What can a 200 amp meter base feed?

[commadore64]

Hi Guys... first post on this forum.

My question involves a consumer with a 200 amp meter base and a 200 amp panel in his house. He wants to tap off the meter base to a disconnect to serve a small shop. My question is, is it legal to feed a 200 amp panel in the house and a 100 amp panel in his shop (total of 300 amps worth of panels) from a 200 amp meter base? If this is OK, is it written in the NEC somewhere as being acceptable?

 

[raider1]

Welcome to the forum.

What is important here is the calculated load and not the ampacity of the panelboards supplied by the meter. As long as the calculated load is lower the the rating of the meter it would be acceptable.

Chris

 

[Strathead]

Hi Guys... first post on this forum.

My question involves a consumer with a 200 amp meter base and a 200 amp panel in his house. He wants to tap off the meter base to a disconnect to serve a small shop. My question is, is it legal to feed a 200 amp panel in the house and a 100 amp panel in his shop (total of 300 amps worth of panels) from a 200 amp meter base? If this is OK, is it written in the NEC somewhere as being acceptable?

What is legal regarding loads has nothing to do with the size of the panels. It has to do with the calculated load per NEC 220 Also, this may just be terminology for you, but a 200 amp meter base does not mean a 200A SERVICE! The available service size is based on the service entrance conductors per table 310.15(B)(7) in the 2011 code book. I think it is changed from earlier versions. The physical installation of the various conductors and the possible need for disconnecting means on each feeder is a whole different story and greatly depends on what is already installed and the locations of new and old. So I caution you if you don't know the nuance of this type of installation.

 

[commadore64]

OK, for the sake of argument, let?s make some assumptions for my education. From 310.15(B)(7), let?s assume the existing service entrance conductor is indeed 4/0 Al and extends from the load side of the meter, through the wall to a 200A service entrance panel. The consumer wants to tap the 4/0 Al at the meter lugs with #2 Al to an adjacent disconnect and on to a small shop. Now I have created a situation where the total capacity of the service entrance conductors (4/0 Al and #2 Al) can carry more than a 200A meter base is rated for. Am I still OK, or have I created a problem (from a code stand point)?

 

[raider1]

OK, for the sake of argument, let?s make some assumptions for my education. From 310.15(B)(7), let?s assume the existing service entrance conductor is indeed 4/0 Al and extends from the load side of the meter, through the wall to a 200A service entrance panel. The consumer wants to tap the 4/0 Al at the meter lugs with #2 Al to an adjacent disconnect and on to a small shop. Now I have created a situation where the total capacity of the service entrance conductors (4/0 Al and #2 Al) can carry more than a 200A meter base is rated for. Am I still OK, or have I created a problem (from a code stand point)?

Take a look at Exception No 3 to 230.90(A) which allows the combination of the ratings of 2 or more service disconnects to exceed the size of the service entrance conductors. So it is not a code violation to have a 200 amp panel and a 100 amp panel connected to a 200 amp meter provided that the calculated load of both panels does not exceed the rating of the 200 amp meter.

Chris

 

[Strathead]

OK, for the sake of argument, let?s make some assumptions for my education. From 310.15(B)(7), let?s assume the existing service entrance conductor is indeed 4/0 Al and extends from the load side of the meter, through the wall to a 200A service entrance panel. The consumer wants to tap the 4/0 Al at the meter lugs with #2 Al to an adjacent disconnect and on to a small shop. Now I have created a situation where the total capacity of the service entrance conductors (4/0 Al and #2 Al) can carry more than a 200A meter base is rated for. Am I still OK, or have I created a problem (from a code stand point)?

No not code compliant. You need no more than 6 disconnects located together per 230.71 You would need to install a disconnecting means outside, bond the nuetral and ground together there and then refeed the existing panel, separate the neutral and ground (isolating the nuetral bus) and install a grounding equipment conductor per 250.122. Similarly with the shop feeder.

Still think you are hung up on the amperage rating though. Look at the samples in the appendix and find the one that most closely parallels the house you are working on. Substitute the values from it and Come up with a calculation. It is likely that you will not exceed the values and you will be fine. The feeder is not based on the size or quantity of circuits, it is based on the size and quantity of loads. For example, you could feed every receptacle in the house on a 20 amp dedicated breaker, unless you knew that they were growing something, you would still be subject to the standard 3VA per square foot for load calculations. You could have 40 20 amp breakers and 100 amps of load. This is an exagerated example to make the point.

