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Old 11-03-2018, 08:10 PM   #1
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New Service Entrance


Hello All! First off, I would like to thank everyone in the community and staff for making this forum possible. It has been an amazing resource to answer questions I have had in residential wiring.

Now, to the nitty-gritty:

I am planning a business around IT outsourcing and found a need to build a home data center to host services for customers and my own operations applications. That being said, I am not up on residential deployments, but have found many issues on my older house wiring that led me to the solution of installing a new service entrance. The existing entrance is neither sufficient, permitted nor up to my understanding of residential code requirements. There is one permit from circa 1982 for a temporary power pole for a trailer hookup or something. Ungrounded 10-2 romex is installed for pretty much every circuit in the house, old fashioned 100A rated fusebox with a 60A pull fuse disconnect, water heater and well pump spliced to the same 30A 240v circuit/fuse. And, to my dismay the kitchen range spliced out to the detatched garage/shop I installed my rack in. The circuit is protected by a 60A 240v pull fuse and the splice that goes to the breaker box in the shop is buried 8-2 grounded romex. *cringe*

After consulting the AHJ (who is seemingly quite happy im wanting to fix these issues) and the PoCo I came to this solution:

<Cant post pictures, so see Power Diagram.jpg>

And this is what I have installed thus far:


<See the two Picture****.jpg images>

I have also installed 2" EMT using rain tight couplers and I need to but bonding locknuts to meet grounding/bonding requirements. THe 23.5" space between the meter socket and main breaker box is to accomodate for a whole-house transfer switch for a 16KwH propane generator which will be installed after this is completed. The current service entrance is to the right of the first pictured window. Which leads me to two questions:

First off, are there any restrictions on running conduit above a window (clearances etc)? This is my planned solution:

<See orientation.jpg>

The top LB is to run a subpanel to the back of the house later down the line. The LB to the right is to penetrate the wall to get to the current fusebox, which will also be replaced with a proper breaker box later. When I re run the shop underground feeder I intend to install a 1-1/2" EMT with rain-tight couplers and a LB conduit body below the main breaker to run under the house and to the underground PVC conduit that will be located on the other side of the house.

Second, to try and shave costs I wanted to run EMT from the top of the main breaker box and use EMT conduit bodies. From what I have read, there is no way to properly connect EMT to the top of a NEMA 3R box and keep the rating, and theres a good bit of controversy to mating EMT to the appropriate threaded hub that comes with the breaker box. I am prepared to purchase IMC, but just wanted to get a definitive answer regarding this topic.

A third and final question is an embarrassing subject. I accidentally knocked out the 2-1/2" knockout on the meter socket and wanted to use reducing washers to fix this issue, since my planned transfer switch only has 2" knockouts. Is there a way to make reducing washers acceptable and maintain the NEMA 3/3R ratings of my boxes?

Thank you in advance!
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Old 11-04-2018, 01:18 AM   #2
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Re: New Service Entrance


After some digging around THIS forum (not the obnoxious union-ran electrician's forums) I found this post and attatched pictures.

https://www.diychatroom.com/f18/outd...2/#post2627561


So my answer to windows may be a yes, since I would figure service wires over a door would be a greater shock risk than feeder wires over a window. Ill probably try to give at least 6-inches to 1-foot of clearance regardless to my horizontal IMC run....
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Old 11-04-2018, 08:21 AM   #3
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Re: New Service Entrance


New Service Entrance-img_0410.jpgChange the emt to grc or imc. No NEC prohibition for conduit above windows or beside windows. The 3r rating is not compromised if the ko is below the terminals of the meter socket(lower side or bottom. You could use reducing washers and sealing washers to ease your mind.

IMO there is no need to use metallic conduit beyond the service mast. PVC is compliant(in most areas) and much easier to work with.

My first comment refers to the service mast if it is emt.

Assuming the transfer switch is service rated, all grounding and bonding is done within the transfer switch thus rendering the first and all subsequent panels as sub-panels requiring four wire feeders.

Last edited by brric; 11-04-2018 at 08:38 AM.
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Old 11-04-2018, 01:45 PM   #4
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Re: New Service Entrance


Quote:
Originally Posted by brric View Post
Attachment 538689Change the emt to grc or imc. No NEC prohibition for conduit above windows or beside windows. The 3r rating is not compromised if the ko is below the terminals of the meter socket(lower side or bottom. You could use reducing washers and sealing washers to ease your mind.

IMO there is no need to use metallic conduit beyond the service mast. PVC is compliant(in most areas) and much easier to work with.

My first comment refers to the service mast if it is emt.

Assuming the transfer switch is service rated, all grounding and bonding is done within the transfer switch thus rendering the first and all subsequent panels as sub-panels requiring four wire feeders.

