Tap into a panel
- Thread starter cppoly
- Start date
- Status
- Location
- Massachusetts
Most, if not all taps must end in an overcurrent device.
If you are stuck with a MLO panel you may have to install a fused disconnect or a single breaker enclosure outside the panel.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
it depends a lot on whether the conductors are truly tap conductors. If they are tap conductors, they need to terminate at an OCPD.
Curious about how to interpret this:
For 10' tap 240.21(B)(1), the ampacity of the tap conductors is to be "not less than the rating of the device supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors."
Here is says device or OCPD.
Yet for 25' tap, 240.21(B)(2) the ampacity of the tap conductors is "the ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors."
For 10' tap it says device or OCPD and in 25' tap it only says OCPD... interesting
For 10' tap 240.21(B)(1), the ampacity of the tap conductors is to be "not less than the rating of the device supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors."
Here is says device or OCPD.
Yet for 25' tap, 240.21(B)(2) the ampacity of the tap conductors is "the ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors."
For 10' tap it says device or OCPD and in 25' tap it only says OCPD... interesting
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Even if you had a 10' tap you would still need to comply with this:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I think you will see a bit of a change in 2014
Last edited:
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What actually changes in the 2014?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Under 2014's 10' tap rule, the ampacity of the conductors must not be less than the MLO panel's rating, but...
The MLO panel is still required to be protected per 408.36. That protection would be the feeder OCPD. This makes the whole issue of taps to supply an MLO panel moot.
- Location
- Illinois
- Occupation
- retired electrician
The change for 2014 is a problem when you are using a fusible disconnect at the load end of the tap conductors. The tap conductor must have an ampacity equal to the rating of the disconnect itself, and not of the fuses that are installed in the disconnect. The wording needs some tweaking.
Is that because the switch is ahead of the fusing? That is, the tap conductors do not directly terminate to the OCPD even though it is integral with the device.
kwired
Electron manager
- Location
- NE Nebraska
In a recent thread this was brought up where you would run into a device that could be used under this section - one example that was brought up was switchboards without a single main, as they would not necessarily require the same overcurrent protection of the bus as a panelboard would. (This all from memory, go ahead and shoot holes in it if you see fit)
No holes to shoot. I may have been the one to bring that up..
- Location
- Illinois
- Occupation
- retired electrician
That is how the words read to me.
K8MHZ
Senior Member
- Occupation
- Electrician
kwired
Electron manager
- Location
- NE Nebraska
Is that because the switch is ahead of the fusing? That is, the tap conductors do not directly terminate to the OCPD even though it is integral with the device.
That is how the words read, something tells me that is not the intent though.
I would think a typical fused disconnect is considered an overcurrent device just like a circuit breaker is, even though it is an assembly of two major components, it is sold as a single listed unit. A fuseholder with a separate adjacent disconnecting means as is mentioned a time or two in the NEC is likely an example of where this "device" comes to play. JMO.
I would think that it would be because there's always the chance that a larger fuse could be installed in the disconnect in some cases, thus "Overfusing" the Tap Conductor.
For example a 125 amp tap to a 125 amp fuse installed in a 200 Amp Rated Disconnect or a 225 Amp tap to a 225 Amp Fuse installed in a 400 Amp Disconnect.
For example a 125 amp tap to a 125 amp fuse installed in a 200 Amp Rated Disconnect or a 225 Amp tap to a 225 Amp Fuse installed in a 400 Amp Disconnect.
- Location
- Illinois
- Occupation
- retired electrician
Not sure about that...the previous code said that the 10' tap conductor had to have an ampacity not less than the rating of the device, but did not require that the device contain an OCPD. The intent of the change is to require that the tap conductor terminate on an OCPD, or at equipment that contains an OCPD. The rule clearly requires that the tap conductor have an ampacity of not less than the rating of the equipment that contains an OCPD. The equipment that contains the OCPD is the disconnect itself and the fuse is the "contained OCPD".Originally Posted by Smart $
Is that because the switch is ahead of the fusing? That is, the tap conductors do not directly terminate to the OCPD even though it is integral with the device.
That is how the words read, something tells me that is not the intent though.
I would think a typical fused disconnect is considered an overcurrent device just like a circuit breaker is, even though it is an assembly of two major components, it is sold as a single listed unit. A fuseholder with a separate adjacent disconnecting means as is mentioned a time or two in the NEC is likely an example of where this "device" comes to play. JMO.
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