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Joined: May 2001
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I was wondering what is the maximum limit of sub-panels that can be installed from a sub-panel that is fed from a main panelboard?
the sub-panel has a main as well as the main panelboard. the first sub-panel is protected on the supply side by a 100A two pole.
the voltage is 120/208.
i want to install a 100 amp sub panel from a 200A sub-panel that is fed from a 200A main panelboard, that also has a 200A main.
i want to use 3 #4 in a 1" emt, using the emt as the egc.
i will place a 100A main in my subpanel.
is this legal? what about 408.16 (A)?
thanks for any replies.
[This message has been edited by frodo (edited 10-28-2001).]
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Joined: Mar 2001
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frodo, If you really need the second 100 amp panel due to load requirements, you might end up shutting down the first 100 amp panel due to overload. It sounds like a co-ordination issue. Can you feed the second 100 amp panel from the main panel. Also, do you mean 4 #3s? And, as has been seen before, using the EMT as EGC is hotly debatable.
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there is not much load on the first sub-panel. the main panel is a different story.
i located the subpanel in the building while searching for a route from the main panel.
it would be very difficult to get from the main panel to where the circuit terminates at a 125 subpanel with a 100A main. i decided it would be legal to feed my new subpanel from the 1st subpanel.
as far as the number of conductors i plan to use, i want to use the 1" conduit for the ground, so as to only have to pull in 3 #4's...EMT is permitted as the EGC isnt it?
if not do i have to pull in a foruth conductor?
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Joined: Jan 2001
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How are you , without violating 310-16, going to protect #4 with 100 A OCP?
[This message has been edited by Glenn (edited 10-28-2001).]
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short time overload calculation....
also see 240-3 & 240-3(b)& 110-14(c) and 210-19(a) "#4 is routinely used for 100A services here" western, ky...i am assuming i can apply the same rule to the #4 with a 100A OCPD? if not i would have to reduce to a 90A OCPD?
the panel is rated 125A
[This message has been edited by frodo (edited 10-28-2001).]
[This message has been edited by frodo (edited 10-28-2001).]
[This message has been edited by frodo (edited 10-28-2001).]
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the load is "non-continuos" conductors are 90 degree celcius THHN 120/240 vac
[This message has been edited by frodo (edited 10-28-2001).]
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i guess i cant get away with using a 100A OCPD on #4 THHN. the best thing to do would be to reduce the OCPD to 90A at both ends.
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Joined: Oct 2000
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Frodo,
The #4 is only allowed for a service to a Dwelling. Anywhere else you have to go according to the tables for ampacity.
Bill
Bill
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Frodo, Read 310.15B6 and table, per Bill's post
Also, the code does not limit how many subpanels are in any given premisis, we could do a 'frankenstien home' with OCPD's in every room ( ok, not the bath..) and as long as 220 was met it would be compliant.
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Joined: May 2001
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hi, thanks for all the input. i appreciate it...i am going to try and find a 90A main to limit the load to 90A...
as always you can count on solid info from ECN
-regards
frodo
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