Hayward Ecostar VS Pool Pump Flow Rates & Cost Savings

July 4, 2014 at 7:08 pm Leave a comment

Sort of off my normal topics, but somewhat related to budgeting…  My pool pump started making a terrible noise on Sunday evening.  Today, I replaced the pump with a new variable speed pump.  Instead of running full speed, like my old model, this one lets me adjust the RPM in 50 RPM increments from 600 RPM all the way to 3450 RPM.  I’m trying to determine the optimal RPM to run my pump at.  The VS pump should let me run at a much lower rate over a longer period of time and save energy (which should translate directly to saving money on my electric bill).  Apparently, running just a few hundred RPMs less cuts the energy use in half, so this could end up saving me serious money every summer.

I plan to run my pool pump 24 hours per day while turning over the water at least once each day.  First, I needed to figure out the Gallons Per Minute (GPM) rate of my pump…

(Below information from a post in a forum on troublefreepool.com)

Variable Speed Pump Flow Rate Approximations

The following formulas use the affinity equations to yield a very rough estimate of flow rate.

1.5″ Return Line with 1 x 1.5″ Suction Line:
Intelliflo Flow Rate (GPM) = RPM / 47
EcoStar Flow Rate (GPM) = RPM / 48
Plumbing Head (ft)= 0.0167 * GPM^2 – CEC Curve A

1.5″ Return Line with 2 x 1.5″ Suction Lines or 1 x 2″ Suction Line
Intelliflo Flow Rate (GPM) = RPM / 44
EcoStar Flow Rate (GPM) = RPM / 45
Plumbing Head (ft)= 0.0140 * GPM^2

2″ Return Line with 1 x 2″ Suction Line
Intelliflo Flow Rate (GPM) = RPM / 37
EcoStar Flow Rate (GPM) = RPM / 38
Plumbing Head (ft)= 0.0093 * GPM^2

2″ Return Line with 2 x 2″ Suction Lines or 1 x 2.5″ Suction Line
Intelliflo Flow Rate (GPM) = RPM / 35
EcoStar Flow Rate (GPM) = RPM / 36
Plumbing Head (ft)= 0.0083 * GPM^2 – CEC Curve C

2.5″ Return Line with 1 x 2.5″ Suction Line
Intelliflo Flow Rate (GPM) = RPM / 34
EcoStar Flow Rate (GPM) = RPM / 35
Plumbing Head (ft)= 0.0074 * GPM^2

2.5″ Return Line with 2 x 2.5″ Suction Lines
Intelliflo Flow Rate (GPM) = RPM / 33
EcoStar Flow Rate (GPM) = RPM / 34
Plumbing Head (ft)= 0.0069 * GPM^2

In my case, I have a line from my main drain and a line from my skimmers.  They are 2 inches when they come out of the ground, but if I recall correctly, before my pool was refinished, they were 1 1/2 inches.  I’m sure the pipes weren’t replaced, so I’m going to say I have a single 1 1/2 inch return line and two 1 1/2 inch suction lines.  Since my pump is an Ecostar, that means the RPM / 45 should give me an approximate GPM rate.

My pool is 27000 gallons.  Running 24 hours a day, that means my GPM needs to be 27000 / 1440 = 18.75 GPM.

RPM  :  GPM
600  :  13.33700  :  15.55
800  :  17.77
900  :  20  – Minimum speed to run 24 hrs a day to turn the pool over once
1000 :  22.22
1100  :  24.44
1200  :  26.66
1300  :  28.88 – Turn over my pool 1.5X per day (Or run pump for 16 hours/day)
1400  :  31.11
1500  :  33.33
1600  :  35.55
1700  :  37.77  – Turn over my pool 2X per day  (Or run pump for 12 hours/day)
1800  :  40
2000  :  44.44
2200  :  48.88
2400  :  53.33
2600  :  57.77  –  Turn over my pool 3X per day  (Or run pump for 8 hours/day)
2800  :  62.22
3000  :  66.66
3200  :  71.11
3400  :  75.55  – Turn over my pool 4X per day (Or run pump for 6 hours / day)

My old pool pump was a StaRite 1.5 HP pump, part number P2RA5F-182L.  It runs at 3450 RPM.   I have no idea of the GPM performance, but I can tell you that when I ran my new pump on 3250 RPM (the default “quick clean” RPM), the returns felt much stronger than with my old pump.

According to the label, my old pump drew 9.6 watts at 230V.  Multiple them together (per this page:  http://www.spectralightuv.com/pool-pumps.html) and that’s 2208 watts.  Divide by 1000 to get KWh = 2.208 KWh.  Most recently, I’ve been running this 24 hours a day, for a total of 52.99 KWh per day.  My local electric rate is about .11 per KWh, so since I started running my pump 24×7, it was costing me about 5.83 every day!

If I run my new pump at 1000 RPMs, it consumes 105 Watts (it shows the live Watt usage right on the display panel).  If I run it 24×7, and go through the same math process described above, that yields 2.52 KWh per day, costing me about .28 per day.  That’s less than $9 per month!

Wow!

Up until about a month ago, I ran my pump on a timer, running it as few as about 2 hours a day during the winter, on up to 6 – 12 hours a day through spring, and finally started running it 24 hours a day last month.  I don’t know what a good “average” number per day would be, but if it were 8, my average cost over a year would be a little over $700.  With the new pump, running 24 hours a day at 1000 RPM every day of the year would cost just over $100 per year.  Of course, I’ll run it at a medium speed for a few hours here and there to vacuum, but that shouldn’t substantially increase the cost.

So, the budget side of this story is that I’m going to be saving a bunch of money on my electric bill from now on.  This pump cost $870 before tax.  The single speed pump I was looking at was around $500.  By the end of the year, I should have recouped that cost difference.   Assuming the pump lasts two years, it pays for itself completely with the energy savings.

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Entry filed under: General.

YNAB and Savings accounts HP N54L is on the way

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