Ask Me Help Desk - Difference between 400A Meter Mains

I new to this and am trying to learn as much as I can so I apologize if this is a stupid question. I was wondering what the differences are between these two Milbank Meter Mains. Is it just the way the box is configured, meter on top or meter on the side? Why do these boxes have to be sooo big? Is it to accept the 400A service lines? The dimensions are very different. I'm looking into flush mounting a meter main being supplied with a 400A over head service and would like to choose the best one for my application. Also, what does it mean by "Accepts 5th terminal"? The two boxes I'm curious about are:

Milbank U4835-X-2/200
Milbank U5059-X-2/200
Utility/Commercial Metering Quick Selector | Milbank Manufacturing

Does anyone know if Square D makes a Meter Main for a 400A service? I looked on their website but can seem to find anything larger than 225A. Is Milbank better than Square D or is it just preference? In my area, Burbank, CA, a lot of the electrical supply places mainly carry or advertise Square D.

Thanks for the help,
Royce M
Burbank, CA

I see no difference other than the dimensions between the two you have chosen.

The "5th terminal " is a neutral jaw for those meters that are needed for utility grids that are 120/208 volt 3 phase, and the customer has chosen 120/208 1 phase for their service.

For grids that are 120/240 volt, the 5th term is not needed. This is dictated by the utility. Be sure to consult with your local utility for their preference and requirements on any metering equipment.

Square D makes the UTH-4330, which is 36.65" x15" x 5.68" found on pg 39:

http://ecatalog.squared.com/pubs/Ele...0110PL9401.pdf

Neither brand is better or worse than the other, just competition. You may be surprised to know that Square D dos not even make their own metering, it is all made by another popular meter equipment company, Landis & Gyr, which also makes metering for Siemens.

If the meter enclosure will be flush mounted, and the service entrance is overhead, how will the riser conduit enter the meter? Keep in mind, that the service riser conduit that will feed the meter will not be allowed to be hidden inside the building structure or finish. You should run this concept by your local inspector before proceeding too far.

You may also want to discuss using a current tap meter with your power company if space is an issue. With this type of meter the main conductors don't pass thur the meter pan directly and the meter boxes are usually smaller in size. There's several different ways to set up this type of system so you should discuss it with your local inspector and power company.

Thanks guys for the responses. Just a few more questions.

Quote:

Originally Posted by tkrussell

Square D makes the UTH-4330, which is 36.65" x15" x 5.68" found on pg 39:
http://ecatalog.squared.com/pubs/Ele...0110PL9401.pdf

Isn't this just the meter box? Would I then need to source a 400A box to house two 200A breakers? Wouldn't buying an all in one meter main like the Milbank I mentioned above be a more compact installation? This is what I couldn't find in the Square D catalog. Would there be a better way of doing this?

I guess I should explain in more details what I'm doing. I just had a meter spotting done and I'm moving the main service for my home to the detached garage addition at the rear of my property I'm constructing. Currently the meter is on the main dwelling and the overhead lines traverse the back yard and garage which is a little unsightly. I would like to place a relatively small 400A meter main box on the side of the garage addition (where the meter spot was approved for) and from there feed two 200A services. One to the original main dwelling's currently location and the other to a new 200A sub panel in the garage.

Quote:

Originally Posted by tkrussell

If the meter enclosure will be flush mounted, and the service entrance is overhead, how will the riser conduit enter the meter? Keep in mind, that the service riser conduit that will feed the meter will not be allowed to be hidden inside the building structure or finish. You should run this concept by your local inspector before proceeding too far.

I thought the Milbank boxes I mentioned above have knockout provisions for overhead service? But maybe I'm misunderstanding your comment.

I understand what you mention about the hidden riser conduit. Is it uncomon for the rules to allow for it here in Burbank.