Whether you can handle the load can not be answered here. It requires dwelling specific calculations.

 

[kwired]

OK, for the sake of argument, let?s make some assumptions for my education. From 310.15(B)(7), let?s assume the existing service entrance conductor is indeed 4/0 Al and extends from the load side of the meter, through the wall to a 200A service entrance panel. The consumer wants to tap the 4/0 Al at the meter lugs with #2 Al to an adjacent disconnect and on to a small shop. Now I have created a situation where the total capacity of the service entrance conductors (4/0 Al and #2 Al) can carry more than a 200A meter base is rated for. Am I still OK, or have I created a problem (from a code stand point)?

Don't forget 310.15(B)(7) only applies to the dwelling. The shop can not use this section because it is not a dwelling, therefore you will need at least a 1AWG aluminum for a 100 amp feed as 2AWG is only good for 90 amps.

 

[augie47]

One of the main stumbling points is actually making the connection. Most 200 amp meter bases have lugs which are listed for only one wire so you can not simply add a second wire under that lug.
As mentioned by others, if you overcome the above, you can not mount one service disconnect outside with the other inside,

A majority of similar installs in this area are accomplished by adding a breaker to the existing panel for the other load.
Another method is to replace the existing 200 amp meter base with a 320 amp which normally accepts multiple lugs.
Reconnect your 200 amp panel and run the new service conductors to the shop from the 320 amp base without disconnect at the house (allowed by NEC but run it by POCO).
You can then calculate your load and increase the service conductors feeding the meter if need be,
Keep in mind kwired input on sizing conductors.

 

[suemarkp]

(looks like I was too slow to type - pretty much redundant to the previous post)
This is no different than a typical 320/400A meter install. Those meters are designed to have 2 wires connected to each lug (whereas most 200A residential meters can not be double tapped). If you wanted a 300A Service and had 300A service conductors, you could still have two 200A panels connected as long as the calculated load was 300A or less.

I don't know why your customer wants a separate tap from the meter. The only cost savings I see is he can run 3 service conductors instead of a 4 wire feeder, and save the cost of the feeder breaker.

I think the better design is to either put a 100A breaker in the 200A panel to feed the outbuilding, or put in 320/400A meter which can be double lugged. If using the 320/400A meter, I'd definitely do a load calc to see if the service entrance conductors need to be upsized. In residential, I like the Service to be rated for the sum of mains, but code does not require that.

If you don't change the meter, I don't know how you could easily tap off for the outbuilding without installing some splicing gutter for the service conductors. If going to that trouble, I think it would be nicer to just change the meter.

 

[commadore64]

Take a look at Exception No 3 to 230.90(A) which allows the combination of the ratings of 2 or more service disconnects to exceed the size of the service entrance conductors. So it is not a code violation to have a 200 amp panel and a 100 amp panel connected to a 200 amp meter provided that the calculated load of both panels does not exceed the rating of the 200 amp meter.

Chris

I think 230.90(A)Exception No.3 comes as close to answering my question as anything I've read so far. My only hangup is the article refers specifically to the service conductors... am I still OK as far as the rating of the meter base itself at 200A? Or is the rating of the meter base itself just not considered anywhere in the code?

No not code compliant. You need no more than 6 disconnects located together per 230.71 You would need to install a disconnecting means outside, bond the nuetral and ground together there and then refeed the existing panel, separate the neutral and ground (isolating the nuetral bus) and install a grounding equipment conductor per 250.122. Similarly with the shop feeder.

Still think you are hung up on the amperage rating though. Look at the samples in the appendix and find the one that most closely parallels the house you are working on. Substitute the values from it and Come up with a calculation. It is likely that you will not exceed the values and you will be fine. The feeder is not based on the size or quantity of circuits, it is based on the size and quantity of loads. For example, you could feed every receptacle in the house on a 20 amp dedicated breaker, unless you knew that they were growing something, you would still be subject to the standard 3VA per square foot for load calculations. You could have 40 20 amp breakers and 100 amps of load. This is an exagerated example to make the point.

Whether you can handle the load can not be answered here. It requires dwelling specific calculations.

230.40Exception No.3 I believe allows me to do what I suggest without the need for service disconnection means to be located in one location, therefore negating 230.71 in this case. Each service still has a disconnect at the termination of the service entrance conductors. I am referencing a 2011 NEC Handbook commenting on this situation in the commentary section.

