Thread: Main Electrical "Maximum" Feed Length

Question for an electrican...
Is there a limit on the distance from the meter base to the interior panel with no exterior disconnect?
I did a home today with an exterior disconnect next to the meter base. (100amp, One breaker) that powered a remote distribution panel, in the basement. About 20 feet away.
I was told that if the interior panel was not on the same wall, that the "exterior disconnect" (In this case a main panel) was required, but I never heard of that.
Is it OK to just have the meter base, at the exterior, feed an interior, main panel with a run of say 20-30' between the meter and main panel? (No disconnect at the exterior)

Thanks in advance.

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The NEC requires the unfused feeders to be "as short as practical". There is no distance measurement actually spelled out. Some areas seem to allow 5=6 feet being common, while others require back to back mounting of meter to panel.

Originally Posted by Jim Port

The NEC requires the unfused feeders to be "as short as practical". There is no distance measurement actually spelled out. Some areas seem to allow 5=6 feet being common, while others require back to back mounting of meter to panel.

"Some areas seem to allow 5=6 feet being common, while others require back to back mounting of meter to panel."

Back to back mounting of the panel to the meter typically ends up being about 4-6 feet of unfused service entrance inside the the structure.

The distance is not the distance between the meter and the panel, the distance is the length of the conductors: figure 1/2' through the wall + 3' up into the panel + another 1'-2' for the bends in the panel, and you are right at 4-6 feet of conductor length inside the house ... and that is for back to back meter and panel (unless the electrician takes care to mount the meter high and the panel low so the conductors can be run right to the main terminals without going up or down within the service panel.

Originally Posted by Jerry Peck

"Some areas seem to allow 5=6 feet being common, while others require back to back mounting of meter to panel."

Back to back mounting of the panel to the meter typically ends up being about 4-6 feet of unfused service entrance inside the the structure.

The distance is not the distance between the meter and the panel, the distance is the length of the conductors: figure 1/2' through the wall + 3' up into the panel + another 1'-2' for the bends in the panel, and you are right at 4-6 feet of conductor length inside the house ... and that is for back to back meter and panel (unless the electrician takes care to mount the meter high and the panel low so the conductors can be run right to the main terminals without going up or down within the service panel.

Jerry is right on the money here. The 5' rule is/was 5' of unfused wire! But if there is a disconnect on the outside next to the meter as the OP stated in his second sentence, that is different! If you are fused properly outside you are only limited in distance by the wire size and voltage drop.

I don't know if this is possible in the US, but in Canada, the rule is "short as possible", but the unfused portion can be extended, usually under the house, if it is completely buried in no less than 2" of concrete.
In a crawlspace, the service conductors would be buried under concrete or if installed later, a trough is constructed out of 2X4's and filled with concrete. Since the disconnect is always indoors, creative ways have to be invented to protect the conduit with concrete.

Thanks Guys!
I got my answer.

Rich,

Just curious, but what was the answer you, "Got"?

Originally Posted by John Kogel

I don't know if this is possible in the US, but in Canada, the rule is "short as possible", but the unfused portion can be extended, usually under the house, if it is completely buried in no less than 2" of concrete.

The NEC does not consider the conductors as being inside the structure if they are:
- 230.6 Conductors Considered Outside the Building.
- - Conductors shall be considered outside of a building or other structure under any of the following conditions:
- - - (1) Where installed under not less than 50 mm (2 in.) of concrete beneath a building or other structure
- - - (2) Where installed within a building or other structure in a raceway that is encased in concrete or brick not less than 50 mm (2 in.) thick
- - - (3) Where installed in any vault that meets the construction requirements of Article 450, Part III
- - - (4) Where installed in conduit and under not less than 450 mm (18 in.) of earth beneath a building or other structure

Don,
The answer I "GOT" was... It is not OK to have a long run (Meter to main panel) into a house, without an outside main / disconnect.

Thanks, Jerry. I imagine the local authority needs to be consulted for any long runs, same as up here.

I recall a city property with a seriously renovated, almost completely rebuilt 100 yr old house, where the service mast is on the left front corner. The service conductors go down to the meter on the left then down into the new slab, across to the mid right side where the conduit emerges outside the foundation. From there it turns and goes back into the house, runs along on top of the slab, under a berm of concrete in the laundry room, to a wall in the hallway, where the conduit runs up the wall to the service panel. That's a run of about 40 feet. Pretty unusual, and a goofy bump in the floor, but it was allowed.

I have pics here of a service run in a crawlspace. Good intentions, but they never did get all the concrete in there.

Originally Posted by John Kogel

I have pics here of a service run in a crawlspace. Good intentions, but they never did get all the concrete in there.

