Service upgrade

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  #1  
Old 11-09-05, 06:34 PM
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Service upgrade

Hi all,
I am in the process of adding an extention/garage on to my house, which is now being framed.
I have a few questions about mounting the 2 new 150A main panels side by side:

A- The outside wall where the new underground service will be coming through, is a 2X6 stud wall. The area I have to work with is about 40" wide. What is the best way to mount the panels? I am assuming recessing them in the wall would be best. Is there a particular way to frame the wall to fit the panels, to make the cabling easier?


B- The feed will be 2 sets of 2/0 thwn in 2 sets of 2" sch 80 conduit.
Is there a better way of bringing in the conduit, than runnig them up the face of the wall and LNBing in to the back of the panel?
I would prefer to go through the foundation wall with the sweeps and enter the panels from the bottom.
Are there any tricks to help bring the conduit under the panel after it enters the garage ( since the 8" concrete wall brings the conduit way off)?
I have heard of heating the conduit in a barbaque. Anyone have first hand experience with this?

C- The conductors I plan on using are:
*weather head to 300A meter down the pole - 250 kcml copper in 2" PVC
*meter to the 2 panels 85 ft away underground- 2/0 copper thwn (2 sets in 2 sets of 2" PVC)
*2 ground rods at meter - #4? bare copper
*ground rod at panels - #4? bare copper
*subfeed to old 100A panel in main house 35 ft away - #4 SE cable

Does this sound right?
Any tips and advise will be greatly appreciated.

Mike
 
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  #2  
Old 11-09-05, 06:50 PM
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You didnt' say where you are mounting the panel boxes exactly.

Unless the 150 amp box is thicker than I think, you'd think the standard application of setting the boxes out the thickness of what your finsihs wal wil be (liek 1/2 or 5/8 inch) from the front edge of the studs, so that the box is flush with the finish wall, would be the way you'd do it. Btu I sure would look at how the knockouts work out for this, with this particular box.

It sounds like youi want the panel boxes on a first floor level and youwould rather get the main feed to enter from below? Correct? i follow. Wel, that is abnormal, I believe. Hmmm. That's a good one. What to do.what to do. How about turn the panel box upside down? You want to have no "mast" outside, is what it sounds like. Hmmm. I'm trying to think if I have ever run into or seen such a methodology before.

I think you could accomplish your goal by coming up from below with the conduit and then come up aloingside the box and 90 your way into the top side panel of the box. How's that?
 

Last edited by mattison; 11-10-05 at 05:11 AM. Reason: No need to quote the entire post above.
  #3  
Old 11-09-05, 07:51 PM
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I am installing the panels in the garage wall.
the feed is below ground.
I am trying to avoid running the 2" PVC on the face of the outside wall and then in to the garage.
I have attached a sketch of the wall.
sketch

Since the wall on top of the foundation is set back 2", and the panel is recessed, I am trying t figure how to close the gap I have indicated in red in the sketch.

Do I have the wire sizes right?

How do you frame around the panel without blocking the knockouts?

Thanks,
Mike
 
  #4  
Old 11-10-05, 02:19 PM
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Bump. Bump.
 
  #5  
Old 11-10-05, 02:26 PM
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So the conduits will have to come up through the wood floor plate? Sounds like a tough design.
 

Last edited by thinman; 11-10-05 at 02:59 PM.
  #6  
Old 11-10-05, 02:27 PM
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Where is the 2 inch pvc elbow in your sketch? Is it *in* the foundation? Inside the garage? You say you don't want it *outside* your garage. Or, haven't you figured where that elbow that turns up, should go yet?
If you had the elbow in the cement pour, your troubles would have been over, right? But now you are dealing with either going outside the wall, up to the panel box, and then in, or, up on the inside of the garage, right?

And is the foundation made of cement block or poured concrete?
 
  #7  
Old 11-10-05, 02:29 PM
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Originally Posted by thinman
Is the meter going to be mounted on the outside wall?
I don't think so, as I believe this is just going to be a sub panel box application. The meter is probably on his house.
 
