Electrical Engineering
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EPC-NPD-PG-006
Network Customer Built Transformer
Vault Guidelines
Electrical Engineering
EPC-NPD-PG-006
Network Customer Built Transformer
Vault Guidelines
ENMAX Power Corporation (EPC)
Network Customer Built Transformer Vault Guidelines
Last Revised: January 2, 2014
Electrical Engineering
ENMAX Power Corporation (EPC)
141 - 50 Ave. SE Calgary, Alberta T2G 4S7
Important - Please note the following:
If there is any inconsistency between this document and any applicable EPC tariff or
agreement, the terms of that tariff or agreement will prevail.
The contents of this document are provided for information purposes only. The
information contained within this document is not binding on EPC and can be modified
by EPC without notice.
Electrical Engineering
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EPC-NPD-PG-006
Network Customer Built Transformer
Vault Guidelines
Electrical Engineering
EPC-NPD-PG-006
Network Customer Built Transformer
Vault Guidelines
TABLE OF CONTENTS
1. INTRODUCTION................................................................................................................. 1
1.1 Purpose of This Guideline............................................................................................................... 1
1.2 Types of Transformers To Be Used ................................................................................................ 2
1.3 Easements ....................................................................................................................................... 2
1.4 Customer Checklists ....................................................................................................................... 2
2. DESIGN GUIDELINES FOR STRUCTURES AND FACILITIES ................................ 3
2.1 Location of Customer Built Transformer Vault.............................................................................. 3
2.2 Customer Built Transformer Vault Dimensions ............................................................................. 4
2.3 Location of Emergency Disconnect Device Room ......................................................................... 4
2.4 Electrical Load Criteria for Customer Built Vaults......................................................................... 5
2.5 Grounding Of Transformer Vaults.................................................................................................. 5
2.6 Customer Equipment Bonding........................................................................................................ 6
2.7 Painting ........................................................................................................................................... 6
2.8 Vault and Emergency Disconnect Device Room Wall Construction.............................................. 6
2.9 Floor/Ceiling Loading Weights....................................................................................................... 6
3. EQUIPMENT AND PERSONNEL ACCESS REQUIREMENTS .................................. 7
3.1 Air Testing ...................................................................................................................................... 7
3.2 Equipment Access........................................................................................................................... 7
3.3 Lift Out Well Equipment Access .................................................................................................... 8
3.4 Equipment Access Door Ramp Requirements ................................................................................ 8
3.5 Personnel Access Doors.................................................................................................................. 9
4. LIQUID CONTAINMENT ................................................................................................ 10
4.1 Door Sill........................................................................................................................................ 10
4.2 Drainage System ........................................................................................................................... 10
4.3 Sump Pits And Covers .................................................................................................................. 10
5. FIRE PROTECTION AND DETECTION....................................................................... 12
5.1 Alarms........................................................................................................................................... 12
5.2 Smoke and Heat Detectors............................................................................................................ 12
5.3 Sprinkler Systems ......................................................................................................................... 12
5.4 Fire Rated Walls ........................................................................................................................... 13
5.5 Fire Rated Doors ........................................................................................................................... 13
5.6 Fire Dampers................................................................................................................................. 13
5.7 Fire Extinguishers ......................................................................................................................... 13
6. LIGHTING AND DUPLEX RECEPTACLES................................................................. 14
6.1 General Room Lighting And Duplex Receptacle Requirements .................................................. 14
6.2 Emergency Lighting And Duplex Receptacles ............................................................................. 14
7. VENTILATION SYSTEM................................................................................................. 15
7.1 Customer Built Indoor Vaults ....................................................................................................... 15
7.2 Emergency Disconnect Device Room .......................................................................................... 16
8. DOCUMENTATION HISTORY ...................................................................................... 17
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Vault Guidelines
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1. INTRODUCTION
1.1 Purpose of This Guideline
In Calgary, unlike many other cities, the customer has the option of constructing the
building’s transformer vault. To ensure that the integrity and quality of service of the
network system is maintained, the Electrical Engineering section has written this
guideline that lists the basic procedural and technical requirements that must be met in
the construction of the customer built vault.
The term “Network,” as it is used in this publication, refers to the area of EPC’s electrical
distribution system that is located in Calgary’s downtown core and portions of the
adjacent communities (see Network Boundary Map).
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Please note the following:

For all other aspects of Network servicing, please refer to the Network Servicing
Policies and Guidelines

This guideline does not exempt the customer from the City of Calgary building
codes.

