Electrical disconnect switch types and code requirements

What an electrical disconnect is, and the job it does

An electrical disconnect is a switch in an enclosure that opens a circuit so the equipment downstream can be de-energized and worked on safely. The supply may still be live up to the switch, but on the load side, the power is gone once the handle is thrown. That is the whole point of it. It gives one obvious place to kill the power, prove it dead, and keep it dead while a person has their hands in the machine.

On a drawing it shows up as a safety switch, an enclosed switch, a disconnect, or just a fused or non-fused disco. The NEC calls the requirement a disconnecting means, which is the function, not the device. The function can be filled by a switch, a circuit breaker, or in some cases a cord and plug. Most of the time on commercial and industrial work it is a NEMA-rated safety switch on the wall beside the equipment.

The decisions on a disconnect come down to four things: where it goes, how it is rated, whether it carries fuses, and whether it can be locked off. Get those right and the install passes and protects the worker. Get the location or the lockability wrong and it fails inspection, or worse, somebody gets hurt because they could not see whether the power was off.

Why does the code require a disconnect?

The disconnect exists for the person who has to service the equipment. Someone is going to open that motor, that rooftop unit, that pump, and before they touch it they need a way to cut the power, confirm it is off, and lock it in the off position so nobody re-energizes it while they work. That is lockout/tagout, and the disconnect is the device that makes it possible at the equipment instead of back at a panel three rooms away.

There is the safety reason and the code reason, and they point the same way. OSHA's control-of-hazardous-energy rule, 29 CFR 1910.147, requires that energy be isolated and the isolating device locked out before servicing. The NEC requires the disconnecting means in the first place and says where it has to be. One rule covers the act of locking out, the other makes sure there is something to lock.

Think of it from the worker's side, not the inspector's. The man in the attic with the air handler apart cannot see the breaker in the basement. He can see the disconnect two feet away with his lock on it. That sight line, his lock, and a meter reading of zero are what stand between him and a live circuit. The code is built around that moment.

The disconnecting means: the NEC concept

Disconnecting means is the NEC term for the device that disconnects the conductors of a circuit from their source of supply. It is a requirement attached to equipment, not a product on a shelf. A service needs a disconnecting means. A motor needs one. Air-conditioning equipment needs one. The code states the requirement, then sets the rules for type, location, and rating in the article that governs that equipment.

The device that satisfies the requirement varies. For a service it is the main breaker or main switch. For a motor it can be a switch, a molded-case switch, or in many cases a circuit breaker, sized to the rules in Article 430. For a small appliance it might be a cord and plug or the branch breaker. The label on the enclosure does not matter to the code. What matters is that the means opens all the ungrounded conductors and meets the location and rating rules for that equipment.

Reading it as a function instead of a part keeps you out of trouble. The question on the job is never just what disconnect to buy. It is what the disconnecting means has to do here, where it has to sit, and what rating it has to carry. Answer that and the part follows.

What is the difference between a fused and non-fused disconnect?

A fused disconnect is a switch plus fuses in the same enclosure, so it does two jobs: it opens the circuit and it provides overcurrent and short-circuit protection right at the equipment. A non-fused disconnect is the switch alone. It opens the circuit and nothing more, so the overcurrent protection has to live somewhere upstream, usually a breaker in a panel or a separate set of fuses.

The choice is about where the protection already is. If there is no overcurrent device ahead of the equipment, or the design wants short-circuit protection local to the load, you fuse the disconnect. If a properly sized breaker already protects the circuit, a non-fused switch does the disconnecting job and you are not paying for fuses you do not need. Putting a non-fused switch where the equipment had no other overcurrent protection is the mistake that leaves a circuit unprotected.

On an air-conditioner the maximum overcurrent protection is set by the nameplate and is usually a breaker at the panel, so the unit disconnect is commonly non-fused. On a piece of equipment fed straight off a feeder tap with no local breaker, the disconnect gets fused so the load has its own short-circuit protection. The fuses also let you tune the protection to the equipment, which a shared upstream breaker cannot always do.

The safety switch: heavy duty vs general duty

A safety switch is the enclosed disconnect you bolt to the wall: a switch mechanism, an operating handle on the outside, and an enclosure rated for the location. The handle stays outside the box so you operate it without opening the door, and on most switches the door is interlocked so it will not open with the handle on. They come in fused and non-fused versions and in a span of ampere ratings, commonly 30, 60, 100, 200, 400, 600 A and up.