  #8  
Old 11-10-05, 03:08 PM
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Originally Posted by Bonehead
Where is the 2 inch pvc elbow in your sketch? Is it *in* the foundation? Inside the garage? You say you don't want it *outside* your garage. Or, haven't you figured where that elbow that turns up, should go yet?
If you had the elbow in the cement pour, your troubles would have been over, right? But now you are dealing with either going outside the wall, up to the panel box, and then in, or, up on the inside of the garage, right?

And is the foundation made of cement block or poured concrete?
The meter is going on a new pole on the property, getting an over head feed, running down under ground and into the garage.
The wall is poured concrete.
I can drill the two holes for the 90s to enter through the wall (slab floor not poured yet) and enter the 2 new panels.

I just need to know how to get back towards the main panel, since the 90 is way into the garage.
And also is it better to run THWN in the PVC or run SEU.

Thanks,
Mike
 
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Old 11-10-05, 03:37 PM
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So, you are going to drill through the poured wall, and enter the garage with the 90, and then turn up?

Let me ask you something; You ever plan on sheetrocking or otherwise finishing off the walls in the garage? If you do, you will forever kill the ability, in any easy sense, to run new wire into these panel boxes, as they will be built into the wall. Maybe you will want to surface mount the panel boxes. That way you will solve al your problems. The boxes will be out closer to the pvc that will be turning upward. And, you will have all wiriing exposed so you can add new wire easily to the box.

The only other thing I can think of off hand is to creat a recessed cavity for the built-in (if you went this route) panel boxes. Then, you could insulate and sheetrock the walls up to the cavity that will house the panel boxes. You may want to put at least a minimal amount of pink or blueboard foam insulation behind the panel box.

Just a thought.
 

Last edited by mattison; 11-13-05 at 08:48 AM.
  #10  
Old 11-10-05, 07:24 PM
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Originally Posted by Bonehead
So, you are going to drill through the poured wall, and enter the garage with the 90, and then turn up?

YES.

Let me ask you something; You ever plan on sheetrocking or otherwise finishing off the walls in the garage? If you do, you will forever kill the ability, in any easy sense, to run new wire into these panel boxes, as they will be built into the wall. Maybe you will want to surface mount the panel boxes. That way you will solve al your problems. The boxes will be out closer to the pvc that will be turning upward. And, you will have all wiriing exposed so you can add new wire easily to the box.


I was thinking of surface mounting and boxing around the panels to hide the wires. Like you said it would bring the panels closer to the pvc. and also leave the back of the panels open for running up in the wall.


The only other thing I can think of off hand is to creat a recessed cavity for the built-in (if you went this route) panel boxes. Then, you could insulate and sheetrock the walls up to the cavity that will house the panel boxes. You may want to put at least a minimal amount of pink or blueboard foam insulation behind the panel box.

This was the original idea. The only thing remaining was the pvc too being far problem.

Question: is there a 300A main panel? or do I have to split the 300A to 2 panels? If there is a 300A panel, it would save me the trouble of the second pvc and drilling the hole for it.


Just a thought.

Thanks for your reply and help.
Mike
 
  #11  
Old 11-11-05, 05:29 AM
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IMHO (in order of preference):

First choice: use sweeps and conduit cast into the foundation wall when poured, so that the conduit is 'stubbed up' into the cavity space from the beginning. Conduit enters panels from below.

Second choice: use sweeps and conduit coming up the outside of the foundation wall to an LB just above the sill plate. Have another LB just inside the cavity space, and enter panels from below.

Third choice: Sweeps and conduit up the outside of the foundation wall and building to the level of the panels. Enter panels from behind.

Fourth choice: Drill foundation wall. Come through foundation wall with a sweep, then use a custom bent 'offset' conduit to enter panels from below. You may be able to use 'liquid tight flexible nonmetallic conduit for part of this. I would not use it for the initial sweep, but would consider using it for the offset; you need to remember that you will be pulling cable through this, so any sort of tight bend in the conduit is a big no-no.