Prior to any construction that will affect EPC’s Network system EPC requires a
site coordination meeting. At the meeting, an ENMAX Network representative will
review, with the project manager, any outstanding conflicts that will need to be
corrected prior to the beginning of the construction of the vault. The EPC
Network coordinator will then establish a tentative schedule for construction that
will commence when the customer meets all the requirements in the Network
guidelines.
1.2 Types of Transformers to Be Used
The transformers that are used in the customer built vault are filled with an insulating
fluid that is approved for indoor application. EPC will supply and install the transformers
at the customer’s expense.
1.3 Easements
Please contact the EPC Electrical Engineering section for further details.
EPC requires the customer to grant a general easement to EPC for the customer built
transformer vault, the emergency disconnect room, and the associated conduit system.
The conduit system includes the conduit connecting the customer built vault(s) to the
external EPC system.
1.4 Customer Checklists
Checklists for the construction and energization of the customer transformer vault and
Emergency Disconnect Device room can be obtained from the EPC Network
Coordinator at (403) 514-2917. Failure to have the respective checklist signed off by the
EPC Network Coordinator may result in a delay in the construction or energization of the
transformer vault.
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2. DESIGN GUIDELINES FOR STRUCTURES AND FACILITIES
2.1 Location of Customer Built Transformer Vault
The customer built transformer vault must be located in a manner so that EPC is
provided with the following:

There are two (2) access points. EPC personnel must have 24 hour direct access
from outside the building via one of the access points. Direct access, 24-hours a
day, is necessary so that EPC personnel can perform emergency and/or routine
switching and maintenance on the ENMAX system without delays.

The installation of equipment access doors meet all of the conditions outlined in
Section 3. Access Requirements and/or the installation of a standard EPC vault
steel hatch and slab assembly.

Sufficient space in the area immediately outside of the customer built transformer
vault to allow EPC work vehicles to maneuver.

The customer built transformer vault must be located on the customer’s property
and cannot be located above the +15 level of the building.

Grade level vault locations will require the following additional requirements:
o
A flat level platform that will eliminate any grade deviation between the
floor of the vault and the outside grade level (2.1 meters (W) x 3.0 meters
(L)).
o
The platform must be

removable for storage inside of the vault for future equipment
removal or installation

light enough to be carried by 2 men without the aid of a
mechanical device

able to temporarily attach to the building to avoid any movement
during use

Capable of handling the weight of the network transformer
(Engineering drawing that is stamped and signed by a
professional engineer)

Smooth surface that will permit the use of an air pallet device
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2.2 Customer Built Transformer Vault Dimensions
The size of the customer built transformer vault must be large enough to house a
minimum of four (4) Network style transformers with protectors. There must also be
enough room to permit safe operation of the equipment by EPC Network staff and allow
for safe removal of the equipment if required.
The minimum internal dimensions for a customer built transformer vault are shown in the
table below. Also, see EPC drawings 536-1010-202/203/211 in the Appendix.
Typical Internal Vault Dimensions
(L x W x H)
5m x 11m x 4.5m (120/208 - volt)*
5m x 11m x 4.5m (277/480 - volt)*
11m x 12m x 4.5m (347/600 - volt)*
*These dimensions exclude the space requirement for the mechanical ventilation
equipment.
Please contact the EPC Electrical Engineering section regarding any vault for 347/600
volts.
2.3 Location of Emergency Disconnect Device Room
EPC requires an emergency disconnect device room that contains the equipment that
will disconnect the EPC primary cable system from the transformers in the event of an
emergency. To facilitate access to a building during an emergency, it is essential the
emergency disconnect devices be installed at a location that is always accessible to
EPC crews.
The emergency disconnect device room must be located in a manner so that EPC is
provided with the following:

24-hour direct access from outside the building.

may be incorporated as part of the customer built transformer vault lift out well.
Please contact the EPC Electrical Engineering section for details.

