# Thread: Help with understanding motor information

1. ## Help with understanding motor information

I'm wanting to know the wattage of this motor. My problem is with how the amps is written on the nameplate. My understanding has been that the stated amps should be multiplied by the SF (service factor), and to then multiply that number by the voltage to arrive at the wattage. But this motor says "AMPS SF" 10. Have they already done the math, meaning it pulls 10 amps if the service factor is 1.5?

2. Originally Posted by tipsrfine
But this motor says "AMPS SF" 10. Have they already done the math, meaning it pulls 10 amps if the service factor is 1.5?
It is the amps the motor will pull at it's rated service factor.

Here is some info at this site -

http://franklinaid.com/2007/07/25/se...e-factor-amps/

3. Thanks. I could not have wished for a better person to answer my question than you.

4. Originally Posted by tipsrfine
I'm wanting to know the wattage of this motor. My problem is with how the amps is written on the nameplate. My understanding has been that the stated amps should be multiplied by the SF (service factor), and to then multiply that number by the voltage to arrive at the wattage. But this motor says "AMPS SF" 10. Have they already done the math, meaning it pulls 10 amps if the service factor is 1.5?
VxAxPF=W

For determining the watts of the motor, you need to know the Power Factor of the motor, not the Service Factor, they are not the same thing.
The PF of a motor can never be higher than 1.
Since the SF is always 1 or higher, using it to calculate watts will give you numbers that are much higher than actual.

5. Originally Posted by mark beiser
VxAxPF=W

For determining the watts of the motor, you need to know the Power Factor of the motor, not the Service Factor, they are not the same thing.
The PF of a motor can never be higher than 1.
Since the SF is always 1 or higher, using it to calculate watts will give you numbers that are much higher than actual.
Do you have an educated guess as to how many amps this pool pump is pulling when running? Residential home in Missouri.

I probably should have said, do you have an educated guess as to how much wattage this motor is using when running. I need its kwh to enter into energy modeling software. I'm going with a .9 power factor. So this motors wattage is 2070, or 2.07 KWH. Thanks.
Last edited by tipsrfine; 02-10-2013 at 01:05 PM.

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Name plate says its 1.5 HP. If you need to know wattage multiply HPx745.6. In your case its 1118 Watts.

7. What a manufacturer decides to list as HP is a work of fiction. This is why when replacing a motor with one from a different manufacturer you have to go by amps, not listed HP.

8. Originally Posted by tipsrfine
What a manufacturer decides to list as HP is a work of fiction. This is why when replacing a motor with one from a different manufacturer you have to go by amps, not listed HP.
How much of a factor is motor efficiency when converting amps to HP? 746W per HP is with 100% efficiency, which isn't going to happen.

9. Last time I checked, Horse Power was not listed on Ohm's Wheel.

10. Originally Posted by tipsrfine
Do you have an educated guess as to how many amps this pool pump is pulling when running?
It is impossible to calculate.
To even make an educated guess, you need performance information for the specific motor and pump combination, assuming the manufacturer of the assembly even has that information available. Even that may not reflect the reality of the installation, since it would be very likely that the conditions that exist in the actual installation don't match those the manufacturer tested the performance of the assembly in.

Originally Posted by tipsrfine
Last time I checked, Horse Power was not listed on Ohm's Wheel.
Motor watts and HP are both units used to rate the power of of electric motors, and you can convert directly between the two.
1 hp = 746 W

In the USA we use HP, most of the rest of the world rates electric motors in watts.

Handy calculator:http://www.rapidtables.com/convert/power/hp-to-watt.htm

11. If 746W = 1HP how much does a real world motor typically draw to get 1HP? If 80% motor is used then your @ 932W per HP. If incoming voltage is 230V and motor power factor is 80% then your'e at 5.06amps. This assumes the motor has a full 1HP load attached to it. Point is there are a LOT of "ifs".

I ran the home's energy use through energy modeling software which uses actual utility bill information along with cooling degree days for that same period and it confirms that this home is using roughly the same amount of increased KWH as what I predicted using the voltage x amps = wattage formula.

13. Great Article !!

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