Detached garage grounding

[LarrylLix]

For lightning you want grounds as close to the building and strike points as possible. If you connect grounds together the lightning can go look for a better ground through your house and, as above per Lou, damage stuff in between.
 
In the event of step potential in the ground, which happens when grid people tie 3 phase 4 wire system neutrals to ground at different points (yeah it's a problem for utilities too) when you ground several points you are bridging the bad earth conductor with your conductor. When system faults happen cows get fried sometimes and your equipment will not handle that well either.
 
In the end the best combination is only one bonding point for your neutrals so that grounds do not carry any current ad develop voltage drops in them creating your own step potential problems. At the same time ground every piece of equipment to a standing plate in the floor around it  (Think small Faraday cage)
 
 
I worked in grid protection schemes for 35 years and had to deal with this crap in theory and saw the ashes of faults many times. When a 230kV conductor faults to ground the ground at that point will be about 100kV to the rest of the world. Rings of step potential surround the fault point radiating outward for miles and miles. Telephone companies love this stuff. Demarcation points and equipment burns out miles away 'cause they conectin' the telephone lines from somebody else's ground to power lines and their own ground. Surprise!
 
As above the other side of the coin is to run a ground rod  ring around your life, live in a Faraday cage and disconnect everything you have from ground. Let it float so there is no return path like bird on a wire.
 
I feel as if I am rambling here but I think Lou stated it quite well.

 

[apostolakisl]

Just to illustrate.  Someone at my church connected our sanctuary and activity building with a cat5 wire in a buried conduit.  We had a lightening strike.  The two buildings are on separate electric service and have their own grounds, but the cat5 connected those grounds.  We ended up frying an IP camera, a router, our sound system digital recorder, and an entire bank of our audio system IO device.  This all worked out to a couple thousand dollars.
 
I replaced said cat5 with fiber.  This is very easy and cheap.  I used two of these http://www.amazon.com/MC200CM-Converter-1000Mbps-multi-mode-mountable/dp/B003AVRLZI/ref=sr_1_3?ie=UTF8&qid=1444355058&sr=8-3&keywords=multimode+fiber+to+ethernet and a strand of appropriately lengthed multi-mode fiber (like 150 ft, I forget).  If it doesn't work on your first try, swap the TX and RX fibers, you probably have them backwards (like I did).
 
Currently doing the same thing at my office complex.  Here we have 6 buildings.  We're using single mode fiber  since the distances are a bit longer and single mode has an upper speed limit that is astronomical.  The fire alarm guys want to tie the alarm panels together with copper.  I'm going to have to have a good talk with them to here how they plan on avoiding the grounding issue.

 

[rsw686]

I'm interested to know from the OP
 
When you say that the detached building is connected directly to the meter do you mean before the meter of after the meter? Just curious.

 
The meter base is the standard 200A with one set of lugs. The splice is after the meter on the inside wall of the house in a junction box. From the splice box one side goes to the house panel and the other to a 175A fused disconnect box. From the disconnect it goes out the wall and is buried to the detached shop. I haven't seen the inside of the junction box as I don't move in for two weeks. I'm just trying to plan and gather a parts list.

 

[rsw686]

I've read over the NEC code and it clearly states that both builds must have a ground rod driven. I found an IAEI post, which has pictures showing my current setup per NEC 2005 code. The catch is there can be no other metallic paths between the buildings. I could run fiber for network, but that leaves me stuck on the security side. I could forgo the OmniPro expansion enclosure and just home run a few zones, but I feel like I am fighting the inevitable.
 

 
It looks like the best/correct answer, which is what NEC 2008 requires, is to just run a new feeder with 4 conductors. I'm going to follow NEC code and leave the ground rod connected at the shop. I also will need to rewire the shop panel so the neutral and grounds are separated.
 

 
After looking at the below picture it makes sense that with 3 conductors between the buildings ethernet, security cable, etc would become a potential source for stray current to destroy the equipment. It just doesn't seem worth the risk to fry equipment over a few hundred dollars of cable. Since I do have a disconnect at the house for the shop feeder I can abandon the 4/0 3 conductor cable, install a new 125A breaker, run 1/0 aluminum 4 conductor cable, and hookup the shop panel myself. After that is working I can pay an electrician to pull the meter, remove the splice box and fused disconnect, and connect the house panel directly to the meter.
 

 

[mikefamig]

Today I am going to look and see if I installed a ground between the buildings. I did the job five years ago and my memory is that I did but my memory sucks these days. I'm sure that I did what the electrical inspector wanted at the time.
 
Mike.

 

[LarrylLix]

@rsw686
 
You don't need to rewire the shop. Look for a bonding screw through the top of the neutral bar and remove it. It connects the neutral to the case of  the distribution panel.
 
