jyohnyb
Member
- Location
- wilmington nc
If i have a main panel with six throws of the hand but no main breaker what do i size the wire on? Say it has a 100 amp to a subpanel and a 125 amp to the heats. Do i use 125% of largest breaker?
Wire size
- Thread starter jyohnyb
- Start date
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luckylerado
Senior Member
- Location
- Lake of the Ozarks
There is no OCP ahead of the MLO?
jyohnyb
Member
- Location
- wilmington nc
Nah.
Nah.
They are using the 6 throws of the hand rule. Its a 3/0 copper from the meter to the lugs. Then it is a 125 amp breaker to a heat subpanel and a 100 amp breaker to the house subpanel.
Nah.
They are using the 6 throws of the hand rule. Its a 3/0 copper from the meter to the lugs. Then it is a 125 amp breaker to a heat subpanel and a 100 amp breaker to the house subpanel.
luckylerado
Senior Member
- Location
- Lake of the Ozarks
What wire are you wanting to size?
jyohnyb
Member
- Location
- wilmington nc
The wire from the meter to the lugs is 3/0.
The wire from the meter to the lugs is 3/0.
3/0 copper is good for 200 amps. However you have a total of 225 with the 2 breakers. How do i size the feeder
The wire from the meter to the lugs is 3/0.
3/0 copper is good for 200 amps. However you have a total of 225 with the 2 breakers. How do i size the feeder
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
You don't size it by adding the breakers, you size the main by doing a load calculation. I doubt you're other two panels will pull the rated load. You already have the 3/0 for the MLO panel. Just size the wire for each load/subpanel respectively, 125A for one and 100A for the other.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
In many residential services, especially in San Antonio, even in new construction, there is no OCPD ahead of the MLO panel. It seemed strange to me the first time I saw it, but now I have seen lots of them.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Terminology is important. The wire from the meter to the MLO panel is aa service entrance conductor and NOT a feeder. So if you have 3/0 copper then the wire size is fine in all probability.
If this is a residence then 3/0 is good for 225 amps. As stated above you don't add the breakers but you add the calculated loads of those feeders or branch circuits.
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