Replies

1. 
   MarkH | Sep 25, 2013 06:10am | #1

   I would just wire a #12 to

   I would put a small breaker box at the outlet with 2 20a circuit breakers and hard wire the pump.  I don't like using gfci on motors, and I don't like plugs on pumps.  There is too little information in your question for a really good answer.

   I'm assuming this is a 120v circuit.  If it's a 240v there are other considerations.

2. 
   DanH | Sep 25, 2013 06:53am | #2

   You can do as you suggest -- the short length of #12 will not seriously increase voltage drop.  And I see nothing wrong with using 2 #12s -- it's hardly a "parallel circuit" when the length of the run is a few inches.  (Of course, I'm speaking based purely on the physics of it -- an inspector might have something else to say about these points.)

   A bit more troublesome is the plug and socket.  This is the weak link in such setups, and a traditional 3-prong plug is apt to develop contact resistance, overheat, and destoy the socket (and possibly damage the pump).  At the very least make sure the plug is somehow mechanically secured in the socket and well protected from weather.

3. 
   MarkH | Sep 25, 2013 06:58am | #3

   My second take on this is to run 2 circuits.  At 150 feet, #12 is sufficient to run the pump, #10 would be better, #8 is excessive in my opinion.  So, I think 2 circuits both #10 or #12 would be better.  I'm assuming they are going to be burried so it's no real work to lay tyo circuits in the trench.

4. 
   gfretwell | Sep 25, 2013 10:34am | #4

   You can pigtail a short #12 on the #8. That will not affect the voltage drop.

5. 
   MarkH | Sep 25, 2013 12:12pm | #5

   He said he wanted the outlet for other uses.  The pump takes 19 amps on startup. I calculate 5% voltage drop at 19 amps on #10 wire .9 power factor.  #8 wire with 30 amps will have a hair over 5% voltage drop.  So you cant have much more than a 10 amp load when the pump kicks on.  I would rather have 2 circuits in #10.  That would supply a full load on the outlet when the pump starts.  To each his own.

1. 
   gfretwell | Sep 25, 2013 03:26pm | #6

   You do not have to size the circuit for start current, only for 125% of full load amps.

   Obviously you still have to be anble to start the motor but you don't have to go nuts.

   What sized motor are we talking about here?

1. 
   MarkH | Sep 25, 2013 04:45pm | #7

   The original poster didn't say what motor he had, or if it's 220v. But I already said it would work on #12, he is planning on #8.

2. 
   DanH | Sep 29, 2013 07:41am | #9

   The point is the 150 foot run.  At 19 amps startup there would be a voltage drop of 9 volts on #12 and 5.7 volts on #10, but only 3.6 volts on #8.  The only real argument against using #8 is that it's pretty pricy, more than twice as much as #12.  In that regard one would be tempted to use #10, which is only 30-50% more expensive than #12.

6. 
   crosscountry | Sep 29, 2013 12:03am | #8

   clarification

   Thanks for all the advice. The pump has a 1.5 hp motor that runs on 110V. The choice of runing #8 was 'dictated' by the manufacturer due to the long run. I should have also explained that the other items I'd power on the circuit wouldn't be used concurrently with the pump in use...primarily a deicer used during the winter, but also misc pier-side uses. Thanks again, the information provided by all was a great help.

1. 
   gfretwell | Sep 29, 2013 10:25am | #10

   Manufacturers make unreasonable recommendations about wire size. That would run fine on #12 and #10 will be plenty. If you are really worrird, tap the motor 240v and run it that way..

   Bear in mind that if you upsize the ungrounded conductors you also need to upsize the ground proportionally.

   If you use #8, the ground needs to be #8. You won't find that in a normal cable. It will need to be wire in pipe.

   250.122(B) Increased in Size. Where ungrounded conductors are increased in size, equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.

2. 
   junkhound | Sep 29, 2013 02:34pm | #11

   Just for comparison:

   I have a 1.5 HP compressor motor 450 feet away from main breaker panel.  200 ft of 8 AWg to barn, then the last 250 ft (1 roll of UF underground* ) of just 14 AWG from barn to a back lot garage.  Compressor runs just fine as motor rated 208-240 V. 

   Everything wired directly off the 14 AWG pair.  I use a surplus 240-120 isolation transformer for the 120 V loads.

   It would probably be less $$ to buy a 208-240V motor than running 8 AWG, huh?. 

   *ta keeps youse guessing, it may just be 250 feet of old taped up and spliced OSHA reject frayed 14 AWG extension cord taped up too, eh? <G>