Subject:
24-meters & no exterior disconnect
Date:
Wed, 27 Jun 2001 14:17:13 -0800
From:
mike_stoianoff@dot.state.ak.us
Organization:
Dear Sir:
When I was in Guam in 1990, I saw an installation that looked like it should have been a violation of the NEC but had been approved by the electrical
inspector.
Installation Description:
Building type: 24 unit, three story residential apartment buildsing reinforced concrete block construction.
Applicable Electrical Code: NEC - 1988
Local Amendments to NEC: None
Utility: Guam Power Authority
AHJ: Guam Public Works
Service Voltage; 120/208-volt three-phase four-wire, 60 Hz.
Service amps - 600 consisting of two sets of 350kcmil conductors.
Service type: Aerial to building
Utility: transformers: three 50kVA pole mount with single fused primary disconnects (Not Ganged)
Grounding: Consisted of one 3/4-inch 10-foot ground rod connected to a #2/0 ground conductor in the wireway with a #6 AWG bare copper conductor. The
domestic water system was plastic so the grounding electrode system consisted only of the ground rod. Ground conductors toeach of the 24 panels #8 AWG.
Conductors: Copper, THW insulation.
The conductors were fed from the weather head down to a 12"x12" NEMA-3R wireway. Below the wireway were mounted 24 100-amp single-phase
three-wire five-jaw, meter sockets without disconnects. From each meter socket an 1 1/4 inch IMC conduit, with three #4 AWG and one #8 AWG ground
conductors ran down to the ground and under the building where it rose into a load center electric panel with an 100-amp main circuit breaker. The panel and
conduit were installed within the concrete block walls of the building.
Each meter socket were connected to two ungrounded and the neutral of one of the two sets of 350kcmil conductors and the ground conductor with tape and
insulating compound insulated split-bolt connectors so that the the load was evenly distributed (12 meters per set of 350kcmil conductors) and the 2/0 ground
conductor. The #8 to 2/0 ground connections were not insuated All tap connectors were less tha 10-feet long
The only way to kill power to the building was to open the fused cutouts on the primary side of the three 50kVA pole mounted transformers, enter each of the
24- apartments and turn off each panel, or as suggested by a fireman to pull each of the 24 meters one at a time.
The electrical inspector said the installation was not a violation because all conductors were outside of the building or encased in 2-inches of concrete, and no
the #6 AWG ground conductor from the ground rod was correct per the NEC even if it was tied to the 2/0 conductor in the wireway.
Question: Is there a code violation here?
Note: From an installation aspect the wiring was neatly laid out with all associated conductors secured with nylon straps. Each meter connection to the
350kcmil was labeled with nylon tie markers. Each meter was marked with an engraved apartment number. The #4 to 350kcmil taps appeared to be well
made and insulated. The contractor could afford to because at that time an electrician in Guam was paid about $8.00 / hour and if the worker was an H2
(foreign) worker many were lucky to be making $2.00 / hr after their expenses [food, housing, transportation, and miscellaneous fees] were deducted. Metal
conduits between the meter and the panels were grounded to the #8 on both ends.
Note: All conduits within the apartment were PVC and contained a ground conductor based on the largest circuit breaker trip rating, and all wiring devices
including switches were bonded.
Michael L. Stoianoff, P.E.
Stoianoff Technical Services
2901 Kimberlie Court
Anchorage, AK 99508
Tel: (907) 269-0653 (w)
PS sorry no photos of this apartment house. Except for the electrical service it looks very nice and well constructed.
Michael Stoianoff
Utility Engineer - Central Region
MIKE_STOIANOFF@DOT.STATE.AK.US
State of Alaska
P.O. Box 196900, MS 2525, 4111 Aviation Avenue ;Anchorage;AK;99519-6900;USA
Fax
907-269-0654
Work
907-269-0653
