Seperate stuctures/bonding question...

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sparkydon

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Oh can't a dead horse just rest in peace?!?!

I tried reviewing previous posts, but am still puzzled..

On a residential property, there is a MeterMain mounted all alone 180ft. from where the first subpanel on a pump house is, and then an additional 210ft. to a house with the remaing loads to be used. The idea is to feed from the main where no loads will be directly utilized (only the feeder) to a Subpanel on a pumphouse 180ft away, and then tap from that panel an additional 210ft. to the subpanel for the house.
So basically I have a pole mounted main feeding its service in parallel :)-?) to one structure and then to another (house) as opposed to two seperate feeder runs from the main...

Does this special circumstance affect the way that I design/terminate my grounding system? Do I bond my grounded conductor to the grounding electrode at each panel/structure, or still only at the main??

Thanks for aiding in my attempt to being a well grounded individual:D

Don..
 
that's in the air..,.

that's in the air..,.

My local inspector told me that I needed only three conductors from location to location...L1, L2, and a neutral, and to provide seperate grounding electrodes. He was stumped when I brought up the issue of bonding neutrals at each location!! I just want to know in stone what the industry standard for this particular installation is.

If I need to provide a continuous EGC from the main, I still have that option....
 
4 wire system leaving the "Service Disconect" at the pole. Proper sized main breaker at the pumphouse with 2 ground rods or (ufer ground if in the 2005 code). Proper sized breaker and 4 wire system to house subpanel with 2 grounds rods or ufer and proper sized disconect.
 
I would think because of 250.24 you would to run a 3-wire L-1, L-2, N, Gr. from main meter disconnect
Also 250.32 says that you need a grounding electrode at a sep. building or structure. The pump house Im not sure because I dont know how many circuits (if any) are feeding it. At the house I think you need a seperate grounding electrode system. Gr. rods ect... with no neutral ground bond art. 250.6(a). If Im wrong someone will let me know:)
 
sparkydon said:
My local inspector told me that I needed only three conductors from location to location...L1, L2, and a neutral, and to provide seperate grounding electrodes.
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The preferred method is to run 4 conductors and keep all downstream neutrals and grounds separated.

With 3 conductors......see 250.32 for the full rundown. I have to make a few assumptions here, but....assuming you don't have any parallel metallic paths between the structures (what kind of pipe is going from that pump house to the house?), and assuming you're not in one of those hoity-toity states like Washington where electrons are special :) , then you can run your 3-wire feeder to each remote panel, bond the neutral at all of those panels along with the ground rods, and you should be OK.
 
ceknight said:
With 3 conductors......see 250.32 for the full rundown. I have to make a few assumptions here, but....assuming you don't have any parallel metallic paths between the structures (what kind of pipe is going from that pump house to the house?), and assuming you're not in one of those hoity-toity states like Washington where electrons are special :) , then you can run your 3-wire feeder to each remote panel, bond the neutral at all of those panels along with the ground rods, and you should be OK.
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Making the same assumptions I agree with Chris. You may use three wire feeders.
 
thank you..

thank you..

OK, so after reviewing those sections spoke of in the previous posts, I think grounding and bonding between structures is pretty clear now..

I will certainly run the grounding conductor continuously, bonding to the seperate grounding electrodes, while the neutral (grounded) conductor remains isolated in the two subpanels downstream from the Main.

Now I must apologize for being vague in my initial post, but I failed to mention that none of the feeders were actually installed yet...That being said, when I did my voltage drop calc. for the loads from the house, I had come up with 250mcm Cu for the feed. (150A @ 370ft., underground in RNC) Does my grounding conductor have to be sized according to the lowest rated ampacity of the feed or to the adjusted wire size?
 
sparkydon said:
That being said, when I did my voltage drop calc. for the loads from the house, I had come up with 250mcm Cu for the feed. (150A @ 370ft., underground in RNC) Does my grounding conductor have to be sized according to the lowest rated ampacity of the feed or to the adjusted wire size?
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You'll have to size the grounding conductor based on the size of the feeder, not the ampacity. I was just about to type up an explanation when I remembered that George already did it for us:

http://forums.mikeholt.com/showpost.php?p=649545&postcount=27

Good luck,
 
gotcha

gotcha

Crystal clear... I like the explanation of increasing the ground fault potential by sizing up the conductors, so the ECG must be proportionatly adjusted. Thanks for everyone's input, hopefully the horse can RIP now:cool:
 
sparkydon said:
Crystal clear... I like the explanation of increasing the ground fault potential by sizing up the conductors, so the ECG must be proportionatly adjusted.
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I am not so sure that is the reason. The amount of SC current might increase but that would just cause the protective device to open faster.

My guess is that most of the time conductors are up sized for VD concerns over long runs of wire. The impedance in a long run of green insulated wire increases with distance just as it does with other colors, so the requirement to increase the size of the green insulated wire has the effect of reducing the impedance in the wire so the circuit clearing device can function properly.
 
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Also take a look at 310.15(B)(6) and make sure you understand what the main power feeder is and isn't. You may not be able to use 4/0 Al to the pump house.
 
sparkydon said:
I will certainly run the grounding conductor continuously, bonding to the seperate grounding electrodes, while the neutral (grounded) conductor remains isolated in the two subpanels downstream from the Main.
Click to expand...

Based on your reply here, I assume you opted for the 4 wire feeder?
 
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