Pardon my pictures since I took these at night just now. It is an installation on my neighbors house where the 200A meter/main panel are flush mounted and the service is overhead. From what I understand the riser conduit is all within the finished stucco. Is this what you are referring to as incorrect? This work was all done this past November 2006 and it was permitted from what I understand.

http://home.earthlink.net/~roycemek/...terFlush01.jpg

http://home.earthlink.net/~roycemek/...terFlush02.jpg

This is what the installation looks like on my house.

http://home.earthlink.net/~roycemek/...rSurface01.jpg

Quote:

Originally Posted by JackT

You may also want to discuss using a current tap meter with your power company if space is an issue. With this type of meter the main conductors don't pass thur the meter pan directly and the meter boxes are usually smaller in size.

Space isn't really my main concern. It is mostly asthetics. Is this wrong? But since you mentioned it do you have any pictures of a "current tap meter"? I'll have to look through the Milbank and SquareD catalog a little more.

Again I'm new at this so maybe I'm making something out of nothing. That's why I'm trying to learn. Thanks so much for all your help.

Royce M

To encase the riser conduit in masonry is the exception, so if your neighbor stucco is masonry walls, then that is why it is allowed. If the structure was wood, then the riser conduit could not be hidden as it is.

Yes the meters you chosen are for overhead.

Yes the Square D meter I found is only the meter, not what your looking for, but it is the only 320 amp meter socket they have. What you have chosen from Milbank with the two 200 amp breakers is fine, and I understand how you will use it. These units with two subfeed breakers are slick to split up into 2 200 amp panels.

While the "current tap" meter Jack is referring is also known as a CT, or current transformer system. The meter, or test cabinet, may be a smaller than the meter/disconnect you chose, but the CT method also needs someplace to house the current transformers. The 320 amp meter you chose is self contained. The current tap method, which will not be 320 amp but a 400 amp ,uses a test cabinet for the meter, and will usually need a 3 foot x 3 foot enclosure to contain the CT's.

Some utilities do allow the current transformers to be mounted in plain view, actually mounted at the service entrance weather head, where the feeder conductors pass through the CT, single phase would need two CT's. This will be dictated by your utility.

With the CT method, two 200 amp breakers and enclosures would still be needed also. I think the Milbank self contained is more appropriate with what your trying to achieve.

I hope this explanation helps, we can proceed if you have more questions.

Tkrussel is correct, the ct meter instalation won't help you in this application. From how you described your problem I guess I thought you were cramped for space. Just curious but do you use the "National Electric Code " in India?

Quote:

Originally Posted by tkrussell

To encase the riser conduit in masonry is the exception, so if your neighbor stucco is masonry walls, then that is why it is allowed. If the structure was wood, then the riser conduit could not be hidden as it is.

I haven't checked with the inspectors yet, but I will try to this week.

Are the rules for this in the NEC or are they mainly local city ordinances?

Just for conversations sake, I did speak with my neighbor this morning and all the exterior walls to the house are wood framed (2x6) with stucco covering. This is the same way I'm building the garage so I'm assuming based on what you mentioned it should be OK with a flush mount installation? (I know I still have to check with my local electrical inspector)

Thanks,
Royce M

The rules are in NEC, which all states and localities adopt, with minor amendments and waivers. Having the riser conduit inside wood structure means there is non protected conductors inside a structure. If they were in concrete,then they would be considered as outdoors.

Service entrance conductors are to go through a circuit breaker before entering a structure. This is either waived or not considered by the local authority. Best to check with your local inspector before proceeding even thou seems the neighbor was able to get his done in this fashion.

If the wires were to be damaged, say a nail or screw driven into the conduit, there is no fuse or circuit breaker to trip in the event of a short. Any short would cause the fault to continue to burn until the short was cleared.

Quote:

Originally Posted by roycemek

I haven't checked with the inspectors yet, but I will try to this week.

Are the rules for this in the NEC or are they mainly local city ordinances?