when the emergency disconnect device room cannot be incorporated into the
customer built transformer vault lift out well the customer has 2 options:
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‫ـ‬
construction of a room inside the building that meets the access
requirements under section 3.(2.5 meters (W) x 5.0 meters (L) x
2.1 meters (H))
‫ـ‬
an external underground chamber constructed by EPC on
customer property with minimum internal dimensions of 2.4
meters (W) x 3.6 meters (L) x 2.1 meters (H).
EPC will supply and install the emergency disconnect devices, at the customer’s
expense.
2.4 Electrical Load Criteria for Customer Built Vaults
The following table outlines the maximum aggregate service panel size that can be
connected to a customer built vault at the given voltages.
Design Criteria for Customer Built Vaults
(Maximum Allowable Service Size)
Secondary Voltage
(Volts)
Transformer Size (kVA)
Maximum Aggregate Service Panel Size
(amps)
120/208
750
7,600
120/208
1000
8,800
277/480
750
2,800
277/480
1000
3,600
277/480
1500
6,000
277/480
2000
7,600
347/600
2500
8,000
2.5 Grounding of Transformer Vaults
For the protection of EPC staff, a ground grid is required for all indoor customer built
vaults. The location of the ground grid has to be either under the lift out well or the first
EPC structure external to the building. The ground grid must be installed as shown in
drawing 536-1200-001.
EPC will verify and record the impedance value of the ground grid before energizing the
EPC equipment.
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2.6 Customer Equipment Bonding
It is the customer’s responsibility to bond any metallic component that extends into
public space. The customer must install his own ground plate in the indoor vault room
and connect the ground plate to the building’s ground grid.
2.7 Painting
The customer is responsible for painting all of the interior vault surfaces, emergency
disconnect device room (if applicable) and lift out well including the ceiling and floors. All
floors must be smooth and free of irregularities to permit the use of air-pallet equipment.
Non-slip surfaces are NOT to be installed on any floors. The color of the paint must be
white and be latex based.
2.8 Vault and Emergency Disconnect Device Room Wall Construction
The walls of the customer built vault and emergency disconnect device room (if
applicable) must be a “cast in place” concrete with a fire resistant rating of not less than
3-hours.
2.9 Floor/Ceiling Loading Weights
The customer is responsible for ensuring that the floor and/or ceiling load ratings are
capable of supporting the EPC installed equipment. The table below outlines the
approximate weights for transformers and the associated secondary buss work and
cables.
ENMAX Power Standard Weights
(per Transformer with Protector)
Service Voltage
Base Footprint
(W x L))
Unit Weight
120 / 208 Volts
1.3m x 1.6m
6500kg
277 / 480 Volts
1.5m x 1.6m
9000kg
347 / 600 Volts
1.4m x 2.1m
10000kg
Secondary Buss Work and
Cables
N/A
2000kG
*The base footprint is not the same as the transformer dimensions and the secondary
buss work and cables are supported via I-beams mounted to the walls
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3. EQUIPMENT AND PERSONNEL ACCESS REQUIREMENTS
EPC personnel must have 24-hour access via one of the access points. This access
must be directly from the outside of the building and not require the permission or
assistance of a third party such as building security or the fire department.
A minimum of two (2) access points at the floor grade of the vault are required and (1)
access point at floor grade for the emergency disconnect device room (if applicable).
Note: EPC will be installing signage on the customer side of the doors to the electrical
vault room (see Appendix section for details).
3.1 Air Testing
Provision to test the air quality of the indoor vault, lift out well or emergency disconnect
room will be required. The testing method must be such that opening of the door or lid is
not required. Contact EPC Electrical Engineering for details.
3.2 Equipment Access
Either a ceiling or wall access design may be used to provide the entrance to install the
EPC electrical equipment in the vault.
An outside ceiling access to the customer built transformer vault room can be built by
installing a standard EPC vault steel hatch and slab assembly. Please contact the EPC
Electrical Engineering section for details.

This assembly is installed in the portion of the customer built transformer vault
room roof that is outside the building. The minimum overhead clearance at the
slab assembly is 7.62 meters.

EPC will supply the vault steel grates and slabs but it will be at the customer’s
expense.

