Honeywell UMC800 manual Electrical considerations, Controller grounding

Pre-Installation Considerations

Introduction

Electrical considerations

The controller is considered “open equipment” per EN 61010-1, Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use, Part 1: General Requirements. Conformity with 72/23/EEC, the Low Voltage Directive requires the user to provide adequate protection against a shock hazard. The user shall install this controller in an enclosure that limits OPERATOR access to the rear terminals.

Controller grounding

PROTECTIVE BONDING (grounding) of this controller and the enclosure in which it is installed shall be in accordance with National Electrical Code (ANSI/NFPA 70) and local electrical codes.

Taking electrical noise precautions

Electrical noise is composed of unabated electrical signals that produce undesirable effects in measurements and control circuits.

Digital equipment is especially sensitive to the effects of electrical noise. You should use the following methods to reduce these effects:

•Supplementary bonding of the controller enclosure to a local ground, using a No. 12 (4 mm2) copper conductor, is recommended. This may help minimize electrical noise and transients that may adversely affect the system.

•Separate External Wiring - separate connecting wires into bundles (see Table 4) and route the individual bundles through separate conduits or metal trays.

•Use shielded twisted pair cables for all Analog I/O, Process Variable, RTD, Thermocouple, dc millivolt, low level signal, 4-20 mA, Digital I/O, and computer interface circuits.

•Use suppression devices for additional noise protection. You may want to add suppression devices at the external source. Appropriate suppression devices are commercially available.

•Refer to document 51-52-05-01How to Apply Digital Instrumentation in Severe Electrical Noise Environments for additional installation guidance.

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