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Why is my 0.5 HP Pool Pump putting 1000 Watts of Load on my Inverter?

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Solana

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May 13, 2022
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Hi guys,

Inverter: Deye Hybrid 5KW
Battery: Meritsun 200ah
Panels: 14 x 330w

Pool Pump: 0.5HP Pentair WhisperFlo Standard Efficiency Pool Pump
0.5 HP = 372.85 Watts, correct?

When I turn on the pump I see a load increase by approx 1000 Watts and i am confused by that since the pump should be running closer to 400 watts.

Please help me to understand whats happening. Thx
 
A significant part of it is probably the power factor of the pump. Put a 10-15 µF run capacitor on the motor and you should see the wattage go down.

Having said that, it seems unlikely that the power factor would create that large of a difference. Even if the power factor is .5 you should only see ~ 700W
 
I have a 1/2 hp sump that runs at 800 watts. Energy conversion through mathematics vs a motor are very different.
 
People are always confusing pump power values. The pump is rated at it's horsepower OUTPUT, not the INPUT. That means the force of the water coming out of the pump is equivelent of 1/2 hp. Since electric motors are about 1/3rd efficient, you should assume it takes ~3X the amount of electricity to generate that 0.5hp.

So, with 1hp = 746W, the math is approximately..... 746W/hp X 0.5hp X 3X= 1119W of electricity. So, it appears your pump is actually slightly more efficient then average.
 
MichaelK said:
People are always confusing pump power values. The pump is rated at it's horsepower OUTPUT, not the INPUT. That means the force of the water coming out of the pump is equivelent of 1/2 hp. Since electric motors are about 1/3rd efficient, you should assume it takes ~3X the amount of electricity to generate that 0.5hp.

So, with 1hp = 746W, the math is approximately..... 746W/hp X 0.5hp X 3X= 1119W of electricity. So, it appears your pump is actually slightly more efficient then average.
Click to expand...

My motors have a horsepower rating even if I buy them without a pump attached.
I've got to believe the rating is the mechanical power of the rotating shaft.
Of course, many motors deliver more than 100% of rating at full load. There is a number on the nameplate regarding this.

I doubt electric motors are 1/3 efficient. That would be a LOT of heat. Maybe require 3x the VA compared to W.
 
Hedges said:
My motors have a horsepower rating even if I buy them without a pump attached.
I've got to believe the rating is the mechanical power of the rotating shaft.
Of course, many motors deliver more than 100% of rating at full load. There is a number on the nameplate regarding this.

I doubt electric motors are 1/3 efficient. That would be a LOT of heat. Maybe require 3x the VA compared to W.
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It’s not that motors are 1/3 efficient, it’s that work output is. Water falling down a pipe has less output power than the gravity imparted… there are losses. Friction, etc… if you are rating the output, obviously the input will be more.
 
Sure, but I don't believe that when I mate a "1 HP" motor to a pump head, it delivers 1 HP worth of water flow and therefore draws 3 HP worth of electricity (unless severely overloaded)

A 1 HP motor should deliver 1 HP of shaft power under moderate load. Maybe it is 1.5 HP under heavy load, and motor is intended for that.
Other motors are rated for the max load they are expected to be presented with.

Of course, if you replace a 3600 RPM 1 HP motor on a pool pump with a 3600 RPM 0.5 HP motor, it will either deliver the same ~ 1 HP and strain harder, or it will turn slower and strain.
 
I suppose I could have said "the rating is the mechanical power of the rotating shaft", instead of "it's the force of the water coming out of the pump". The salient point here is that the rated power is NOT the consumed power. I keep on seeing this important concept being totally misunderstood by new people.
 
For what it's worth, I'm at a pool with a 1.5 horse rated (1118w) 115v Hayward pump. Running; 9.55a, ~1100w. LRA; 60a, ~7000w.

Pool pumps can be hard to guess at because of so many variables. Head pressure, inlet vacuum, any air leaks, restrictive eyeball fittings, or just an old, worn out impeller. The same motor thats sitting 3 ft from the pool at surface level could pull almost twice the power if it has to pull or push the water up or down from a distance.
 

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Aren't the specs in your pic saying that the pump is 1hp? But, by my math the running wattage should have been ~2200W. I don't have any kind of explaination for that?
 
MichaelK said:
Aren't the specs in your pic saying that the pump is 1hp? But, by my math the running wattage should have been ~2200W. I don't have any kind of explaination for that?
Click to expand...
It's definitely a 1.5, I just put it in. Like I said, the variation between setups never ceases to amaze me, even with identical equipment.
 