The split that catches estimators is general duty versus heavy duty. General duty switches are rated to 240 V and come only in NEMA 1 and 3R enclosures. They are built for residential and light commercial loads that do not cycle hard. Heavy duty switches are rated to 600 V, come in the full run of enclosures including 4, 4X, 12, and 7, have a positive door interlock, and accept options like auxiliary contacts. They are built for the voltage, the cycling, and the fault duty of commercial and industrial work.

Spec a general duty switch onto a 480 V motor and it is the wrong device for the voltage, full stop. When in doubt on commercial work, heavy duty is the safe default. The price difference is real but small against a callback or a failed inspection, and the door interlock alone earns it on equipment people open under load.

What NEMA rating disconnect for the location?

The NEMA enclosure type has to match where the disconnect lives, and it is one of the first things an inspector checks, because it is visible from across the room. Indoor and dry takes a NEMA 1. Outdoors in the rain takes a 3R. Washdown and corrosive take a 4 or a corrosion-resistant 4X. A classified, explosive atmosphere takes a 7. Get this wrong and water, dust, or vapor gets into a switch that was never built to keep it out.

The failure mode is slow and then sudden. A NEMA 1 switch mounted outside fills with water over a season, the contacts corrode, and one day the switch fails or the enclosure becomes a shock hazard. A 3R on a coastal site without the stainless rating rusts through at the seams. Pick the enclosure for the worst weather and the worst exposure the location sees, not the average day.

Enclosure ratings are their own deep topic, covered separately by topic, but the short version below covers the types you will spec on most jobs. When the location is anything but a clean indoor room, stop and confirm the type before you order.

The motor disconnect within sight (NEC 430.102)

Motors get the most-asked disconnect requirement on the job, and it lives in NEC 430.102. There are two parts to it. A disconnecting means is required for each motor controller and has to be located within sight of the controller, that is 430.102(A). A disconnecting means is also required for the motor and the driven machinery, located within sight of the motor location and the machinery, that is 430.102(B).

One device can do both jobs. The disconnect serving the controller is allowed to serve as the motor and machinery disconnect too, as long as it meets the within-sight rule for both. So on a simple motor with the controller close by, a single switch within sight of the motor usually covers the whole requirement. On a motor fed from a controller across the building, you can end up needing a second disconnect at the motor itself.

Sizing the motor branch circuit feeding that disconnect, the conductor, the overload, and the branch device, is its own job with its own rules, and the motor circuit conductor sizing guide walks through it. Here the question is only the disconnecting means: that it exists, that it is within sight, that it is rated for the motor, and that it can be locked off.

Does a motor disconnect have to be within sight?

Yes, as a rule, and the code is specific about what within sight means. The NEC defines in sight from as visible and not more than 50 ft from the equipment. So a motor disconnect that the worker can see from the motor and that sits within roughly 50 ft satisfies the rule. The sight line is the point. The worker servicing the motor needs to see that the disconnect is off without walking out of view of the machine.

There is a relief valve. The within-sight requirement for the motor disconnect has an exception that allows a remote disconnecting means where in-sight is impracticable or introduces a hazard, or on supervised industrial installations under written safety procedures, provided the remote disconnect can be locked in the open position. The lock provision is what replaces the sight line. If the worker cannot see it, they have to be able to lock it, and the lock has to stay with them.

The exact wording, the distance, and the conditions on the exception move between code cycles, so confirm them against the adopted edition and any local amendments. The 50 ft figure and the in-sight rule are stable in spirit, but do not quote a number on a submittal you have not checked against the edition the jurisdiction enforces.

The service disconnecting means (NEC 230)

Every building service needs a service disconnecting means, the switch or breaker that disconnects all the conductors of the service from the inside of the building. NEC Article 230 governs it. It has to be readily accessible, and it has to be located either outside the building or inside at the point nearest to where the service conductors enter, so the run of unprotected service conductor inside the structure stays as short as possible.

The number of disconnects is where recent editions changed things. The service is allowed to have a single disconnect, or under the two-to-six rule, up to six. In the 2020 cycle the NEC removed the old permission to group six in a single enclosure: the two-to-six disconnects now have to be in separate enclosures, or in panelboards or switchboard sections that each hold a single service disconnect. The trend across editions has been toward a single main where practical.

Because the grouping and enclosure rules moved, this is a section to verify against the adopted edition every time. The location rule, readily accessible and nearest the entrance, has held steady. The count and grouping rules have not, so check the year the jurisdiction enforces before you lay out the gear.