However, I do think you are correct in your assessment of considering calculated loads and not just looking at amp ratings.

Don't forget 310.15(B)(7) only applies to the dwelling. The shop can not use this section because it is not a dwelling, therefore you will need at least a 1AWG aluminum for a 100 amp feed as 2AWG is only good for 90 amps.

Man you guys are good... good catch!

 

[Strife]

It depends on the demand, not the connected load. And DEFINITELY not on the combined ampacities of panels.
In houses the demand is pretty forgiving (the one I use most is first 10KVA(WITHOUT AC) at 100%, rest at 40%, plus the AC load, unless is a VERY SMALL SERVICE like 60-70A)
In all other, is pretty much connected load, but just because there are 20 breakers at 20 amps, it doesn't mean connected load is 400A.

Hi Guys... first post on this forum.

My question involves a consumer with a 200 amp meter base and a 200 amp panel in his house. He wants to tap off the meter base to a disconnect to serve a small shop. My question is, is it legal to feed a 200 amp panel in the house and a 100 amp panel in his shop (total of 300 amps worth of panels) from a 200 amp meter base? If this is OK, is it written in the NEC somewhere as being acceptable?

 

[commadore64]

OK, I guess I should come clean? I work for an electrical utility (it?s in my profile) and I am trying to determine to what extent (and under what circumstances) I can allow a consumer to do the work as I have described. As a utility, most of our work does not fall under the NEC (indicated by my lack of knowledge thereof). However, when it comes to specifying, recommending or endorsing meter base work, the lines between the utility and the NEC merge? I have to make sure what I tell my members? is OK with the NEC.

Milbank is the vendor we use for meter bases. They have accessories to convert from one to multiple lugs, so I know a 200A meter base can be converted to two lugs but I wanted to know what the code was for doing such work. We do carry a 320A panel that a member can use, but if the account is existing, it would be a lot easier and cheaper to modify the existing meter base than change it out. I am actually trying to save the members some money and work but not at the expense of doing something against code or against better engineering judgment.

My customer has indicated that it would be very difficult to sub the shop panel from his existing panel? I have not actually seen his home to verify. Additionally, as a utility, if I do not let him do something at the meter, and he does not (cannot) pull a service from his own panel, we will have to install an additional meter at his shop. A minimum monthly account charge will be applied forever? that will be his largest cost over time (and the reason he asked if he could sub-feed from the meter).

Bottom line is that I want to make sure whatever I tell my consumers is not dangerous and will not violate any NEC codes on their side of the meter.

Any other opinions on this subject are very much welcome. And BTW, forgive my ignorance? but what is ?POCO?

 

[raider1]

OK, I guess I should come clean? I work for an electrical utility (it?s in my profile) and I am trying to determine to what extent (and under what circumstances) I can allow a consumer to do the work as I have described. As a utility, most of our work does not fall under the NEC (indicated by my lack of knowledge thereof). However, when it comes to specifying, recommending or endorsing meter base work, the lines between the utility and the NEC merge? I have to make sure what I tell my members? is OK with the NEC.

Milbank is the vendor we use for meter bases. They have accessories to convert from one to multiple lugs, so I know a 200A meter base can be converted to two lugs but I wanted to know what the code was for doing such work. We do carry a 320A panel that a member can use, but if the account is existing, it would be a lot easier and cheaper to modify the existing meter base than change it out. I am actually trying to save the members some money and work but not at the expense of doing something against code or against better engineering judgment.

My customer has indicated that it would be very difficult to sub the shop panel from his existing panel? I have not actually seen his home to verify. Additionally, as a utility, if I do not let him do something at the meter, and he does not (cannot) pull a service from his own panel, we will have to install an additional meter at his shop. A minimum monthly account charge will be applied forever? that will be his largest cost over time (and the reason he asked if he could sub-feed from the meter).

Bottom line is that I want to make sure whatever I tell my consumers is not dangerous and will not violate any NEC codes on their side of the meter.

Any other opinions on this subject are very much welcome. And BTW, forgive my ignorance? but what is ?POCO?

POCO Stands for Power Company or utility company.

As far as the NEC is concerned provided that you group the 2 disconnects that are tapped off the meter and the calculated load does not exceed the rating of the meter you can have 2 sets of service entrance conductors run from the meter to 2 disconnects. The ratings of those fuses or breakers in those disconnects are permitted to exceed the size of the service entrance conductors and the meter provided that the load does not.

