ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Recent Posts
Countertop Receptacles
by HotLine1 - 05/18/23 12:40 PM
Windows 10, who's upgraded?
by LindaParker - 05/15/23 04:29 AM
We can all breathe easy....
by gfretwell - 05/11/23 01:00 PM
What's your Hobby?
by gfretwell - 05/11/23 12:57 PM
Your favourite food?
by renosteinke - 05/10/23 09:28 PM
New in the Gallery:
Burger King crown sillyness
Burger King crown sillyness
by wa2ise, December 11
240/208 to a house
240/208 to a house
by wa2ise, October 9
Who's Online Now
0 members (), 67 guests, and 12 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#164946 06/14/07 06:13 PM
Joined: Jan 2006
Posts: 558
Rewired Offline OP
Hey again!
I ran into something a little bizarre today and I was wondering if anyone else had seen this before.
To make a very long story short, the owner NOW is going to replace a 3/4 H.P pump motor with another 3/4 H.P motor only the new motor F.L.A is way different as is the service factor..
The old pump is 10A @ 120V, 5A @ 240V with a service factor of 1.0.. The new one is 16.5A @ 120V, 8.25A @ 240V with a service factor of 1.85!!
I was just wondering if anyone has ever seen a service factor on a motor as high as that??? Those amperages seem more like what I would find on a 1 horse motor of the same design, BUT being a 3/4 horse with a service factor of 1.85, Technically that motor could put out almost 1.4 horsepower and not be overloaded?


Joined: Jan 2005
Posts: 5,389
Likes: 1
Cat Servant
"Service Factor" is how motor vendors cheat. That's how they claim that the motor is bigger than it really is. What you are really doing is replacing a 3/4 hp motor with a 1/2 hp. motor, getting more power by running the motor hotter.

Keep your gear pullers and Allen wrenches handy; you'll be replacing that "bargain" motor pretty soon- especially since I am sure that there is no starter, with electronic 'heaters,' in use!

Joined: Sep 2003
Posts: 650
There is another more positive way that service factor can be used:

When you call a motor '1 horsepower', that implies certain things about starting torque and other aspects of motor design. If a motor has the starting capability of a 1 hp machine, but once up to speed can tolerate a 1.5 hp mechanical load without overheating, then it is fair to call that a 1 hp motor with a 1.5 service factor.

You can end up with a very high service factor if the motor has a low resistance rotor; this makes the motor more efficient, so you get less heating when you are up at running speed, but it also drops the starting torque and increases the starting current.

You could also end up with a high service factor if you take exactly the same motor design, but use wire that has a higher temperature rating; the starting and running characteristics would be exactly the same, except that you can push the motor harder simply because it can tolerate a higher temperature.

Without knowing more details of the motors involved (like the running current and temperature rise at the actual pump load), we don't know if this new motor is a suitable replacement for the old motor; we don't know if the manufacturer is cheating or providing a better motor.


Joined: Apr 2004
Posts: 349
Motor HP & SF rating are one thing - What, may I ask, is the actual load rating (in HP)?

Also - does it start & stop a lot? What kind of duty cycle will it experience?

There are 10 types of people. Those who know binary, and those who don't.
Joined: Jun 2007
Posts: 301
Just checked a recently published motor catalog and noticed they are providing service factors for fractional single phase and efficiency percentages for 3 phase. There were no single phase pump motors @3/4 hp and 240 volt that had a current rating over 5.30 at 1.15 SF.

Rewired, can you get all the info off of the nameplate including the manufacturers name?

Now, I do know that motors are costing less money than 10 years ago due to importation.
But, I am finding excellent quality. Better laminations, coated magnet wire and higher end bearings. Mandated requirements,and efficiencies have led the motor industry to improve and meet certain standards.

Joined: Jan 2006
Posts: 558
Rewired Offline OP
Well, I can't get any info off the motor as of now, I assume its in and running properly BUT the "motor" or what I meant by it was an entire pool pump itself. The owner took out one and is replacing the unit complete. I DO remember the motor said " 3/4 H.P , 115 / 230V, 16.5, 8.25A, S.F 1.85"..
The pump was manufactured by Hayward and thats what was on the pump rating plate, but the motor did look identical to pump motors that I have seen made by Franklin Electric.
Oh, this pump as far as I know is started and stopped 1-2 times a day, no overloads except for the thermal built right into the motor..

Off topic a bit, I have a Hayward pump on my pool that HAD a Franklin motor on it but 2 years into its life it decided to fail violently by spitting smoke, fire, spare parts and molten lava out the vents.. I opted for the more expensive route and changed out the motor only with one of those " switchless" ones made by Magnetek
( switchless as in no centrifugal switch or start winding, just 2 identical windings with a capacitor in series with one).. This motor I like for the #1 reason there is no centrifugal switch to stick open but it seems quieter, starts quicker and at the same time does not cause such a flicker in the house when it starts.
The old Franklin I believe was rated 1 H.P, 115 / 230V, 16.0 8.0 A, S.F of 1
The new Magnetek is rated 1 H.P, 115/ 230V, 14.4 / 7.2 A with a S.F of 1.4


Link Copied to Clipboard

Tools for Electricians
Tools for Electricians

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Posts: 362
Joined: April 2003
Top Posters(30 Days)
Trumpy 11
Popular Topics(Views)
306,956 Are you busy
234,802 Re: Forum
219,135 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5