10 foot tap rule

Status
Not open for further replies.
Grouch1980

Grouch1980

Senior Member
Location
New York, NY
I'm following the 2008 NEC code cycle... my question is regarding the 10 foot tap rule in section 240.21(B)(1).

I always have the tap conductors terminate in a single OCPD in previous projects, whenever i needed a tap.

I'm working on a project now where I'm showing the tap conductors terminating in a switch & fuse board, with multiple switches. However, I'd like to avoid having a main switch. I believe this is possible, is that correct? The section doesn't specifically say the tap conductors have to terminate in a SINGLE device, as (B)(2) states for the 25 foot tap rule.

As long as the tap conductors terminate in a "device" (the switch & fuse board), where the ampacity of the tap conductors is not less than the rating of that device, I should be fine? For example, 100 amp tap conductors terminating in a main lug only board rated for 100 amps is code compliant? I'm also aware that the calculated load of the circuits fed by the tap conductors cannot exceed the tap conductor ampacity.

Thanks!
 
Last edited:
What exactly is a fuse board is it by definition a panelboard? A panelboard has it's own requirement for a single OCPD.
 
infinity said:
What exactly is a fuse board is it by definition a panelboard? A panelboard has it's own requirement for a single OCPD.
Click to expand...
Yes, I mean a panelboard... with disconnect switches instead of circuit breakers. it's a distribution board, with integral disconnects (switches and fuses).
 
I understand 408.36... that's very clear.

So when would this apply? I took the excerpt below from the 2017 NEC. Where I underlined... that sounds like a device that doesn't have a main OCPD. The next section, the 25 foot tap rule, specifically says the 25 foot tap conductors have to terminate in a single device. Where I underlined below, it doesn't mention a single device. What type of installation is this where I underlined?

(1) Taps Not over 3 m (10 ft) Long.

If the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:

(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors
 
Last edited:
Grouch1980 said:
I understand 408.36... that's very clear.

So when would this apply? I took the excerpt below from the 2017 NEC. Where I underlined... that sounds like a device that doesn't have a main OCPD. The next section, the 25 foot tap rule, specifically says the 25 foot tap conductors have to terminate in a single device. Where I underlined below, it doesn't mention a single device. What type of installation is this where I underlined?

(1) Taps Not over 3 m (10 ft) Long.

If the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:

(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors
Click to expand...
An mlo switchboard could comply with that section.
 
Got it. What if the 10 foot tap conductors terminate in a trough, where the trough feeds multiple disconnect switches? I don't think this would comply. The trough is not 'equipment' that contains the OCPD devices... rather it's an assembly that has to be put together. Is this correct?
 
240.21 states "Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.".
Basically, you can't tap other conductors off your tap
 
augie47 said:
240.21 states "Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.".
Click to expand...
Since that sentence says "conductor" rather than "wire-type conductor" does that mean that the MLO switchboard example for the 10 foot rule would violate the above? The bus in the switchboard is certainly a conductor.

Cheers, Wayne
 
wwhitney said:
Since that sentence says "conductor" rather than "wire-type conductor" does that mean that the MLO switchboard example for the 10 foot rule would violate the above? The bus in the switchboard is certainly a conductor.

Cheers, Wayne
Click to expand...
FWIW, the scope of 310 states that article doesn't apply to conductors internal to equipment. Also even something like a fused disco will have a short piece of bussing that connects the lug to the fuse.
 
Grouch1980 said:
So when would this apply? I took the excerpt below from the 2017 NEC. Where I underlined... that sounds like a device that doesn't have a main OCPD. The next section, the 25 foot tap rule, specifically says the 25 foot tap conductors have to terminate in a single device. Where I underlined below, it doesn't mention a single device. What type of installation is this where I underlined?
Click to expand...
We once had a dimmer rack in a theater that complied with the 10' rule and no main OCPD.
 
Status
Not open for further replies.
Top