The ceiling access can be combined with the emergency disconnect device vault
for equipment access.
The wall style equipment access door must meet the following requirements:

The minimum internal dimension for the wall access equipment doors is 2.1
meters wide x 2.743 meters high. Typically this is a double door without a centre
piece. Doors must swing out from the transformer vault room and the emergency
disconnect device room (if applicable).
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
The equipment access doors must either be equipped with removable door hinge
pins so the doors can be taken off of their hinges or the doors must be able to
open a full 180 degrees.

Each of the equipment access doors must accept a Best lock system and EPC
will supply the cores and retain the keys. The equipment access door must be
equipped with a pull style “D” handle, panic bar that has active trim and a night
latch. A copy of the proposed door hardware specification accompanied by a
drawing showing the door swing and pinning is to be submitted to the Network
Coordinator prior to the customer ordering the material.
3.3 Lift Out Well Equipment Access
When a transformer vault is constructed below grade, a lift out well is required for the
removal of EPC equipment. The minimum size for the lift out well is shown on drawing
536-1010-207 in the Appendix. To safely remove equipment from the vault, a minimum
overhead clearance of 7.62 meters, above the removable concrete slabs, is required.

The preferred location of the lift out well is the outside of an exterior wall of the
building and adjacent to the transformer vault.

The lift out well must be equipped with a sump pit (please see Section 4.3 Sump pit and cover). The sump pit must have a perforated cover and a
removable hatch with a minimum diameter of 0.2 meters to allow for pumping out
any liquid.

A pump will be supplied by EPC. It will be connected to the building storm
system. The sump pump connection to the building and liquid discharge into the
storm system must be covered by an appropriate agreement between the
building owner and EPC.

The lift out well must drain towards the sump pit.

The location of the sump pit must be approved by the EPC Electrical Engineering
section before construction.
3.4 Equipment Access Door Ramp Requirements
This subsection which discusses concrete ramps and removable sills, applies ONLY to
the customer built vaults that do not have an attached lift out well.
The purpose of the concrete ramp or removable sill at the equipment access doorway is
to confine the oil or transformer liquid in the case of a leak from one transformer
(drawing #536-1010-208 in the Appendix). The EPC Electrical Engineering section will
provide details on the volume of liquid that must contained which are based on the type
of units being installed. The following requirements must be adhered to:
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
The concrete ramp at the equipment access doorway must have a height of
100mm at the centre.

The ramp must have a gradual slope on each side of the doorway with a
minimum span of 1.0 meter.
3.5 Personnel Access Doors
EPC personnel must have 24-hour access via one of the access points. This access
must be from outside of the building and lead directly into the vault when the customer
built transformer vault is not equipped with a lift out well.
For locations where the emergency disconnect device chamber is a room, the access
must be from outside of the building and lead directly to the emergency disconnect
device room.
If the access to the personnel doors of the customer built vault room is via the ceiling, a
fixed in place EPC ladder is required to permit access via the grates. EPC will supply the
ladder at the customer’s expense. Installation of the ladder may only be performed by
EPC personnel and at a time deemed appropriate by the EPC coordinator.
Wall located personnel access doors must include the following items:

The personnel access doors shall have dimensions of 0.91 meters wide x 2.1
meters high.

Entrance hardware that will accept a Best lock 7-pin core. A Best lock 1E rim
cylinder is typically used – EPC will supply the cores and retain the keys.

A pull style “D” handle, panic bar that has active trim and a night latch. A copy of
the proposed door hardware specification accompanied by a drawing showing
the door swing is to be submitted to the Network Coordinator prior to the
customer ordering the material.

A concrete sill with a minimum height of 100mm. The sill must be high enough to
confine oil or transformer liquid in the case of a leak or spillage from one
transformer (drawing 536-1010-208 Detail 2 in the Appendix). The EPC Electrical
Engineering section will provide details on the volume of liquid to be contained
based upon the units being installed.

The door may be alarmed if required by the customer. The supply and installation
of any building security related equipment is the responsibility of the customer.

