Emerson IP221 appendix Control unit installation, Wiring Cable

2.3 Control unit installation

The control units should be installed in an area suitable to their specifications. They are designed to be used indoors, but could be installed outside using a suitable weatherproof enclosure. The front panel should be accessible to the operator.

The standard control unit MEP*L is installed by undoing the two screws on the top and bottom of the unit, and removing the base. This can now be mounted as required, making sure that the connection terminals are on the left-hand side of the base.

The 19” rack unit should be mounted in a suitable cabinet in the usual fashion. It accepts up to fourteen rack modules to type MEP*R. It should be noted that I.S. control units MEP3R will only fit into an I.S. rack MEP3B and that the rack is included in the approval. Mounting details are shown on the previous page.

Allow at least a 50mm gap between each rack on multiple rack installations to allow air circulation. On installations of multi-rack systems, the fitting of a cabinet air circulating fan is recommended.

Wires to the MEP*B rack units are connected to the terminal blocks mounted on the rear panel of the rack. In the factory the modules are fitted starting from the left hand side when viewed from the front of the rack. If desirable, the connectors and modules can be repositioned in the rack. To assist with cable wiring, the connector block wire access faces the rear of the rack and the screw terminals are therefore angled. To fit cable to the 5 modules closest to the right hand end of the rack (numbers 10- 14) it is necessary to release the connector and rotate it slightly to allow screwdriver access.

2.4Wiring

i) Cable

The connection from amplifier to the control unit should be made with two-core twisted pair instrument cable with overall screen. The cores should be at least 0.5mm2 and the cable length not more than 1 km, the screen may be omitted on cable runs of 10m or less, provided that the installation will not be subject to excessive electrical noise.

A summary of wiring arrangements is shown in figure 2.4.

Please consult the factory if this specification does not cover your needs, and for recommended cables.

Sensor	Head amplifier
		N.B. Relays are
		shown in their
		‘normal’
		operating states
		Do not connect
		screen
		Alarm relay
		Fault relay
	35m *Max	(MEP*R only)
		1km max.
(cable supplied with sensor)
MEP*A* and MEP*X*
	only

Control unit

Supply

Protective earth

N.B. Control unit contacts may not be in the order

* 15 max on i.s. systems

SECTION THROUGH CABLE

Connect screen at this end only

illustrated

Cores

Min. area 0.5mm2

Max loop Impedance 35Ω

Outer Sheath	Screen
	Inner Sheaths

Refer to section 2.5 for I.S. requirements

Figure 2.4 - Wiring summary for illustration only

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