240 volt 3 phase grounded leg fusing

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es2doug

Member
Location
Jasper, IN
on a 240 volt 3 phase service with a grounded leg the utility meter man is advising not to put a fuse in the disconnect on the grounded leg but instead use a piece of copper tubing. He says if the fuse would blow you would lose the ground. Is this legal by code? Is it advisable?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Give the utility man a cigar :)

240.22 Grounded Conductor.
No overcurrent device shall be connected in series with any conductor that is intentionally grounded, unless one of the following two conditions is met:
(1) The overcurrent device opens all conductors of the circuit, including the grounded conductor, and is designed so that no pole can operate independently.
(2) Where required by 430.36 or 430.37 for motor overload protection.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Or look here for services:

VII. Service Equipment — Overcurrent Protection
230.90 Where Required.
Each ungrounded service conductor shall have overload protection.
(A) Ungrounded Conductor. Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor. A set of fuses shall be considered all the fuses required to protect all the ungrounded conductors of a circuit. Single-pole circuit breakers, grouped in accordance with 230.71(B), shall be considered as one protective device.
Exception No. 1: For motor-starting currents, ratings that comply with 430.52, 430.62, and 430.63 shall be permitted.
Exception No. 2: Fuses and circuit breakers with a rating or setting that complies with 240.4(B) or (C) and 240.6 shall be permitted.
Exception No. 3: Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.
Exception No. 4: Overload protection for fire pump supply conductors shall comply with 695.4(B)(1).
Exception No. 5: Overload protection for 120/240-volt, 3-wire, single-phase dwelling services shall be permitted in accordance with the requirements of 310.15(B)(6).
(B) Not in Grounded Conductor. No overcurrent device shall be inserted in a grounded service conductor except a circuit breaker that simultaneously opens all conductors of the circuit.
 
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