If the personnel access door does not open into public space, the next door must
also be equipped with a panic bar.
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4. LIQUID CONTAINMENT
4.1 Door Sill
All access points to the customer built transformer vault room must be equipped with a
concrete sill (drawing 536-1010-208 Detail 2 in the Appendix).
Locations with equipment access doors must be equipped with a removable sill supplied
by EPC (drawing 536-1010-208 Detail 4 in the Appendix)
4.2 Drainage System
4.2.1 Customer Built Transformer Vault Room
The floor of the transformer vault room must drain towards equipment access doors as
seen in the drawing 536-1010-208 in the Appendix. Please contact the EPC Electrical
Engineering section for approved locations for the dry sump pit (0.3 x 0.3 x 0.3 meters).
Lift out well drainage may be designed as a floor drain connected to the buildings Storm
water system. An agreement between EPC and the building owner is required to cover
the connection. An alternate design consisting of a dry sump (0.6 x 0.6 x 0.6 meters)
may be considered.
4.2.2 Emergency Disconnect Device Room
Floor drains are not allowed in the emergency disconnect device room.
4.3 Sump Pits and Covers
When the sump pit is connected to the building’s storm water system, the lift out well
sump pit must be designed with a passive flow drainage system.
When the lift out well sump pit is not connected to the building’s storm water system then
the sump pit must be large enough to contain 200 litres of liquid.
To maintain safety and still ensure ease of entrance into the sump pit, the sump pit must
be equipped with a removable steel cover with a minimum thickness of 6.35mm. For
stand alone systems (no storm water connection) the lid must have a separate hinged or
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removable cover 0.3 meter in a diameter to facilitate the insertion of a pump hose for
liquid removal.
The sump pit cover must be perforated to permit liquid to enter the sump pit.
The sump pit within the vault must be 0.3 meters in depth. All joints must be properly
sealed to prevent any leakage. As part of the design a method must be included for the
removal of any liquid. For sump pits with storm water connection, an oil containment
system must be provided.
For safety and ease of maintenance, the sump pit must be equipped with a removable
steel cover with a minimum thickness of 6.35mm. The cover must be perforated to allow
liquid to enter the sump pit.
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5. FIRE PROTECTION AND DETECTION
5.1 Alarms
EPC does not require alarms within the vault. The location and type of alarms deemed
necessary by the customer must be approved in advance by the EPC Electrical
Engineering section.
5.2 Smoke and Heat Detectors
Each room of the customer built transformer vault must be equipped with two (2) ceiling
mounted heat detectors and two (2) smoke detectors. The detectors must be located so
that there is a smoke detector between each pair of Network transformers. The specific
location for each project must be confirmed by EPC Electrical Engineering in advance.
This will provide detection of overheating or potential hot spots.
If the emergency disconnect device room is inside the building but not part of the lift out
well, the room must be equipped with (1) ceiling mounted heat detector and (1) smoke
detector.
All of the smoke and heat detectors must be connected to the building alarm system and
actuate the main building alarm if fire or overheating occurs in the vault room. EPC
requires access to the alarm points so its staff can install an additional connection to the
EPC monitoring system. The following requirements must be adhered to:

The alarm points (EPC use) must be dry contacts.

Smoke detectors must be configured to disable the ventilation system when
activated.

Heat detectors must be equipped with an alarm point (EPC use) at 40 Celsius to
indicate room high temperature.
o
5.3 Sprinkler Systems
If the City of Calgary building code stipulates that the customer must install a sprinkler
system, then the following is required:

A non-pressurized, dry type, sprinkler system.

The approval of the EPC Electrical Engineering section for the location of the
sprinkler heads.
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5.4 Fire Rated Walls
The floors, ceiling and walls of the customer built transformer vault room and emergency
disconnect device room (if applicable) must be “cast in place” concrete that has a fire
resistant rating of not less than three (3) hours.
Special consideration will be given to proposals for different ceiling materials and must
be approved by EPC Electrical Engineering prior to construction.
5.5 Fire Rated Doors
In those locations where the customer built transformer vaults and emergency
disconnect device room have wall access style personnel and equipment access doors,
the doors must have a fire resistant rating of not less than two (2) hours.
5.6 Fire Dampers
When an intake or exhaust outlet is not on an exterior building wall, the outlet must have
a fire damper rated for a minimum of two (2) hours.
5.7 Fire Extinguishers
EPC field staff will be responsible to supply and mount a fire extinguisher beside each
vault doorway and the entrance/exit of the emergency disconnect device room (if
applicable).
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6. LIGHTING AND DUPLEX RECEPTACLES
6.1 General Room Lighting and Duplex Receptacle Requirements
The customer is responsible for the cost of supplying and installing the general room
lighting and duplex receptacles, in accordance with the following EPC standards (see
the Appendix section for further details). Note all lighting and power is to be on a
generator equipped circuit. Note that the general room lighting must be rated for
temperatures down to 0 degrees Celsius.
Typical Customer Built Vault Lighting Standard for Customer – 208 or 480 Volt (5361010-211).
Typical Customer Built EDD Room Lighting Standard (536-1220-100).
Note that vault lighting for 600-volt vault rooms must be submitted to EPC Electrical
Engineering in advance.
6.2 Emergency Lighting and Duplex Receptacles
The customer is responsible for the cost of supplying and installing the emergency
lighting for the customer built vault and the emergency disconnect device room (if
applicable). Note that the general room lighting must be rated for temperatures down to
0 degrees Celsius