Just for conversations sake, I did speak with my neighbor this morning and all the exterior walls to the house are wood framed (2x6) with stucco covering. This is the same way I'm building the garage so I'm assuming based on what you mentioned it should be ok with a flush mount installation? (I know I still have to check with my local electrical inspector)

Thanks,
Royce M

Hi Royce M,
If you are constructing in Burbank, the current 2004 California Electrical Code allows RMC overhead drop risers in wood structure walls. Commercial is different to where this is not allowed. The NEC states a special permission clause for National in wall installations per Article 90 Section [90.2.C] "The AHJ Code may grant exception... not under control of electric utilities... provided such installations are outside a building or terminate immediately inside a building wall."
The caveat is stretching the definition of 'immediately' that qualifies the application.
Nm

Thanks guys. I will post up what the inspector from the city says when I find out.

Royce M

Quote:

Originally Posted by roycemek

Thanks guys for the responses. Just a few more questions.

Isn't this just the meter box? Would I then need to source a 400A box to house two 200A breakers? Wouldn't buying an all in one meter main like the Milbank I mentioned above be a more compact installation?

Space isn't really my main concern. It is mostly asthetics. Is this wrong? But since you mentioned it do you have any pictures of a "current tap meter"? I'll have to look through the Milbank and SquareD catalog a little more.

Again I'm new at this so maybe I'm making something out of nothing. That's why I'm trying to learn. Thanks so much for all your help.

Royce M

There is possibly an easier solution to what you are undertaking... depending on the garage location relevant to the main structure.

First up, that is a combo meter main (rusty at that) you are trying to get rid of to start. If the inside wall has no obstructions, an interior 200Amp panelboard will work to connect up all the existing branch circuits.
Selecting Milbank may not be a good idea because of the existing brand is probably not interchangeable with Milbank, thus costing you more $$$$ for more breakers.
Secondly, You can setup the meterbox Milbank split main (two 200 amp disconnects) to be side-by-side with an inside garage 200 amp panelboard of brand choice and lateral underground in-wall sweep going back to the main structure 200 amp subpanel (not Milbank). This will cut down the flushmount meter main size and cost to make a clean transition.
Third, if you have a crawl space, the lateral sub can be reached up through the underfloor framing to a new interior 200Amp panelboard, thus getting rid of the unsightly rusty main.

If the house is on slab, then you are stuck with getting the underground conduit to the old main location. Jack-hammering the slab footer into the house under the old panel would be my first choice without seeing what you have as all depends on where the garage is and if it can be partially attached near the original service. BTW, SQ D would be considered the Cadillac compared to Milbank an Oldsmobile. The current brands on the market are good, what must be paid attention to is the interchangeability of breakers that are not warranted by mixed breaker brands in panels that UL will qualify as not acceptable in litigeous cases.

Lets hear more on what you have. Slab floor, garage location, underground run to old panel, cement coverage that needs jackhammering, existing panel brand... etc. Nm

Quote:

Originally Posted by roycemek

Does anyone know if Square D makes a Meter Main for a 400A service? I looked on their website but can seem to find anything larger than 225A. Is Milbank better than Square D or is it just preference? In my area, Burbank, CA, alot of the electrical supply places mainly carry or advertise Square D.

Thanks for the help,
Royce M
Burbank, CA

Royce M,

Also consider putting in a Ufer ground in the garage slab footing for the Grounding electrode system. Make sure the Ground Electrode Conductor is a #2 copper [250.66] from the stubbed up #4 x 20ft. Footer rebar. (#3 rebar is not allowed.)
This means the feeder from the garage to the house panel is a 4 wire system. The metal water pipes still need to be bonded back to the new 200amp subpanel terminal ground bus. (not the neutral terminal bus) nm

Quote:

Originally Posted by roycemek

Thanks guys for the responses. Just a few more questions.
Space isn't really my main concern. It is mostly asthetics. Is this wrong? But since you mentioned it do you have any pictures of a "current tap meter"? I'll have to look through the Milbank and SquareD catalog a little more.

Again I'm new at this so maybe I'm making something out of nothing. That's why I'm trying to learn. Thanks so much for all your help.

Royce M

If asthetics is key, why not run a lateral from the utility pole also? You will be trenching anyway and this makes more 400 amp panel brands available for underground interface. SQ D has a 400amp 1 ph meter main that is surface convertible to semi-flush UG using a flange kit. [QO Class 320 CU12L400B] nm