Two of the factors that need to be considered are the SF number on the motor and the head loss.

The numbers you are quiting seem to be a bit high.

Is your equipment more than 50' from the pool?
Is your pool using 1.5" plumbing?
SF stands for Service Factor. In simplest terms, it's a multiplier that represents how much "intermittent" overload a motor can take.

One HP is 746 Watts. However, the Startup current draw is normally almost 2x at startup.

Assume voltage at 220VAC
Power is expressed in watts. Current in amps. Power is Volts x Amps.

Assume a Service Factor of 1.25.
746/220 is about 3.4 amp times the SF of 1.25 is about 4.25 amps per HP.

At startup (the 1st 3 seconds or so)it may be as much as twice that before setting down.

Both your motors, you said are 3/4 HP ea. Something is wrong somewhere and I suspect it's the device connected to the panel.

Only the VF model will give you GPM. The other models will give you pump RPM and wattage used.

Since your i9 system predates the Inteliflow's release, it will need updating. Whether the system needs new boards for the the panel and indoor controller or just to be re-flashed, I don't know but a call to Pentair support will let you know.

If you go with the Intelliflow upgrade, you can eliminate the booster pump. The Intelliflow has enough power to drive the sweep when needed.

Scott

"Is your equipment more than 50' from the pool?
Is your pool using 1.5" plumbing?
SF stands for Service Factor. In simplest terms, it's a multiplier that represents how much "intermittent" overload a motor can take. "

The more water a pump moves the more energy it consumes. If the pipe run is long, and has small pipe, the motor will draw less amperage.

This is one of the problems with oversizing pipes. You need to make sure that the pump is operating inside of it's nameplate amperage otherwise you will have premature motor failure. You'd have to put a re-stricter valve on the effluent to bring the amperage back down.

In fractional HP motors this isn't that common, we typically see this in 5hp+ motors.

Pumps use more current at higher flow rates and lower head loss as Racket pointed out. However, even though the pump uses higher current at higher flow rates, the GPM/Watt actually goes up (GPM climbs faster that Watts) with flow rate so the overall efficiency of the pump is higher. So larger pipes are still a good idea and will result in a lower energy cost per turnover.

Also, a full rated 3/4 HP Whisperflo (WFE-3) will use about 1700 Watts @ 78 GPM and 51' of head.

Note that the labeled current is really specified as 5.6a@230v OR 6.0a@208v. As voltage drops current must increase to meet the power demands of the pump. This label seems to reflect the current use at the far left of the head curve or at 33 GPM and 73' of head. I'm not sure why they label it that way but it is way off from reality.

Thanks for the quick responses.

The pool equipment is approximately 25' - 30' from the pool. All piping appears to be 2" or 2.5". The 3/4 HP Whisperflo has a 1.67 Service Factor.

I did notice the much larger startup current draw, but I waited 10-20 seconds for things to stabilize before taking the 1,700 and 1,500 watt readings.

I tested my current reading device and it appears to be very accurate with other things I turn on and off through the house, so I am inclined to give it some believability.

It sounds as if the 3/4 HP pump is at the very bottom end of what I really need and is struggling at running full bore. Does that seem like a reasonable assumption?

As far as the Intelliflo VF goes, it would be great to be able to replace both the 3/4 circ pump and the 3/4 booster pump. I assume I just connect the booster pressure line back into the main circulation pressure lines and run the VF at high speed when I want to clean?

"It sounds as if the 3/4 HP pump is at the very bottom end of what I really need and is struggling at running full bore. Does that seem like a reasonable assumption?"

No, I would say the pump is not "struggling" at all and seems to be operating within the normal parameters of the pump. 1700 Watts is in the normal range for that pump. The operating point is in the right portion of the head curve but near the best efficiency point. GPM/Watt is 2.75 which is pretty good for a single speed pump.

The amps on the label of the WFE-3 represents "Full Load Amps" not "Service Factor Amps" that are specified on some pumps so it is not representative of the actual amps used in the pump.

"the GPM/Watt actually goes up (GPM climbs faster that Watts) with flow rate so the overall efficiency of the pump is higher. So larger pipes are still a good idea and will result in a lower energy cost per turnover. "

There is a peak efficiency point with all pumps, they used to publish this. So yes the gpm to watt could go up but at what cost to the longevity of the pump motor?

I have seen many times where the GPM went up 5%, but the amperage went up 15%.

