# Well Pump



## Jlarson (Jun 28, 2009)

Is it a 2 wire that starts across the line or it a 3 wire with a control box (with a couple of caps, a relay, and a terminal block)? From what you said it sounds like a two wire 1/2HP. If that's true I would use a 15 amp breaker then a fused disco. with 10 amp time delay motor fuses. If its a 3 wire with a control box you could just put it on a breaker (if its within sight of the well head), the overloads in those boxes will clear faster than a breaker or even a regular fuse, I would put in fuses still though. 

A couple of other things I have learned the hard way, megger it right away after the well guys install it. If it dosen't read near OL or the top 3/4 of the scale after about a minute you could be looking at problems down the road. If it reads really low they probaly cut the cable open going down or made a bad splice. Also, put in a lightning arrestor. 

Wells really are not the bad until you have to pull one yourself and then accidently drop it all the way down the shaft and then have to get it back out. (there's a story behind this if you want to hear it.)


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## micromind (Aug 11, 2007)

A 20 amp 2 pole breaker is OK for a motor up to about 1 HP. The circuit breaker provides short circuit and ground fault protection only. Overload protection is provided in either the control box, or built into the motor. 

The SFA stands for Service Factor Amps. This is the absolute maximum current that the motor can handle continuously without damage. 

Most motors have a service factor rating. Usually it's 1.15. This means that, for example, a 10 HP motor with a service factor of 1.15 is actually an 11.5 HP motor. It's rated at 10 HP so that it has a bit of extra built in, for momentary overloads, low voltage, etc. 

Most of the time, it's not a good idea to operate a motor in its service factor, because there's no margin for error. 

Most submersible pump motors will operate very close to their FLA (Full Load Amps), and sometimes into the service factor a bit. This is OK because the motor is water cooled, and usually the water is colder than needed. Most submersible pump motors are designed for 30C (86F) water. Most wells are considerably colder than that. 

Rob


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## Dude Man (Dec 15, 2008)

yeah so that would be my max fuse size right like I thought?


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## Jlarson (Jun 28, 2009)

The stuff I said was just off the top of my head, so I dug out this big book of well motor specs. I have and looked it up for real. 

This is the data straight from the book:

1/2 HP 230V 
-15 amp breaker 
-8 amp motor fuses (recomended) 
-10 amp fuses max. per NEC.


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## Dude Man (Dec 15, 2008)

Thanks for your help. Where did you get those numbers from? I could be wrong but this is what I am coming up with.

1/2 HP Motor 230V Amps 5 S.F. Max Amps 6 is what I can read.

Table 430.428 1/2Hp 230 Volt Motor FLC=4.9 Amps

4.9 Amps x 125% = 6.125 A So I can use 14 AWG wire.

Overcurrent 4.9 Amps X 250% Inverse Time Breaker = 12.25A so 15 Amp Breaker

then 430.55 to 430.32 (A)(1) Service Factor 1.15 = 125% x 4.9 Amps = 6.125 Amps. 240.6 (A)My fuse would then be 6 Amps.

Summarize
14 AWG
15 Amp 2 Pole Breaker
6 Amp Fuses In my 30 Amp Fusible Disconnect.

Unless I missed something. Once a again. Thanks for the input. I appreciate the help. I guess what I really want to know is if you see S.F. Max Amp, if that pretty much means Max Fuse size. I have never seen that on a nameplate before.


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## Jlarson (Jun 28, 2009)

Are you sure the S.F. is 1.15. Most of the 1/2hp well motors I have worked with had an S.F. of 1.6. 
If it a 1.15 I would go with 6 amp time delay fuses too. The numbers I put up were for a 1/2hp with an S.F. of 1.6. 

I always have hated trying to figure out what type of motor was down there on old wells. Without the original pump info form or seeing the data plate on the pump its hit or miss. Most of the time I hook it up and check the amps. Some other little tricks that have helped me; casing size, winding resistance, and the size of the column pipe, they can all get you pretty close to the right HP.


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