KROHNE VFM 3100 EN - Manual (Page 19)

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Installation with Conduit:
• The junction box is pre-wired. A conduit box or conduit may be
mounted directly to the 1/2 NPT connection at the remote hou-
sing. A box or a standard 3-piece union/coupler may be mounted
directly over the knurled nut. Do not disassemble pre-wired
connection at junction box.
• Run remote cable to the remote electronic module housing via
conduit. If required, prepare cable as shown in Table 5. Feed it into
the housing following Steps in the procedure for "Interconnection
Wiring for Remote Electronics" on page 13 and Table 6 on page 17.
• Mount conduit box or conduit to the 1/2 NPT connector directly
or via a 3 piece union/coupler, if necessary. Make connection to
the 1/2 NPT connector after the knurled nut has been tightened
to provide a compression fit for the cable. Refer to Table 6 on
page 17.
• At this point, follow Steps in the procedure for "Installation
Without Conduit" on page 13.
CENELEC Flameproof Version:
• The junction box side of the remote confirguration is pre-wired.
Add flameproof cable gland or E-Y fitting and conduit directly
to the special Foxboro adapter or via an approved CSA/UL 3-
piece union/coupler, if necessary. For this reason, the second
conduit plug is fitted with a grounding screw (see Figure 9).
NOTE: CENELEC certification requires that an infallible physical
earth (PE) connection be made to the junction box.
• Run the remote cable to the remote electronic module housing
via cable trays or conduit.
• Place knurled nut and rubber bushing over the cable as shown
in Table 5 on page 15.
• Prepare the remote cable as shown in Table 5.
• Remove the locked electronic module component cover from
remote electronic module housing. Unscrew captive mounting
screws and remove the electronic module without disconnecting
loop power wiring.
• Feed prepared remote cable into the electronics housing through
connector at bottom of housing. Push it in until the outer jacket
bottoms out inside the connector. See Table 6.
• Ensure that the cable is pushed in all the way and then push the
rubber bushing into position. Tighten the knurled nut to create a
compression fit. See Table 6.
• Inside the remote electronics housing, connect the four wires of
the remote cable to the 4-position terminal block on the rear of
the electronic module.
Follow the color-coded label. See Figure 9 on Page 16.
• Ensure that the excess remote cable and loop power wires are
tucked in under the electronics module. Without pinching, place
the module back into the housing and tighten the mounting
screws.
• Replace the housing cover tightly to prevent moisture and other
contaminants from entering and then lock it in place.
1.3. Field Termination
The following section addresses Wiring, conduit, and Earth (Ground)
Connection details.
1.3.1. Conduit Connections
NOTE: The wiring installation shall be in accordance with the local or
national regulations applicable to the specific site and classification
of the area.
The electronics housing has an electronic module compartment and
a field terminal compartment. It also provides 1/2 NPT conduit ope-
nings for access from either side of the VFM 3100 and for ease in
wiring to the field terminals. See Figure 10.
NOTE: One conduit opening contains a threaded plug. Do not dis-
card this plug.
Remove the field terminal compartment cover (shown in Figure 10)
to make electrical connections. Keep the electronic module com-
partment cover closed to ensure protection for the electronic module
and to prevent moisture and atmospheric contaminants from en-
tering the compartment.
There are three wiring combinations that depend on how the
VFM 3100 is to be used.
2-Wire Hook-up
4 to 20 mA and HART (1200 baud)
3-Wire Hook-up
4 to 20 mA, HART (1200 baud) and Scaled Pulse
4-Wire Hook-up
4 to 20 mA, HART (1200 baud) and Scaled Pulse
Two-Wire Hook-up
A dc power supply must be used with each transmitter and receiver
wiring loop to supply power for the mA signal. The dc power supply
may be either a separate signal unit, a multiple unit supplying power
to several transmitters, or built into the receiver. Connect the supply
and receiver loop wiring (0.50 mm2 or 20 AWG typical) to the
terminals in the field-terminal compartment of the transmitter,
as shown in Figure 11.
Electronic module
compartment Electrical conduit
opening
Field terminal
compartment
Figure 10. Electronics Housing