Cut Sheet

Volume 7—Logic Control, Operator Interface and Connectivity Solutions CA08100008E—June 2015 www.eaton.com V7-T1-361
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1.11
Pushbuttons and Indicating Lights
30.5 mm Class I Division 2 Hazardous Locations—10250T/E34
Summary of Basic Methods Available for Class I, Division 2 Locations
Factory Sealed Contact Blocks Hermetically Sealed Reed Contact Block
Explosion Proof Enclosure
Method
Features
Configuration Advantages Disadvantages
Factory sealed contact block Closed-ended labyrinth contact block with an
incendive circuit incapable of external ignition
Higher continuous carrying amperages—up to 10A
Direct drive contacts—contacts can be forced open
Suitable for use in all enclosures
Best suited for motor control applications
May not be suitable for logic level circuits
Hermetically sealed block Reed switch sealed against an external
atmosphere
Suitable for low energy level circuits
Suitable for use in all enclosures
Lower continuous carrying amperages are not
suitable for motor control applications
(typically 3A to 5A rated)
Contacts cannot be forced open
Permanent magnet attracts metallic dust and
filings that can reduce the electrical creepage
distance between live terminals
Explosion proof enclosures
(Class I, Division 1 and 2)
Enclosures capable of withstanding an internal
explosion while preventing external ignition.
Enclosures designed for Class I, Division 1 can
safely be used in Class I, Division 2
Higher level of protection than required for Class I
Division 2
Higher material and installation costs
Conduit sealing is still required
Time consuming maintenance
Direct Drive Contacts
Contacts can be
mechanically forced
apart if subject to an
arch/fault current.
Cooled
Escaping
Gas
Internal
Ignition
•
Hermetically sealed
reed does not allow
external atmosphere to
enter switching chamber.
Depression of plunger
rotates magnet and either
opens/closes contacts.
Contacts can not be
forced apart if subject to
arch/fault current, because no
mechanical connection exists.
Cooled
Escaping
Gas
Threaded Joint
Flat Joint
Internal
Ignition
Internal
Ignition
Cooled
Escaping
Gas