Does pump size matter?

newpoolj

Member
Oct 15, 2020
21
California
I'm planning a new pool build and am trying to learn quickly. My builder suggested a 1.65 hp Jandy variable speed pump. The pool is going to be about 14,000 gallons. If our goal is just a certain gpm out of the pump while minimizing energy usage, and both pumps are variable speed, does having a larger pump provide any benefit? The manual shows a power curve for both pumps that is not that different at the same RPMs, but it's hard to tell how that might impact energy usage. Any guidance?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,404
Bedford, TX
np,

In general, the larger the pump the more water it can move at a lower RPM...

Cost wise, I have a 3 HP IntelliFlo that runs 24/7, most of the time at 1200 RPM.. This allows me to skim and run my salt system, all for less than $20 bucks a month..

Other than the initial cost, there is just no downside to having a larger pump.

In my case, I have a Pentair Automation system which basically "requires" the IntelliFlo pump..

Thanks,

Jim R.
 

newpoolj

Member
Oct 15, 2020
21
California
np,

In general, the larger the pump the more water it can move at a lower RPM...

Cost wise, I have a 3 HP IntelliFlo that runs 24/7, most of the time at 1200 RPM.. This allows me to skim and run my salt system, all for less than $20 bucks a month..

Other than the initial cost, there is just no downside to having a larger pump.

In my case, I have a Pentair Automation system which basically "requires" the IntelliFlo pump..

Thanks,

Jim R.
Thanks for the response. Energy in TX is way cheaper than CA :) How many kwh does your pump use?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,404
Bedford, TX
np,

At 1200 RPM my pump uses 183 Watts.. You don't have to run 24/7, it is just what works best for me.. It is not required.

While I agree that our electrical rates may be lower, the pump uses the same amount of electricity no matter what State it is in.. :mrgreen:

Jim R.
 
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newpoolj

Member
Oct 15, 2020
21
California
np,

At 1200 RPM my pump uses 183 Watts.. You don't have to run 24/7, it is just what works best for me.. It is not required.

While I agree that our electrical rates may be lower, the pump uses the same amount of electricity no matter what State it is in.. :mrgreen:

Jim R.
Thanks for the response. That's not too bad at all actually. If I ran for 16 hours a day, I could could cover that by adding 2 solar panels to my existing array. Do you know how many gpm you're doing at that pump speed?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,404
Bedford, TX
Do you know how many gpm you're doing at that pump speed?
NP,

I have no clue and can't think of any reason I would care... :mrgreen:

Most people worry about "flow rate" because they still believe in the old X turnovers per day myth.. It is just not true. Chemicals keep your pool clear and sanitized and not how many times the pool water passes through the filter. Filters are there to capture things that fall into your pool, not to keep your pool algae free.

I have an IntelliChlor SWCG and the manual says it need 25 GPM to close the flow switch. I know the switch is closed at 1100 RPM, but have no idea how accurate the flow switch is. I run it at 1200 RPM just to make sure the switch stays shut..

Thanks,

Jim R.
 
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JamesW

TFP Expert
Mar 2, 2011
21,075
Notice that the power usage is not linear to the flow rate.

Doubling the flow theoretically takes 8 times more power (real world is about 6 to 7 times). The approximate equation is (flow 1 ÷ flow 2)^2.8.

So, even if you have to run twice as long to get the same amount of circulation, the total energy used (kilowatt-hours) ends up being 1/3 to 1/4.

That's why it pays to run as slowly as possible.

Usually the best flow is determined by the skimmer effectiveness or a piece of equipment that requires a specific flow such as a SWG, gas heater, solar etc.

Automation can be useful for variable flow requirements.

For example, if a gas heater requires 40 gpm, the automation can increase the pump speed to satisfy the heater when it's on and then drop back down to a lower speed when the call for heat is satisfied.