Can you share the ground wire?

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Maven85

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I am designing two light poles that are 480V 1Phase and was going to run two different home runs back to panel with 2#4's, 1#8G, in 1-1/4" conduit each (i understand that this conduit could work in 3/4" but hey have 1-1/4"c. to utilize)

now i'm considering running one home run for both light poles with 4#4's, 1#8G, in 1-1/4" conduit.

Do i need to add a second ground? if not do i need to upsize the ground wire? I thought you could share the ground but it would need to be upsized to match the #4's?

Thank you!
Jonathan
 
I don't understand , What is a electrical designer? ( your profile)

I will answer if the moderators allow.
 
Sierrasparky said:
I don't understand , What is a electrical designer? ( your profile)

I will answer if the moderators allow.
Click to expand...

I work for a engineering firm but i'm not a PE I'm an electrical designer that puts together construction documents a PE would review for approval.

Thanks for responding :)
 
Check this out

250.122 Size of Equipment Grounding Conductors.


(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.
Click to expand...
 
Maven85 said:
I am designing two light poles that are 480V 1Phase and was going to run two different home runs back to panel with 2#4's, 1#8G, in 1-1/4" conduit each (i understand that this conduit could work in 3/4" but hey have 1-1/4"c. to utilize)

now i'm considering running one home run for both light poles with 4#4's, 1#8G, in 1-1/4" conduit.

Do i need to add a second ground? if not do i need to upsize the ground wire? I thought you could share the ground but it would need to be upsized to match the #4's?

Thank you!
Jonathan
Click to expand...

You only need one EGC per homerun conduit. The EGC is required to be sized per Table 250.122 based on the largest OCPD serving the circuits in the homerun conduit. So if you have two circuits, one with a 20 amp OCPD and one with a 30 amp OCPD, in the same conduit, you would need one #10 EGC. If the conduit is EMT, IMC, or RMC, you don't even need an EGC as the conduit is permitted to serve as the EGC. If you need to upsize the phase conductors for voltage drop, the EGC also needs to increase in size a proportionate amount per section 250.122(B).
 
jrohe said:
You only need one EGC per homerun conduit. The EGC is required to be sized per Table 250.122 based on the largest OCPD serving the circuits in the homerun conduit. So if you have two circuits, one with a 20 amp OCPD and one with a 30 amp OCPD, in the same conduit, you would need one #10 EGC. If the conduit is EMT, IMC, or RMC, you don't even need an EGC as the conduit is permitted to serve as the EGC. If you need to upsize the phase conductors for voltage drop, the EGC also needs to increase in size a proportionate amount per section 250.122(B).
Click to expand...

Thanks you both for the assistance and the quick responses I do appreciate it. I like to do some research prior submitting to the engineer for my final design review. I singed up on this forum awhile back and plan on being more of an active member.

This is a great community to be apart of!

Have a great day!
 
Sierrasparky said:
What is a electrical designer?
Click to expand...
I have worked with a number of electrical designers over the past 20+ years. Most of them started their careers by taking drafting classes, and by performing the drafting (later CAD) tasks for designs that were prepared by engineers. Later, as they grew more familiar with the design process and the rules and methods of designing electrical systems, they became more and more capable of performing independent design. Their work would always be performed under the supervision of a PE, but there is no doubt in my mind that they have been very valuable members of the design team.
 
A #4 wire is good for 85 amps. At 480 volt single phase that equates to 40,800 watts. The lights on the two poles are likely to only draw less than one tenth of that amout of power. So I would say the circuit conductors are already larger than in needed for ampacity purposes. That tells me that you probably will need an EGC that is larger than the size given in table 250.122. Can you tell us how many watts of lighting you are installing, and what size breakers you plan to use?
 
jrohe said:
You only need one EGC per homerun conduit. The EGC is required to be sized per Table 250.122 based on the largest OCPD serving the circuits in the homerun conduit. So if you have two circuits, one with a 20 amp OCPD and one with a 30 amp OCPD, in the same conduit, you would need one #10 EGC. If the conduit is EMT, IMC, or RMC, you don't even need an EGC as the conduit is permitted to serve as the EGC. If you need to upsize the phase conductors for voltage drop, the EGC also needs to increase in size a proportionate amount per section 250.122(B).
Click to expand...

I Replied with a big thanks! for the quick responses from everybody and expressed how much i appreciated being apart of a great community but doesn't look like it posted...

I like to do my research before submitting to the engineer for final review and with your assistance i was able to put together a solid design.

Thanks!
Jonathan
 
charlie b said:
A #4 wire is good for 85 amps. At 480 volt single phase that equates to 40,800 watts. The lights on the two poles are likely to only draw less than one tenth of that amout of power. So I would say the circuit conductors are already larger than in needed for ampacity purposes. That tells me that you probably will need an EGC that is larger than the size given in table 250.122. Can you tell us how many watts of lighting you are installing, and what size breakers you plan to use?
Click to expand...

Charlie

each light pole (for a high school practice field) are 24,000 watts protected with a 70/2 breaker.

What i ended up submitting for review was one home run for the two lights with 4#4's, #4G, 1-1/4" conduit (this occurs on each side of practice field). I also confirmed voltage drop and conduit fill.

Thanks
 
I already knew what an electrical designer was before I approved the post. I have worked with designers over 45 years. Some of the best advice I ever received from my first supervisor (a PE) was to give full respect to designers and treat them as undegreed engineers.

Truthfully, if my career depended on detailed lighting design today, I'd be lost. I'm sure I could learn it again, but it's been over 30 years since I've done much more than check a few load calcs.

Since my retirement, one of the best designers that ever worked for me has now become the electrical department manager.
 
Sorry for the late response
The others seemed to have helped out.
By the way Welcome to the Forum. :D
 
charlie b said:
I have worked with a number of electrical designers over the past 20+ years. Most of them started their careers by taking drafting classes, and by performing the drafting (later CAD) tasks for designs that were prepared by engineers. Later, as they grew more familiar with the design process and the rules and methods of designing electrical systems, they became more and more capable of performing independent design. Their work would always be performed under the supervision of a PE, but there is no doubt in my mind that they have been very valuable members of the design team.
Click to expand...
This is something of which I am painfully aware. My company had a draftsperson who was a power user of AutoCAD and Sketchup Pro. She had only rudimentary electrical experience when she hired on, but as time went by she became more attuned to the concepts that were the underpinning to the drawings she produced. She was an expert at manipulating sheet sets and managing data files, Xrefs, title blocks, fields, etc. She sometimes could turn a design change around in minutes.

My company decided that they needed to lay someone off to save money, so they chose her. They should have laid off an engineer instead.
 
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