Many (not all) panels are actually designed to be inverted, with the main breaker on the _bottom_. Code does not require the main to be in any particular location; simply that if the main flips _up and down_ that _down_ be off. With a suitably designed panel, you can bring the feed in from the bottom, connected to the main at the bottom, and then proceed normally with the rest of the panel.

-Jon
 
  #12  
Old 11-11-05, 01:38 PM
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Jon, see my comments below:

Originally Posted by winnie
IMHO (in order of preference):

First choice: use sweeps and conduit cast into the foundation wall when poured, so that the conduit is 'stubbed up' into the cavity space from the beginning. Conduit enters panels from below.

Agree this would be best, but too late for it.

Second choice: use sweeps and conduit coming up the outside of the foundation wall to an LB just above the sill plate. Have another LB just inside the cavity space, and enter panels from below.

This would be easier than drilling the concrete, but wouldnt the 2 LBs make it hard for the 3 2/0 wires to bend? Also I think that would max out the 360 degree bends allowed correct?

Third choice: Sweeps and conduit up the outside of the foundation wall and building to the level of the panels. Enter panels from behind.

Not too pleasant on the eyes.

Fourth choice: Drill foundation wall. Come through foundation wall with a sweep, then use a custom bent 'offset' conduit to enter panels from below. You may be able to use 'liquid tight flexible nonmetallic conduit for part of this. I would not use it for the initial sweep, but would consider using it for the offset; you need to remember that you will be pulling cable through this, so any sort of tight bend in the conduit is a big no-no.

Many (not all) panels are actually designed to be inverted, with the main breaker on the _bottom_. Code does not require the main to be in any particular location; simply that if the main flips _up and down_ that _down_ be off. With a suitably designed panel, you can bring the feed in from the bottom, connected to the main at the bottom, and then proceed normally with the rest of the panel.

-Jon
What about the cable sizes I have mentioned? are they right for the job?
250 cu kcml thwn for connection point to 300A pan.
2 sets of 2/0 from pan to the 2 main panels.
Also, not sure about the size of the GND wire, #4 or #6 or ?

Thanks ,
Mike
 
  #13  
Old 11-11-05, 09:25 PM
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On the back to back LBs: Yes this would present a wire bending issue. You would need to get LBs that were listed for the size and number of conductors that you were pulling. Sometimes these LBs have curved covers that provide more wire bending space. However this would not cause a problem with the 360 degree bend limit. The 360 degree limit is for the total amount of bend between 'pull points', and the LB, rather than counting as a bend, counts as a pull point.

You would pull the conductors into the first LB, then pass them to the second, and then pass them up to the panel. You _never_ pull _through_ an LB (the bend is too tight), but instead pull from or to an LB.

On your cable sizing, you will need to perform a proper load calculation; it is not enough to say that you have a pair of 150A breakers; you actually need to determine that the load on each panel is less than 150A, and that the total load is less than the service conductor ampacity.

It appears to me that you are using table 310.15(B)(6) for sizing all of your feeders; I do not believe that this is correct, but you will need to check with your local inspector. My opinion is that you could use 310.15(B)(6) for the main service, in which case all of the other feeders would not be the 'main power feeders to dwelling units' and thus one would need to size all of the other conductors using table 310.16. Or one might argue that the feed to the old main panel is the main power feeder to a dwelling unit, but that the service and the other feeders are not main power feeds to the dwelling unit. If you use 310.16 for 100A, then you need at least #3 conductors. For 300A you need 350kcmil conductors.

Grounding electrode connections to ground rods need only be #6 copper or #4 aluminium. A #4 or larger conductor is permitted to be exposed to severe physical damage; so you might go with the larger conductors simply because they need less mechanical protection at installation.

Grounding electrode connections to underground piping require large conductors, based upon table 250.16 and the size of conductors used. For the 300A service, a #2 grounding electrode conductor is required. See NEC 250.66

-Jon
 
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