Box Fill Calculations, Building Distribution Systems, Switches & Receptacles

Unit substation ... A.K.A ... ?

"transformer load centers"

What are unit substations an assembly of?

- A PRIMARY SWITCH & FUSE OR CIRCUIT BREAKER - A STEP-DOWN TRANSFORMER - Meters - Controls - Buswork - A SECONDARY STEP-DOWN TRANSFORMER

What is a programmable switch also known as? What does it use to operate the switch?

- Also known as solid-state switch - Utilizes electronics or computer control to operate switch

What is a time-controlled switch? Is it in the new or is it old?

- Any switch whose operation is based on time - Antiquated technology

What are the three designs of panelboards?

- Bolt-on & plug in - Circuit breaker panelboard - Fusible panelboards --> Print out & look at the pictures!!!

What is conductor fill?

- Each conductor that originates outside the box and terminates or is spliced within the box shall be counted once. - Each conductor that passes through the box without splice or termination shall be counted once. The conductor fill shall be computed using Table 314.16(B). - A conductor, no part of which leaves the box, shall not be counted

What is device or equipment fill?

- For each yoke or strap containing one or more devices or equipment - A double volume allowance in accordance with Table 314.16(B) shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap

Explain the ratings of a bolt-on & plug in panelboard. How many volts? Amps? Will it have a main breaker?

- Maximum 240V - Up to 400 amps - May not have main breaker ("lugs in mains only")

Explain the ratings of a circuit breaker panelboard.

- Maximum 600V - Up to 1200 amps

How does the operator control the equipment within a unit substation?

- Push buttons - Insulated handles

What are the special switch types listed in the PPT?

- Remote-control switches - Automatic transfer switch - Time-controlled switch - Programmable switch

NEC guidelines state where equipment may be installed such as:

- Space requirements - Indoor or Outdoor locations

When determining box fill calculations where the wire is #4 AWG of larger, what are the two scenarios you need to be familiar with?

- Straight pulls - Angle or U pulls

What components comprise a building distribution system?

- Transformers - Motor control centers - Wire, cable, and busway - Wire management methods - Power distribution main equipment (switchboards, switchgear, unit substations) - Panelboards - Metering equipment - Combination service entrance devices (CSEDs) - Surge protection devices

Where are remote-control switches utilized? What are they also known as?

- Utilized on lighting circuits primarily - Also known as an electrically operated mechanically held contractor

What is equipment grounding conductor fill?

- Where one or more equipment bonding jumpers enter a box - A single volume allowance in accordance with Table 314.16(B) shall be made based on the largest equipment grounding conductor or equipment bonding jumper present in the box ** - Where an additional set of equipment rounding conductors, as permitted by 250.146(D), is present in the box, an additional volume allowance shall be made based on the largest equipment grounding conductor in the additional set **

What is clamp fill?

- Where one or more internal cable clamps, whether factory or field supplied, are present in the box - A single volume allowance in accordance with Table 314.1(B) shall be made based on the largest conductor present in the box - NO ALLOWANCE SHALL BE REQUIRED FOR A CABLE CONNECTOR WITH ITS CLAMPING MECHANISM OUTSIDE THE BOX

What is support fittings fill?

- Where one or more luminaire (fixture) studs or hickeys are present in the box - A single volume allowance in accordance with Table 314.16(B) shall be made for each type of fitting based on the largest conductor present in the box

When determining a box fill calculation for an angle or U pull, what is the process?

- Where splices or where angle or U pulls are made, the distance between each raceway entry inside the box and the opposite wall of the box shall not be less than SIX TIMES THE METRIC DESIGNATOR (TRADE SIZE) OF THE LARGEST RACEWAY IN A ROW. - This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box. - Each row shall be calculated individually, and the single row that provides the maximum distance shall be used

Explain the process of sizing #6 AWG or smaller.

- Wires, devices, and clamps all count as "volumes" which are essentially conductors - Add up all the "volumes" and the box can be sized using Table 314.16(A)

When sizing with boxes and dealing with #6 AWG or smaller, what are the 5 different "fills" that need to be considered?

1. Conductor fill 2. Clamp fill 3. Support fittings fill 4. Device or equipment fill 5. Equipment grounding conductor fill

What do switchboards & switchgears both do? What is the difference between the two?

A large, free-standing assembly of: - Switches - Fuses - Circuit breakers Provides switching & overcurrent protection to many sources at once May include meters & other devices DIFFERENCE: - Switchboards are < 600V - Switchgears are > 600V

What article and page number are essential to box sizing?

Article: 314.16 Page number: 176

A panelboard's open metal cabinet is often referred to as a ____.

Backbox

Fusible panelboards have similar ratings to what other type of panelboard?

Circuit breaker panelboard (CB)

Other components of a panelboard include?

Dead front and live front --> Is it exposed to "live" electrical equipment ...

Panelboards are generally the last ____ before utilization equipment.

Distribution point

In regards to unit substations and the circuit breaker that is a part of the system ... If a bayonet-type contact circuit breaker is included, it is generally mounted on a movable drawer (often described as a ____ type.

Drawout

What is an automatic transfer switch an essential part of?

Essential part of all emergency and stand-by power arrangements

When performing box fill calculations, if the sizes of the wires vary, what must be done?

If the sizes of the wires vary the volume of each conductor must be taken times the value given in Table 314.16(B)

When determining a box fill calculation for a straight pull, what is the process?

In straight pulls, the length of the box shall not be less than EIGHT TIMES THE METRIC DESIGNATOR (TRADE SIZE) OF THE LARGEST RACEWAY

What are panelboards comprised of?

Main bus & circuit breakers

In a unit substation, what is all the equipment housed within?

Metal enclosure

Where are Switchgear space requirements found?

NEC Article 110

Print out the different NEMA pictures of disconnects and pay attention especially to NEMA 7 & NEMA 4X.

NEMA 7 and NEMA 4X have enclosures to protect against spark in an explosive environment.

Start new Quizlet for Receptacles and Switches

Ok

Side note about service switches: They provide the main method of doing what for the building? How are they rated?

Provides the main method of disconnecting power to building Switches are rated by: - Volts, Amps - HP (if used to control a motor) - General or Heavy duty - NEMA Type: (1-Indoor; 3R-Outdoor [rain proof]; 4-Wash down; 12-Dust tight [industrial]; 7-hazardous)

Panelboards serve essentially the same function as a ?

Switchboard --> Except on a smaller scale

Box fill example calculations. Did the math in the notebook, go review that ya wanker!

Yeah nah yeah mate sounds bloody good

In addition to limiting the number of wires in a conduit, the number of wires in a ____ is also limited.

box

For boxes containing wire #4 AWG or larger, what determines the box size?

conduit size determines the box size

For boxes containing #6 AWG wire or smaller, what determines the box size?

volume of the conductors determines the box size