Thanks everyone for your replies. Still trying to make sense of this. Compared my numbers with a friend, checked the amps on the wires, had an electrician check the complete installation.

MichaelK said:
People are always confusing pump power values. The pump is rated at it's horsepower OUTPUT, not the INPUT. That means the force of the water coming out of the pump is equivelent of 1/2 hp. Since electric motors are about 1/3rd efficient, you should assume it takes ~3X the amount of electricity to generate that 0.5hp.

So, with 1hp = 746W, the math is approximately..... 746W/hp X 0.5hp X 3X= 1119W of electricity. So, it appears your pump is actually slightly more efficient then average.
Click to expand...
What worries me right now is the fact that my friend is using a 1.5 HP Hayward pump and it consumes 1463w. Our 0.5 HP consumes 1127w. That doesnt make sense.

Even more confusing since your math example would make perfect sense in our case: 1118w which is pretty spot on, we are getting closer to 1200w the more I test and observe.

And then we have this reply and my friend:
A.Justice said:
For what it's worth, I'm at a pool with a 1.5 horse rated (1118w) 115v Hayward pump. Running; 9.55a, ~1100w. LRA; 60a, ~7000w.
Click to expand...
That doesn't back up that calculation watts x 3.
 
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Post the model details / specifications.

Mine is a Hayward Maxflow SP2300VS. Variable speed pump.

It is rated at 1100W power output which is ~1.5 hp.

Actual power draw is ~900 W during the 5-minute long maximum pump speed priming cycle (@ 3,000 rpm) then it drops back to ~320 W for the rest of its all day cycle (@ 1,900 rpm).
 
Solana said:
What worries me right now is the fact that my friend is using a 1.5 HP Hayward pump and it consumes 1463w. Our 0.5 HP consumes 1127w. That doesnt make sense.
Click to expand...
Where in relation to the water is the pump? Is it high above or below the water line? High head pressure directly correlates to more power used.
Also, is it possible that your filter is clogged up? Pumps see a clogged filter the same way as elevated head.

I've worked on pools with pumps so high over the water they had multiple check valves, and a separate hose bib on the pump inlet for priming. Even then it takes over 5 mins to catch a prime. I've never checked power use on those, but they are all 2+ hp, and you can hear them strain when operational. I imagine they are pulling much more power than they would be at "sea level".

If it's not anything external causing the issue, I wonder if a bunch of rust / corrosion is causing friction on the motor itself. Is it a new (less than 2 seasons) pump? It could be a clogged or pinched pipe as well.

Also, are you 100% sure that it is in fact a .5 horse? Nameplates get damaged in the sun and numbers disappear pretty often on the ones with stickers.
 
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wattmatters said:
Mine is a Hayward Maxflow SP2300VS. Variable speed pump.

It is rated at 1100W power output which is ~1.5 hp.

Actual power draw is ~900 W during the 5-minute long maximum pump speed priming cycle (@ 3,000 rpm) then it drops back to ~320 W for the rest of its all day cycle (@ 1,900 rpm).
Click to expand...


MaxFlo VS | Pumps | In Ground Pool Pumps - Hayward Pool Products

MaxFlo VS™ brings variable-speed technology to the popular MaxFlo pump family. They are a drop-in variable-speed pool pump upgrade that delivers up to 80% energy cost savings over single speed models.
www.hayward-pool.com www.hayward-pool.com

Permanent magnet motor. This would be inverter drive, and could adjust drive waveform (PWM) so it only deliverers the power used for a given load, no reactive power.
It may have a rectifier/capacitor front end, or could be some other PF corrected design.

It's behavior will be quite different from an induction motor.
 
Solana said:
What worries me right now is the fact that my friend is using a 1.5 HP Hayward pump and it consumes 1463w. Our 0.5 HP consumes 1127w. That doesnt make sense.
Click to expand...

Watts? or Volts x Amps?

I think a motor with higher service factor might draw excess amps, but out of phase with volts, when less than fully loaded. At full load (higher than 0.5 HP) current would be more in phase with voltage.

Alternatively, an overloaded motor would draw excessive current and get hot. How is its temperature? Does it sound strained?

Some time when filter media is missing, or if you have a bypass valve, you could check draw under less backpressure.
And of course there is inlet strainer. When mine gets plugged, or when I connect leaf canister backwards in hose, my pump complains more loudly.
 
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