An emergency exit sign and battery powered emergency light will be located
directly above each point of exit.

In locations where the emergency exit from the indoor vault leads into a second
room, the customer will install a 24-hour light in the second room.

The installation of these emergency services must comply with drawings 5361010-211, for the indoor customer vault, and 536-1220-100, for an Emergency
Disconnect Device Room (if applicable).
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7. VENTILATION SYSTEM
7.1 Customer Built Indoor Vaults
The customer built transformer vault must have both sufficient heat and ventilation to
prevent the ambient air temperature from falling below freezing (0 degrees Celsius) or
exceeding +40 degrees Celsius (CEC 2-318, 2009). Typical transformer heat losses for
EPC equipment, on a per transformer basis, are listed in the following table.
EPC Standard Heat Loss
(per Transformer)
Service Voltage
Transformer Size
Transformer Loss
120 / 208 Volts
500kVA
7000 Watts
120 / 208 Volts
750kVA
8000 Watts
120 / 208 Volts
1000kVA
12000 Watts
277 / 480 Volts
750kVA
8000 Watts
277 / 480 Volts
1000kVA
11000 Watts
277 / 480 Volts
1500kVA
12000 Watts
277 / 480 Volts
2000kVA
14000 Watts
347 / 600 Volts
2500kVA
19000 Watts
A typical ventilation system will be comprised of a passive air intake opening, an exhaust
fan, and exhaust opening. The location of the air intake and exhaust system inlet must
maximize the air flow across the EPC transformers. Location of all ventilation equipment
requiring routine maintenance must be located external to the room to facilitate the
maintenance activity. Note that the annual testing and maintenance of the ventilation
system and components (air filters, motors, etc.) is the responsibility of the building
owner.
The air intake must provide fresh outside air (non parking lot) and be covered by louvers,
a bird screen, and include an air filter. The air filter(s) must be a common standard size,
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disposable, available locally, and may be required to meet the City of Calgary’s current
building codes and have a two hour rated fire damper.
To ensure a safe and efficient outlet for the exhaust air, the exhaust outlet must be
installed in a place that will not allow the room exhaust to be drawn into the vault air
intake. For this reason the location of the exhaust outlet cannot be in the lift out well. The
exhaust system outlet must be covered by louvers and a bird screen. A two hour fire
rated damper may be required for the exhaust opening to meet the City of Calgary’s
current building codes.
It is the customer’s responsibility to supply and install the control panel and supply the
energy to power all the ventilation related equipment within the transformer vault. The
control panel must be installed at the designated 24-hour access point which has been
reviewed by the EPC Electrical Engineering section. The control panel must have a
manual off, manual on, and an automatic position. The switch must have a light that
indicates the status of the ventilation equipment.
The design of the ventilation equipment is the responsibility of the customer. The
ventilation equipment must meet current building regulations and be approved by the
City of Calgary Building Inspection Division.
Prior to construction, a copy of the plans of the physical layout for the ventilation
equipment must be submitted to EPC Electrical Engineering for review and approval.
7.2 Emergency Disconnect Device Room
Ventilation is not allowed in the emergency disconnect device room.
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8. DOCUMENTATION HISTORY
Date
August 31, 2011
January 2, 2014
Description of Changes
Updated document format; changes to section 2.2 and 2.9
Updated document format
January 2, 2014
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