INSPECTINGTHE

SUBPANELSUBPANEL1

Inspecting a subpanel is verylsimilar to inspecting a service

panel with the exceptions ofpanel, with the exceptions ofa few interior redred flagsflagsa few interior redred flagsflags.

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SubpanelSubpanelSubpanelSubpanel

1. Thehotwires,redandblack,areeachconnectedtoalugonth b bthebusbars.

2. Theneutralwire(whitewire)areconnectedto)theneutralbusbar.

3. Theground(bare)wireis connected to theisconnectedtothegroundbus.

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REMEMBERTHISRULEREMEMBERTHISRULE::DO NOT GROUND THE NEUTRAL AFTER THE MAIN DISCONNECTDONOTGROUNDTHENEUTRALAFTERTHEMAINDISCONNECT.

THENEUTRALMAYNOTBEUSEDTOACCOMPLISHGROUNDING.

COMMONSUBPANELFAULTSCOMMONSUBPANELFAULTS:: BONDINGJUMPERCONNECTEDTOTHENEUTRALBARBONDINGJUMPERCONNECTEDTOTHENEUTRALBAR

GROUNDS AND NEUTRALS SHARE THE SAME BUSGROUNDS AND NEUTRALS SHARE THE SAME BUS BARBARGROUNDSANDNEUTRALSSHARETHESAMEBUSGROUNDSANDNEUTRALSSHARETHESAMEBUSBARBAR

NeutralwiresnotisolatedfromthesubpanelNeutralwiresnotisolatedfromthesubpanel

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6SubpanelSubpanel

Remember: In a panelor a subpanel eachor a subpanel, eachscrew on the neutralbus bar can only holdbus bar can only holdone wire.

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NEUTRALBUSBARNEUTRALBUSBAR

When this panel is used as a sub panelWhen this panel is used as a subpanel,the neutral (white) wires areconnected here.

Note the Sshaped piece of metalsecured by a green screw. This is calleda "bonding strap" and is used toconnect (or "bond") the neutral bus toground (the metal case) only when thepanel is being used as a main panel.

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Ifthebondingstrapisused,thestrap is inserted into one of thestrapisinsertedintooneoftheneutralterminalpoints.

BUTWECAN'TDOTHIS...Ifthepanelisusedasasubpanel.

Th t l d d i MUST bTheneutralandgroundwiresMUSTbeconnectedtogether,butONLY atthemainpanel.

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SafetyHazardSafetyHazardf yf y

11SUBPANELWITHBONDINGSTRAPSUBPANELWITHBONDINGSTRAPNOTREMOVEDNOTREMOVED

Why not connect the neutralWhynotconnecttheneutralandgroundwiresinasubpanel?

Because if a neutral wire became disconnected, the return path for electric current could be, palong a ground wire. While that itself may not be a hazard, if that ground wire also becamedisconnected somewhere, parts of the ground system could be energized. That's not EVERsupposed to happen.

The neutral wire is essentially a "lowrisk" return path for the electric current in that branchof the system. All of the neutral wires all have the same electrical potential... nothing. Atleast, no potential compared to ground. There is, of course, 120 volts of potential differencebetween a neutral wire and any hot wire in the residential system.

If you touched the metal part of a live neutral wire you should not receive a shock. (But don'ttry it!) By tying the neutral to ground at one point half of the conductors (in a typical 120try it!) By tying the neutral to ground at one point, half of the conductors (in a typical 120volt circuit) have no dangerous electrical potential. Of course, the hot wires are stilldangerous.

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OLDCERAMICFUSEBOXESAREOBSOLETEANDPOSEARISKOFSHOCKORC OC O C S O OS C C CO C S

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ELECTROCUTIONBECAUSEOFTHEEXPOSEDELECTRICALCONTACTS.

Old ceramic fuse blocks are a safety hazardsafety hazard

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Oldceramicfuseblocksareasafetyhazardsafetyhazard.

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Oldceramicfuseblocksareasafetyhazard.

EQUIPMENT GROUNDING CONDUCTORS IN SUBPANELS MUSTBE ON THEIR OWN GROUND BAR.

IT IS NOT ACCEPTABLE TO SIMPLY BUNDLE THEM TOGETHERAND RUN ONE CONDUCTOR TO THE PANEL ENCLOSURE.

THE SUBPANEL NEUTRAL MUST BE ISOLATED AND MAY NOTBE USED FOR GROUNDING.

THE GROUND BAR MUST BE BONDED.

ALL METAL ENCLOSURES CONTAINING LIVE ELECTRICALWIRING, INCLUDING SUBPANELS, MUST BE GROUNDED SO THEYREMAIN AT ZERO VOLTAGE POTENTIAL TO GROUND AND SOREMAIN AT ZERO VOLTAGE POTENTIAL TO GROUND, AND SOTHEY HAVE AN EMERGENCY GROUNDING CONNECTION TOCLEAR POSSIBLE FAULTS.

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REPORTREPORT

17SUBPANEL

SUBPANELSUBPANELSUBPANELSUBPANELIn a subpanel, the white

l d h ineutral and the equipmentgrounds must not bebonded together.

The neutral MUST beisolated from contactingisolated from contactingthe metal enclosure andany equipment grounds.

XBonding these conductorsis hazardous as it creates

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another path for current.

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Whatkindofpanelisthisandhowmanythingsarewrong?

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SubpanelsSubpanelsSubpanelsSubpanels

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