In a high rise office building there is an existing 400A panelboard, main lug only w/ (1) 3P 100A & (2) 3P 20A circuit breakers installed. This panelboard is fed from a 1200A bus duct running thru the building. The feeders is tapped off the bus. Is this a code violation because there is no OCPD in the panelboard or does the 6 disconnect rule also apply to this panelboard?
Overcurrent Protection for Panelboard
- Thread starter bwyllie
- Start date
- Status
charlie
Senior Member
- Location
- Indianapolis
Re: Overcurrent Protection for Panelboard
Which of the tap rules in 240.21(B) are you using?
Which of the tap rules in 240.21(B) are you using?
Re: Overcurrent Protection for Panelboard
NEC 368.12 Feeder or Branch Circuits.
"Where a busway is used as a feeder, devices or plug-in connections for tapping off feeder or branch circuits from the busway shall contain the overcurrent devices required for the protection of the feeder or branch circuits."
NEC 368.12 Feeder or Branch Circuits.
"Where a busway is used as a feeder, devices or plug-in connections for tapping off feeder or branch circuits from the busway shall contain the overcurrent devices required for the protection of the feeder or branch circuits."
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Overcurrent Protection for Panelboard
Looks like 240.21(B)(1) says it is OK!
Looks like 240.21(B)(1) says it is OK!
Re: Overcurrent Protection for Panelboard
IMHO 240.21(B)(1) allows the tap conductors to be used this way without overcurrent protection at their point of supply, but it doesn't remove the requirement in 408.16(B) that the panelboard be protected by "an overcurrent protective device having a rating not greater than that of the panelboard". By using 240.21(B)(1), that protection could be a main breaker at the panelboard.
bwyllie,
I am assuming this is a power panelboard. Does the feeder include a neutral? You say this is an existing panelboard. This requirement is in section 384-16(b) of the 99 code but there is a line by it in the margin. I haven't looked back farther to see what is in the 96 code. If it's not a power panelboard, then the installation would be a violation of 408.16(A).
IMHO 240.21(B)(1) allows the tap conductors to be used this way without overcurrent protection at their point of supply, but it doesn't remove the requirement in 408.16(B) that the panelboard be protected by "an overcurrent protective device having a rating not greater than that of the panelboard". By using 240.21(B)(1), that protection could be a main breaker at the panelboard.
bwyllie,
I am assuming this is a power panelboard. Does the feeder include a neutral? You say this is an existing panelboard. This requirement is in section 384-16(b) of the 99 code but there is a line by it in the margin. I haven't looked back farther to see what is in the 96 code. If it's not a power panelboard, then the installation would be a violation of 408.16(A).
- Location
- Massachusetts
Re: Overcurrent Protection for Panelboard
Isn't there a OCPD at the bus duct connection?
How are they tapping the bus duct?
Isn't there a OCPD at the bus duct connection?
Re: Overcurrent Protection for Panelboard
There is no OCPD between the bus duct and panelboard, there is a tap box on the bus duct with bus off of the bus duct that transitions into wire and then to the panelboard. The OCPD in this panelboard feed two HVAC units and a lighting panelboard. There is a neutral.
[ August 29, 2003, 02:32 PM: Message edited by: bwyllie ]
There is no OCPD between the bus duct and panelboard, there is a tap box on the bus duct with bus off of the bus duct that transitions into wire and then to the panelboard. The OCPD in this panelboard feed two HVAC units and a lighting panelboard. There is a neutral.
[ August 29, 2003, 02:32 PM: Message edited by: bwyllie ]
- Location
- Illinois
- Occupation
- retired electrician
Re: Overcurrent Protection for Panelboard
First, we need to look at 368.12 which requires that the conductors that tapped off of the busway have overcurrent protection. In general this requires that the bus tapping device have an OCPD that will protect the conductors at their ampacity. However, Exception #1 permits the rules in 240.21 to be used. It appears from the information that 240.21(B)(1) would apply. The panel is rated at 400 amps, so 240.21(B)(1)(1) would require that the ampacity of the conductors between the busway and the panel be at least 600 kcmil copper. If the conductors are of this size or larger and the calculated loads served by the panel are 400 amps or less then the tap conductors do not require over current protection. If the conductors are smaller than 600 kcmil, an OCPD would be required at the bus tap. This brings us to the protection of the panel itself. 408.16(B) requires that this panel be protected at its ampacity either within the panel or anywhere on the line side of the panel. This requirement for overcurrent protection of panel is triggered because the panel has a neutral and more than 10% of the OCPDs installed in the panel are rated 30 amps or less. If the 20 amp breakers were 40 amp devices, neither the tap conductors nor the panel would require overcurrent protection.
Don
[ August 30, 2003, 01:05 PM: Message edited by: don_resqcapt19 ]
First, we need to look at 368.12 which requires that the conductors that tapped off of the busway have overcurrent protection. In general this requires that the bus tapping device have an OCPD that will protect the conductors at their ampacity. However, Exception #1 permits the rules in 240.21 to be used. It appears from the information that 240.21(B)(1) would apply. The panel is rated at 400 amps, so 240.21(B)(1)(1) would require that the ampacity of the conductors between the busway and the panel be at least 600 kcmil copper. If the conductors are of this size or larger and the calculated loads served by the panel are 400 amps or less then the tap conductors do not require over current protection. If the conductors are smaller than 600 kcmil, an OCPD would be required at the bus tap. This brings us to the protection of the panel itself. 408.16(B) requires that this panel be protected at its ampacity either within the panel or anywhere on the line side of the panel. This requirement for overcurrent protection of panel is triggered because the panel has a neutral and more than 10% of the OCPDs installed in the panel are rated 30 amps or less. If the 20 amp breakers were 40 amp devices, neither the tap conductors nor the panel would require overcurrent protection.
Don
[ August 30, 2003, 01:05 PM: Message edited by: don_resqcapt19 ]
Re: Overcurrent Protection for Panelboard
I agree with your thoughts Don as well as Bennie. I am not sure when this instalaltion was performed and even though it is an existing condition and we are not adding to this panelboard I felt as the PE for this project it is my responsibilty to make the tenant & building owner aware of this possible violation(depending on when it was installed) & possible fire hazard.
I agree with your thoughts Don as well as Bennie. I am not sure when this instalaltion was performed and even though it is an existing condition and we are not adding to this panelboard I felt as the PE for this project it is my responsibilty to make the tenant & building owner aware of this possible violation(depending on when it was installed) & possible fire hazard.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Overcurrent Protection for Panelboard
bwyllie,
I agree with you. If I were in your situation, I think I would recommend the same. It certainly would be much safer.
bwyllie,
I agree with you. If I were in your situation, I think I would recommend the same. It certainly would be much safer.
- Status