Thanks for the clarification. I remember seeing a picture or a post somewhere about conduit near openable windows. Must be crazy.


Everyone keeps thinking I used EMT for the mast Never would I ever. Poco requires RMC.



As for the remaining conduit, I want to use metallic because it lasts longer to my knowledge. More rugged, more protective. Its a personal preference really...


I am doing a phased upgrade due to fund constraints. The ATS is service rated (Generac 200A whole house ATS) and i presumed bonding would happen there once I install it and I would remove the bonding bolt from my main panel and move the ground wire from the main panel to the ATS.


My concerns about the insulated washers is if they are correct for bonding requirements. It makes the EMT between the meter socket and the breaker box isolated thus ungrounded. I was presuming I could just use a bonding bushing and kill two birds with one stone as far as ensuring bonding is correct and the feeder wires are protected from damage.

Last edited by sciens; 11-04-2018 at 01:48 PM.
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Old 11-04-2018, 01:55 PM   #5
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Re: New Service Entrance


Also, quick picture update





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Old 11-05-2018, 01:51 PM   #6
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Re: New Service Entrance


Quote:
Originally Posted by sciens View Post
I am planning a business around IT outsourcing and found a need to build a home data center to host services for customers and my own operations applications.
How did you size the service entrance conductors? The exception for undersizing SE conductors and feeders to a dwelling unit may no longer apply if the occupancy type has changed.

Quote:
Second, to try and shave costs I wanted to run EMT from the top of the main breaker box and use EMT conduit bodies.
What do you mean by EMT conduit bodies? What I would consider an "EMT conduit body" is the type with set screws and no threads. Those are for dry locations only.

Quote:
From what I have read, there is no way to properly connect EMT to the top of a NEMA 3R box and keep the rating, and theres a good bit of controversy to mating EMT to the appropriate threaded hub that comes with the breaker box.
On outdoor enclosures it is best to avoid using the top hub for anything unless you absolutely need to. Water will always find a way in from leakage or condensation. The hub places the conduit perfectly for dripping water directly into the most vulnerable parts of the panelboard. You will encounter this whether you are using EMT or IMC. Consider coming out of the side of the enclosure using an LB or LL to make the vertical transition.

Quote:
I accidentally knocked out the 2-1/2" knockout on the meter socket and wanted to use reducing washers to fix this issue, since my planned transfer switch only has 2" knockouts. Is there a way to make reducing washers acceptable and maintain the NEMA 3/3R ratings of my boxes?
Raintight reducing washers are available.


A better solution is to switch this particular conduit to PVC when you install the transfer switch. You can install a 2 1/2" terminal adapter to connect to the meter enclosure and use a 2 1/2"-2" reducing bushing to attach 2" conduit.

This is because a metallic service entrance raceway causes current to flow through the conduit itself. The service neutral is bonded to the meter enclosure. The neutral is also bonded to the service equipment enclosure. The conduit is bonded to both enclosures and becomes a conductor in parallel to the service neutral. It's best to avoid this when possible and switching to PVC is an easy way to do so.

While I'm on the subject, PVC is also a better choice to protect the grounding electrode conductor. You presently have it installed in EMT. EMT in this situation needs to be continuous between the service panel and the grounding electrode, not just installed from the service panel to the earth. It also needs to be bonded to the GEC at the service panel and to the grounding electrode on the other end. Using ferrous metal in this application gets ugly.

Quote:
My concerns about the insulated washers is if they are correct for bonding requirements. It makes the EMT between the meter socket and the breaker box isolated thus ungrounded. I was presuming I could just use a bonding bushing and kill two birds with one stone as far as ensuring bonding is correct and the feeder wires are protected from damage.
You would need bonding bushings whether the reducing washers were the sealing type or not. Conduits containing service entrance conductors have more stringent bonding requirements.
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Old 11-06-2018, 03:07 AM   #7
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Re: New Service Entrance


Quote:
Originally Posted by Fishbulb28 View Post
How did you size the service entrance conductors? The exception for undersizing SE conductors and feeders to a dwelling unit may no longer apply if the occupancy type has changed.

200A SE wires 4/0 for hots and 2/0 for the neutral. Was suggested by the material source.




Quote:
Originally Posted by Fishbulb28 View Post
What do you mean by EMT conduit bodies? What I would consider an "EMT conduit body" is the type with set screws and no threads. Those are for dry locations only.
Based on this alone I'll use IMC. Ive been looking for EMT conduit bodies and theyre all too small and the only correct sized ones are for RMC/IMC.



