Pump swap out question

[bigkevj]

I don't know about this stuff, so I am coming to the experts. Just bought this house with a pool late summer last year.

Currently, on my pool I have a 1HP Pentair WhisperFlo pump that is 1 speed and about 6 yrs old. I will open the pool in late April/early May here in KS, and probably close in late Sept/early Oct. My guess is it will be open 5 months max. I have been looking to swap out the pump for a new Pentair 2 speed pump. There is nothing wrong with the current pump, just wondering how much money I can save by doing this swap.

If I keep the current pump, I will not run 24 hours....would like to, but the $$$ is ridiculous. Does anyone know if I ran this pump 24 hours, how much electricity it would use for a time period of 150 days? And the same question on the new pump? I can find out how much I pay per kWh and do the math from there....just don't know how to tell how much electricity the two pumps would use.

Trying to determine if the savings would be worth ripping out a perfectly good pump.

 

[mas985]

A 1HP Whisperflo, assuming it is a WFE-4, will use about 2300 watts on high speed. But you don't have to replace the entire pump, you could just replace the motor with a two speed motor. On low speed, the same pump would use about 500 watts.

Also, there is really no reason to run a pump 24 hrs a day.

 

[JVTrain]

Find your current pump here: PENTAIR Inground On each model page, you can click on the Specs link. This will show you voltage and amps for your pump. You need to know if your pump is 230V or 115V as the amps rating is different for each, but the calculated wattage is identical. Voltage x Amperage = Wattage Then you can plug your wattage into this calculator: Electricity bill calculator | Energy cost calculator for each pump based on calculated wattage, hours, rate. The two-speed pumps have two amperages listed, the first is high speed, second is low speed.

 

[mas985]

The two-speed pumps have two amperages listed, the first is high speed, second is low speed.

Ratings are just that. They are not very good predictors of energy use.

 

[JoyfulNoise]

A related question - is there anyway to relate electrical horsepower to hydraulic horsepower or is that something you just have to measure in the field to get an exact idea on? On the IntelliFlo VSP it's easy because the automation panel displays it. Not sure how anyone measures this with a standard 2-speed pump...

 

[mas985]

Here is an excerpt from Hydraulics 101:

Total HP (THP) or Service Factor HP (SFHP) = NPHP * Service Factor. This is the maximum load that can be safely driven by the motor and must always be greater than the maximum load from the impeller. A motor can be driven above the THP but will likely fail in a short period of time.

Electrical Horsepower (EHP) = Input Watts / 745.7 = Volts * Amps * Power Factor / 745.7 - Electrical power input delivered to the motor.

Brake Horsepower (BHP) = EHP * Motor Efficiency - Power delivered by the motor shaft to the impeller. This is not the same as THP or SFHP. BHP is a function of the load on the motor shaft and will change with Head, GPM and RPM.

Hydraulic HP (HHP) = BHP * Pumping Efficiency = Head (ft) * GPM / 3960 - Power delivered to the water. Sometimes called water HP (WHP) or pumping HP (PHP).

Motor Power Efficiency = BHP / EHP - I2R, magnetic and mechanical losses in the motor only.

Pumping Power Efficiency = HHP / BHP - Re-circulation and internal friction losses in the wet end only.

Total Pump Power Efficiency = Motor Efficiency * Pumping Efficiency = HHP / EHP (note this is why total pump efficiency approaches 50%).

Energy Factor - Gallons/watt-hr = GPM * 60 / Watt-hr; A CEC definition used to measure a pump's true pumping efficiency.

You can relate all of the powers, the problem is knowledge of efficiency. The easiest way to determine the power draw of the motor, other than measuring it, is to use the Energy Star/APSP/CEC measurements. I put them in a Google sheets table for easy lookup: Pump Database - Google Sheets

Unfortunately, it doesn't have every pump on the planet but you can use proxies by matching head curves. There isn't much difference in the efficiency of motors within types (VS or induction). However, the pump wet end plays a big part in pump efficiency because the shape of the head curve drives pump efficiency.

 

[bigkevj]

When you say 2300 watts or 500 watts, is that per day? It is only one speed, so not sure where you get the high speed/low speed numbers from. Or are you talking a new 2 speed Whisperflo? If you are talking about the latter, how many watts would my older 1 speed Whisperflo use? It is a WF-23

 

[mas985]

Watts are independent of time. If you want kwh for energy calculations, multiply the watts by the run time in hours then divide by 1000. So for 24 hrs per day and 150 days, that is 8280 kwh on full speed. On low speed, that is 1800 kwh.

I am giving the high speed and low speed wattage numbers IF you were to change out the motor to a two speed motor. Energy consumption of a pump is primarily determined by the wet end of the pump so the numbers I gave you were for the WFDS-4 which uses the same wet end as your pump but has a two speed motor.

The WF-23 uses about 1350 watts or 4860 kwh for the 150 days 24/7.

 

[bigkevj]

Thanks mas985....that gives me an idea on what I am looking for. We pay about 11 cents/kWh from what I can see, so that gives me some numbers to compare. 1 question - you said you are giving the high/low speed if i were to change out the motor for a 2 speed motor. If I just replaced the entire pump with a new one that was 2 speeds, would that lower the energy consumption even more?

 

[mas985]

There is no difference in energy use if you replace the entire pump or the just the motor if they are the same size. However, if you downsize the pump (i.e. smaller impeller), you can save more energy. But again, you can do that on the existing pump as well. The only difference is the cost of a new pump vs just the motor and/or impeller.

Forgot to mention that if you have a spa and using the same pump to run the spa and pool, you don't want to downsize the pump or the spa jets will suffer.

 

[JoyfulNoise]

I think it's important to point out that there is almost never a good reason or a need to run a pool pump 24hrs/day. With proper water chemistry management, one can run a pool pump for only a few hours per day and not suffer any problems with water quality or cleanliness. I live in a much hotter (and harsh) climate than Kansas and, last season, I did not run my pool pump more than 6 hours per day (my average run time was just under 5 hours per day for the season). I realize that your trying to calculate worst-case scenario costs but know that if you properly manage your pool using the TFPC Method of pool care then you should not have to run your pump more than 4-6 hours per day.