Tap clarification

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nickelec

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Here's the set up. Coming from the poco I have a set of Secs that land right in a combination type trans-s with built in disconnect all in one enclosure. The SECS hit the switch first rated 600a this is fed via 2sets of 350 mcm

Coming off the switch we have double lugs

And ran a set of 500s to two different main lug panels

Is this compliant?

Is this considered a tap?

If we landed the 500s to a 400a main breaker would it then be compliant ? I say yes

Also I suggested to just change the main fuse to 400a protecting the 500s Wich in my opinion is fine?

Am I wrong for thinking potentially the 500s could be overloaded because there is the main 600a fuse?

I know that tap rules don't apply to service conductors but after the main switch these are no longer service conductors so I guess my question is . Isa double lug considerd a tap?

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Yes, you have a "tap".
Lowering the fuse to 400 would be one solution
A 400 amp overcrurrent device at the end of the 500s is a second solution as long as you obey the 240.21 tap rules on
length,
(in both cases provided neither load is over 380 amps)
 
So without changing the main fuse this is a violation I am thinking clearly

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Also if it were fused at 400 la are the 500s still considered a tap

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No.
Look at then definition of a "tap" at 240.2
At 400, It is basically protected at it's ampacity
 
If the 500 kcmil conductors are the tap conductors they're too small to terminate in a 400 amp OCPD.
 
If the main fuse is 400a then the 500s are not tap conductors at all there just conductors. Jsut to clarify here there calculated load is less then 340 or so

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What were trying to do is make it compliant without re piping and doing the service over. I suggested jsut and I put a 400a main fuse

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My answer may be a little to generic... The devil is in the details.
How long is the tap ?, what is the load ?
You really need to look at 240.21 tap rules.

The Code cycle you are under could make a difference also.
 
First it needs to be clear if they actually are taps fused at 400amps Then we can have that conversation. In my opinion there not

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If you have two sets of 500's going off a 600 breaker to two different panels, then they are taps. Problem is the panels would need to be main breaker, not main lug (also you would need to comply with the tap rule distance restrictions etc).

If you change the breaker to a 400, then you can use the next size up rule and come off with two feeders to each main lug panel. not sure if 400 frame breaker will have room for 2 500's though.
 
electrofelon said:
If you have two sets of 500's going off a 600 breaker to two different panels, then they are taps. Problem is the panels would need to be main breaker, not main lug (also you would need to comply with the tap rule distance restrictions etc). I agree with this

If you change the breaker to a 400, then you can use the next size up rule and come off with two feeders to each main lug panel. not sure if 400 frame breaker will have room for 2 500's though.
Click to expand...
it's a fused switch



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The tap rules apply when a conductor protected from overcurrent at the load end rather than the supply end.

Once protected from overcurrent at the supply end (by changing the fuses to 400A) then they are no longer 'taps'. They are simply circuit conductors protected with overcurrent protection.

(Of course they still are tapping power...but they are no longer covered by the special permission that we call tap rules.)

Jon
 
augie47 said:
...
A 400 amp overcrurrent device at the end of the 500s is a second solution as long as you obey the 240.21 tap rules on
length,
...
Click to expand...
The provisions of 240.4(B) do not apply to tap conductors. A tap conductor with a 400 amp OCPD at its load end must be 600 kcmil if you are using one conductor per leg.
240.21 (B) Feeder Taps.
Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (B)(5). The tap shall be permitted at any point on the load side of the feeder overcurrent protective device. Section 240.4(B) shall not be permitted for tap conductors.
Click to expand...
 
Correct. But with the 600 amp if you kept the 500kcmil you could not use 400 amp mains at the panels
 
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