Quote:
Originally Posted by Fishbulb28 View Post
On outdoor enclosures it is best to avoid using the top hub for anything unless you absolutely need to. Water will always find a way in from leakage or condensation. The hub places the conduit perfectly for dripping water directly into the most vulnerable parts of the panelboard. You will encounter this whether you are using EMT or IMC. Consider coming out of the side of the enclosure using an LB or LL to make the vertical transition.

Ive been suggested this outside this thread and am considering it... Condensation for the long horizontal run would end up either in the walls or in the top of the panel...



Considering this, would it be smarter to run all the feeder wires for the subpanels through the side or would it be safe to still run the attic-bound wires for the back-of-house panel through the top?





Quote:
Originally Posted by Fishbulb28 View Post
Raintight reducing washers are available.


A better solution is to switch this particular conduit to PVC when you install the transfer switch. You can install a 2 1/2" terminal adapter to connect to the meter enclosure and use a 2 1/2"-2" reducing bushing to attach 2" conduit.


This is because a metallic service entrance raceway causes current to flow through the conduit itself. The service neutral is bonded to the meter enclosure. The neutral is also bonded to the service equipment enclosure. The conduit is bonded to both enclosures and becomes a conductor in parallel to the service neutral. It's best to avoid this when possible and switching to PVC is an easy way to do so.

Ive said it before elsewhere, I prefer metal. To me - especially since grounding/bonding happens at the panel, not the meter - I feel better having the meter socket bonded through the conduit to the panel. Feel free to correct me if this isnt even a little sane.


The point made about the conduit becoming a grounded conductor in paralell with the neutral conductor makes me a bit nervous though. Is it ever common to use metallic conduit between the meter and breaker box?



Quote:
Originally Posted by Fishbulb28 View Post
While I'm on the subject, PVC is also a better choice to protect the grounding electrode conductor. You presently have it installed in EMT. EMT in this situation needs to be continuous between the service panel and the grounding electrode, not just installed from the service panel to the earth. It also needs to be bonded to the GEC at the service panel and to the grounding electrode on the other end. Using ferrous metal in this application gets ugly.

I was told this in another forum. Is there a code refrence for this subject? And how would you bond both sides of this conduit? Just curious.... Yall are almost making me want to go with PVC.... I hate PVC...


Quote:
Originally Posted by Fishbulb28 View Post
You would need bonding bushings whether the reducing washers were the sealing type or not. Conduits containing service entrance conductors have more stringent bonding requirements.

Duly noted. I am about to begin more work on this project and will make the necessary updates to the installation and come back with a status update!


Love the feedback everyone! Keep the comments and criticisms coming!


Edit: Found some material that is the source of my PVC concerns though:
Quote:
On the downside, conduits manufactured from PVC are brittle when cold, and they sag when hot. PVC is commonly used as an underground raceway because of its low cost, ease of installation, and resistance to corrosion and decay.

Last edited by sciens; 11-06-2018 at 03:23 AM.
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Old 11-07-2018, 01:09 AM   #8
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Re: New Service Entrance


Quote:
Originally Posted by sciens View Post
200A SE wires 4/0 for hots and 2/0 for the neutral. Was suggested by the material source.
Do you yet have an actual calculated load for the home and the planned data center?

Quote:
Considering this, would it be smarter to run all the feeder wires for the subpanels through the side or would it be safe to still run the attic-bound wires for the back-of-house panel through the top?
If it was my home or a project I was directly involved with I would not use the hub at all. An LL or LB conduit body doesn't much care if it gets filled with water. Circuit breakers, buses, terminals, and the steel enclosure of the panelboard do. Let the conduit body collect the water instead of the other equipment. Perhaps drill a 1/16" hole in the bottom to let any accumulated water drain.

Quote:
Ive said it before elsewhere, I prefer metal. To me - especially since grounding/bonding happens at the panel, not the meter - I feel better having the meter socket bonded through the conduit to the panel. Feel free to correct me if this isnt even a little sane.
The meter enclosure is already bonded to the service grounded conductor. If the grounded conductor to the service disconnect was somehow lost AND the utility's ground at the transformer was compromised while somehow still retaining service the meter enclosure would no longer be touch safe. It's not anything to worry about.

Quote:
The point made about the conduit becoming a grounded conductor in paralell with the neutral conductor makes me a bit nervous though. Is it ever common to use metallic conduit between the meter and breaker box?
Yes, but not with meter enclosures which have a bonded service grounded conductor.

Quote:
I was told this in another forum. Is there a code refrence for this subject? And how would you bond both sides of this conduit? Just curious.... Yall are almost making me want to go with PVC.... I hate PVC...

250.64 Grounding Electrode Conductor Installation.
(E) Raceways and Enclosures for Grounding Electrode Conductors.
(1) General.
Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.


