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Enclosure requirements

General requirements

Megablocks may be mounted in hazardous (classified) areas – see sections 8 & 9.

The following conditions must also be satisfied to ensure safe and reliable operation.

a) Prevent any form of pollution that could compromise the operation of the unit.

For example, choose an unpolluted location or a suitable enclosure to protect the

assembly.

b) Provide an adequate level of mechanical protection. This can be achieved by

selecting a protected location, a suitable enclosure, or a combination of both.

c) Ensure that all cable entries and connections are secure by making provision for

the careful routing and securing of all cables.

d) Provide adequate security against unauthorized interference.

e) Conform to the permitted ambient temperature range of –50°C to +70°C.

Outdoor mounting

In addition to the General Requirements above, if the Megablock is mounted in an

outdoor location, use a suitable enclosure with a minimum of IP54 ingress protection.

A higher level of ingress protection rating will be necessary if the working atmosphere

is, or can be, corrosive, or if the enclosure is subject to wet or dusty environments.

Simple and reliable interconnection

Each Megablock has dedicated connections for the fieldbus “home run” or trunk

cable. Trunk connections are identified by their black connector. Numbered (grey)

connectors are provided for each spur.

Wiring connections to the Megablock are made using pluggable connectors (screw

terminal type are standard, but other connection styles are available). These allow

wire terminations to be made to the individual connectors, which are then plugged

into the Megablock.  Devices can be connected and disconnected easily during

commissioning. On completion, the connector retaining screws are tightened to

secure each connector to the Megablock.

MECHANICAL

Mounting orientation

Megablocks mount vertically or horizontally on 35mm DIN rail within a field junction

box.  The use of DIN rail end stops are recommended to prevent sliding (especially

for vertical installations).

Eight, and twelve port Megablocks have areas on their body for labelling so that

segments can be easily identified according to plant standards.

OVERVIEW

F200-IS Megablocks are DIN-rail mounted, device couplers for FOUNDATION™ fieldbus

or Profibus PA networks. They allow connection of field devices to the segment trunk

cable and provide short-circuit protection to the segment.

Megablocks minimize hand wiring and allow individual devices to be added to and

removed from the segment without disrupting network communication.

Megablocks are available in four, eight, and twelve port versions. Multiple Megablocks

are easily wired together to allow larger segments to be constructed.

Individual surge-protector modules (FS32) can also be fitted to any of the Megablock

fieldbus terminals to provide protection against induced surges and transients that can

potentially destroy or degrade certain components inside the F200-IS Megablocks.

Removal from DIN-rail

Refering to Figure 4.1. push the Megablock against the edge of the DIN rail, tilt the

other side of the Megablock up and away from the DIN rail, then release the side

pressure to disengage the DIN rail clips from the DIN rail ledge.

F300 Megablock hazardous area approvals permit

installation in a variety of configurations in Zone 2 and Division 2

hazardous areas. Typically, F300 Megablocks may be installed with

non-sparking (non-arcing) trunk and spur connections. Alternatively,

when connected to suitably certified fieldbus power supplies, the trunk

may be non-sparking (non-arcing) with non-incendive or intrinsically

safe Ex ic spur connections.

When installed on a non-sparking trunk with Ex ic spurs, an

F300-A01 trunk-spur partition must be installed on the F300 Megablock.

The trunk-spur partition is supplied as a pack of 5. as detailed in the

Accessories section of this document.

SpurGuard™ is a device-port, short circuit protection technique

that minimizes susceptibility to single points of failure. The F300

Megablock has built-in SpurGuard™ protectors that prevent a short

circuit in any of the individual field devices or spur cable runs, from

bringing down the entire fieldbus segment. A red LED near each

spur connection indicates when a spur is shorted and hence in “over

current” mode.

The optional FS32 modules can provide surge protection for the

F300 products on both the trunk and spur terminals. These pluggable

modules are simple to fit in a new installation, or as a retrofit option.

A range of MTL Process Junction Boxes in stainless steel and carbon

loaded, glass-reinforced polyester are available for mounting Megablock

wiring components. They offer plenty of space for termination and

wiring, making it easy to install and maintain the fieldbus system.