Does an AC unit need a disconnect within sight?

Yes. NEC Article 440, at 440.14, requires the disconnecting means for air-conditioning and refrigeration equipment to be within sight of and readily accessible from the equipment. The disconnect is allowed to be mounted on or within the unit, but it cannot be on a panel that gives access to the equipment, and it cannot obscure the equipment nameplate. It also has to meet the working-space rules of 110.26.

On a residential or light-commercial split system the common solution is a 60 A non-fused pullout disconnect on the wall beside the condenser. The unit is protected by a breaker at the panel sized to the nameplate maximum overcurrent protection, so the disconnect at the condenser does not need fuses. It just has to break the circuit within sight, in a 3R enclosure since it lives outdoors.

The within-sight rule here matters for the same reason it does on motors. The service tech who pulls the access panel on the condenser needs to cut the power right there and watch it stay off. A disconnect they cannot see while they work does not protect them. The most common violation is a disconnect that obscures the nameplate or sits on a removable access cover, both of which the code calls out directly.

HVAC ratings: MCA, MOCP, and HACR

Air-conditioning equipment does not size to a simple full-load amps figure the way a plain motor does, because a unit has more than one motor load and the manufacturer has already done the math. The nameplate gives you two numbers that drive the electrical: the minimum circuit ampacity, MCA, and the maximum overcurrent protection, MOCP. The MCA sets the smallest conductor you can feed the unit. The MOCP sets the largest breaker or fuse you can put ahead of it.

You do not get to round the MOCP up to the next standard size the way you can with general overcurrent rules. The nameplate number is a maximum, so if it reads 35 A maximum overcurrent protection, you do not go to a 40 A breaker. You use 35 or smaller. That single point trips up crews who are used to the round-up habit from branch-circuit work.

Most manufacturers allow either fuses or an HACR-rated circuit breaker as the protective device. HACR stands for heating, air-conditioning, and refrigeration, and a breaker marked HACR is listed for the multimotor and group loads these units present. The disconnect at the unit is usually the non-fused pullout, with the actual overcurrent protection back at the panel sized to the MOCP.

How do you size a disconnect switch?

Size the disconnect to the load it carries and the system it serves, and check four ratings before you order: ampere, voltage, horsepower if it is a motor disconnect, and short-circuit. The ampere rating has to be at or above the circuit ampacity. The voltage rating has to be at or above the system voltage, which is the line that rules out a 240 V general duty switch on a 480 V circuit.

The standard ampere frames are 30, 60, 100, 200, 400, 600 A and larger, and you pick the frame that covers the load. A 50 A load takes a 60 A switch, not a 30. Do not oversize wildly either, because the switch has to coordinate with the conductor and the overcurrent device, and an oversized switch on a small conductor is just wasted enclosure.

For a motor, the horsepower rating is the one people forget, and it gets its own section below because a motor switch has to do more than carry the running current. The short-circuit rating, the SCCR, has to be checked against the fault current available at that point in the system. A disconnect that carries the load fine but cannot survive the available fault is a hazard waiting for a bad day.

The horsepower rating on a motor disconnect

A motor disconnect carries an ampere rating and a horsepower rating, and the horsepower rating is the one that matters when the switch is used as a motor disconnecting means. A motor pulls several times its running current at the instant it starts, the locked-rotor current, and if you open the switch while the motor is running, the contacts have to break that load without welding or arcing themselves shut. The horsepower rating is the switch's certification that it can do that.

An ampere rating alone does not tell you the switch can break a motor. A switch rated 60 A might be fine for a heating load at 60 A but be the wrong device to interrupt a motor whose locked-rotor draw spikes far past its nameplate current. That is why motor switches carry a horsepower rating at a given voltage, and why you match the switch horsepower to the motor horsepower at the system voltage, not just the running amps.

On the job, read both ratings off the switch label. If the disconnect serves a motor, the horsepower rating at your voltage has to cover the motor. A switch with no horsepower rating, or one rated below the motor, is not a motor disconnect even if the ampere number looks fine.

SCCR: the short-circuit rating against available fault current

The short-circuit current rating, the SCCR, is the maximum fault current the disconnect can take without coming apart. Every point in a distribution system has an available fault current, the current that would flow into a bolted fault there, and it is highest near the service and falls off down the system. The disconnect's SCCR has to be at or above the available fault current at the point where it is installed. Below it, the device can rupture or fail to clear in a fault.

