Submersible Pump -- Wire & CB sizes

Status
Not open for further replies.
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Ran into a well pump guy who quite knowlegeable about pumps. He showed me some charts and I got very confused.

Submersible well pump

Franklin Electric Pump 230 volts, 2 HP, 13.2 max. amp . This is a 3 wire submersible pump-- Common, starting winding, & running winding. I am sure you have seen them. Without concern of VD what is the smallest size conductor I can use and the largest CB allowable? Code ref. please.
 
Thanks Bob but what article helped determine the % allowable. There are so many types of motors, etc- I hate art. 430.
It's good I stick to residential because I would be lost figuring this out. I know the load is calulated at 125% for the conductor size but I thought that was the same for the CB. Obviously we can go higher but what % and where is it in art 430.
 
It is a table, off the top of my head I think 430.50 something.

Depending on the overcurrent device it can be sized up to 800% the FLA.

250% to 300% is a much more common application.
 
bphgravity said:
Probably 250%. See 430.52.

I see most of these served with #12 AWG and protected by a 20A breaker.
Click to expand...

Right. I always do that but I got this friend that installs pumps and he wants 35 amp breakers on this 2 hp pump.

Then I found this chart

http://www.franklin-electric.com/Manual/pdf/FullAIM_60Hz.pdf

Go to page 16 and look at model prefix 224301. It says 25 amps. That's less than 250%
 
Dennis Alwon said:
Go to page 16 and look at model prefix 224301. It says 25 amps. That's less than 250%
Click to expand...

Dennis you would have to use the tables at the back of 430 to find the NEC FLA of a single phase 240 volt 2 HP motor than you could increase that value by 250%.

Even at 13 amps FLA I get 32.5 amps @ 250% for the short circuit and ground fault protection.
 
I apologize for my denseness (if that's a word). Table 430.248 2 hp motor at 230 volts is 12 amps. If I multiply it by 250% I get 30 amps. The Franklin Electric Chart says max allowed by NEC to be 25 amps. Why the difference? I am not following-- sorry
 
Dennis, Franklin has two charts, one is for a typical hook up, the other is Max. per code, what chart were you looking at....


Never mind, reread your post... :) Not sure why the difference...
 
Dennis Alwon said:
I apologize for my denseness (if that's a word). Table 430.248 2 hp motor at 230 volts is 12 amps. If I multiply it by 250% I get 30 amps. The Franklin Electric Chart says max allowed by NEC to be 25 amps. Why the difference? I am not following-- sorry
Click to expand...

Maybe they made a mistake? :confused:

I try not to trust outside sources for this type of info. I use my Uglies book for quick rough planing but will still verify the table info from the NEC.
 
Well I now know I am not completely off my rocker. I did learn a few things here and I appreciate the responses. Thanks to you all.
 
Well there must be a bunch of mistakes because I found one on the 5 hp pump also. I don't know what's going on? Wish I understood more. I guess I go by the nec and leave it at that.

If I take the fla of the 2 hp motor at 13 amps and multiple by 125% I get 16.25 amps. Is there any reason why this pump would not work on a 20 amp circuit.? Would it be wise to use the lower rating and go up if you have to?
 
Dennis Alwon said:
Well there must be a bunch of mistakes because I found one on the 5 hp pump also. I don't know what's going on? Wish I understood more. I guess I go by the nec and leave it at that.

If I take the fla of the 2 hp motor at 13 amps and multiple by 125% I get 16.25 amps. Is there any reason why this pump would not work on a 20 amp circuit.? Would it be wise to use the lower rating and go up if you have to?
Click to expand...


Any help here--
 
overloads

overloads

Some of the older submersible pump motors had their overloads build into the motor controller instead of the motor. If yours is that way (I have an old one) make sure the controller you use has overloads otherwise you won't have any motor OC protection.
 
These are new pumps but I am talking about a hypothetical situation. Basically should a pump have an OCP at 250% if it will run with the OCP at 125%.

I still don't see why the charts from Franklin don't match what I am finding in the NEC.
 
Dennis Alwon said:
Basically should a pump have an OCP at 250% if it will run with the OCP at 125%.
Click to expand...

Either way is fine, one is no worse than the other.

For the purposes of this thread we all have to stop calling the breaker or fuse 'overcurrent protection'. It is not over currentover current protection at all.

In this thread the only purpose the fuse or breaker serves is short circuit and ground fault protection. That being the case a 14 AWG with a short circuit will have no trouble tripping a 15, 25, 35, 40 amp breaker.

This is the same thing as using a 8 AWG EGC to trip a 100 amp breaker. Short circuits and ground faults are different than overloads.

The over current protection for this entire motor circuit is provided by the motor overloads.
 
iwire said:
For the purposes of this thread we all have to stop calling the breaker or fuse 'overcurrent protection'. It is not over currentover current protection at all.

In this thread the only purpose the fuse or breaker serves is short circuit and ground fault protection.
Click to expand...


Thanks Bob. That explains my confusion in using Table 430.52. I was looking for OCP instead of short circuit & ground fault protection.
 
Status
Not open for further replies.
Top