Upgrade to VS Pump - Spa Compatibility

[Dave3204]

My pool is c. 15000 gallons, and has an adjacent spillover spa. Current equipment is a Hayward Northstar pump rated at 119 gpm with 50-ft head, powered by a 1.5 hp single-speed motor. Filter is a 60 sq ft DE canister. The pump feeds both spa and pool via a T-junction and a valve - one setting returns all water to the spa, another to the pool, and the center position splits the return between the two. The latter is default, so the waterfall from the spa is active and also water returns directly to the pool. The return to the spa has a spring-loaded gate that limits the flow.

I'm thinking of replacing the pump with a variable speed unit, but have a few concerns:

• I see claims for enormous energy savings for a VS pump relative to single-speed; one calculator from Jandy tells me I would save 94% on electricity cost. Most of the claims come from sources trying to sell VS pumps, and many are implausible. As I understand it, assuming you need to circulate a fixed number of gallons daily, a VS pump does it by running at a lower speed for more hours. This is said to be more efficient than a higher speed for fewer hours. This makes sense, but it's hard to believe it's as dramatic as often claimed. Is there any disinterested information available on energy efficiency? (My electricity costs the same at all times, so it's not a factor when the pump is running.)

• Given the spa plumbing, will the lower pressure of a VS pump still work and keep the spillover active?

Thanks,

Dave

 

[ajw22]

Welcome to TFP.

When you have automation the automation can raise and lower the pump speed depending on the flow devices need. When a high flow device like the heater turns on the RPM will be increased and when the heater turns off the speed will be decreased.

When you do not have automation the minimum speed you can run the VS pump at is the speed the highest flow device needs. In your case it is probably your heater that needs at least 40 GPM or your spa jets that can need more flow then that.

In my case my VS pump runs at 1400 RPM using 210 watts and about 30 GPM which is satisfactory for my SWG. When my MasterTemp heater turns on the pump is increased to 2400 RPM using about 950 watts and 60 GPM.

VS pump energy efficiency follows this curve...

 

[colonelkirby]

My pool is c. 15000 gallons, and has an adjacent spillover spa. Current equipment is a Hayward Northstar pump rated at 119 gpm with 50-ft head, powered by a 1.5 hp single-speed motor. Filter is a 60 sq ft DE canister. The pump feeds both spa and pool via a T-junction and a valve - one setting returns all water to the spa, another to the pool, and the center position splits the return between the two. The latter is default, so the waterfall from the spa is active and also water returns directly to the pool. The return to the spa has a spring-loaded gate that limits the flow.

I'm thinking of replacing the pump with a variable speed unit, but have a few concerns:

• I see claims for enormous energy savings for a VS pump relative to single-speed; one calculator from Jandy tells me I would save 94% on electricity cost. Most of the claims come from sources trying to sell VS pumps, and many are implausible. As I understand it, assuming you need to circulate a fixed number of gallons daily, a VS pump does it by running at a lower speed for more hours. This is said to be more efficient than a higher speed for fewer hours. This makes sense, but it's hard to believe it's as dramatic as often claimed. Is there any disinterested information available on energy efficiency? (My electricity costs the same at all times, so it's not a factor when the pump is running.)

• Given the spa plumbing, will the lower pressure of a VS pump still work and keep the spillover active?

Thanks,

Dave

View attachment 601271

View attachment 601272

The savings is dramatic. I cannot offer you empirical data just antectdotal. I run 1350 RPM 24x7x365 and it barely dents my electric bill. My spillover spa is fine at that RPM.

 

[ajw22]

The savings is dramatic. I cannot offer you empirical data just antectdotal. I run 1350 RPM 24x7x365 and it barely dents my electric bill. My spillover spa is fine at that RPM.

You have IntelliCenter automation while the OP does not.

 

[colonelkirby]

You have IntelliCenter automation while the OP does not.

True. But if the new pump was say a Pentair IntelliFlo3 he would have at least rudimentary automation that would allow changing the RPM on demand spa side right?

 

[wireform]

True. But if the new pump was say a Pentair IntelliFlo3 he would have at least rudimentary automation that would allow changing the RPM on demand spa side right?

True and lots of vsp's have a scheduling capability which is nice.

 

[ajw22]

True. But if the new pump was say a Pentair IntelliFlo3 he would have at least rudimentary automation that would allow changing the RPM on demand spa side right?

