Feed Through On MDP

Question for you all.
We have specified a 2500A main service disconnect to protect our 2500A MDP.
MDP has 2 breakers (2000A & 600A) Serving SDP1 (2000A) and SDP2 (600A).
SDP2 is 200' away from MDP and does not currently have an MCB.

Electrician is proposing on tapping SDP2 feeder straight off MDP bus in a feed through fashion, and installing an enclosed 600A circuit breaker near SDP2 gear as its "MCB" OCPD.
Is this code compliant? If not, please post an article or reference. Technically its protected at its source through 2500A service disconnect, and 600A ECB.
Hypothetically if 600A lugs will even allow the tap on 2500A bus, what issues may result aside from potential increase in Fault current?

Thanks in advance.
 

infinity

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Location
New Jersey
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Journeyman Electrician
If I'm reading this correctly you want to tap the 2500 amp bus and run tap conductors 200' to the enclosed circuit breaker near SDP2? Unless those tap conductors are run completely outside of the building you would need to comply with the 25' tap rule, 200' is too far.
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I'm confused. The OP states he has a 2500 and a 600 amp breaker in the MDP. Why does he need an OCPD at the distant panel?
2500 amp main breaker as the service disconnect and then two feeder breakers in the MDP, 2000 and 600 amp.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I meant to say a 2000 (not 2500) and a 600 in a MDP with a 2500 amp main. So why does he need another breaker at the distant 600 amp panel?
Good question, maybe so that they will have the 600 amp for another load or to keep it as a spare?
 
If I'm reading this correctly you want to tap the 2500 amp bus and run tap conductors 200' to the enclosed circuit breaker near SDP2? Unless those tap conductors are run completely outside of the building you would need to comply with the 25' tap rule, 200' is too far.
Conductors wont be ran to the building exterior, as the shortest path (by 75'or so) is through the interior. "I" am not wanting to, EC is suggesting alternatives to my design.

So technically, per tap rule, (rather than using 600A breaker inside MDP enclosure) EC can tap off MDP buss to feed 600A ECB (serving SDP2), if and only if, ECB is within 10' of MDP.

I've never used ECB in this way before. Usually I've only used ECB as equipment local disconnect or coordination purposes for MLO panels.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Conductors wont be ran to the building exterior, as the shortest path (by 75'or so) is through the interior. "I" am not wanting to, EC is suggesting alternatives to my design.

So technically, per tap rule, (rather than using 600A breaker inside MDP enclosure) EC can tap off MDP buss to feed 600A ECB (serving SDP2), if and only if, ECB is within 10' of MDP.

I've never used ECB in this way before. Usually I've only used ECB as equipment local disconnect or coordination purposes for MLO panels.
If the conductors are 1/3 or larger than 2500 amps then you can use the 25' tap rule otherwise you're correct you're stuck with the 10' tap rule.
 

jap

Senior Member
Question for you all.
We have specified a 2500A main service disconnect to protect our 2500A MDP.
MDP has 2 breakers (2000A & 600A) Serving SDP1 (2000A) and SDP2 (600A).
SDP2 is 200' away from MDP and does not currently have an MCB.

Electrician is proposing on tapping SDP2 feeder straight off MDP bus in a feed through fashion, and installing an enclosed 600A circuit breaker near SDP2 gear as its "MCB" OCPD.
Is this code compliant? If not, please post an article or reference. Technically its protected at its source through 2500A service disconnect, and 600A ECB.
Hypothetically if 600A lugs will even allow the tap on 2500A bus, what issues may result aside from potential increase in Fault current?

Thanks in advance.
This doesn't complete sense to me yet.

Why would your design not incorporate the 600a feeder breaker into Panel SDP1 and make Panel SDP1 a 2500 amp piece of gear?
Why have a 2500 amp service disconnect feed a Panel MDP with only 2 breakers in it?

You say your 2500 amp MDP already has a 600 amp breaker in it to feed panel SDP2.
Regardless of how far Panel SDP2 is from Panel MDP, if it's inside the same building, It doesn't require a Main Circuit breaker "At" Panel SDP2.
The "Feeder" to panel SDP2 is already protected by the 600a breaker in Panel MDP.

My question is, Is the 600a Panel SDP2 "existing"? or are you adding a new 600a Panel SDP2 to the building and need somewhere to feed it from?

Why would the electrician even bring up tapping the 2000 amp buss and setting a 600a ECB if there was an existing 600a breaker to begin with?

To me, it sounds like you have an existing 2000 amp feeder an existing Panel SDP1, but, nowhere to originate an additianal 600a Feeder.

Is that the case? or am I all wet?

JAP>
 
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