Chapter 23 EO test
When making a calculation for sizing a service or feeder, you must include 125 percent of the rating of the total connected fixed space heating load.
False
When Class 2 control wiring is used with central heating and air-conditioning equipment, what is the Code section that prohibits running Class 2 wiring in the same raceway as power conductors?
The Code section is NEC 725.136(A).
Explain how NEC 422.11 affects selection of branch circuit conductors for appliances, including electric furnaces.
The branch-circuit overcurrent protection must be sized according to the value indicated on the nameplate.
Explain what the NEC requires for a white wire used as an ungrounded (hot) conductor.
The white wire must be permanently reidentified at all points where connections are made or where it is visible and accessible.
Baseboard heating units can be controlled by ____.
both a and b
The NEC permits flexible cords to be used to supply appliances where ____.
both a and c
A receptacle is not required for one and two-family homes if the HVAC equipment is a(n) ____________________. These require minimal servicing.
evamporative cooler
LCDIs are devices that can sense ____________________ flowing between or from the cord conductors in room air conditioners
leakage current
A "reversing valve" inside a heat pump changes the direction of the flow of the system's
refrigerant
NEC 422.12 requires that central heating equipment, other than fixed electric space heating equipment, be ____.
supplied by a separate branch circuit
The article that covers cord-and-plug connected air conditioners is ____.
Article 440
The disconnect for motor-driven appliances having a motor of greater than ____ must be within sight of the appliance.
1/8 hp
When a flexible cord is used to supply a room air conditioner, the length of the flexible cord shall not exceed ____ for 120-volt units.
10 ft (3.0 m)
The disconnecting means and branch circuit conductors for an electric furnace shall be sized not less than ____ percent of the total nameplate load shown on the furnace.
125
The total load of an air conditioner shall not exceed ____ percent of the rating of a separate branch circuit.
80
The maximum current and voltage rating permitted by Code for a cord-and-plug connected air-conditioner is ______________________________ at 250 volts, single phase.
40 amperes
For ease of identification, NEC 424.35 requires that leads on heating cables be color-coded. Match the voltages below with the required colors. a. red b. blue c. orange d. yellow e. brown 120 volts 208 volts 240 volts 277 volts 480 volts
D B A E C
Match the following abbreviations used for current values associated with HVAC (heating, ventilating, and air-conditioning) equipment with their meanings. a. Maximum size overcurrent protection, fuse, or circuit breaker b. Equals at least 64.1% of the hermetic refrigerant motor-compressor's maximum continuous c. Minimum circuit ampacity requirement to determine the conductor size and switch rating MCA RLC MOP
CBA
List at least three advantages of electric heating as compared to other types of residential heating systems.
Electric heating has several advantages. It is flexible when baseboard heating or wall insert, fan-operated heaters are used, because each room can have its own thermostat; it is safer than heating with fuels; the system does not require storage space, tanks, or chimneys; it is quiet; it does not add or remove anything from the air so it is cleaner; it is considered to be healthier than fuel heating systems that remove oxygen from the air; there is a minimum of maintenance.
Although two-wire cables, such as Type NM and Type AC, contain one black and one white insulated conductor, they are frequently used in residential wiring to supply 240-volt electric baseboard heaters. Explain why this can be permitted.
NEC 200.7(C) allows the use of 2-wire cable for 240-volt loads provided the white conductor is permanently reidentified by paint, colored tape, or other effective means. This is necessary because it might be assumed that an unmarked white conductor is a grounded conductor having no voltage to ground. Actually, the white wire is connected to a "hot" phase in the panelboard and has 120 volts to ground on it. A person could be subjected to a lethal shock by touching this conductor and the grounded baseboard heater (or any other grounded object) at the same time. The white conductor must be permanently reidentified at the electric heater terminals and at the panels where these cables originate.
Explain why baseboard heating manufacturers do not permit their baseboard heaters to be installed below wall receptacle outlets.
The reasoning for generally not allowing electric baseboard heaters to be installed below receptacle outlets is the possible fire and shock hazard resulting when a cord hangs over and touches the heated electric baseboard unit. The insulation on the cord can melt from the heat.
