Tap Rule and OCP

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Specificly, does a tap from a feeder need to be landed in a OCP device or can it landed in a device disconnect or lugs.

Persuant to 240.21 (B) (1)

I believe that an OCP device is not required in this situation.

My example is;

The engineer design has a Feeder protected at 200 amps, 4/0 conductors ran to multiple floors.

On each floor there is a wireway / gutter with feeder taps not more than 10 feet of tap conductor to be landed inside a unit heater/ac unit. Each ac/heater unit has a disconnect (not an ocp device). Of course after the disconnect, there are fuses for the associated heater elements, fan motor, and compressor.

The spec calls for #8 Taps and #8 ground to each unit.

I believe this is OK, however, I'm not sure if the disconnect inside each unit needs to be in fact a ocp device or not.

Otherwise a ocp device would need to be added prior to the heater/ac unit.

chris kennedy

Senior Member
Miami Fla.
60 yr old tool twisting electrician
b. 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.
What is the rating of this device in your case?


Staff member
State Electrical Inspector (Retired)
A little fuzzy to me. If you look at the 240.21 tap rules most of them state "terminate in a single overcurrent device" , but on the 10 ft rule they must terminate in a "device" and be not less than the overcurrent protection at the termination. Your switch is a device and it appears the install meets the other requirements of 240.21(B)(1)


Senior Member
Columbus, Ohio
In the first paragraph of 240.21 it requires that "Overcurrent protection shall be provided in each ungrounded conductor and shall be located at the point where the conductors receive their supply except" A through H.

So the OCP is required. The tap rule of (B)(1) allows it to be at the load end. I would interpret it to allow the disconnect to feed the fuses, but OCP is needed.


Senior Member
Here's an article that you don't see applied very often but i think it applies in this case.

240.10 Supplementary Overcurrent Protection.
Where supplementary overcurrent protection is used for luminaires, appliances, and other equipment or for internal circuits and components of equipment, it shall not be used as a substitute for required branch-circuit overcurrent devices or in place of the required branch-circuit protection. Supplementary overcurrent devices shall not be required to be readily accessible.



Senior Member
I have a feeling that the 37 amps is an mca on the nameplate in which case the 125% has already been taken into consideration by the manufacturer. Thus # 8 will be fine if that is in fact the case.
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