Tap from existing Service entrance

[mepengineer]

I receive an RFI , about tapping from existing service.
am tapping from existing main service to a 400A disconnect to feed a separated building in a 4"C.
according to the contractor, there is no way entering the existing main service with a new 4"C due to troughing on the top and side of the main switch.
there is very little room to safely tap the existing wires, gutter space is limited.
what can be done? any recommendations will be appreciated.

 

[electrofelon]

Fairly vague on the details to offer specific advice. What size is the existing service? What kind of service equipment (safety switch, panelboard, switchboard). Generally your options include, replacin g or adding lugs to the existing equipment, putting a splice box in, tapping the conductors with some sort of connector.....

 

[mepengineer]

Fairly vague on the details to offer specific advice. What size is the existing service? What kind of service equipment (safety switch, panelboard, switchboard). Generally your options include, replacin g or adding lugs to the existing equipment, putting a splice box in, tapping the conductors with some sort of connector.....

existing 800A service, the tap is a 400A service disconnet to a DP panel.

my thought was to extend the bus at the existing service CT cabinet and have the tap there

 

[electrofelon]

existing 800A service, the tap is a 400A service disconnet to a DP panel.

my thought was to extend the bus at the existing service CT cabinet and have the tap there

Can you add or replace with more ports the lugs in the ct cabinet?

 

[drktmplr12]

existing 800A service, the tap is a 400A service disconnet to a DP panel.

my thought was to extend the bus at the existing service CT cabinet and have the tap there

there isn't enough detail here, a picture of the location in question and a one-line would be helpful.

 

[mepengineer]

there isn't enough detail here, a picture of the location in question and a one-line would be helpful.

 

[Strathead]

View attachment 21067

OK, so I am betting there is a solution to your problem here, but assuming the contractor is competent, I doubt the best solution is going to be obvious without far more detail. We can't tell means and methods from you picture. We can't see the space available within 10 feet of the splice point for the disconnect. What should be worst case would be run new conduit and wire from the CT cabinet to the existing disconnect through a junction box or gutter and tap in the junction box. Then try to improve from there.

 

[electrofelon]

The first thing I would investigate is adding/replacing lugs in the ct or the SB.

 

[infinity]

Looking at the drawing the #1/0 EGC in the raceway is incorrect.

 

[victor.cherkashi]

Looking at the drawing the #1/0 EGC in the raceway is incorrect.

(I assume you refer to the tap sizing, not the wire to water service)
Do you mean that #1/0 EGC doesn't participate in tap?
(OR) Do you think that Rating Overcurrent Device in Circuit Ahead is higher than 800A, in this case #1/0 is not enough.

 

[infinity]

(I assume you refer to the tap sizing, not the wire to water service)
Do you mean that #1/0 EGC doesn't participate in tap?
(OR) Do you think that Rating Overcurrent Device in Circuit Ahead is higher than 800A, in this case #1/0 is not enough.

There is no EGC on the line side of the service disconnect. The drawing shows 4-500's and a #1/0 "ground" there should be no #1/0 EGC in that raceway with the service entrance conductors.

 

[victor.cherkashi]

I receive an RFI , about tapping from existing service.
am tapping from existing main service to a 400A disconnect to feed a separated building in a 4"C.
according to the contractor, there is no way entering the existing main service with a new 4"C due to troughing on the top and side of the main switch.
there is very little room to safely tap the existing wires, gutter space is limited.
what can be done? any recommendations will be appreciated.

Maybe the electrician can do a tap somewhere downstream of 800A main service switch without additional cost. If the service is 800A, you can't have load higher that 800A on service conductors, what is the point to tap 400A upstream of 800A?

 

[victor.cherkashi]

Also another point that bother me for years, I still didn't find an answer. All engineering drawings I saw, also on this post (picture of riser). Engineer doesn't apply tap rules (240.21) for fire alarm disconnect switch. "The tap conductor must be not less than onetenth the rating of the overcurrent device protecting the main feeder to which the tap is being made". WHY #6 (65A@75C) tap is shown on 800A service?

 

[Cow]

If I was an engineer on a project, I would ask the electrical contractor on that project.

 

[packersparky]

Also another point that bother me for years, I still didn't find an answer. All engineering drawings I saw, also on this post (picture of riser). Engineer doesn't apply tap rules (240.21) for fire alarm disconnect switch. "The tap conductor must be not less than onetenth the rating of the overcurrent device protecting the main feeder to which the tap is being made". WHY #6 (65A@75C) tap is shown on 800A service?

The conductors supplying the FA disconnect are service conductors and not tap conductors.

 

[infinity]

The conductors supplying the FA disconnect are service conductors and not tap conductors.

Yup, the 10' and 25' tap rules are for feeder taps not conductors connected before the service disconnect.