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Chapter 2
Electric Service Handbook 2022 — Non-residential Projects
Transformer locations
PSE will install padmount transformers using the clearances listed in Table 4 and shown
in Figures 10 and 11.
Clearances between padmount transformers and structures must be measured from
the metal portion of the transformer closest to the building or structure, including any
building overhangs, within the following clearances:
Table 4 Clearances for padmount transformers
Feature Clearance distance
Combustible walls or roof (including stucco).10 feet (3 feet from a
combustible wall if using
a reduced flammability
transformer). See Figure 10.
Noncombustible walls (including brick, concrete,
steel, and stone), provided the side of the
transformer facing the wall does not have doors.
Materials that pass UBC Standard 2-1 or ASTM
E136-79 are considered to be noncombustible.
3 feet. See Figure 10.
Fire sprinkler valves, standpipes, and fire hydrants.6 feet. See Figure 11
Doors, windows, vents, fire escapes, and other
building openings.
10 feet. See Figure 11.
The water’s edge of a swimming pool or any body
of water.
15 feet. See Figure 11.
Individual domestic and irrigation wells.100 feet. See Figure 11.
Facilities used to dispense or store LP or
hazardous liquids or fuels.
20 feet. See Figure 12.
10 feet. See Figure 12.
Gas service meter relief vents.3 feet. See Figure 11.
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Electric Service Handbook 2022 — Non-residential Projects
Figure 10 Clearances for transformers from structures
TRANSFORMER CLEARANCES FROM COMBUSTIBLE SURFACES
TRANSFORMER CLEARANCES FROM NONCOMBUSTIBLE SURFACES TRANSFORMER CLEARANCES FROM NONCOMBUSTIBLE WALLS WITH COMBUSTIBLE ROOFING
REDUCED FLAMMABILITY TRANSFORMER CLEARANCES
FROM COMBUSTIBLE SURFACESCOMBUSTIBLE BUILDING WALLS AND ROOFNONCOMBUSTIBLE BUILDING WALLSNONCOMBUSTIBLE BUILDING WALLSCOMBUSTIBLE BUILDING WALLS AND ROOFAPPROVEDTRANSFORMERAREA
APPROVEDTRANSFORMERAREA
APPROVEDTRANSFORMERAREA
NONCOMBUSTIBLE ROOF AND SOFFIT
COMBUSTIBLE ROOF OR SOFFIT
APPROVEDTRANSFORMERAREA
10'3'
3'10'
10'
3'
3'3'
3'
10'
10'
10'
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Chapter 2
Electric Service Handbook 2022 — Non-residential Projects
Figure 11 Clearances for transformers
Figure 12 Minimum clearances from oil-filled equipment to LP, hazardous liquid, or fuel tanks
10'
100'
15'
6'
10'
20'
3'FUELTANK
POOLS OR BODIES OF WATER
DOOR, WINDOW, VENT, OR OTHER OPENING
WELL HEAD
TRANSFORMER
GAS METER
RELIEF
VENT
SPRINKLER VALVE, STANDPIPE, OR
HYDRANT
FIRE ESCAPE
6'
MIN
20'
MIN
10' MIN
LP TANK
LP TANK
OIL-FILLED
ELECTRICALEQUIPMENT
OIL-FILLED
ELECTRICAL
EQUIPMENT
DIKE OF ADEQUATE HEIGHT TO CONTAIN OIL AND NOT ALLOW IT TO FLOW TOWARDS THE LP TANK
TRANSFORMER
TOP VIEW
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Chapter 2
Electric Service Handbook 2022 — Non-residential Projects
Landscaping and other obstacles
Landscaping and other obstructions shall not encroach on the clearances shown in
Figures 13 and 14.
Working space
A clear and level working area equal to the full width of the equipment operating
compartments shall extend a minimum of 10 feet from the compartment opening for
padmount equipment and 10 feet in front of subsurface equipment in vaults (see
Figures 13 and 14).
A minimum of 3 feet of clear working area for subsurface equipment and 18 inches
for padmount equipment (see Figures 13 and 14) shall be provided on the sides of the
electrical equipment without operating compartments (including sides with cooling fins).
A clearance of 36 inches is required on padmounted equipment with cooling fins (see
Figure 14).
Figure 13 Plan view of subsurface equipment clear working space
3' MIN
3' MIN CLEAR WORKING SPACE
CLEAR WORKING SPACE
3'
MIN
10'
MIN
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Chapter 2
Electric Service Handbook 2022 — Non-residential Projects
Figure 14 Plan view of padmount equipment clear working space
Guard posts for padmount and subsurface equipment
Washington Administrative Code (WAC) requires guard posts around padmounted
equipment that is exposed to vehicular traffic. PSE guard post location requirements are
shown in Figure 15. You are required to supply and install these guard posts or pay PSE
to supply and install them.
Figure 15 Guard post location requirements
NOTE: Installation of guard posts must be completed before the primary cable
is installed and energized.
36"
MIN
18" MIN
10' MIN
18" MIN
VAULT LID
COOLING FINS
EQUIPMENT
ACCESS DOOR
EQUIPMENT ACCESS DOOR
CLEAR
WORKING SPACE
CLEAR
WORKING SPACE
18"
MIN 18"
MIN
3'
MIN
3'
MIN
4' MAX
ACCESS
DOOR SWING
TYPICAL 8' X 8'CONCRETE PAD
GUARD POSTS
5'
MAX 5'
MAX
5'MAX
5'MAX
5'
MAX
5'
MAX 5'MAX
5'MAX
TYPICALTRANSFORMER
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