jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
320amp vs 400amp
- Thread starter fireryan
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Carultch
Senior Member
- Location
- Massachusetts
I'm trying to ask how to add up non-continuous loads, when using a 320A meter socket. Do non-continuous loads add up to 320A? Or do non-continuous loads add up to 400A?
It is my understanding that continuous loads, when using a 320A meter socket, can add up to 320A, and then multiply by 125% to determine the 400A breaker and 400A service. I also understand that most serviceequipment is in general, sized by 100% non-continuous plus 125% continuous. Please correct me if I am wrong.
In otherwords, is 320A "continuous duty" rated equipment suitable for all applications where a 400A standard OCPD would be used?
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- Location
- Massachusetts
There is nothing different in sizing a meter socket from a panel or service.
Add all the non-continuos loads up.
Add all the continuos loads up and multiply by 1.25.
Take the result of that multiplication and add it to the first figure, if the resulting sum is 400 amps or less a 320 class meter is fine.
- Location
- Massachusetts
I am going to point out that a 320 meter is not '320 amps' it is a class 320 meter.
http://www.cooperindustries.com/con...ing_equipment/ring-type_metering/Class320.pdf
http://www.cooperindustries.com/con...ing_equipment/ring-type_metering/Class320.pdf
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Non continuous loads add up to 400A
Continuous loads add up to 320A
Combo example: 200A non continuous plus 160A continuous (multiply 160 x 1.25 = 200A) = 400A Service.
Apply the rules to the 320(400) meter base.
Yes. Service conductors would be need to be sized for 400A also.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Aha. That could be the source of confusion. Good catch.
- Location
- Massachusetts
It would really help if we stopped calling it 320 and call it 400 because it is as much a 400 as a 400 amp panel is.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
That would be a good idea.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If you performed an Article 220 load calculation and came out with 375 amps to size the service what would you use?
- Location
- Massachusetts
A class 320 meter.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
With 400 amp conductors and a 400 amp service disconnect?
peter d
Senior Member
- Location
- New England
Irrelevant and off topic but the poco will still connect that 320/400 amp service to a 25 kva transformer. 
- Location
- Massachusetts
Yes.
And that service disconnect is in fact rated 320 amps continuos just as the meter socket.
- Location
- Massachusetts
Irrelevant and off topic but the poco will still connect that 320/400 amp service to a 25 kva transformer.
With 4 AWG aluminum.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I have always did what iwire describes also.
Carultch
Senior Member
- Location
- Massachusetts
Thanks for clarifying. And that is just as I thought.
I agree completely. To me, it would make the most sense if every power distribution product were rated on the same standard of ampacity, with a common calculation from the loads, no matter what kind of equipment it is.
Anything else seems like the thought process of, "we'll raise the speed limits 25%, but we will also make the speedometers falsely display 125% of the speed".
There is another issue, that I've seen discussed regarding 320 meterbases. It is common that they may only have a single terminal per phase. In the 400A realm, I commonly see parallel sets strategically specified. So if you plan on doing this, be aware that the meterbase may not be able to directly connect to such a feeder, and could need the equivalent single set instead.
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peter d
Senior Member
- Location
- New England
And it will be just fine. :thumbsup:
kwired
Electron manager
- Location
- NE Nebraska
What metering equipment? Whatever the POCO wants me to use, if it is dwelling unit the chance of it being a 320 socket is much greater then for non dwelling application.
That happens too.Irrelevant and off topic but the poco will still connect that 320/400 amp service to a 25 kva transformer.
I have a project coming up where I will be installing 1200 amp 208/120 service disconnecting means. POCO is only going to provide a 225kVA transformer, but actual load calculation is only around 600-700 amps (225 is 625A). If there is ever more load added in future however all that needs changed is the transformer (if demand data warrants it at that time).
- Location
- Massachusetts
CTs could be used for any size service, if you need to install CT metering is a choice the power company makes.
Keep in mind direct reading plug in meters are limited to 400 amps, so in many areas any service more than 400 amps is gong to get CTs.
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