The rulebook

The current a conductor may carry, read from the ampacity table in the column its terminals allow: #3/0 copper carries 200 A at 75 °C, which is why a 200 A feeder is #3/0.

How much of a raceway's inside area conductors may fill — 53% for one, 31% for two, 40% for three or more.

Air-conditioning and refrigeration equipment gets a disconnect within sight of it and readily reached, so the rooftop unit's circuit ends in a disconnect on the roof.

The building code's side of the exit lights: the path out stays lit on emergency power for 90 minutes when the normal power fails.

The conductor from the service to the water pipe and the ground rods is sized from the service conductors, and #3/0 copper service conductors want a #4 copper grounding electrode conductor.

How long an emergency lighting source must carry its load with the normal power out, 90 minutes, which is why every exit sign and emergency light on a small job carries a battery.

A run of EMT may turn no more than 360° in total between pull points, the equal of four quarter bends, so a run with more needs a box or conduit body in it.

Where EMT is strapped, within 3 ft of every box or termination and at least every 10 ft along the run, which is the strap count on a takeoff.

The ground that rides with a feeder is sized from the breaker ahead of it, not from the phase wires, and a 200 A breaker wants a #6 copper ground.

The code limits what may share a branch circuit with equipment fastened in place, and the simple way to live within it is a circuit each, as the restaurant gives its dishwasher, pump and rooftop unit.

Where a commercial building's receptacles must be ground-fault protected, as the course counts them in a restaurant (restrooms, kitchens, food and beverage areas with a sink, within 6 ft of a sink), and the dishwasher's own GFCI.

When a kitchen hood's fire-suppression system fires, the electric power to the cooking equipment under it shuts off by itself, usually through a shunt-trip breaker wired to the system.

The foot of conduit the app adds to every vertical it writes, for the box entry and the bend that plan view never shows.

The heights above finished floor the app starts each device at — 18" receptacles, 44" GFCI at a counter, 48" switches, 78" panel top — so the Chain tool can write the vertical.

The energy code wants the lights in rooms people leave, restrooms, storage and break rooms among them, on sensors that turn them off by themselves, and every other area on a time switch.

A service or feeder is sized by the engineer's load calculation under Article 220 (for a new restaurant, the optional method of 220.88), never less than the calculated load, and in practice with room for what the owner adds later.

The largest breaker the code lets protect the small copper sizes, 15 A on #14, 20 A on #12 and 30 A on #10, which is why a 20 A circuit is #12.

The resistivity figure the estimator's single-phase voltage-drop formula uses — 12.9 for copper, 21.2 for aluminum, in ohm-circular-mils per foot.

The app flags a branch circuit whose drop to the farthest device exceeds 3% — the NEC's informational recommendation, not a requirement.

The clear space the code keeps in front of a panel someone may work on live, as the course teaches it at 120/208 V: 36 in deep from the panel's face, 30 in wide, 6 ft 6 in high.

A diffuser's neck is picked from the maker's sound and throw data and the push its flex needs; makers keep neck velocity under about 1,000 feet a minute, and the app's own neck suggestion puts up to 150 CFM on an 8 in neck and up to 300 on a 10 in, so the neck size is the flex and tap size on the bid.

The simplified gauge schedule the Duct tool picks metal with — by the duct's larger side or diameter and the system's pressure class — before you override it.

The estimating knobs the Duct Schedule starts with — seam and waste, the quick-bid fitting factor, the design friction rate and velocity cap the ductulator suggests sizes from, and the terminal allowance the static-path check adds at the end of the critical path.

Where a duct passes through a fire-resistance-rated wall, the code wants a listed fire damper at the penetration unless an exception removes it, so each crossing of a rated wall is a damper, an access door and a sleeve on the bid.

A commercial kitchen hood's exhaust duct is welded carbon steel of at least 16 gauge or stainless of at least 18 gauge, never the galvanized gauge schedule, so the Duct tool prices a grease run at that fixed gauge and its own sheet weight.

A commercial kitchen hood that exhausts air needs make-up air brought in to replace it, delivered while the hood runs and interlocked with its exhaust fan, so a hood on a plan means a second unit, its duct and its controls on the bid.

Occupied spaces get a code minimum of outdoor air, set by the kind of room, the people in it and its floor area (a dining room 7.5 CFM a person plus 0.18 a square foot); on a bid the question is whether the plan's supply already carries it or a separate unit does.