The fused and non-fused versions behave differently here, and it surprises people. A non-fused switch under UL 98 has a relatively low standalone short-circuit rating, commonly in the 10 kA range. Add the right current-limiting fuses and the rated combination can reach 100 kA to 200 kA, because the fuses clear the fault before the switch sees the full let-through. So on a high-fault service, the fused or fuse-coordinated assembly is doing the heavy lifting, not the switch alone.

Available fault current is calculated for the specific system, so do not guess it. Get the number from the engineering study or the utility, and confirm the disconnect's rated SCCR, standalone or as a fused combination, covers it. This is a place where the marked rating and the application have to be matched deliberately, by topic, not assumed.

Does a disconnect have to be lockable?

In most service situations, yes, and this is the requirement worth stressing because it is the one that protects the worker directly. OSHA's lockout/tagout rule, 29 CFR 1910.147, requires that the energy-isolating device be capable of being locked out. A device qualifies if it has a locking mechanism built in, or a hasp or other means to which a lock can be attached, and it can be locked out without dismantling, rebuilding, or altering the device.

Since 1990, OSHA has required that when equipment is replaced, repaired, renovated, or newly installed, the energy-isolating device be designed to accept a lockout device. So on new work the disconnect has to take a lock, period. Most safety switches ship with a provision for a padlock on the handle in the off or open position. The NEC carries its own lockable-in-the-open-position language in several places, including the motor disconnect exception, where the lock replaces the sight line.

Lockout is the practical safety procedure built on top of the disconnect, and it is a topic worth its own treatment, but the hardware point is simple: the disconnect has to physically accept a lock in the off position. A switch with no lock provision is a finding on new work and a hazard on any work, because there is nothing stopping someone from flipping it back on while a worker is in the equipment.

Readily accessible and working space (NEC 110.26)

A disconnect has to be readily accessible, which means you can get to it and operate it without climbing over things, moving obstacles, or using a ladder. A switch behind stored pallets, above a drop ceiling, or blocked by ductwork is not readily accessible even if it is technically there. The whole reason it exists is so a worker can reach it fast, including in an emergency.

Working clearance comes from NEC 110.26. The space in front of equipment likely to be examined or serviced while energized has to be kept clear, and for the common low-voltage case the depth is often 36 in, with the width and height also specified, and the depth growing with voltage and with what is on the other side of the space. Treat 36 in as the usual starting figure for ordinary 120 V to 240 V work and confirm the actual dimension for the voltage and condition against the adopted code.

Do not block it after the install, either. The classic violation is a clear working space at rough-in that becomes a storage shelf or a parked cart by the time the building is occupied. Working space is covered by topic in its own right, but on a disconnect the rule is plain: clear in front, reachable without a ladder, and nothing stacked where a worker has to stand to throw the handle.

Marking and identification

A disconnect has to be marked with what it controls, so the worker at the switch knows it is the right one before they throw it. On a wall of identical safety switches, an unmarked disconnect is a guess, and a guess at a live panel is how the wrong circuit gets opened or the wrong machine gets worked on hot. The marking has to be durable and legible, not a faded label maker strip that fell off two years ago.

Beyond the what-it-controls label, modern installs carry arc-flash and shock-hazard warning labels where the assessment requires them, identifying the available incident energy or the required arc-flash boundary and the PPE. Those labels come out of the facility's electrical safety program under NFPA 70E and the arc-flash study, and they are a topic of their own, but the disconnect is one of the places they belong.

When you commission a disconnect, label it as part of the job, not as a someday task. The person who needs the label is not you. It is the tech six months out who is standing in front of five switches and needs to kill the right one fast.

The fused disconnect and the fuses inside it

When the disconnect is fused, the fuse class and rating are part of getting it right, not a detail you hand to whoever has a fuse on the truck. Fuses come in classes, and the class sets the physical size, the interrupting rating, and whether the fuse is current-limiting. Common branch and feeder classes you will see include RK5, RK1, J, and the time-delay versions of each. The fuse holder in the switch is built for a specific class, so you cannot freely swap classes.

For motor circuits, time-delay fuses are usually the right choice because they ride through the starting inrush without blowing, then open on a sustained overload or fault. A fast-acting fuse sized to the running current will nuisance-blow every time the motor starts. The fuse class and the time-delay characteristic come out of the overcurrent protection rules for the equipment, which is a topic in its own right.

