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I'm finding all sorts of conflicting information on this, some of which is hearsay, local, or outdated.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

  • Generally speaking, "readily accessible" disconnecting means is relevant to heavy industrial locations, the issue being Goober McNab finds a breaker turned off in the 2nd floor service panel that powers a 3rd floor stamping machine... The repairman should've used lockout-tagout procedures, but in the real world repairmen often don't bother. The rule is to put the disconnect close enough that Goober can turn his head and see the repairman's cart. This doesn't really apply to residential. – Harper - Reinstate Monica Oct 7 '17 at 1:47
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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.

  • In many instances the word "tool" includes the use of a key to open a locked cabinet door, even if it can be reached quickly. – Upnorth Oct 7 '17 at 2:26
  • @Upnorth -- this was clarified in the 2017 NEC, see my edit – ThreePhaseEel Oct 7 '17 at 2:34
  • Okay, 2017 NEC. Sweet. I have been dinging people on that since the 1980s, when I was involved in UL testing and risk management. The 2017 NEC doesn't go into effect here until 2018. – Upnorth Oct 8 '17 at 18:40
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I have found that it is open to interpretation by the individual authority. Where I work if an air handler has a breaker built in to the unit it is not concidered a disconnect because there is still power in the unit. I install a disconnect outside the air handler and only use it as a disconnect (no additional fuses as the unit is protected by the built in breaker.). The breaker on the panel is then sized based on the wire size. I have heard from my distributor that some jurisdictions accept the built in breaker. The National Electrical code is only a suggestion. The local authority can accept all of it, none of it or part of it. The local building department should have it documented what is acceptable or not for them. Our area is often a couple versions behind and use the older version until they formally accept the newer codes.

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