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Variable Speed Pump Schedule

Posted by SteveScan (My Page) on
Sat, Oct 29, 11 at 9:20

Hi all. Just wanted to share with you guys how we run our filter pump. We had an in-ground pool built this year (24,000 gallons, raised spa, Pentair Intelliflow pump, 2 skimmers, Polaris sweep, saltwater chlorinator). I wanted to minimize our electrical cost, so I installed a flowmeter and made some observations about how pump speed affects flowrate and electrical usage. What I learned is that minimum electrical usage occurs at minimum speed. At high speed (3450 RPM), one turnover takes 3.8 hours at a cost of $1.07. At minimum speed (1100 RPM), one turnover takes 15.9 hours and costs $0.22 (assuming $0.1 per KWH)

So, I run the pump as slow as possible. The saltwater chlorinator needs 30 GPM minimum which occurs at 1250 RPM so this is our low speed. We run the sweep (with booster pump) two hours a day. It runs at the correct speed (28-32 RPM) with the filter pump at 3000 RPM, so this is our high speed. I could probably remove the flow restrictor in the sweep line and slow the pump, but would make for less surface cleaning action at the skimmers. We enjoy the sound of the spa fountain in the evening, which is nice at 1500 RPM, so this is our medium speed.

During the swim season, we filter the water two turnovers per day. Off-season, we filter the water one turnover per day. To get this, we run at low speed 16 hours during the swim season and 3 hours in the off-season.

Here is the schedule:
Swim Season: Two turnovers total
7 - 8 am Low speed (to start up)
8 - 10 am High speed (to sweep and skim)
10 am - 5 pm Low speed (to filter)
5 - 8 pm Medium speed (to enjoy)
8 pm - 4 am Low speed (to filter)
4-7 am Off

Off-Season. One turnover total.
7 - 8 am Low speed (to start up)
8 - 10 am High speed (to sweep and skim)
10 am - 12 pm Low speed (to filter)
5 - 8 pm Medium speed (to enjoy)
8 pm - 7 am Off

At 1250 RPM, flow is 30 GPM and power is 236 Watts
At 1500 RPM, flow is 39.9 GPM and power is 281 Watts
At 3,000 RPM, flow is 91.5 GPM and power is 1870 Watts
Notice that going from low to high speed, flow increases by 300% and power by 800%. That is why minimum electrical cost occurs at minimum speed.
Flow is per a Cole-Parmer S-05611-14 flowmeter
Power is per the Pentair pump


Follow-Up Postings:

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RE: Variable Speed Pump Schedule

Please share your plumbing size, other equipment models, spa jets, etc...and what pool sweep you are using.

Scott


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RE: Variable Speed Pump Schedule

Interesting post. I second what Scott said...


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RE: Variable Speed Pump Schedule

The Intelliflo should be able to go down to 400 RPM but what you will find is that the gallons/watt-hr will start to drop again below about 800 RPM so the most efficient speed is usally between 800 and 1200 RPM depending on the plumbing which I think you found out.


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RE: Variable Speed Pump Schedule

Why did you install a flowmeter? The pump has a flowmeter and watt meter built in.


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RE: Variable Speed Pump Schedule

@ncreal, only the VF has that. The VS and SVRS models do not show GPM rates, just RPM and power (Watts).

Scott


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RE: Variable Speed Pump Schedule

If you like your pool you have to like your light bill. My bill jumps up about $60 a month when its running. Thats why its on a timer.


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RE: Variable Speed Pump Schedule

@obrionusa,
That seems high. I would bet you that we could cost effectively lower your pool's energy consumption if we knew more about your pool. Having a timer is not the only factor that needs to be considered. BTW, the timer used in the original poster's system is built in.

There is pool size, plumbing size, power costs, features, and so on.

Not all pool pumps are the same. Not by a long shot. Generally speaking, bigger is usually not better.

Scott


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RE: Variable Speed Pump Schedule

interesting, my intelliflo pulls about 210 watts at 1500 rpm and i thought that was high because i've seen some others who reported slightly under 200 watts at 1500 rpm. now i see you show 281 watts for 1500 rpm. i guess the pipes and configuration makes this vary greatly.


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RE: Variable Speed Pump Schedule

As does the filter's state. As a filter gets "dirty", pressure will rise, though with VSPs, the usual 10 PSI change normally expected is reduced to about 3 PSI or so because of the reduced flow.

Scott


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RE: Variable Speed Pump Schedule

For reference my newly installed Intelliflo (model 011018) pulls about 300 watts at 1700rpm (about 50 gal/min) where I have mine set. Of note though, the filter is very dirty and I'll clean it this weekend. Curious to see if the power usage will drop with a clean filter.


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RE: Variable Speed Pump Schedule

It will. Less friction.

Scott


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RE: Variable Speed Pump Schedule

What if the pump is about 5 feet below grade of the pool?


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RE: Variable Speed Pump Schedule

A centrifugal pump will draw more power when the head loss decreases. The operating point moves to the right on the head curve, flow rates increase, and power draw increases.

With a VS and the same RPM, the pump will draw more power for the reasons mentioned above.

However, with a VF where the flow rate is constant, the power draw decreases because the drive reduces RPM to maintain the same flow rate (i.e. head curve drops because of lower RPM and operating point shifts to the right).


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RE: Variable Speed Pump Schedule - Pump Elevation

The elevation of the pump does not affect power draw only the difference between suction head and return head. Suction head will decrease by 5 feet but return head will increase by 5 feet so there is 0 net change in total head.


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RE: Variable Speed Pump Schedule

mas985 is absolutely correct. I just cleaned my filter. Before cleaning the wattage displayed was 315. After cleaning and adding Fiber Clear the wattage displayed is 365. Both readings are at 1700 rpm.


