Originally Posted By: jtedesco
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http://www.nachi.org/bbsystem/viewtopic.php?t=5227
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Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: jtedesco
This post was automatically imported from our archived forum.
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Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: dbozek
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You cannot help men permanently by doing for them what they should and could do for themselves. Abraham Lincoln
Originally Posted By: jtedesco
This post was automatically imported from our archived forum.
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Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: dbozek
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You cannot help men permanently by doing for them what they should and could do for themselves. Abraham Lincoln
Originally Posted By: jpeck
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jtedesco wrote: |
It is better to see that thermostat wiring run in a separate cable or conduit, or wrapped around the cable or conduit that will supply the unit. |
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Jerry Peck
South Florida
Originally Posted By: jtedesco
This post was automatically imported from our archived forum.
Quote: |
Not wrapped around the cable or conduit, that will act as a choke coil should there be a ground fault or high surge in the thermostat cable. |
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Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: Greg Fretwell
This post was automatically imported from our archived forum.
Originally Posted By: MarK Heller
This post was automatically imported from our archived forum.
Quote: |
250.134 Equipment Fastened in Place or Connected by Permanent Wiring Methods (Fixed) ? Grounding.
Unless grounded by connection to the grounded circuit conductor as permitted by 250.32, 250.140, and 250.142, non?current-carrying metal parts of equipment, raceways, and other enclosures, if grounded, shall be grounded by one of the following methods. Section 250.134 eliminates any conflict between 250.134(A), which requires an equipment grounding conductor to be used for equipment grounding, and 250.32, 250.140, and 250.142, which permit the grounded circuit conductor to be used for equipment grounding if certain specified conditions are met. (A) Equipment Grounding Conductor Types. By any of the equipment grounding conductors permitted by 250.118. (B) With Circuit Conductors. By an equipment grounding conductor contained within the same raceway, cable, or otherwise run with the circuit conductors. One of the functions of an equipment grounding conductor is to provide a low-impedance ground-fault path between a ground fault and the electrical source. This path allows the overcurrent protective device to actuate, interrupting the current. To keep the impedance at a minimum, it is necessary to run the equipment grounding conductor within the same raceway or cable as the circuit conductor(s). This practice allows the magnetic field developed by the circuit conductor and the equipment grounding conductor to cancel, reducing their impedance. Magnetic flux strength is inversely proportional to the square of the distance between the two conductors. By placing an equipment grounding conductor away from the conductor delivering the fault current, the magnetic flux cancellation decreases. This increases the impedance of the fault path and delays operation of the protective device. |
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300.11(B) Raceways Used as Means of Support. Raceways shall only be used as a means of support for other raceways, cables, or nonelectric equipment under the following conditions:
(1) Where the raceway or means of support is identified for the purpose; or (2) Where the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 circuit conductors or cables that are solely for the purpose of connection to the equipment control circuits; or (3) Where the raceway is used to support boxes or conduit bodies in accordance with 314.23 or to support luminaires (fixtures) in accordance with 410.16(F) The purpose of 300.11(B)(3) is to prevent cables from being attached to the exterior of a raceway. Electrical, telephone, and computer cables wrapped around a raceway can prevent dissipation of heat from the raceway and affect the temperature of the conductors therein. This section also prohibits the use of a raceway as a means of support for nonelectric equipment, such as suspended ceilings, water pipes, nonelectric signs, and the like, which could cause a mechanical failure of the raceway. However, 300.11(B)(2) does allow the installation of Class 2 thermostat conductors for a boiler or air conditioner unit to be supported by the conduit supplying power to the unit... |