Electrical – the proper disconecting device for a heater + air handler not in sight of the panel

code-complianceelectricalhvac

I'm finding all sorts of conflicting information on this, some of which is hearsay, local, or outdated.

For an electric heater and air handler unit, with #6 wire, that will be either 50 or 60 amps, what type of device is code compliant to be the "readily accessible" disconnecting means?

This is for new construction and the unit is not in sight of the panel. NEC 2017 and IRC 2012 apply here.

Some say the breaker built in to the air handler is enough. Some say it isn't. Some say to use a non-fusible disconnect, like this. Others say that the door on the front make it not "readily accessible" and some inspectors will fail it.

Can you please tell me what the correct device should be and cite a code reference to support it?

Best Answer

The applicable NEC cite for a typical air handler of this nature is 424.19(A)(2) (424.19(A)(1) does not apply to most air handlers as the fan motor in them is over 1/8 HP):

424.19 Disconnecting Means. Means shall be provided to simultaneously disconnect the heater, motor controller(s), and supplementary overcurrent protective device(s) of all fixed electric space-heating equipment from all ungrounded conductors. Where heating equipment is supplied by more than one source, feeder, or branch circuit, the disconnecting means shall be grouped and marked. The disconnecting means specified in 424.19(A) and (B) shall have an ampere rating not less than 125 percent of the total load of the motors and the heaters and shall be lockable in accordance with 110.25.

(A) Heating Equipment with Supplementary Overcurrent Protection. The disconnecting means for fixed electric space-heating equipment with supplementary overcurrent protection shall be within sight from the supplementary overcurrent protective device(s), on the supply side of these devices, if fuses, and, in addition, shall comply with either 424.19(A)(1) or (A)(2).

(2) Heater Containing a Motor(s) Rated over 1/8 Horsepower. The above disconnecting means shall be permitted to serve as the required disconnecting means for both the motor controller(s) and heater under either of the following conditions:

(1) Where the disconnecting means is in sight from the motor controller(s) and the heater and complies with Part IX of Article 430.

(2) Where a motor(s) of more than 1/8 hp and the heater are provided with a single unit switch that complies with 422.34(A), (B), (C), or (D), the disconnecting means shall be permitted to be out of sight from the motor controller.

Given that the motor controller in an air handler is going to be inside the air handler (it's the fan relay there), unless your air handler has a unit switch on the outside to serve as a disconnecting means, then you need a motor-rated disconnecting means in sight of the air handler. A non-fusible molded case disconnect like the one you linked works; you can also use a breaker-based "spa panel" type disconnect like the ones used for air conditioners provided the current rating is suitable, or even a subpanel if you wish to run the serviceman's receptacle and whatnot off the same set of wires as the air handler.

Also, having a door on a cabinet or cutout box does not violate "readily accessible" under the 2017 NEC:

Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to actions such as to use tools (other than keys), to climb over or remove obstacles, or to resort to portable ladders, and so forth.

Note: Use of keys is a common practice under controlled or supervised conditions.

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