The full load amps should be observed on the rating plate, otherwise you will be replacing motors frequently.

So, at my 3/4 hp running at 1,700 watts, this is considered normal, which is good to know. Even though, as you say, this is near the best efficiency point for the pump, is this considered normal today on the efficiency scale? I assume I can run the Intelliflo VS 1 hour a day at a higher flow for the cleaner then scale it way back to 30-40 gpm for 12 hours (or even 20 gpm for 23 hours) for circulation, and that will net some good power savings. This low flow assuming I don't care about the spill on the spa looking good. Is there a downside to running a pump with such a slow gpm? Surface friction issues with the skimmer?

I don't understand what you mean by the GPM/Watt is 2.75. What does this mean?

Just for example:

At 60 GPM
1700 watts/hour = 28 1/3 watts per min.
60/28.333=2.1111

I forgot in my earlier posting that regular induction motors found on most single speed pumps are only about 50% efficient. In order to get the 746 watts of work, you will need to multiply times just over 2 to account for the added wattage used. The extra, unused wattage turns to heat.

Tack on the extra current for load and the wattage comes in right where you are seeing it. I hate it when I brain fault.

Scott

The pump draws 1700W whenever its running. Its not a per minute equation. You pay for power per KWH which is an hour of sustained load of 1KW, or 1000 watts.

"The full load amps should be observed on the rating plate, otherwise you will be replacing motors frequently."

I disagree with this statement. "Full Load Amps" on the label simply specifies what the current draw is when the motor is loaded to the labeled horse power. Pumps are designed to load the motor to the service factor HP and not the labeled HP. "Service Factor Amps" or sometimes labeled as "Max Amps" is the current draw when the motor is loaded to the service factor HP.

On the WFE-3, the "Full Load Amps" is specified as 5.6a@230v OR 6.0a@208v which is around 1250 Watts. This motor actually draws 1700 watts in this pump application so you can see that the label is simply a reference and not what the motor will draw in a pump application.

'There is a peak efficiency point with all pumps, they used to publish this. "

There are several types of efficiency when discussing pumps. First there is the electrical efficiency of the motor. This can be expressed as the ratio of the shaft HP to the electrical input HP. The WFE-3 has a published electrical efficiency of 68.7%.

The total efficiency of the pump is related to the how much energy is delivered to the water (pumping HP) compared to the amount of energy input to the motor (input HP). This is expressed as

Total Pump Efficiency = Pumping HP / Input HP
Pumping HP = Head * GPM / 3960
Input HP = Input Kw * 1.341

Total Pump Efficiency = Head * GPM / 3960 / (Input Kw * 1.341)

This is dependent upon the head curve operating point and has peak efficiency slightly to the right of the middle of the head curve. This point is typically referenced as the "Best Efficiency Point" or BEP and where the pumping efficiency is maximized.

However in swimming pool applications, it is desireablye to have the highest GPM for least amount of Watts. So this is why the California Energy Commission has chosen to use GPM/Watt as the primary metric of rating pump efficiency instead of BEP. From an energy use perspective, GPM/Watt is more important than BEP.

I agree that the motor will use more energy and run hotter the further to the right on the head curve and you really don't want to operate all the way to the right. However, the pump is designed to work in the region of the published head curve without a significant reduction in pump life. So as long as you stay within the head curve, the pump should be fine.

This is all very good info. What is the general though of pumping 20 gallons pr hour over 3x the time of pumping 60 gallons per hour? Aside from making the spa spill look anemic is there any downside to the lower flow rate?

Poor skimmer function, heaters won't fire, salt cells won't make chlorine. And its Gallon Per Minute. 30 GPM seems to be the safe number for everything except the skimmers. There, a couple of hour long cycles at 60 GPM fills that need nicely.

Scott

Great, thanks. I never use my heater (except for very few times in spa, and can have a higher flow set up when using it) and don't have salt cells, so am good there. So, say 2 hours at high speed for the skimmer + pool sweep, then coasting at 30 GPM seems to be the way to be most efficient?

Any idea what it would take for the Intelliflo to run both the skimmer well and the pool cleaner? Do I need to max it out for the piping size I have? I assume most of the flow needs to go through the pressure side return for the pool cleaner, but since that would be tied in to all the other returns now they would all have to be high flow now? Does it make any sense to keep the booster pump, or would you all just get rid of it and use the Intelliflo for it all?