DIRECTOR’S RULING
February 2006
97-DR-034
Page 1 of 3
DIELECTRIC-FILLED PAD-MOUNTED TRANSFORMERS
DISCUSSION
Currently, the Alberta Building Code 1997 contains provisions for clearances and construction
requirements for the protection of dielectric-filled pad-mounted electrical transformers. These
provisions are to be deleted from the next edition of the Alberta Building Code.
The provisions are Alberta-specific and were originally identical to the CSA C22.1-94,
“Canadian Electrical Code, Part 1” at the time of adoption. These requirements involve the
installation of a concrete or masonry block wall if a transformer is installed within 3 m of a
combustible surface of a building or within 6 m from any window, door or ventilation opening.
However, over time, the requirements in the Canadian Electrical Code were modified to amend
the requirements for protection provided the transformer was installed with certain properties
that would provide an equivalent level of safety. These properties included an internal currentlimiting fuse and a pressure relief device that comply with Rule 26-242(3) of the Canadian
Electrical Code.
As a result of this modification, a conflict was created between the Canadian Electrical Code and
the Alberta Building Code 1997.
ISSUE OF THIS RULING IS AUTHORIZED
UNDER ARTICLE 2.5.1.4. OF THE ALBERTA
BUILDING CODE 1997 BY THE DIRECTOR/
ADMINISTRATOR.
C.M. TYE
th
Alberta Municipal Affairs, 16 Floor, Commerce Place, 10155 – 102 Street, Edmonton, Alberta, Canada, T5J 4L4
Safety Codes Council, Suite 800, 10707 – 100 Avenue, Edmonton, Alberta, Canada, T5J 3M1
CODE REFERENCES
Alberta Building Code 1997:
3.6.2.8. Electrical Equipment Vaults
…
10) Where a liquid filled pad-mounted distribution transformer is located near a
building, it shall be located at not less than 3 m from any combustible surface and
not less than 6 m from any window, door or ventilation opening on the building.
11) Where clearances required in Sentence (9) are not practical, a solid concrete block
barrier not less than 200 mm thick or a reinforced concrete barrier not less than 150
mm thick, shall be erected between the building and the transformer. (See Appendix
A.)
12) When a transformer is installed below grade, the walls of an adjacent building shall
not have
a) combustible surfaces within a distance of 3 m, or
b) doors, vents, or openings adjacent to the grills in the sidewalk within a 6 m
distance of the transformer.
CSA C22.1-04, “Canadian Electrical Code, Part 1”
26-242 Outdoor Transformer Installations
…
(2) Dielectric liquid-filled pad-mounted distribution transformers shall be installed at
least 3 m from any combustible surface or material on a building and shall be
installed at least 6 m from any window, door, or ventilation inlet or outlet on a
building.
(3) Notwithstanding the requirements of Subrule (2), transformers that are protected by
an internal current-limiting fuse and are equipped with a pressure relief device shall
be permitted to be installed within the distances specified in Subrule (2), provided
that a working space around the transformer is at least:
a) 3 m on the access side of the transformer; and
b) On all other sides:
i)
1 m for three-phase transformers; and
ii)
0.6 m for single-phase transformers.
(4) Notwithstanding the requirements of Subrule (2) or (3),transformers shall be
permitted to be installed within the distances specified in Subrule (2) or (3), provided
a wall or barrier with noncombustible surfaces or material is constructed between the
transformer and that door, window, ventilation opening or combustible surface
2 / 97-DR-034
RULING
Dielectric-filled, pad-mounted electrical transformers are permitted to be installed with
clearances to combustibles and openings less than allowed by Sentence 3.6.2.8.(10) of the
Alberta Building Code 1997 without requiring the installation of reinforced concrete or masonry
block barricades as required by Sentence 3.6.2.8.(11), provided the installation conforms to the
requirements in Rule 26-242(3) of the Canadian Electrical Code (above).
Dielectric-filled, pad-mounted electrical transformers that are installed with clearances to
combustibles and openings less than allowed by Sentence 3.6.2.8.(10) of the Alberta Building
Code 1997 and do not conform to the requirements in Rule 26-242(3) of the Canadian Electrical
Code are still required to be protected in conformance with Sentence 3.6.2.8.(11).
3 / 97-DR-034