Questions and Answers
A signal circuit means any electrical circuit that controls any other circuit through a relay or an equivalent device.
False
Section 16 covers Class 1 and Class 2 circuits and this includes communication circuits.
False
The doorbell circuit installed in a dwelling unit is considered to be a Class 2 circuit when supplied by a 120/24 V, 40 VA Class 2 transformer.
True
An extra-low voltage power circuit may be wired with copper conductors smaller than No. 14 AWG.
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Which of the following would be classified as an Extra-Low-Voltage power circuit?
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All Class 1 circuits that extend aerially beyond a building must comply with Rules 12-300 to 12-318.
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Conductors for use in a Class 2 circuit shall be of copper.
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A 24 V gas valve-thermostat circuit is an example of a Class 2 low-energy power circuit.
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Class 1 circuits shall not be run in the same cable with communication circuits.
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The control circuit of a forced air furnace, which meets the limitations of a Class 2 circuit, may be wired with copper conductors as small as #19 AWG if the conductors form part of a cable.
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A 'circuit' is generally considered to be that portion of a wiring installation which is connected to the load side terminals of an AC or DC system and forms a complete path or paths through which electrical current is intended to flow, including utilization equipment.
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A primary battery for a Class 2 circuit is allowed to be rechargeable.
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In order for a circuit to be classified as a Class 1 Extra Low-voltage Power Circuit it must be supplied from a transformer or other device restricted in its rated output to 1000 VA at 30 V.
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Conductors of Class 2 circuits shall be separated by at least 30 mm from conductors of electric lighting circuits, operating at 300V or less.
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It is permissible to supply a Class 1 extra-low-voltage power circuit from a transformer with an output of 60 V, 500 VA.
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Conductors of Class 2 circuits shall be separated by at least 50 mm from insulated conductors of non-metallic sheathed cable supplying electric lighting, power or Class 1 circuits operating at 300 V or less.
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The thermostat control circuit of a forced-air furnace fed from a 120/24 V 40VA transformer is usually classified as a Class 1, extra-low voltage power circuit.
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Class 1 Extra Low Voltage Power circuits are circuits which are neither remote control nor signal circuits but which operate at not more than 30 V and where the current is not limited in accordance with 16-200.
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Section 16 applies to all circuits, including those that form part of a device.
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A Class 2 low energy power circuit may be wired with copper conductors smaller than No. 14 AWG.
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Study Notes
Class 1 and Class 2 Circuits Overview
- Signal circuits control other circuits using relays or equivalent devices, but this is not classified as a signal circuit under relevant standards.
- Section 16 pertains to Class 1 and Class 2 circuits, including communication circuits, but does not cover communication circuits specifically.
- A doorbell circuit running on 120/24 V with a 40 VA Class 2 transformer qualifies as a Class 2 circuit.
Conductors and Voltage Specifications
- Extra-low voltage power circuits can utilize copper conductors smaller than No. 14 AWG.
- A 30V circuit rated at 500 VA is classified as an Extra-Low-Voltage power circuit.
- Class 1 circuits extending aerially must adhere to specific rules from 12-300 to 12-318.
Class 2 Circuit Characteristics
- All conductors in a Class 2 circuit must be made of copper.
- A 24 V gas valve-thermostat circuit illustrates a low-energy Class 2 power circuit.
- Class 1 circuits cannot share cables with communication circuits.
Wiring and Circuit Definitions
- Control circuits for forced air furnaces can use copper conductors as small as #19 AWG.
- A circuit is defined as the wiring installation connected to the load side of an AC or DC system, completing a path for electrical current flow.
- Primary batteries used in Class 2 circuits cannot be rechargeable.
Class 1 Extra Low-Voltage Power Circuits
- To classify as a Class 1 Extra Low-Voltage Power Circuit, it must be supplied by a transformer limited to 1000 VA at 30 V.
- Conductors of Class 2 circuits must maintain a separation of at least 30 mm from electric lighting conductors operating at 300 V or less.
- It is not permissible to supply a Class 1 Extra Low-Voltage power circuit from a transformer outputting 60 V, 500 VA.
Compliance and Separation Rules
- Class 2 circuit conductors must be spaced at least 50 mm from insulated conductors in non-metallic sheathed cables supplying various electrical circuits.
- The thermostat control circuit for a furnace supplied by a specific transformer is not identified as a Class 1 extra-low voltage circuit.
- Class 1 Extra Low Voltage Power circuits do not encompass remote control or signal circuits but operate at a maximum of 30 V without current restrictions in accordance with existing standards.
Section Applicability
- Section 16 does not pertain to all circuits, specifically excluding those that form parts of devices.
- Copper conductors in Class 2 low energy power circuits can indeed be smaller than No. 14 AWG.
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Description
Explore the fundamentals of Class 1 and Class 2 circuits in this quiz. Understand the specifications for signal circuits, voltage requirements, and conductor classifications. Test your knowledge on extra-low voltage power circuits and their characteristics.