The field discipline is to replace fuses with the same class and rating that the design called for, and to record what is in the switch. Pull a current-limiting fuse and drop in a cheaper class with a lower interrupting rating, and you have quietly downgraded the short-circuit protection the whole assembly was built around. The fuse is doing real work in a fault, and the wrong fuse only shows that on the worst day.

The enclosed circuit breaker as a disconnect

A disconnecting means does not have to be a switch. An enclosed circuit breaker, a molded-case switch, or a molded-case breaker in its own enclosure can serve as the disconnect, and on a lot of equipment that is exactly what is used. The breaker opens all the ungrounded conductors, and where it is listed and marked suitable, it does double duty as both the disconnecting means and the overcurrent device.

A molded-case switch is a breaker frame without the automatic trip, used purely as a switch where the overcurrent protection is provided elsewhere. It looks like a breaker and mounts like one, but it is functioning as a disconnect, not as protection. People mix the two up by sight, so read the label to know which device is actually in the box.

The practical reason to reach for an enclosed breaker instead of a fused switch is that you get the disconnect and the resettable overcurrent device in one enclosure, with no fuses to stock or replace. The trade-off is that a fused switch can hit higher short-circuit ratings through current-limiting fuses, which is why high-fault and certain motor applications still go fused. Pick the device by what the application needs, which is its own decision by topic.

Grounding and bonding the disconnect enclosure

The metal enclosure of a disconnect has to be bonded so that a fault to the case has a low-impedance path back to the source and trips the protective device fast. The equipment grounding conductor lands on the ground bar or lug in the switch, and the enclosure is bonded to it. Leave that connection out or make it loose, and a fault to the case leaves the metal energized with no path to clear the fault. The handle a worker grabs is then live.

At a service disconnect the rules change, because that is where the grounded conductor and the grounding system are bonded together through the main bonding jumper. Downstream of the service disconnect, the grounded conductor and the equipment grounding conductor stay separate. Bonding them again at a downstream disconnect creates parallel neutral paths and puts current on the equipment grounding conductor, which is a common and dangerous error on subpanels and remote disconnects.

Grounding and bonding is a deep topic on its own, but at the disconnect the field checks are short. The EGC is landed and tight. The enclosure is bonded. At a service, the main bonding jumper is in place. Past the service, neutral and ground are kept apart. Miss any of those and the protection you sized so carefully has no path to act through.

Where disconnects are required: the requirement map

Disconnects are required across a predictable set of equipment, and each one points to the article that governs it. The service, the motors, the air-conditioning equipment, and most fixed equipment all need a disconnecting means, with the location and rating rules set by their own article. The table below is the field map of what needs a disconnect and the headline rule for each.

How the raceway or cable actually reaches each disconnect, EMT, rigid, PVC, flex, or MC, is the wiring method question, and the wiring methods and conduit types guide covers picking and installing it for the location. Here the point is only that the disconnect is required, where it sits, and how it is rated. Two adjacent decisions, two separate calls.

Equipment and data-center disconnects

On data-center and large equipment work the disconnect questions are the same in principle but tighter in practice, because the fault currents are high and the cost of an unplanned outage is brutal. Available fault current near big service gear runs high, so the SCCR matching gets real attention, and the fused or fuse-coordinated assemblies earn their place where a standalone switch cannot make the rating.

Maintainability drives a lot of the layout. Equipment that has to be serviced live or transferred without dropping the load gets disconnects placed and labeled so a tech can isolate exactly the right piece, no more, and lock it. The working space and access rules matter more, not less, when the room is packed with gear and every aisle is fighting for clearance.

The thermal and reliability standards that govern these rooms are a separate topic, but the disconnect discipline carries straight over: within reach, clearly marked, rated for the fault, lockable, and laid out so isolating one machine does not mean killing the row. That last point is where a careless layout costs an operator real money.

What the inspector checks on a disconnect

An inspector works a disconnect fast because the findings are visible. The first look is location: is the motor or AC disconnect within sight of the equipment, is the service disconnect readily accessible and near the entrance. The second look is the enclosure: does the NEMA type match the location, is a NEMA 1 sitting outside where a 3R belongs. Both of those are caught from across the room before any cover comes off.

Then it gets specific. Can the switch be locked off. Is it marked with what it controls. Is the working space in front of it clear and adequate. Is it rated for the load, and for a motor, does it carry the horsepower rating. Is the EGC landed and the enclosure bonded, and at a service, is the main bonding jumper correct and neutral-to-ground separated downstream.