 
Also, I don't understand why you  would want to rearrange your service feed to the shop powering the capacity of the whole shop system. If you ever wanted to run a welder or other heavy machine you will appreciate the size of the conductors. OTOH is the cost when adding your 3 conductor with ground.
 
Your splitter box will remain without huge costs to clean it all out.

 

[mikefamig]

LarryILix
 
Am I clear that you are saying that the buildings should have only three conductors between them - Line1, Line2 and neutral?
 
Mike.

 

[LarrylLix]

Ground conductors are not counted in cables. 14/2 has a neutral, hot and ground wire.
 
If you find cable that has no ground it probably isn't legal to install anymore.
 
Our code may be a little tighter on this stuff.  IF a conductor is not the right colour you can't use it. No coloured tape allowed under 2/0??? size.

 

[mikefamig]

Ground conductors are not counted in cables. 14/2 has a neutral, hot and ground wire.
 
If you find cable that has no ground it probably isn't legal to install anymore.
 
Our code may be a little tighter on this stuff.  IF a conductor is not the right colour you can't use it. No coloured tape allowed under 2/0??? size.

 
But you said in an earlier post to not connect the grounds together between the buildings which I don't understand.

 

[rsw686]

Also, I don't understand why you  would want to rearrange your service feed to the shop powering the capacity of the whole shop system. If you ever wanted to run a welder or other heavy machine you will appreciate the size of the conductors. OTOH is the cost when adding your 3 conductor with ground.

 
The service feed technically isn't right. I have a 200A meter base with 2 200A panels connected. There is no fuse or breaker limiting both panels to only pulling 200A max. In the rare chance I drew over 200A combined I'm fairly certain something would burn up.
 
To do it right the I was told I would need to upgrade to a 400A dual lug meter base and have the utility company upgrade my service feeder to 400A. I was also looking at adding a whole house transfer panel and it's half the cost for a 200A unit.
 
The Miller welder I am looking at only requires a 30A breaker even though they use a 50A plug. The shop comes with a 60gal 220V compressor which I would assume is 20-30A. It also has a 4 ton commercial heat pump, which I need to confirm the draw on. If these were all running I would probably be at 100A. Since it is just me in the shop I don't think realistically I would need more power. The welder wouldn't be used continuously either.

 

[rsw686]

You don't need to rewire the shop. Look for a bonding screw through the top of the neutral bar and remove it. It connects the neutral to the case of  the distribution panel.

 
I'll double check, but during the home inspection I remember the ground and neutral wires combined on the same bus bar. It looks like some panels require you to purchase the ground bar separately, which installs above the neutral bus bar. I'm almost positive it was a cutler hammer panel.

 

[rsw686]

Ground conductors are not counted in cables. 14/2 has a neutral, hot and ground wire.

 
From what I've read I can't pull a sheathed cabled through conduit. I keep finding posts saying I have to purchase individual conductors of THWN-2 or XHHW-2 and pull them through the conduit.

 

[LarrylLix]

But you said in an earlier post to not connect the grounds together between the buildings which I don't understand.

I didn't connect the grounds together and the inspector told me not to. I didn't think I said not to. I have two ground rods for just my out building system panels.
 
This concept is quite controversial and it appears your codes are changing on how to do it. Canadian code is slightly different in some aspects and I have lost track of the latest changes to ours.
 
If you have other metallic connections between buildings it may be a good thing to nullify any differences with a decent ground conductor. I don't have any signal cables between buildings so I stop transients in the ground system from coming home. I use Wi-Fi via a router put into bridge mode to talk to my home router for Cam, weather station reporting etc. HA is Insteon dual mesh, phone is wireless. Building being all metal foil clad insulation and metal roof is a bit of an RF problem so window lineup is necessary for phone and Wi-Fi but not Insteon signals that find their way through powerlines also.

 

[LarrylLix]

You have to use conductors or cables that are good for underground wet locations. It can get expensive.
 
Pipe underground eventually fills up with water.

 

[pete_c]

I have a Square D fuse panel here with all metal conduit / boxes.  There is no ground bus bar inside of the fuse panel.  The neutral is bonded to the ingress main water lines via a ground strap wire in a conduit that runs about 25 feet.  I have attached a simpler than my fuse panel drawing.
 
I would have assumed that the remote sub panel ground strap is local (ground bus in panel) with three wires between main and sub fuse panel as depicted above which personally makes the most sense. (load 1,2 plus neutral and locally bonded ground to ground).  IE: sub panel neutral comes from main panel and local ground is bonded locally in the remote building.
 
1 - Both panels are treated as main panels and the buildings each have their own ground rods driven.
 
2 - I talked briefly with an electrician and he said detaches structures should have 2 hots, neutral, and ground run so the building grounds are tied together and the shop panel should be wired like a sub panel.
 
Sentence 2 contradicts what is already done properly.  I am thinking the electrician knows what is right and his statement is just dyslexic.