Looking for some help with variable speed pump energy consumption

Jul 28, 2021
22
Arizona
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi All,

I have the Waterway Power Defender 140 1.4HP Variable Speed Pump PD-140. We have 1 skimmer, 3 return vents, and a Zodiac G3 pool cleaner. The run schedule when I moved in was set at 3450 RPM (max speed) for 4 hours from 8am-noon and 1250 RPM for 12 hours from 8pm-8am. I have found that the automatic pool cleaner works best at that high speed and doesn't do very well at lower speeds (duh). At 1250 RPM there isn't enough power to open the skimmer's weir door so it's more for some very low speed circulation (which I know TFP doesn't really care about). I want to more efficiently run my pump to ideally save some money and/or skim the pool a little bit more.

First, I want to figure out/confirm how to calculate my power consumption.
At full power, 1.40HP 3450 RPM, I think the power consumption is right around 2 kWh. I don't know if I'm using 115 or 230 VAC so I'll assume it's about 2 kWh. Now for the variable speeds. From the pump's manual "By reducing your speed to 50% RPM, the horsepower requirement is reduced to 1/8th of the 100%. The calculation is as follows: (50/100 * 50/100 * 50/100) =.125 or 12.5%.)" So at 1250 RPM, which is roughly 36% RPM it should use (36/100 * 36/100 * 36/100) = 0.0466 or 4.66% of the 2kWh giving the hourly power consumption of 1250 RPM to be 0.093kWh. So my current schedule of 3450/4 hours and 1250/12 hours should consume roughly (2kWh*4h)+(.093kWh*12h) = 9.116kW. Is that correct? With an off peak (8pm-3pm) energy charge of $0.05230, I'm paying roughly 0.05230*9.116=$0.476/day or $14.77 a month? Is that right? If so, that's pretty low already and I might just cut out the 12 hours of super low power and replace it with a few hours of enough power to do some skimming.

Sorry for spewing all that math (especially if it's wrong) - but does that all seem correct? Any other suggestions. Thanks as always for everyone's help :D
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,068
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
It looks in the ballpark.

If you want more precise figures get a clamp on ammeter and measure the current your pump uses at different RPM. Then Volts * Amp = Watts. Divide by 1,000 for the kWh used.

You will probably find it looks something like this...

Variable_Speed_Pump_Electrical_Costs.jpg
 

red-beard

Gold Supporter
May 27, 2019
1,395
Houston, TX
Pool Size
25000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
One thing you might want to consider, there is usually a valve that controls how much flow is coming from the main drain vs. the skimmer. What seems to be suggested here is to set the valve so that ~90% is skimmer and 10% main drain. You basically close the main drain then turn is back a notch to allow a small amount of flow. This is how mine is setup. I do get flow into the skimmers even during low flow. It doesn't skim very well which is why I run my pump up to 2800 RPM for 4 hours a day (2 hours morning/2 hours evening).
My pump run 4 hours at 750 Watts (2800 RPM) and 20 hours at 85 Watts (1250 RPM) = 4700 Watt-hours or 4.7 kWh/day. Add in the pool cleaner (200 Watts for 2 hours) and I'm right at 5kWh/day. At 8.9 cents/kWh, it is about 45 cents per day, or about $165/yr.
 
Jul 28, 2021
22
Arizona
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
One thing you might want to consider, there is usually a valve that controls how much flow is coming from the main drain vs. the skimmer. What seems to be suggested here is to set the valve so that ~90% is skimmer and 10% main drain. You basically close the main drain then turn is back a notch to allow a small amount of flow. This is how mine is setup. I do get flow into the skimmers even during low flow. It doesn't skim very well which is why I run my pump up to 2800 RPM for 4 hours a day (2 hours morning/2 hours evening).
My pump run 4 hours at 750 Watts (2800 RPM) and 20 hours at 85 Watts (1250 RPM) = 4700 Watt-hours or 4.7 kWh/day. Add in the pool cleaner (200 Watts for 2 hours) and I'm right at 5kWh/day. At 8.9 cents/kWh, it is about 45 cents per day, or about $165/yr.
I really want to figure out which each of my valves do. I’m assuming I have one for skimmer, main drain, and vacuum. Can I just turn them off one at a time with the pump running? I also have a jandy valve that I’ll have to figure out.
 

red-beard

Gold Supporter
May 27, 2019
1,395
Houston, TX
Pool Size
25000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
On my system, it is a three way valve. Flow goes to the pump and you can adjust the amount from 50/50 to 100/0
 
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