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  1. #1
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    Default Low Voltage routed with High Voltage

    When you see the low voltage control wiring for an HVAC system routed through the furnace cabinet in the same knockout opening with the high voltage cable (same clamp), is this considered a defect? If so, could someone provide me the code that would support this.

    Thank,s
    Rob

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  2. #2
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    Default Re: Low Voltage routed with High Voltage

    Quote Originally Posted by RobertSmith View Post
    When you see the low voltage control wiring for an HVAC system routed through the furnace cabinet in the same knockout opening with the high voltage cable (same clamp), is this considered a defect? If so, could someone provide me the code that would support this.

    Thank,s
    Rob
    That would fall under a manufacturers installation requirement and not a code. I don't see why it would be a problem.

    Now finding low voltage in an high voltage electrical panel is different issue.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  3. #3
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    Default Re: Low Voltage routed with High Voltage

    is this considered a defect?


    Yes

    If so, could someone provide me the code that would support this.



    E4204.1 Separation from other conductors.
    In cables, compartments,
    enclosures, outlet boxes, device boxes, and raceways,
    conductors of Class 2 circuits shall not be placed in any
    cable, compartment, enclosure, outlet box, device box, race-
    way, or similar fitting with conductors of electric light, power,
    Class 1 and nonpower-limited fire alarm circuits.
    Exceptions:
    1. Where the conductors of the electric light, power,
    Class 1 and nonpower-limited fire alarm circuits are
    separated by a barrier from the Class 2 circuits. In
    enclosures, Class 2 circuits shall be permitted to be
    installed in a raceway within the enclosure to separate
    them from Class 1, electric light, power and
    nonpower-limited fire alarm circuits.
    2. Class 2 conductors in compartments, enclosures,
    device boxes, outlet boxes and similar fittings where
    electric light, power, Class 1 or nonpower-limited fire
    alarm circuit conductors are introduced solely to connect
    to the equipment connected to the Class 2 circuits.
    The electric light, power, Class 1 and
    nonpower-limited fire alarm circuit conductors shall
    be routed to maintain a minimum of


    1/4 inch (6.4 mm)
    separation from the conductors and cables of the
    Class 2 circuits; or the electric light power, Class 1
    and nonpower-limited fire alarm circuit conductors
    operate at 150 volts or less to ground and the Class 2
    circuits are installed using Types CL3, CL3R, or
    CL3P or permitted substitute cables, and provided
    that these Class 3 cable conductors extending beyond
    their jacket are separated by a minimum of

    1/4 inch
    (6.4 mm) or by a nonconductive sleeve or
    nonconductive barrier from all other conductors.

    E4204.2 Other applications.
    Conductors of Class 2 circuits
    shall be separated by not less than 2 inches (51 mm) from conductors
    of any electric light, power, Class 1 or nonpower-limited
    fire alarm circuits except where one of the following
    conditions is met:
    1. All of the electric light, power, Class 1 and
    nonpower-limited fire alarm circuit conductors are in
    raceways or in metal-sheathed, metal-clad, nonmetallic-
    sheathed or Type UF cables.
    2. All of the Class 2 circuit conductors are in raceways or in
    metal-sheathed, metal-clad, nonmetallic-sheathed or
    Type UF cables.



    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  4. #4
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    Default Re: Low Voltage routed with High Voltage

    E4204.1 Separation from other conductors.

    In cables, compartments,

    enclosures, outlet boxes, device boxes, and raceways,
    conductors of Class 2 circuits shall not be placed in any
    cable, compartment, enclosure, outlet box, device box, race-

    way, or similar fitting with conductors of electric light, power
    Then how do you place the thermostat wire into the unit if it can not be placed in the compartment or enclosure?

    This is one of those code items that just does not make much sense. Or I should say it does not make much sense to me. I still say the manufacturer would be the one to go to on this and not the code.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

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    Default Re: Low Voltage routed with High Voltage

    Then how do you place the thermostat wire into the unit if it can not be placed in the compartment or enclosure?

    Scott
    The OP's question was about using "same knockout opening ". It is not allowed to feed the LV cable and the A/C througe the same knockout.
    But the cables are allowed to share a cabiner/ enclosure in some cases.
    Note the exceptions.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  6. #6
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    Default Re: Low Voltage routed with High Voltage

    "High Voltage" is not permitted in a residence, & 600V and less is considered low voltage, it would be better to refer to low voltage & line voltage conductors mixed together.


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    Default Re: Low Voltage routed with High Voltage

    "High Voltage" is not permitted in a residence, & 600V and less is considered low voltage, it would be better to refer to low voltage & line voltage conductors mixed together.

    You are correct. Which is why I refered to it as " A/C", not high voltage.
    It is somewhat confusing though.
    I have a "Low Voltage" license. It allows me to work on 30 volts or less, but phone line voltage can be as high as 90 volts, yet I can also work on them. Go figure.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  8. #8
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    Default Re: Low Voltage routed with High Voltage

    Thanks everyone.

    I'm trying to convince a city inspector that 120v can not be routed through the same knockout opening with the low voltage control wiring.

    Rob


  9. #9
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    Default Re: Low Voltage routed with High Voltage

    Quote Originally Posted by RobertSmith View Post
    Thanks everyone.

    I'm trying to convince a city inspector that 120v can not be routed through the same knockout opening with the low voltage control wiring.

    Rob

    Tell him/her to look at the installation instructions - the manufacturer will show separate entries for them too - which puts it to 110.3(B) as a back up for those who do not know or understand the main code and reasons.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  10. #10
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    Default Re: Low Voltage routed with High Voltage

    I often see 2 or more conductor thermo wire routed neatly thru sealtite from a j-box above into a switch and recpectacle mounted on the cabinet. From there it goes into it's seperate k/o, so what's the difference? it sure looks neater.


  11. #11
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    Default Re: Low Voltage routed with High Voltage

    (bold red is mine)
    Quote Originally Posted by Mike Locurcio View Post
    I often see 2 or more conductor thermo wire routed neatly thru sealtite from a j-box above into a switch and recpectacle mounted on the cabinet. From there it goes into it's seperate k/o, so what's the difference? it sure looks neater.
    And it is just as likely to cause a potential problem as having them both enter through the same opening, and NEITHER is any good, and BOTH are not acceptable.

    What do you think would happen to a standard low voltage thermostat when energized with 120 volt to ground, or, worse yet, 240 volts between two of the low voltage cable conductors? Think it would survive in one non-smoldering, non-melted, still-on-the-wall piece?

    What about the person who happened to be turning it on when that happened?

    I simply do not get why some people will spend so much time and energy trying to defend something which is so wrong????

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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