The black Trunk In/Out pluggable connector allows replacement of

a Megablock without breaking the trunk connection to other devices

on the fieldbus segment. The F97 terminator supplied should be

mounted in the Trunk-out connection to provide termination when the

Megablock is located at the end of the fieldbus segment; alternatively,

if the segment is extended, it can be removed to ensure the correct

termination is maintained.

Spur connections to the Megablock are made using pluggable, grey,

screw-terminal or spring clamp terminal connectors. Wire terminations

can be made to the individual connectors before plugging them into

the Megablock. Devices can then be connected and disconnected

easily during commissioning. After commissioning, retaining screws

are tightened to secure each connector to the Megablock. Separate

numbered connections are provided for each spur drop.

Passive hubs for general purpose, zone 2 & division 2 fieldbus networks

• Single-piece Trunk In/Trunk Out connector simplifies installation and maintenance

• Pluggable trunk and spur surge protection option

• Choice of rising cage clamp screw or spring clamp terminals

• Locate Megablock in Zone 2 or Division 2

• Connect to Ex nA, Ex ic or non-incendive devices in Zone 2/Division 2

• Connect to Ex d, explosionproof devices in Zone 1/Division 1

F300 Megablocks are DIN-rail mounted passive hubs for Foundation™

fieldbus H1 and Profibus PA networks for general purpose, Zone 2 and

Division 2 applications. They provide a simple means of connecting field

devices to the network trunk cable, and protect the segment from spur

short circuits. Megablocks minimize hand wiring and allow individual

devices to be added to and removed from the segment without

disrupting network communication. A green power LED on each unit

indicates whether at least 10V dc is present. F300 Megablocks are

available in four, eight, and twelve drop versions.

MECHANICAL

Enclosures

An enclosure is required to house and protect the Megablock device coupler and the

F30 Ex ic adaptor for field operation. The type of enclosure must be chosen to suit

both the hazardous atmosphere likely to be encountered and the general conditions

appropriate to its environmental exposure. For installation in hazardous areas, the

enclosure must meet the requirements of a recognised method of protection

according to IEC 60079-0. clause 1.  In addition, the following conditions should

always be considered to ensure safe and reliable operation.

a) Prevent any form of pollution that could compromise the operation.

b) Provide an adequate level of mechanical protection. This can be achieved

by selecting a protected location, a suitable enclosure, or a combination of

both.

c) Ensure that all cable entries and connections are secure by making

provision for the careful routing and securing of all cables.

d)Provide adequate security against unauthorized interference.

e) Conform to the permitted ambient operating temperature range of  –40°C to +70°C.

The F30 adaptor

The F30 adaptor is connected in series with the trunk wiring to the Megablock (see

Figure 2.1) and limits the voltage to ensure that the ‘Uo’ at the Megablock spurs is

less than the 17.5V value required for compatibility with FISCO-certified instruments.

Where the voltage arriving at the F30 is higher than this (for example, if the trunk

cable is only short in length resulting in only a small voltage drop in the cable), the

F30 regulates the voltage to less than 17.5V.  Final current limiting for each spur is

provided by the short-circuit limiting circuits built in to the F300 Megablock, for which

Ex ic approval already exists. As a result, the combination of F30 and F300 meets the

requirements for Ex ic voltage and current limitation.

The F30 is designed for use only with MTL F304. F308 and F312 Megablock types,

typically providing up to twelve Ex ic spurs per fieldbus segment.  These spurs

may be all from one F312 Megablock in one enclosure, or distributed between two

separate enclosures – see Section 4.7.

The spurs are compatible with FISCO and Entity certified fieldbus instruments, and

where FISCO instruments are selected, cable parameter calculations are not required.

Power supplies

For Ex ic spur applications, the F30 and associated Megablock must be supplied by

9192-FP power supply modules in simplex or redundant configuration. The 9192

FP module has the necessary voltage limiting and is designed to fit on one of the

backplanes from the 918x-x2 range of fieldbus power supply systems, all of which

are capable of providing n+1 redundancy for maximum availability.

The 918x family of redundant power supplies contains a range of solutions to suit

different host interfaces, consult Eaton for the model appropriate to the host and

install the chosen model in accordance with the instructions provided with it.