7.7 Equipment and Devices Case Lab
Key Takeaways
- Mixed equipment cases should be solved by separating load, device, location, disconnect, grounding, and listing issues.
- The fastest exam method is to identify the article path before calculating or choosing hardware.
- Many wrong answers are partly true but ignore a more specific equipment rule or location requirement.
- Good field judgment and good exam strategy both depend on reading nameplates and markings before assuming standard practice.
How to attack mixed equipment cases
Equipment and devices make up a major part of the journeyman outline when the Equipment and Devices and Control Devices domains are combined. The questions are usually not long calculations. They are short practical cases that ask whether the candidate can see the controlling issue: device rating, location, listing, disconnect, grounding, load type, or working/service access.
Use this case method:
| Step | Action | Why it works |
|---|---|---|
| 1 | Name the equipment or device | Receptacle, luminaire, appliance, motor, HVAC, controller, disconnect |
| 2 | Identify the location | Dwelling kitchen, bathroom, outdoor, wet, closet, roof, commercial, equipment space |
| 3 | Read the rating or nameplate clue | Voltage, amperes, watts, MCA, MOCP, horsepower, temperature, wet marking |
| 4 | Pick the article path | 404, 406, 410, 422, 424, 430, 440, 250, 314, 210 |
| 5 | Separate functions | Control, disconnect, overcurrent protection, grounding, support |
| 6 | Check the trap | Edition difference, listing instruction, accessibility, grounded conductor, device type |
This workflow is slower than guessing but faster than random code searching. On the ICC exam, there is no guessing penalty, and results are generally immediate, but time is tight. You cannot look up every word. You should know the article family and then verify the rule in the NEC edition assigned to your exam: 2023 for R17, 2020 for T17, or 2017 for G17.
Case 1: Exterior receptacle replacement
A dwelling exterior receptacle on a 20 A branch circuit is replaced after the old cover breaks. The installer uses a standard indoor duplex GFCI receptacle and a spring cover that is weatherproof only when closed. The receptacle is on a patio where a cord is commonly left plugged in for lighting.
Sort the facts. Device: receptacle. Location: exterior wet or damp depending on exposure, but likely weather-exposed. Protection: GFCI may be required and is present. Missing issues: weather-resistant marking and cover suitable while in use. Article path: 406 and 210, with enclosure and wet-location rules. The correct answer is not "GFCI makes it safe." GFCI protection, weather resistance, and in-use protection are separate requirements.
Exam trap: If an answer choice says "install a weatherproof cover," check whether it protects with the plug inserted. A cover that works only when closed may be insufficient for an unattended cord-connected load in a wet location.
Case 2: Closet luminaire
A clothes closet has a bare lampholder with an exposed incandescent lamp mounted above a shelf. The homeowner wants a larger lamp because the closet is dim.
Sort the facts. Device: lampholder/luminaire. Location: clothes closet near storage. Load: lamp heat. Article path: 410. The issue is not only wattage. Certain lampholders and luminaires are restricted in clothes closets, and clearances from storage space matter. A larger lamp can worsen the heat hazard. A listed enclosed or recessed luminaire suitable for the location and clearances may be required.
Exam trap: Do not answer by adding a larger breaker or increasing conductor size. The hazard is ignition of combustibles and contact with stored material.
Case 3: Dishwasher and disposal
A dishwasher and garbage disposal are installed under a kitchen sink. The dishwasher nameplate shows 9 A, the disposal shows 7 A, and both are cord-and-plug connected to a duplex receptacle in the sink cabinet. The branch circuit is 20 A.
Sort the facts. Devices: appliances and receptacle. Location: dwelling kitchen, under sink. Load: fastened-in-place appliances. Article path: 422, 210, 406, and possibly GFCI rules in the tested edition. Load math: 9 A + 7 A = 16 A. The circuit may be acceptable from a simple ampere standpoint, but the exam could ask about GFCI protection, receptacle accessibility, whether cord-and-plug connection is permitted, or whether the appliance instructions require individual circuits.
Exam trap: A 20 A circuit does not automatically make the installation acceptable. Listing instructions can be more restrictive, and small-appliance branch circuits are not a default supply for fixed dishwasher/disposal loads.
Case 4: Rooftop HVAC unit
A rooftop unit nameplate shows MCA 32 A and maximum overcurrent protection 50 A. The installer pulls conductors with ampacity at least 32 A and supplies the unit from a 50 A breaker. A disconnect is mounted within sight of the unit. The required 125 V service receptacle is supplied from the load side of the HVAC disconnect.
Sort the facts. Equipment: HVAC. Article path: 440 and 210. Nameplate: conductor sizing from MCA and overcurrent limited by MOCP can be correct. Disconnect: within sight may be correct. Service receptacle: supplying it from the load side of the equipment disconnect is suspect because turning off the HVAC disconnect also kills the service receptacle needed for tools. The correct answer may focus on the receptacle even when the nameplate portion is right.
Exam trap: The wrong answer will attack the 50 A breaker because it looks oversized. Check Article 440 and the nameplate before rejecting it.
Case 5: Smart switch in old switch loop
A smart dimmer is installed where the old switch loop has only an ungrounded conductor feed and switched leg. The installer borrows a neutral from a nearby receptacle circuit.
Sort the facts. Device: electronic lighting control. Article path: 404, 300, 250. Issue: grounded conductor availability and circuit conductor grouping. Borrowing a neutral from another circuit can create objectionable current, overload a neutral, defeat GFCI/AFCI operation, and violate conductor grouping rules. If a neutral is required at the switch location and no exception applies, the fix is not to grab any white wire nearby.
Exam trap: Color alone does not prove circuit function. A white conductor in a switch loop may be reidentified as an ungrounded conductor under permitted conditions in older work.
Case 6: Subpanel and equipment grounds
A feeder supplies a garage panel with two ungrounded conductors, one grounded conductor, and one equipment grounding conductor. In the garage panel, neutrals and equipment grounds are landed on the same bonded bar.
Sort the facts. Equipment: panelboard, feeder, grounding and bonding. Article path: 250 and feeder rules. Since an equipment grounding conductor is run with the feeder, the grounded conductor should be isolated from the enclosure and equipment grounding conductor downstream of the service bonding point. The neutral-to-case bond in the subpanel can put normal neutral current on metal parts.
Exam trap: Grounding electrode systems and equipment grounding conductors do different jobs. A ground rod at the garage would not fix an improper neutral-to-case bond.
Final study drill
For each practice question, write a one-line article path before answering. Example: "Exterior receptacle: 406 plus 210 plus wet-location cover." Example: "Condenser: 440 nameplate plus disconnect plus wet-location wiring." Example: "Closet light: 410 luminaire type and clearance." This habit prevents the most expensive exam mistake: selecting a true statement that answers the wrong article.
In the rooftop HVAC case, why might a 50 A breaker be acceptable with conductors sized from 32 A MCA?
A smart switch needs a neutral, but the existing switch box lacks one. What is the best exam answer if no exception applies?
A garage subpanel supplied with an equipment grounding conductor has neutrals bonded to the cabinet. What is the likely issue?