squidbilly
Member
- Location
- Lucedale, MS
Basic Information:
volunteer work (adviser) for a local church
parking lot lighting w/ 4 GE M400 400W fixtures (3.9A each w/ HPS bulbs) on 2 poles (2 fixtures per pole)
fixture operating voltages: 108V - 131V per GE tech. support
120V AC (1 PH) 3-wire, copper conductor with PVC conduit
One 20A circuit feeds the fixtures
All 12 AWG wire (already is place when I arrived)
Relevant Distances:
segment 1: panel to center of parking lot (this point is geometrically between the poles): 175 feet
segment 2: center point to base of pole 1 or 2: 60 feet
segment 3: pole base to top of pole: 31 feet
segment 4: pole out to fixture at arms end: 14 feet
Wiring:
3 wires run from panel to center point of parking lot (175 feet) and feed:
3 wires running north to pole 1 (60 feet) and 3 wires running south to pole 1
These wires run to the base and up to the top of the pole (31 feet) where they feed:
3 wires running to fixture 1 (14 feet) and 3 wires running to fixture 2
My question: In calculating the voltage drop for each fixture via a spreadsheet, I did it in segments as follows:
using Vd=2kIL/Cm (with 12.9 for k and 6530 for Cm) for each segment
* segment 1 *
load amperage: 4 fixtures*3.9A = 15.6A
length: 175 feet
* segments 2 and 3 *
load amperage: 2 fixtures*3.9A = 7.8A
length: 60 + 31 = 91 feet
* segment 4 *
load amperage: 1 fixtures*3.9A = 3.9A
length:14 feet
I estimated the total voltage drop (sum of voltage drop from each segment) at each fixture to be 13.8V or 11.5% of the supplied 120V.
However, I have several "knowledgeable" people within this church arguing that #12 is adequate for the parking lot lighting.
Based on the calculations (and I do realize they are mere estimates if they are indeed correct), the lights will burn dim if the even come on at all.
Since I am probably rusty, I just wanted some advice on my calculations before proceeding.
Thanks in advance
volunteer work (adviser) for a local church
parking lot lighting w/ 4 GE M400 400W fixtures (3.9A each w/ HPS bulbs) on 2 poles (2 fixtures per pole)
fixture operating voltages: 108V - 131V per GE tech. support
120V AC (1 PH) 3-wire, copper conductor with PVC conduit
One 20A circuit feeds the fixtures
All 12 AWG wire (already is place when I arrived)
Relevant Distances:
segment 1: panel to center of parking lot (this point is geometrically between the poles): 175 feet
segment 2: center point to base of pole 1 or 2: 60 feet
segment 3: pole base to top of pole: 31 feet
segment 4: pole out to fixture at arms end: 14 feet
Wiring:
3 wires run from panel to center point of parking lot (175 feet) and feed:
3 wires running north to pole 1 (60 feet) and 3 wires running south to pole 1
These wires run to the base and up to the top of the pole (31 feet) where they feed:
3 wires running to fixture 1 (14 feet) and 3 wires running to fixture 2
My question: In calculating the voltage drop for each fixture via a spreadsheet, I did it in segments as follows:
using Vd=2kIL/Cm (with 12.9 for k and 6530 for Cm) for each segment
* segment 1 *
load amperage: 4 fixtures*3.9A = 15.6A
length: 175 feet
* segments 2 and 3 *
load amperage: 2 fixtures*3.9A = 7.8A
length: 60 + 31 = 91 feet
* segment 4 *
load amperage: 1 fixtures*3.9A = 3.9A
length:14 feet
I estimated the total voltage drop (sum of voltage drop from each segment) at each fixture to be 13.8V or 11.5% of the supplied 120V.
However, I have several "knowledgeable" people within this church arguing that #12 is adequate for the parking lot lighting.
Based on the calculations (and I do realize they are mere estimates if they are indeed correct), the lights will burn dim if the even come on at all.
Since I am probably rusty, I just wanted some advice on my calculations before proceeding.
Thanks in advance