John,

Not only that, but it does not look like they even allowed for minimum 2" of concrete on the sides, or the top, or the bottom (needs to be fully encased, which includes below it too for that except to be applied).

One of the homes I inspected today from the early 60s was allowed at the time and extremely common around here to have the meter at the back of the home at one side of the home and the service panel in the garage at the opposite (angle) side of the home toward the front and that being maybe 60 feet.

As far as new homes in this area it is typically installed with the service disconnect outside and the main inside thru the same wall and no further.

I know as far as the codes say but i am just stating what is acceptable (common to the area) around here now and in the distant past.

Old code references don't necessarily apply unless the AHJ has adopted the specific code in question. While many Cities have adopted the NEC today it was not always that way. Some AHJ's used to write their own versions of the code, some still do to some extent. Miami-Dade County used to print their own version of the code and while much of it was taken verbatim from NEC a good deal of it was not.

In 60's and 70's going by NEC it was not legal to come out of the top of a meter (in conduit or otherwise) and run up and into the attic and across the attic to the MB service panel (regardless of the distance) with unfused utility power. But there are thousands of homes here in Miami, FL that are wired in this manner because it was legal to do it that way here at that time. The only stipulation I recall was that the wiring had to be in rigid metal conduit.

Dade County has since adopted the NEC and no longer writes their own version.

I am curious though, if a HI was to inspect one of those homes today, what code would they apply? NEC or local codes in effect at the time? Would they even know about local codes in effect at the time? Maybe Jerry can shed some light on this?

Originally Posted by Lou Romano

Old code references don't necessarily apply unless the AHJ has adopted the specific code in question. While many Cities have adopted the NEC today it was not always that way. Some AHJ's used to write their own versions of the code, some still do to some extent. Miami-Dade County used to print their own version of the code and while much of it was taken verbatim from NEC a good deal of it was not.

Lou,

Broward County also had their own electrical code, like Miami-Dade, it was the NEC with amendments, with differences between Miami-Dade and Broward counties - just like there were differences between the South Florida Building Code, Dade County Edition and the South Florida Building Code, Broward County Edition.

In 60's and 70's going by NEC it was not legal to come out of the top of a meter (in conduit or otherwise) and run up and into the attic and across the attic to the MB service panel (regardless of the distance) with unfused utility power. But there are thousands of homes here in Miami, FL that are wired in this manner because it was legal to do it that way here at that time. The only stipulation I recall was that the wiring had to be in rigid metal conduit.

Same thing exists in thousands of home in Broward county, but it was not the code language which was different, it was based on what 'the point of entrance' into the structure meant - and the interpretations on that were pretty far fetched and some really had nothing to do with where the conductors entered the structure.

I am curious though, if a HI was to inspect one of those homes today, what code would they apply? NEC or local codes in effect at the time? Would they even know about local codes in effect at the time? Maybe Jerry can shed some light on this?

If you know what the local codes are/were, you would use them and the current nationally accepted codes because accidents and injuries do not care what code allowed or disallowed at any given point in time, and even today's codes are constantly being tweaked for better protection - using the most current *minimum safety standard* (which is what codes are) is the best point of reference ... remember, home inspectors cannot "require" any repairs or corrections, they simply advise and educate their client's as to what they find.

When I do mechanical inspections and find flex duct in the garage, which is not allowed now, but was as various points in time - if the flexible duct has been replaced or installed then I write it up as needing to meet current code as it is required to, however, when I find flexible duct in the garage and it is from the time of construction all I can do is make a note on the inspection report advising the owner that the flexible duct 'should' be (but is not required to be) replaced with proper duct work suitable for use in a garage.

Just last Thursday I had to explain the flexible duct problem to a mechanical contractor who replace the flexible duct in a garage - had he not replaced the flexible duct I could not require him to replace it, but he did install a new section of flexible duct in the garage and he now has to replace it with suitable duct work ... I had to walk him through the code sections one-by-one to where it shows him that flexible duct is not allowed in the garage and why he is required to replace it - he still doesn't like it and is still groaning and complaining that he should not have to replace it, but he knows he has to replace it in order to pass his inspection, and he now knows the applicable code sections.

Protected or unprotected,

Differences, depends.

Determine if "service", "tap" or "feeder" conductors (including main power feeders, etc.)

Local GEC/N bond location.

"Utility" or private power distribution.
Special characteristics,

Local rules, utility/co-op rules, Electrical Code rules.

Vintage of original installation, and of any changes, modifications, replacements, and rules in effect at those events.

De-regulation effects, and changes in the local distribution system subsequently which may have effected the sufficiency, rating, etc. and safety of the remaining equipment.

Ag heavy state - not presuming anything with generic "ohio" location. Some co-op's have had extending authority regarding what is "attached" and "utilizing" of their system(s).