KROHNE H250 M40 NEPSI Ex ia - Manual (Page 16)

4
ELECTRICAL CONNECTIONS
16
H250 M40
www.krohne.com 03/2013 - 4002616701 AD H250 M40 NEPSI Ex ia R01 en
Electrical connections
4.1 General notes
The built-in equipment is connected electrically in the integrated terminal compartment of the
display.
The connecting cables should be selected according to the applicable installation standards and
the maximum operating temperature.
• Before connecting or disconnecting the electric connecting cable of the device, ensure that
all of the cables leading to the signal converter are de-energised relative to each other and to
the reference potential of the hazardous area. This also applies to earthing conductors (FE)
and equipotential bonding conductors (PA).
• The connecting cables must be fixed and laid so they are sufficiently protected against
damage.
• All cores that are not used must be securely connected to the earth potential of the
hazardous area or carefully insulated against each other and against ground (test voltage ≥
500 V
eff
).
• Lay cables so as to ensure that there is sufficient distance between surfaces of the
measuring unit and the connecting cable.
• Supplied blind plugs / cable entries guarantee protection against foreign bodies and water
(protection category) IP66 / 67 in the temperature range T
amb
= -40...+100°C / -40...+212°F.
• The outer diameter of the connecting cable must be within the sealing range of the cable
entry (7...12 mm / 0.28...0.47").
• Unused cable entries are to be closed (>IP66 / 67). Supplied plugs should be replaced with
suitable connecting cables.
• Tighten the signal circuit terminals with a tightening torque of 0.5 ... 0.6 Nm.
Ensure that the seals and cut seals are tight.
4.2 Power supply
The variable area flowmeter does not require a separate power supply. The required supply for
the built-in electronics is provided via the 4...20mA current output and the bus connection.
4.3 Inputs/outputs
The terminal assignment of the built-in electrical equipment is described in the Standard
Installation and Operation Instructions. The variable area flowmeter signal circuits may only be
connected to certified intrinsically safe slave units or circuits. For more information see chapter
"Electrical data"
4.4 Grounding and equipotential bonding
The variable area flowmeter must be included in the equipotential bonding of the hazardous
area. It is connected to the PA terminal on the display. Alternatively, equipotential bonding can
occur via grounded pipelines.
Any existing cable shields should be connected to earth according to applicable installation
regulations. A terminal connection in the terminal compartment permits a short way earthing of
the cable shields.
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