Single speed 2 hp? Change impeller and diffuser and go with 1.5hp? 2 speed? What are your experiences with pump sizing and dual speed? What should I be aware of before I buy a new motor or pump?

 

[257WbyMag]

Welcome to TFP!

We will almost always recommend a two-speed or variable speed pump over a single-speed any day. Why? Because it gives you the owner/operator a choice in how fast you want to move water. I think that the comment that "a two speed won't drive your filter" seems like malarky. All you want is to move water through the filter and whether it moves quickly through the filter or more slowly, it still gets filtered.

I'm thinking that you would probably do fine with a 1.5 HP two-speed. I'll sit back though and let our resident pump experts weigh in on things.

 

[sonoman]

Thanks for your quick reply. The guy at A1 Poolparts said he didn't think the low speed would make it through my solar and he recommended a single speed Whisperflow 11515. My solar only has a manual Jandy valve and the switch is an old intermec mechanical switch; I don't have any kind of pool controller to turn the solar off when the pump is on low speed

I am certainly interested in the promise of greater efficiency but only if it will work for my application. I am interested in what the pump gurus have to say

 

[mas985]

Running solar on low speed can defintely be an issue for many reasons which is why most people, including myself, run their pumps on high speed for solar, vacuuming and skimming and resort to low speed for circulation and filtering. Even with solar several hours a day, I still manage to run on low speed for several more hours. So there are always opportunities to run on low speed and save money.

With a variable speed pump, you have a lot of the same issues although there is also a lot more flexibility in setting the operating point. This allows one to optimize the energy efficiency of the setup. I will usually recommend a VS for a new pool since the incremental cost is not all that much but for a retrofit, it can be an expensive solution which doesn't always pay for itself. However, in California it usually always pays for itself. The real question is if you have the money for the up front costs.

BTW, filters work better on low speed than on high speed so I'm not sure what your pool store is talking about.

 

[sonoman]

Thanks, Mark.

Your description implies I have some automatic valving and control for my solar and vacuum. Is that correct? I would need some way to turn the vac or solar off during low flow times. What is involved with getting something like that set up? It is beginning to sound complex (and expensive)! What do you recommend for retrofits in CA? I am also in the Bay Area where power rates are astronomical.

 

[mas985]

It is hard to make a recommendation for you without all the information. It really depends on your objective.

Do you want to go cheap up front and spend more money over the next few years or spend more money up front and save over the years? A variable with controller and actuator will likely be in the $2000 range without installation but will likely save much more than that over the life of the system.

There are other issues which can affect your decision as well:

Would you consider using a solar cover to reduce the amount of time needed to run at higher speeds and thus allow for more energy savings?

What is the size of your solar panel and do you want to extract as much heat from the panels as possible?

In my sig, there is a link, "Pump Modeling Tools", which has a spreadsheet that allows you to compare lifetime costs of various pool pumps. But the results are of course dependent on your assumptions. For your situation, I would use plumbing curve A for a setup with solar. As for target flow rates on the variable speed, that depends on your panel size and your objective with solar and if you plan on installing a controller.

 

[drkeyes]

I bought my house with a pool last year. During the remodel, before we moved in, I figure the old pool pump was costing me $150/month (Northern CA with high energy prices and smartmeter). I upgraded to an Intelliflow Variable Speed pump and added 9 solar panels to the roof and am very pleased. I can run my pump at very low speed in the winter for $25/mo in electricity. In the summer I increase the speed enough to be able to push through the solar panels and find I am at about $40/mo. I can change the speed to get it where I need it to be, eg. high speed for the spa jets or to accelerate suction crawler.