The fastest way to fail is the within-sight rule and the lockability, because they are the two the inspector is trained to check first and the two that protect the worker most directly. If you walk a job before the inspector, walk it in that order: location, enclosure, lock, marking, rating, working space, grounding.

Field checklist

What to document

A disconnect that nobody can identify later is a problem you handed to the next tech. The record ties the device to the equipment it kills and to the ratings that prove it was right, so when someone troubleshoots or replaces it, they are not reverse-engineering the install. Capture what it serves, its type and ratings, its enclosure, the fault rating against the available fault current, and the two findings that get checked first, within sight and lockable.

If the disconnect is fused, record the fuse class and rating, because the next person has to replace it with the same protection and will otherwise reach for whatever fits. If you used a remote disconnect under the within-sight exception, write down that the lock provision is what satisfies the rule, so the basis of the install is on paper.

Common mistakes

• No within-sight disconnect at the motor or AC unit, or one too far away to count as in sight.
• A motor or HVAC disconnect installed but not lockable in the off position, so LOTO has nothing to secure.
• Wrong NEMA enclosure for the location, most often a NEMA 1 mounted outdoors where a 3R belongs.
• Using a 240 V general duty switch on a 480 V circuit, or a switch with no horsepower rating as a motor disconnect.
• A non-fused disconnect where the equipment had no other overcurrent protection, leaving the circuit unprotected.
• Treating the HVAC nameplate MOCP as a number you can round up, instead of a maximum you must not exceed.
• Blocked or inadequate working space in front of the disconnect, or a switch you need a ladder to reach.
• An unmarked disconnect on a wall of identical switches, so the wrong one gets opened.
• Re-bonding neutral to ground at a downstream disconnect, putting current on the equipment grounding conductor.
• An SCCR below the available fault current at that point in the system.

Standards and references

The NEC, NFPA 70, sets the disconnecting-means requirements, and they live in the article that governs each kind of equipment. Motor disconnects are in Article 430, with the within-sight rule at 430.102 and the readily-accessible requirement at 430.107. Air-conditioning and refrigeration disconnects are in Article 440, with the within-sight and access rule at 440.14. The service disconnecting means is in Article 230, with the location at 230.70 and the number of disconnects at 230.71. The 2020 and later NEC also requires an emergency disconnect at 230.85 for one- and two-family dwellings, outdoors and readily accessible. General switch rules are in Article 404, the lockable-disconnect provision is 110.25, and working clearances are in 110.26.

These section numbers and the in-sight distance shift between code cycles, and the 2020 cycle in particular changed the service-disconnect grouping rules. Confirm every number against the edition the jurisdiction has actually adopted and any local amendments before you cite it on a submittal. The within-sight rule and the lockability are the two points to get right regardless of edition, because they are what protect the worker.

On the product side, enclosed and dead-front switches are built to UL 98, which sets the testing, clearances, and ratings for the device. Lockout/tagout is OSHA's 29 CFR 1910.147, which requires the energy-isolating device to be capable of accepting a lock. Arc-flash labeling and the electrical safety program come from NFPA 70E. Cite the standard that controls the point, and let the project specification and the equipment listing override a rule of thumb when they are stricter.

Units, terms, and synonyms

The same device goes by several names across a drawing set, a catalog, and the field, so the terms below keep them straight.

A disconnect is also called a disconnecting means, a safety switch, an enclosed switch, a disco, or an isolator. Fused and non-fused describe whether fuses sit in the switch. Within sight from is the NEC term for visible and within about 50 ft. SCCR is the short-circuit current rating, checked against the available fault current. MCA and MOCP are the air-conditioning nameplate figures for minimum circuit ampacity and maximum overcurrent protection.

Disconnecting means

The NEC term for the device that disconnects a circuit from its supply; a switch, breaker, or in some cases a plug

Safety switch

An enclosed disconnect with an external handle, fused or non-fused, rated by a NEMA enclosure type

Within sight (in sight from)

Visible and not more than 50 ft from the equipment, per the NEC definition; confirm against the adopted edition

Fused vs non-fused

Fused has fuses in the switch for overcurrent protection; non-fused is the switch only, with protection upstream

SCCR

Short-circuit current rating, the fault current a device can survive; must meet the available fault current

MCA / MOCP

Minimum circuit ampacity and maximum overcurrent protection, the air-conditioning nameplate sizing figures

NEMA enclosure type

The rating for where an enclosure may go: 1 indoor, 3R outdoor, 4/4X wet or corrosive, 7 hazardous, 12 dusty

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