Pool supply

[gfitzgerald]

I am going to install a new electrical supply for the pool equipment. The existing was laid under a slab that has been removed and will not be replaced. The junction box at the equipment will service the two one hp motors, light and a blower. I will also have seven landscape lights. I plan to bury the line 18" pull two black one white #8 and a #12 ground. Question is, is this good enough or "over kill" Thanks

[Robert Meier]

Could you provide some further details? Type of conduit? Lights and conduit distance from edge of pool? Type of lighting?

First thing that seems to be a problem is the #12 EGC with the #8 phase and neutral conductors. If these are 20 amp circuits then 250.122(B) would require that the EGC be the same size as the other conductors.

[gfitzgerald]

My brain kicked in I remember I need the same size ground as the conductors. The run is 70 ft. berried 18" 4' away from the pool.The lights are pole lamps so I can't use low voltage. The pipe is rigid I will use a WP J box to feed the equipment disconnect and the light circuit. What I was wondering is the # 8 over kill ??

[Paul W. Abernathy]

Just to chime in.......when dealing with NEC 250.122(B) we are figuring a ratio situation where we increased the size of the ungrounded conductors for a variety of conditions ( voltage drop might be one of them ) and in doing so we have to increase the size of the EGC in a ratio proportionally to what would have been required if we sized it normally to the load itself.

let me flavor you an example.......

Calculation Example

A 240-volt, single-phase, 250-ampere load is supplied from a 300-ampere breaker
located in a panelboard 500 ft away. The conductors are 250-kcmil copper, installed in rigid nonmetallic conduit, with a 4 AWG copper equipment grounding conductor. If
the conductors are increased to 350 kcmil, what is the minimum size for the equipment
grounding conductor based on the proportional-increase requirement?

Solution
STEP 1.

Calculate the size ratio of the new conductors to the existing conductors:

350,000 cmil (divided by ) 250,000 cmil = 1.4 Ratio

STEP 2.

Calculate the cross-sectional area of the new equipment grounding conductor:
According to Chapter 9, Table 8, 4 AWG, the size of the existing grounding
conductor, has a cross-sectional area of 41,740 circular mils.

41,740 x 1.4 ratio = 58,463 cmil

STEP 3.

Determine the size of the new equipment grounding conductor. Again, referring to
Chapter 9, Table 8, we find that 58,436 circular mils is larger than 3 AWG. The next

larger size is 66,360 circular mils, which converts to a 2 AWG copper equipment
grounding conductor.

So you see....2 AWG is not the same size as the ungrounded conductors...but it is increased proportinally based on the requirements of NEC 250.122(B). The example is straight out of the NEC Handbook if anyone is wondering

[Robert Meier]

Originally Posted by gfitzgerald

My brain kicked in I remember I need the same size ground as the conductors. The run is 70 ft. berried 18" 4' away from the pool.The lights are pole lamps so I can't use low voltage. The pipe is rigid I will use a WP J box to feed the equipment disconnect and the light circuit. What I was wondering is the # 8 over kill ??

It might be overkill and it might not. If you want to check for voltage drop you can use a simple calculator like this one:

http://www.elec-toolbox.com/calculators/voltdrop.htm

Is this an in-ground pool? If so the underground conduit must be 5' from the inside edge of the pool unless feeding equipment in the pool such as an underwater light. Take a look at 680.10.