I don't know what rudimentary automation you think the Intelliflo3 has other then triggering a relay at a specified speed.

 

[colonelkirby]

"It's Easy to Own a Pool When it's Connected​

With the Pentair Home app, simply adjust speed, flow, temp, heat, and timers from a smart device to avoid the trip to the pool pad."

Is something other than the pump using the onboard relays and the Home app required to do the above? I don't have first hand experience using the pump without the IntelliCenter so I could be way off base.

 

[ajw22]

"It's Easy to Own a Pool When it's Connected​

With the Pentair Home app, simply adjust speed, flow, temp, heat, and timers from a smart device to avoid the trip to the pool pad."

Is something other than the pump using the onboard relays and the Home app required to do the above? I don't have first hand experience using the pump without the IntelliCenter so I could be way off base.

That is what the Pentair HOME app can do when you have various Pentair products connected to it. Nowhere does it say that is all done with just the Intelliflo3.

 

[MSchutzer]

The key to savings with a VSP pump is understanding that the flow rate (gals/min) directly scales with the pump rpm. So let’s say you get 80 gals/min at 3450 rpm, if you drop the pump speed to 1725 rpm, 1/2 speed, you get 40 gals per minute.

But look at that chart above with the power consumption numbers. At 3450 rpm the pump uses 2315 watts, at 1725 rpm the pump consumes about 300 watts.

Running at 1/2 speed requires you to run the pump twice as long to move the same volume of water. So if you run at full speed for an hour you will use 2.315 kWh of energy. If you run at half speed for two hours you consume .6kWh to move the same amount of water. For this example that’s almost a 75% savings in energy.

If you run the pump slower, you will have to run it longer but you will save even more energy. The laws of hydrodynamics says that the power required changes by the cube of the linear speed change.

So running your pump at 80% speed results is about half the power consumption for only a 20% reduction in volume of water moved. .8^3 = .51, or 1/2 the power consumption.

 

[Dave3204]

Thanks for the replies! I'm leaning towards installing a Hayward Tristar SP3202VSP, which has a maximum flow at 50 ft head of 95 gpm, compared to my current 119 gpm - probably close enough. I think the current pump is overkill. It looks like the savings will pay for it in a year or two. This model is programmable for multiple durations at different speeds, without any external automation being installed.

Looking at pumps, I'm disappointed at the slow pace of technology implementation. This one requires you to be at the pump to program or override it; my heated coffee mug and garage floodlight both have Bluetooth-enabled phone apps to control them, despite being much cheaper products.

My concern is getting some flow into the spa / spillover while the pump is set to a lower speed. The spa line has a spring-loaded gate in it to restrict flow, and this works properly at the high flow rate of my current single-speed pump. But I expect with lower flow, it would remain shut and not allow any water to the spa. I may need to remove the gate and try to distrubute the flow with the valve alone.

 

[sterfrydude]

Thanks for the replies! I'm leaning towards installing a Hayward Tristar SP3202VSP, which has a maximum flow at 50 ft head of 95 gpm, compared to my current 119 gpm - probably close enough. I think the current pump is overkill. It looks like the savings will pay for it in a year or two. This model is programmable for multiple durations at different speeds, without any external automation being installed.

Looking at pumps, I'm disappointed at the slow pace of technology implementation. This one requires you to be at the pump to program or override it; my heated coffee mug and garage floodlight both have Bluetooth-enabled phone apps to control them, despite being much cheaper products.

My concern is getting some flow into the spa / spillover while the pump is set to a lower speed. The spa line has a spring-loaded gate in it to restrict flow, and this works properly at the high flow rate of my current single-speed pump. But I expect with lower flow, it would remain shut and not allow any water to the spa. I may need to remove the gate and try to distrubute the flow with the valve alone.

FWIW the valve you're describing is a check valve so its primary purpose is to prevent back flow. It's there so your spa doesn't drain into your pool when the pump isn't running so don't take it out.
I have a very similar setup and I'm trying to figure out the same thing. Replacing a very old 2hp pentair that I think is overpowered. I have an old 1.4hp VSP that doesn't work with Hayward automation and I did put it in temporarily, I didn't get the same push over the spa ledge unless it was on full power. I'm just not sure if it actually needs to push that much, we also have a spillover mode which forces more flow over the spa.