Chris

 

[suemarkp]

As someone pointed out earlier, you don't even need a second disconnect at the meter since that tap is serving a separate building. So the disconnect grouping issue could be moot.

Are you sure the lug kits will work? In the resi meters I've seen, the 200A lugs are not removable (but maybe the whole guts comes out). You could use one of those fork insert type lugs into the factory lugs, but will there then be the required bending space at the terminal to the enclosure wall? If you change the to double lugs, is one of the lugs large enough to take his 4/0 aluminum conductor to the existing panel? Need to also assess the neutral lugs for expansion and wall clearance.

What he wants can be code compliant. I'd ask the customer to provide a load calculation which includes the equipment in the new detached building. As a power company, they can leverage their own rules on services. May be time to see if the POCO can issue a policy for marking disconnect panels with a "combined load not to exceed 200 amperes" sign at a residential install where it would be easy to exceed the meter amp rating. Or perhaps establish a policy of how much the sum of disconnects can exceed the rating of the meter or service conductors. Residential is worse than industrial since people move, don't understand restrictions, or their electricians aren't very vigilant.

 

[hurk27]

Heres some food for thought:

First 230.70 only requires a disconnect where conductors "enter" a building.
Second since the SEC tap does not enter a building you do not need to install a disconnect at the house for this other building, you are just running right back into the ground, so the main panel at the house can stay as it is, and since these are service entrance conductors, you only need to run 3 conductors to the out building and treat it like a service without a meter, a meter is only a wide point in the service entrance conductors.

230.72 would not apply for the other building if it is not attached to the house.

Look at 230.40 exception #3 clearly allows the above example.

Now if we are talking about a shop that is attached or part of the house then the above does not apply.

Many of the garages and out buildings I do, are done as above, allot will depend upon how much room you have in the 200 amp meter base, if it is an over head service then you can use a insulated tap such as Polaris taps, that would give you 2 in to 1 that you need, underground , you might not have the room, or if you have a meter base with removable lugs (very rare) then you could get the correct double lugs and install them, most all 320 meters are this way and can be purchased with double lugs.

The key point is if the SEC's do not enter a building or structure then there is no disconnect requirement, and since you will need a service disconnect and grounding electrodes at this shop building anyways, why install two?

Of course if you area or utility wont allow this type of install that is another matter, but we have done it here for many years as the NEC clearly allows it.

 

[kwired]

If you are POCO, NEC does not apply to you.

If you as POCO provides the meter base, NEC does not apply to the meter base. If you do not provide anything past the meter - NEC applies to everything past the meter.

If you wish to supply a meter that helps the EC comply with NEC - you are just being nice to said EC.

A 200 amp meter base is in many ways just a point in the service conductors that happens to be able to be open circuited by removing the meter. It does not require overcurrent protection on the supply end - just like service conductors. You can use it any place where you would use up to a 200 amp conductor. In your scenario there could be 200 amp supply conductors - the meter - then the two load conductors, or 200 amp supply - meter - 200 amp conductor to a junction box - then the two load conductors, or 200 amp supply - no meter - two load conductors. All three are essentially the same thing as far as NEC is concerned.

 

[mjf]

What can a 200 amp meter base feed?



Can feed my whole family and a few friends if I install enough of them:thumbsup:.

 

[commadore64]

Well, after all the help on this forum, I have concluded that what we want to do is OK by the code if things are done correctly. With that said, I contacted Milbank yesterday and we are going to order their kit (K4977-INT) which will allow up to a 1/0 tap to be made on the existing lugs of a 200A meter base.

I would just like to thank everyone for their weigh-in on my question? this is a very helpful forum site and I will be back.

 

[resistance]

Well, after all the help on this forum, I have concluded that what we want to do is OK by the code if things are done correctly. With that said, I contacted Milbank yesterday and we are going to order their kit (K4977-INT) which will allow up to a 1/0 tap to be made on the existing lugs of a 200A meter base.

I would just like to thank everyone for their weigh-in on my question? this is a very helpful forum site and I will be back.

That?s good info to know!! TY

 

[meternerd]

Just for your info...for meter panels, the bussing and wiring ahead of the main disconnect are not rated. The 200A rating is the bussing beyond the main. Milbank and most others have acknowledged this because of the solar connection issues, where the customer wants to connect ahead of the main to avoid the 20% rule. The only consideration is the "continuous load" that the meter will actually see. "Pump panels", where a second main disconnect is factory installed in the meter panel are a prime example.