This article series lists significant Electrical System defects, definitions, and home inspection education topics.

Fused Neutral Bus or Neutral Wire Hazards in the Electrical Panel

In the fuse panel of older homes like the panel shown above, we sometimes find that both the hot and neutral wires were independently-fused.

You'll recognize this condition by noticing that the white wires or neutral wires of one or more circuits in the fuse panel are fused [yellow arrows in our photo].

Watch out: it is unsafe to fuse the neutral wire in addition to or rather than the "hot" wire in an electrical circuit because an over-current may blow the "neutral" fuse while leaving the circuit's hot or feed side wire electrically live. The result of interrupting a circuit only on its neutral or "return" path could be a fire, shock, or even death by electrocution.

This unsafe condition could occur in the fuse panel shown above because the hot and neutral fuses are physically separate, independent devices. It is at least possible that an overcurrent might blow the neutral fuse first or blow it only, leaving the hot wire energized.

Photo: fused neutrals on each circuit in the main fuse panel of a1925 home, courtesy of home inspector Lawrence Transue.

[Click to enlarge any image]

About this panel, Mr. Transue offers more important detail that is not quite obvious in the photo:

The neutral fuses [in this Easton PA home were eliminated. They painted them black. So, actually safer then when it was made. This stately mansion had all the modern conveniences. for 1925.

So when is fusing the neutral "safe"?

The only circumstance in which fusing the neutral wire is safe is that in which the circuit protection assures that in response to an overcurrent both the hot and neutral wires are interrupted at the same time.

Despite the practice of fusing neutral wires, at least in the U.S. even in the 1920's this was considered an improper and unsafe detail that violated electrical code.

Grounded neutral conductors in three-wire systems shall be arranged without automatic circuit-breakers or fuses interrupting their continuity, unless the circuit breaker opens all conductors of the circuit with one operation.

In two-wire branches from three-wire circuits the conductor connected to the neutral is not for the purpose of this rule considered a grounded conductor. - 1920 National Electrical Safety Code By United States National Bureau of Standards [screen shot above] - https://books.google.com found by searching for ""National Electrical Safety Code", issue 2 "grounded neutral conductors""

Also see

• CASE HISTORY: LOSS of NEUTRAL SHOCKS HOMEOWNER
• ELECTRIC POWER LOSS / FLICKERING LIGHTS
• Lawrence Transue is a Pennsylvania building scientist and consultant, a certified ASHI home inspector, a Licensed Pesticide Applicator, a BPI Building Analyst & Envelope Professional, with 18 Years of Home Inspection Experience. He can be reached by Telephone: 610.417.0763, by Email: lawrence@lawrencetransue.com as well as at his WEBSITE and at FACEBOOK.
  
  Mr. Transue is a frequent contributor to InspectAPedia.com.

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