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  1. Replies
    12$$
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    273

    It is a single phase general purpose transformer....

    It is a single phase general purpose transformer. The primary is 456VAC, and the secondary is 120-0-120. I have three circuits---two 120V circuits (Line to grounded center tap, and other line to...
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    12$$
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    273

    But the only circuits using the neutral are the...

    But the only circuits using the neutral are the 120V circuits right? The 240V circuit is not using the neutral at all?
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    12$$
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    273

    Transformer Over Current Protection

    I have a center tapped transformer with a 120-0-120 volt secondary. I have circuits on the 120-0, the 0-120, and the 120 to 120 taps. So, that equates to two 120V circuits and one 240V circuit.
    ...
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    1$$
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    139

    UL 489 AND UL 98

    Are UL 489 MCCB interchangeable with UL 98 switches as a service disconnect? All the information that I am finding is showing that they are..
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    4$$
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    171

    It looks like a valve, I believe it is called a...

    It looks like a valve, I believe it is called a "drain and breather", the one I am referring to is on top so it is a breather. These do not compromise the ability to contain an explosion?
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    4$$
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    171

    Relief Valve on EXP Enclosure

    I have an explosion proof enclosure with a relief valve located on top. Why would this enclosure have a relief valve?
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    4$$
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    313

    Thanks for the input. It is helpful.

    Thanks for the input. It is helpful.
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    4$$
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    313

    SLASH RATED BREAKERS

    If breakers that are rated 480Y/277 VAC are used at 50 Hz, does the slash rating have to derate to 400Y/230 VAC, or doe they keep their 480Y/277 VAC rating at 50Hz? Would it be OK to rate the...
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    10$$
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    449

    I do not understand why the openings are there. ...

    I do not understand why the openings are there. I know that when they are covered the sound is greatly attenuated. My knowledge of acoustics is lacking, but there has to be an electric signal...
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    10$$
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    449

    They are nema 3R, 4X, 12 with approved gasket.

    They are nema 3R, 4X, 12 with approved gasket.
  11. Replies
    10$$
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    449

    Alarm Horn in Type X Purge Enclosure

    For an Type X Purged enclosure that will be going inside a Class I Div 1 location, would an alarm annunciator (please see link below) be allowed to be installed through the panel wall? I know the...
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    6$$
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    389

    Thanks for the suggestion. The purged air is...

    Thanks for the suggestion. The purged air is actually entering the larger enclosure, so the pressure sensor located (without obstruction) in the smaller enclosure should provide the worst case...
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    3$$
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    239

    Thanks for the information, it is helpful.

    Thanks for the information, it is helpful.
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    3$$
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    239

    EMC Requirements in the US

    If a piece of equipment is an "unintentional radiator" or electronic emissions, does it automatically fall into 47CFR part 15? If not, is there another FCC regulation?

    My confusion is what...
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    6$$
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    389

    The pressure switch is inside the purged...

    The pressure switch is inside the purged enclosure and is not XP. For the initial startup the box is not purged, as the purge needs to begin the process of pushing the 4 volumes of air outside of...
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    6$$
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    389

    Pressure Switch for Type X Purge

    A piece of equipment has two sections, a 42" X 36" X 16" Hoffman enclosure, and a secondary section that is approximately 7 times larger than the Hoffman enclosure.

    There is an opening between the...
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    8$$
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    492

    The UL handler for the equipment said that as far...

    The UL handler for the equipment said that as far as he is concerned, according to the standard the machine is listed under, that all that needs to be on the nameplate is Voltage and FLA. The...
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    8$$
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    492

    I just need help explaining to marketing and...

    I just need help explaining to marketing and sales level folks that specifying a true MOCP should not affect anything...that the only numbers that truly matter are the MCA and the FLA.

    If I am...
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    8$$
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    492

    Thanks again. I know some people that think the...

    Thanks again. I know some people that think the OCPD that is specified for the equipment in some way correlates to the service size the user of the equipment has to use. I believe this is...
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    8$$
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    492

    That is definitely helpful. Regarding the MOP,...

    That is definitely helpful. Regarding the MOP, does it have to be the absolute MOP, or can it be anything less than or equal to the MOP? The MOP seems to be more straight forward than the Minimum...
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    8$$
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    492

    MCA and MOP From Article 440

    Article 440.4(B) requires me to list the MCA and MOP on the equipment nameplate. Do I have to list the EXACT MCA, or am I able to use a larger number. For example, if my MCA calculates out to...
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    6$$
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    413

    I can get some warm and fuzzy assurance from my...

    I can get some warm and fuzzy assurance from my NRTL inspector, but I still have to comply with NFPA 70. My initial concern is that whatever I use allows me to size my wiring correctly.

    A general...
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    6$$
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    413

    Thanks for the information. I do not understand...

    Thanks for the information. I do not understand the part about not being able to use the nameplate to size the ampacity of the conductors feeding the machine. What is the end user supposed to use...
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    6$$
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    413

    Machine's FLA Derived From..

    I am interested to know if using tested Full Load Amps is generally acceptable.

    Do you have to use all simultaneously active components RATED amps, or are you actually able to use the maximum...
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    3$$
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    239

    It does not. So as a minimum requirement it is...

    It does not. So as a minimum requirement it is not, but as good design practice I guess it is giving anyone servicing the machine a heads up regarding what voltages are inside the enclosure...
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