- Location
- New Jersey
- Occupation
- Journeyman Electrician
OK, so for practical purposes what does this mean? If the Article 220 load calculation for this service (in the OP) came up with 350 amps would this 320/400 amp equipment be acceptable?
400 amp service
- Thread starter boopheads
- Start date
- Status
- Location
- Massachusetts
In my opinion yes, if the total load calculation including both continuous and non-continuous loads is 350 amps the 320 sockets we use in this area are rated for that.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Assuming your 350 amps is the sum of noncontinuous and 125% of continuous, I would say yes; however, this may be a POCO issue only.
I cannot find a reference for the rating of a meter base in the NEC.
Edit: I meant yes, brain fart.
Last edited:
kwired
Electron manager
- Location
- NE Nebraska
Why? That is exactly how you determine size of conductors, and/or overcurrent devices.
That 350 amp calculated load could have 350 amp conductors and an 350 amp overcurrent device.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I am basing this on the idea that the meter base be sized/rated like the conductors, 230.42, and disconnect,230.79.
- Location
- Massachusetts
Perhaps 110.3(A)(7)?
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
See edited post, I mis-typed.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Maybe, I dunno. Does the meter base fall under the NEC and AHJ, other than bonding in 230.92?
230.66 Marking. Service equipment rated at 600 volts or
less shall be marked to identify it as being suitable for use
as service equipment. Individual meter socket enclosures
shall not be considered service equipment
In Rob's example, what if the load were 350 amps continuous and POCO gave me a 320/400 meter base? Can I be red tagged?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Where does the continuous and non-continuous part of the load calculation come into play when discussing the single family dwelling in the OP? I'm confused. I look at the several example calculations in Annex d and I don't see any SFD calc's that use continuous and non-continuous just a 100%/40% load factor.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
You're going the wrong way with this. You are only allowed to load a 15A receptacle to 80%, which would be 12A. 12A x 125%=15A
See Table 210.21(B)(2)
If you had a calculated load of 350 and you installed a 400 amp service, while code compliant I would question the design.
Starting off with a maxed out service is not a good design IMO.
- Location
- Massachusetts
I can't really think of anything I would really call continuous load in a dwelling. But if you had some you would have to consider it.
So in that case it is all non-continuous and the 320 sockets we use here are rated 400 non-continuous.
- Location
- Massachusetts
I don't know, here we purchase the meter sockets from the supply house and I have always used one that matched the ratings of the main breaker.
- Location
- Massachusetts
Check the ratings of these 320 class sockets.
http://www.cooperindustries.com/con...ing_equipment/ring-type_metering/Class320.pdf
http://www.cooperindustries.com/con...ing_equipment/ring-type_metering/Class320.pdf
Some of these are incorrect
Some of these are incorrect
I just want to interject. I've been reading through some of these, and just want to make clear that some of this is incorrect. Someone mentioned that if it's not CT'd that it has to be a 320 amp service. That's not the case at all. Many companies allow the use of 400 amp self contained metering. His metering has 400 amps of breaker behind the metering. If this were only a 320 amp meter set - if he follows NEC - the main would have 300 amps behind the meter (two 150 amp breakers - or any other configuration that wasn't above 300 amps). This is very likely a 400 amp meter loop.
As far as the utility company only using 350 MCM. You must understand that a home owner / electrician needs to follow NEC rules and regulations. Utility companies are required to use NESC rules and regulations. There is a 40% conductor rating difference between the two standards. A utility company also is only required to size their service to actual load - including diversity. NEC sizing pushes an electrician to size the entrance cable to panel size.
I am an engineer for a large utility company in the midwest. There have been more than one time I've installed very small conductor to a customer that had a very large service. Usually this ends up in the electrician/homeowner freaking out. I explain things to them - tell them if they have voltage flicker (due to our conductor being sized too small) that I will come right back and change it out. I have never, not once, been called back.
In other words - I would not worry for a minute that all they installed was 350 MCM. According to NESC specs - 1 run of 350 MCM w/ a 4/0 neutral - direct buried is capable of 508 amps and installed in duct is 397 amps. You're more than covered. If I was the engineer - depending on the length - you may have gotten smaller conductor installed.
Some of these are incorrect
I just want to interject. I've been reading through some of these, and just want to make clear that some of this is incorrect. Someone mentioned that if it's not CT'd that it has to be a 320 amp service. That's not the case at all. Many companies allow the use of 400 amp self contained metering. His metering has 400 amps of breaker behind the metering. If this were only a 320 amp meter set - if he follows NEC - the main would have 300 amps behind the meter (two 150 amp breakers - or any other configuration that wasn't above 300 amps). This is very likely a 400 amp meter loop.
As far as the utility company only using 350 MCM. You must understand that a home owner / electrician needs to follow NEC rules and regulations. Utility companies are required to use NESC rules and regulations. There is a 40% conductor rating difference between the two standards. A utility company also is only required to size their service to actual load - including diversity. NEC sizing pushes an electrician to size the entrance cable to panel size.
I am an engineer for a large utility company in the midwest. There have been more than one time I've installed very small conductor to a customer that had a very large service. Usually this ends up in the electrician/homeowner freaking out. I explain things to them - tell them if they have voltage flicker (due to our conductor being sized too small) that I will come right back and change it out. I have never, not once, been called back.
In other words - I would not worry for a minute that all they installed was 350 MCM. According to NESC specs - 1 run of 350 MCM w/ a 4/0 neutral - direct buried is capable of 508 amps and installed in duct is 397 amps. You're more than covered. If I was the engineer - depending on the length - you may have gotten smaller conductor installed.
Red tagged?
Red tagged?
Yes. I was an inspector for quite a few years. I would red tag it if your panel was 400 amps and your load was over 320 amps.
Red tagged?
Yes. I was an inspector for quite a few years. I would red tag it if your panel was 400 amps and your load was over 320 amps.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Based on what code reference?
This is an academic question, I would not actually install an undersized meter base/socket.
- Location
- Massachusetts
You would have to show me a code section for that or pass me.
If I calculate the load per article 220 and the final result was exactly 400 amps I can, and I would install a 400 amp panelboard.
The 125% is already accounted for in the calculations.
I agree with Jumper and Iwire, you would have to show me what code section was violated or you would simply be stating your opinion that you didn't like the installation.
Roger
kwired
Electron manager
- Location
- NE Nebraska
One also has to remember that POCO owned or controlled equipment is usually located outside of buildings. If excess heat is developed in overloaded conductors or devices it is not much of threat of starting a fire within the building vs having the same installation within the building. Equipment is not only sized on connected load but also length of time load is expected to operate before allowing a cooling period. NEC for the most part only recognizes the 3 hr continuous time, so everything is either continuous or non continuous. An engineer could design something as he sees fit but many still choose to use the continuous vs non continuous rule in most instances.
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