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Thread: Panels suitable for 240/120 Delta high leg service

  1. #1
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    Panels suitable for 240/120 Delta high leg service

    Hello,

    I'm looking at documentation for a SqD I-Line panel and I'm seeing that a 240/120V Delta 3ph 4 wire high leg service is not listed under the list of service types ?

    Any reason for that ? See attached .pdf

    Square D I-Line.pdf

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    It's a quirk of how Sq. D I-Line panels are marketed. In the instruction manuals for I-Line they do say that the panel is suitable for this use, you just can't buy them that way out of the catalog. What you see in the catalog are what they refer to as "merchandised" panels, meaning what distributors can stock on the shelves for fulfillment from local stock. Because the use of the panel on a 3-phase / 4-wire , 240 /120 V Delta system requires some special markings, Sq. D only sells them as "factory assembled" panels, I think because people were messing up the connections and labels in the field.

    Talk to your local Sq. D distributor, they should know this and if not, find a better one.
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    This is somewhat of mystery to me as the marking indicates suitability on a corner grounded system. If it is rated for that then certainly it would be OK on a center tapped delta system. But maybe jaref has a point and this is a marketing thing with Square D.

    In any event, the following excerpt from the UL Panelboard Marking and Application Guide shows it to be fine:

    6. VOLTAGE RATINGThe basic voltage rating markings must be visible without disturbing wiring and other interior parts.A panelboard designed and intended for use only on a supply circuit involving two differentpotentials (for example, 120/240 volts, three-wire; or 208Y/120 volts, three-phase, four-wire) is somarked.In many cases, however, the basic voltage rating marking — for example, 480 volts, 3-phase —indicates that the panelboard is suitable for various supply systems (such as 208Y/120 volts,3-phase, 4-wire; 120/ 240 volts, 3-wire; 240/120 volts,3-phase, 4wire delta, etc.). These voltageratings may be shown on a wiring diagram affixed to the panelboard or its enclosure.

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    I line panels accept a wide range of breakers compared to "miniature" breaker panels. I could be wrong but I believe the bus assemblies are all 600 volt rated in this series.

    If it can accept a 480 volt or even a 600 volt breaker then it should be fine on a 240 corner ground or high leg delta.

    You may find breakers that are not suitable for corner ground or the high leg however.
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    I've looked at some I-Line panelboards and have seen that the label says Max Voltage, not System Voltage.
    Is it safe to assume that so as long as the voltage on the label is equal to or greater than the voltage of the service then the panelboard is suitable ?

    Would a 240V Delta corner grounded, a 240V Delta center grounded, or a 208Y service impart a different set of stresses on a panelboard and therefore make 240V Delta labeled panelboard unsuitable for a 208Y service ?

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    Quote Originally Posted by conmgt View Post
    I've looked at some I-Line panelboards and have seen that the label says Max Voltage, not System Voltage.
    Is it safe to assume that so as long as the voltage on the label is equal to or greater than the voltage of the service then the panelboard is suitable ?

    Would a 240V Delta corner grounded, a 240V Delta center grounded, or a 208Y service impart a different set of stresses on a panelboard and therefore make 240V Delta labeled panelboard unsuitable for a 208Y service ?
    Short circuit current ratings very well may be different for different voltages, but insulation value wise - if the bus insulators are designed for 600 volts, anything less is fine.
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    Quote Originally Posted by Jraef View Post
    It's a quirk of how Sq. D I-Line panels are marketed. In the instruction manuals for I-Line they do say that the panel is suitable for this use, you just can't buy them that way out of the catalog.
    Almost.
    I agree it is probably a marketing issue.

    Official answers, according to the Schneider FAQ website:

    Issue:
    Why can't one order a merchandised I-line, 120/240V, mid point ground, 3 phase, 4 wire panel?
    Resolution:

    The selectors apparently lead to factory assembled panels . However, the instruction book with an RTI I-Line says this panel can be used on a high leg system so it is acceptable for this use.

    Issue:

    Is it permissible to use a 3 phase RTI (ready to install)I-Line panel for a 120/240v, 3ph-4w high-leg delta system?
    Resolution:
    A standard 3 phase I-Line panel can be used but the user must abide by the notations provided in the Information Manual that is supplied with the panel. These notations state that ``When wired for Delta Systems, phases A and C must be 120V to neutral, Phase B 208V to neutral. Connect only circuit breakers rated 240V AC minimum, NOT 120V or 120/240V, to phase B``. No 1p breakers can be put on the B phase .
    Just because you can, doesn't mean you should.

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    Excellent !

    We are getting somewhere. I'm going to look for an I-Line instruction book.

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    From page 2 of this catalog: https://download.schneider-electric.com/files?p_enDocType=Catalog&p_File_Id=7709720344&p_F ile_Name=2110CT9701.pdf&p_Reference=2110CT9701

    I-Line circuit breaker panelboards can be used on the following
    system voltages:
    • 120/240 VAC; 1-phase, 3-wire
    • 240 VAC; 1-phase, 2-wire
    • 240 VAC; 3-phase, 3-wire
    • 240 VAC Ground, B-phase; 3-phase, 3-wire
    • 208Y/120 VAC; 3-phase, 4-wire
    • 480Y/277 VAC; 3-phase, 4-wire
    • 480 VAC; 3-phase, 3-wire
    • 600Y/347 VAC; 3-phase, 4-wire
    • 600 VAC; 3-phase, 3-wire
    • 125/250 VDC; 3-wire
    • 250 VDC; 2-wire

    As I mentioned earlier, not all breakers are rated for the maximum panel voltage - so the key is selecting right breakers for your application, otherwise looks like they work on almost any system imaginable that is 600 volts AC or under, or 250 VDC.
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    They do not mention two phase. They should be OK for two phase, 3-wire, but not for a full quadrature two phase five wire just because they do not have enough busses.

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