The panel side is done with a bonding bushing. Just feed the GEC through the bushing connector. Attachment to a grounding electrode is done with fittings specific to the purpose:



Most of these fittings are for RMC since few people bury EMT but a few exist which accept both.

Quote:
Found some material that is the source of my PVC concerns though:
They completely omitted the thermal expansion coefficient of PVC! That's one of its main annoyances.

PVC for a 6"-ish stub and for protecting the GEC isn't a problem. You would be okay using it.
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Old 11-07-2018, 10:08 PM   #9
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Re: New Service Entrance


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Do you yet have an actual calculated load for the home and the planned data center?

I just asked if a 200A service would be acceptable by the PoCo. When I say datacenter, all I am referring to is a single rack with a 30A 240v power source. At most, I expect to draw 1.5KwH on this setup. May get more later, but as of now, highly doubt it. It would be the equivalent to running a 1000W heat lamp and a couple CRT TVs.



Quote:
Originally Posted by Fishbulb28 View Post
If it was my home or a project I was directly involved with I would not use the hub at all. An LL or LB conduit body doesn't much care if it gets filled with water. Circuit breakers, buses, terminals, and the steel enclosure of the panelboard do. Let the conduit body collect the water instead of the other equipment. Perhaps drill a 1/16" hole in the bottom to let any accumulated water drain.

I reinstalled the top cap and will now use a 90* eblow on the right side of the box for the subpanel feeders.




Quote:
Originally Posted by Fishbulb28 View Post
The meter enclosure is already bonded to the service grounded conductor. If the grounded conductor to the service disconnect was somehow lost AND the utility's ground at the transformer was compromised while somehow still retaining service the meter enclosure would no longer be touch safe. It's not anything to worry about.

So... Im not crazy for keeping the EMT between the meter and the main panel?





Quote:
Originally Posted by Fishbulb28 View Post
Yes, but not with meter enclosures which have a bonded service grounded conductor.

Ill have to look at this a bit closer I guess...



Quote:
Originally Posted by Fishbulb28 View Post
250.64 Grounding Electrode Conductor Installation.

(E) Raceways and Enclosures for Grounding Electrode Conductors.
(1) General.
Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.


The panel side is done with a bonding bushing. Just feed the GEC through the bushing connector. Attachment to a grounding electrode is done with fittings specific to the purpose:



Most of these fittings are for RMC since few people bury EMT but a few exist which accept both.

I made the change to PVC for this raceway. Less headache.




Quote:
Originally Posted by Fishbulb28 View Post
They completely omitted the thermal expansion coefficient of PVC! That's one of its main annoyances.




PVC for a 6"-ish stub and for protecting the GEC isn't a problem. You would be okay using it.


And again, I made the changes for all the subpanel feeders to PVC. Ill post some pictures in a bit.
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Old 11-08-2018, 12:40 AM   #10
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Re: New Service Entrance


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I just asked if a 200A service would be acceptable by the PoCo. When I say datacenter, all I am referring to is a single rack with a 30A 240v power source. At most, I expect to draw 1.5KwH on this setup. May get more later, but as of now, highly doubt it. It would be the equivalent to running a 1000W heat lamp and a couple CRT TVs.
Okay, not much of a load then. There is a reason I was asking. The SE conductors (more specifically their terminations) aren't actually rated for 200A. It's permissible in a home to do so and the equipment tolerates it well for home usage patterns. Adding a business can change the usage pattern.

Quote:
So... Im not crazy for keeping the EMT between the meter and the main panel?
I won't say crazy, but you're worrying about an obscure event and creating a constant hazard to avoid it.

Quote:
And again, I made the changes for all the subpanel feeders to PVC. Ill post some pictures in a bit.
I didn't mean to dissuade you from using EMT or IMC everywhere, just the two particular segments I mentioned. But PVC here is ok, too.
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Old 11-08-2018, 01:29 AM   #11
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Re: New Service Entrance


First six. In order of the service entrance down.
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Old 11-08-2018, 01:33 AM   #12
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Re: New Service Entrance


Detail shots for the grounding conductor and the 2" PVC out for the house's subpanel feeder(s).


Need to grab some 1-1/4 PVC for the LB below the panel that will penetrate below the floor line under the house that will pass to the shop/garage and eventually a feeder for the well pump house.
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Old 11-08-2018, 07:47 AM   #13
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Re: New Service Entrance


PVC still needs a plastic bushing.
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Old 11-08-2018, 02:12 PM   #14
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Re: New Service Entrance


Quote:
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PVC still needs a plastic bushing.

Good catch! Thanks! 1AWG Feeders are bound out that one.


What about the 3/4" for the GEC?
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Old 11-08-2018, 02:53 PM   #15
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Re: New Service Entrance


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What about the 3/4" for the GEC?
The bushings are only required for insulated conductors.
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