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RE: Variable Speed Pump Schedule

But you're moving a lot more water now.

Scott


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RE: Variable Speed Pump Schedule

I would also add that the Intelliflo VF will use more power when the filter gets dirty because the pump speed is automatically increased to maintain the same flow.

Never understood the VF offering....are there really any pool features that require such critical flow at the cost of more power consumption.


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RE: Variable Speed Pump Schedule

But trhought, the opposite is true too... when the filter is clean, and resistance less, I use less energy because the computer keeps the flow rate the same by reducing the wattage. The same is true for the four when my polaris cleaner is on. The resistance is less for it than the water going through the cleaner, so the energy used decreases quite a bit, even though my flow rate remains the same.


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RE: Variable Speed Pump Schedule

@ncrealestateguy - It sounds like you have the Intelliflo VF. I didn't step up and pay the extra $$ for the VF so with the clean filter I plan to either leave the pump set at 1700rpm and cut the run time or reduce the rpm and keep the run time the same. I think I would save more energy by reducing the RPM and leaving the run time the same.

Separately, I switched over to a robotic cleaner so my filter cleaning interval should be much more spread out than when I used a suction side cleaner.


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RE: Variable Speed Pump Schedule

i run my VF from 5am to 4.30pm at 1100 rpm's and it uses 156 watts 24 GPM .my electric bill went down $60 dollars per month.love this pump


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RE: Variable Speed Pump Schedule

ncrealestateguy and domingos....but as your filter gets dirty, your VF will use more power as speed is increased to compensate for the head loss...this is not true with a VS, 2 speed or 1 speed...power decreases and flow will decrease which gives the pool owner a signal that the filter should be cleaned without costing extra energy consumption.


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RE: Variable Speed Pump Schedule

I would rather keep my filter at a clean level, and have all my water features unaffected if the filter does get dirty.


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RE: Variable Speed Pump Schedule

ncrealestateguy....but your filter is only at a clean level until you put it into service, then the VF starts increasing power each day.


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RE: Variable Speed Pump Schedule

i monitor the pumps speed and watts consumed on a regular basis and its almost always running between 1100 RPM's and 1150 RPM's.i clean the filter on a monthly basis


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RE: Variable Speed Pump Schedule

Trhought... where are you seeing this data that you quote? My RPMs and watts do not increase day by day until I clean my filter again.
I will clean my filter soon and document #s.


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RE: Variable Speed Pump Schedule

ncrealestateguy...as head loss changes, the Intelliflo VF is designed to increase or decrease speed to maintain the same flow. As a filter gets dirty, the head loss increases which decreases flow. The VF senses this decrease in flow and increases pump speed to maintain the flow setpoint.

When you record your VF power, you'll find the power consumed with a dirty filter will be higher than what it is after cleaning.

If your pump was a VS, 2 speed or 1 speed, you would find the power is lower with a dirty filter ( from above rmrc12 reported a 50 watt difference with a VS). This is how pool pumps (a centrifugal pump design) behave when speed is constant and head loss increases. The VF, however, increases speed as the filter gets dirty which consumes more power.

When you post your power results before and after cleaning, please also post the rpm for each.

Clearly, the more frequently you clean the filter, you'll notice less power difference but with an Intelliflo VF, the dirty filter power will always be higher than the clean filter power...that't the way it was designed.

Hope this helps.


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RE: Variable Speed Pump Schedule

throught,
I know all of this... I am just saying that I must keep my filter fairly clean, because I just do not notice much of that increase that you are speaking of. Apparently, the same with domingos35.
And my water features do not deteriorate like they would with a VS.


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RE: Variable Speed Pump Schedule

ncrealestateguy....if your experience is like domingos, then you do see a power increase...you may not notice it day-by-day, more likely week-to-week and certainly month-to-month...just keep that filter clean to avoid rising monthly utilities.

Guess it's personal preference...I would rather the water features and pressure gage tell me it's time to change the filter and know I'm using less energy while the filter is dirty. With the VF, you're paying the price for neglecting to clean the filter without having any obvious visual signals from your pool....the signals are more sublte...the VF display and ultimately the higher monthly utility bill if the filter has been neglected.

Just my 2 cents.


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RE: Variable Speed Pump Schedule

To the guys saying its running to fast or consuming too much power seems you are forgetting the chlorinator needs to see 30 GPM. That effectively is the lowest speed the OP should run.

The lowest any variable RPM/ Flow pump with a chlorinator should be set to is the chlorinators min GPM speed.

In a standard chlorinated pool the min speed should be the slowest speed that still gives actual skimming.

If set too slow like the pumps minimum speed there is a very real chance you get no skimming at all and the skimmer starts into a "bobbing cycle " vs. actually pulling a steady vacuum and skimming.

It doesn't matter how cheap the pump is to run if your pool is dirty all the time.

Uncle Dave


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RE: Variable Speed Pump Schedule

thanks for all the great information you guys have posted

I am new to pool care and own a variable speed pump. pool is about 16000 gallons and we live in sunny southern California. I have a pool guy that keep the chemicals balanced and I add phos free once a week. the pump is running at 1300 rpm for 8 hours a night and 2400 for 4 hours - all while attached to a kreepy krauler sweeper. the water was just changed about 2 months ago and is getting murky and has algae. the pool guy wants me to run the pump at 3400 x 6 hours a day instead of at low revs since he feels I am not turning the water over fast enough. that seems excessive and defeats the purpose of the variable speed pump.

I don't know the pipe size. We use a solar cover about 3 days a week and the water temp is about 82 degrees. 1 caveat is that my dog (golden retriever) swims in the pool about 4 times a week.

Any suggestions?

Thanks in advance for all your input


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