IM-P192-02 MI Issue 2 23
3.4 Electrical installation
The TVA owmeter is a loop powered device. This Section describes loop wiring and shows
typical conductor terminations (The EIA 232C (RS 232) wiring is discussed in Section 4.11,
page 41). It also considers the effect of connecting additional equipment (e.g. recorder, loop
powered display) to the loop, plus the pressure sensor connection.
Wiring the TVA flowmeter
The wiring terminals can be accessed by removing the end cap of the enclosure. A typical
loop wiring diagram is shown in Figure 20.
If an M750 display unit is purchased from Spirax Sarco for use with the TVA owmeter, the
M750 must be congured to the ow of the TVA owmeter @ 20 mA. If the TVA owmeter
4 - 20 mA output is rescaled (see Section 4.6.1), it is important that the 20 mA input valve
on the M750 is also rescaled.
Recommendations:
-
Ensure the provided EMC gland is used to connect the wiring to the electronics housing.
-
When using the RS232/485 port, PVC covered steel conduit should be used.
-
All cables that run through conduit should be screened. The screens must be earthed at
the far end of the installation and not at the owmeter.
-
If using the loop and switch pulse ports:
- Either combine both port outputs to one screened four core cable which is terminated
with an EMC gland.
-or, use exible conduit as described above.
Notes:
The flowmeter must be earthed. The TVA is supplied with a 350 mm earthing lead
attached to a 4 mm threaded hole at the rear of the enclosure close to the 20 mm
conduit holes.
Remove the silica gel from the enclosure after commissioning.
When connecting the superheat kit to the TVA, the cable from the pressure sensor
must be threaded through the 20 mm conduit hole on the rear of the electronics housing.
Plug the connector on to the pin header (as indicted in Figure 20) making sure that the
blanking pin is aligned correctly with the missing pin on the plug.
Refit the end cap ensuring that no wires are crushed and tighten the cable gland
to 13 N m (9.58 lbf ft) to ensure an IP65 seal.
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