The cubic feet per minute per square foot the app assumes for a room type when no target is given — office 1.0, conference and break 1.5, storage 0.5.

Pounds per square foot of galvanized steel sheet at each gauge — the basis of every duct weight the schedule reports.

A drain gets a cleanout wherever a snake has to go in, at the turns of more than 45 degrees, at or just upstream of where the building drain meets the sewer, and at least every 100 feet along a horizontal run.

How many drainage fixture units a building drain or sewer may carry by size and slope; at 1/8 inch per foot a 3 inch sewer carries 36 and the course's 4 inch carries 180.

Horizontal waste pipe falls at least 1/4 inch per foot at 2-1/2 inch and smaller, 1/8 inch per foot at 3 to 6 inch, and 1/16 inch per foot at 8 inch and larger, except that pipe upstream of a grease interceptor falls at least 1/4 inch per foot at any size.

Every gas appliance has its own shutoff valve, in the same room and within 6 feet of it, upstream of its connector, so one appliance can come off the line without shutting the rest.

Each section of gas pipe is sized for the load it carries downstream, in Btu per hour, over the longest run from the meter to the farthest outlet, so like water it shrinks as it goes.

Kitchen, dish and bar fixtures that carry grease drain through a grease interceptor, and the restrooms join the sewer downstream of it, because the interceptor is for grease-laden waste only.

How far apart cast-iron pipe may be supported — 5 feet horizontal (10 feet where 10-foot lengths are installed), 15 feet vertical.

How far apart copper tube may be supported — 6 feet horizontal at 1-1/4 inch and smaller, 10 feet at 1-1/2 inch and larger, 10 feet vertical.

How far apart steel gas pipe may be supported under the fuel gas code, by size, 6 feet at 1/2 inch, 8 feet at 3/4 and 1 inch, 10 feet horizontal at 1-1/4 inch and larger, and vertical pipe at every floor.

How far apart PEX tubing may be supported — 32 inches horizontal at 1 inch and smaller, 48 inches at 1-1/4 inch and larger, 10 feet vertical.

How far apart PVC pipe may be supported — 4 feet horizontal, 10 feet vertical.

How far apart steel water and drainage pipe may be supported under the plumbing code, 12 feet horizontal and 15 feet vertical; steel gas pipe hangs closer, under the fuel gas code (plumb.hanger.gas-steel).

When a kitchen hood's fire suppression system discharges, the gas to every appliance under the hood shuts off automatically, and stays off until someone resets it by hand, so the gas line carries a valve the system trips.

A sink or machine that handles food drains through an air gap (an air break is allowed for a commercial dishwasher and a pot or dish sink) to a floor sink or other receptor, never straight into the waste pipe, so a sewer backup rises onto the floor and not into the food side.

How far a fixture's trap may sit from its vent along the drain, by trap size: 5 feet at 1-1/4 inch, 6 feet at 1-1/2 inch, 8 feet at 2 inch, 12 feet at 3 inch, 16 feet at 4 inch.

Every fixture trap holds a water seal 2 to 4 inches deep, and a trap that can dry out, a floor drain that sees no water for months, gets seal protection such as a trap primer.

A vent stack ends open above the roof, at a height the adopting jurisdiction sets (the model code leaves it blank), 7 feet up on a roof people use, and clear of air intakes, at least 10 feet away from a door, window or intake unless it rises 3 feet above the top of it.

The drainage system carries vent piping that lets air in and out, so no fixture trap sees more than 1 inch of water column of pressure difference and no seal siphons out when the fixture upstream drains.

The water service pipe from the main to the building is never smaller than 3/4 inch; the pipes past it are sized to the fixtures they serve.

The smallest pipe that may supply each fixture, 3/8 inch for a lavatory or a tank water closet up to 1 inch for a flush-valve water closet.

The inside diameter the velocity is computed from, per nominal size, for PEX (SDR 9), copper Type L, CPVC CTS and Schedule 40 galvanized steel.

The velocity the app sizes a water run to, 8 feet per second cold and 5 feet per second hot. Design practice under the IPC, which prints no velocity limit; the UPC caps copper tube at the same figures.

The design flow a load of water supply fixture units stands for, in gallons per minute, read off the code's demand table in its flush-tank and flush-valve columns.

The load a fixture puts on the water supply, in water supply fixture units (WSFU), cold and hot, by the private or public column and the kind of supply control.