Model 1011
Installation and Operation Manual
13
Par
t No
. 51
2083 Dra
wing No
. 1
29-0205a 03/09
Electrical Supply Requirements
General Wiring Requirements
WARNING: THIS DEVICE CONTAINS ELECTRICAL
PARTS THAT CAN CAUSE SHOCK OR INJURY
All electrical connections, conduit and fittings on the protected
enclosure must be suitable for the hazardous location in which
they are installed. In addition, all conduit and wire must be
installed in accordance with NEC as required and all relevant
plant and local codes.
Note:
Do not use seals on conduit used as a protected
“wireway” to supply protective gas to adjacent protected
enclosures. The same conduit can be utilized for both electrical
and pneumatic service to an adjacent protected enclosure(s),
provided the conduit is oversized to allow a minimum free
clearance equal to or larger than the pipe size required between
multiple enclosures as stated on page 6, “Getting Started.”
Enclosure Power Requirements
The protected enclosure(s) electrical power source must
originate from a circuit breaker or fused disconnect suitable for
the hazardous location in which it is installed. The switch must
be located within fifty (50) feet of the protected enclosure(s) and
the protection system and be properly marked.
Alarm Signal Requirements
For Type Y and Z purge systems, audible alarms or visual
indicators must be used to notify operators that pressure inside
the enclosure is below the NFPA minimum.
Alarms are connected directly to the enclosure and monitor
the differential air pressure between the enclosure and the
environment outside it. These alarms are activated by the
reduction in flow or pressure within the protective enclosure
and have a direct connection to the enclosure, eliminating the
need for an alarm on the protective gas supply.
• The alarm must be located where the operator can see it
easily.
• The alarm must take its measurement from the enclosure
only.
• Alarms located in the hazardous area must be rated for the
area.
• Valves cannot be connected between the alarm and the
enclosure.
IMPORTANT NOTE: NFPA 496 requires the use of an
alarm or an indicator to detect the loss of safe enclosure
pressure. In addition, the NFPA 496 requires that if
an indicator alone is utilized, a protective gas supply
alarm must also be installed between the last valve in
the protective gas supply and the protected enclosure.
Therefore, the protective gas supply to all Model 1011
systems must be equipped with the above mentioned
protective gas supply alarm. Exception: Systems utilizing
an EPSK or GPSK enclosure pressure loss alarm switch
accessory will satisfy the above mentioned NFPA
requirement.
Typical Enclosure Wiring Methods
Protected enclosures should be wired similar to explosion
proof enclosures, in accordance with Article 500 of the National
Electric Code - NFPA 70.
Single conductor wiring should be placed in rigid metal conduit,
seal-flex conduit or other mediums approved for use in the
hazardous location surrounding the protected enclosure.
Additionally, NFPA 496 requires the use of approved seals on
all pressurized enclosure conduit wiring entries, in accordance
with NFPA 70. Furthermore, the use of an approved seal is
simply the most practical way to prevent excessive leakage
through conduit connections.
However, while explosion proof enclosures require conduit
seals on all cable entries, in accordance with NFPA 70. Other
methods of sealed cable entries that are suitable for hazardous
locations can be used, such as compression glands.
In conclusion, there are two primary goals. First, the installer
should ensure that all associated wiring and cable is protected
by pressurization or other means, such as explosion proof
conduit or intrinsic safety barriers. Secondly, the installer should
ensure that all associated conduit and wireways are sealed
to conserve protective gas, unless they are used to supply
protective gas to other enclosures or devices.
Typical Enclosure Wiring Connections
Adjacent
Ppressurized
device
Explosion
proof device
Seal
Intrinsically
safe or fiber
optic device
Independently
pressurized
device
Intrinsically
safe or fiber
optic device
Seal
Conduit
Conduit
Conduit
Gland
fitting
Cable
Seal
Pressurized
raceway
Protected enclosure
or device
