Intek RheoVac 950A - Manual (Page 9)

- 7 -
2.1.2 Electronics Unit Site Selection
The Model 950 typically has two or three electronics enclosures (see Figure 1). The processor
enclosure and other electronics boxes should be installed in a convenient location and should be
kept away from direct sources of heat, such as non-insulated steam lines, or moisture. The
maximum temperature rating of electronics is 120(F; ensure that this temperature will not be
exceeded inside the enclosure. Once the wiring connections are made, close and latch down the
box lid to protect the contents from damage and debris. All these enclosures should be located in
a dry area and should be kept clamped shut during normal operation. Do not allow water to get
into the enclosures. If installed outdoors, build a roof over all enclosures to prevent potential
water infiltration.
x Processor Enclosure: This 12x10 NEMA 4 enclosure houses the display and central
processing unit. Input power (100-250 Vac, 50/60 Hz) is connected inside this enclosure.
x Distribution Box: This 8x6 NEMA 4 enclosure is typically located near the probe that is
closest to the processor enclosure unit. It is connected to the main processor with an RS-
485 bus DeviceNet™ cable, which can be hundreds of feet long. The probe and
transmitter RS-485 cable connections are also made within this box. The probe and
transmitter cable lengths should be 15 ft or less.
x Transmitter Box (optional): This 10x8 NEMA 4 enclosure contains terminals for
accessing the eight 4-20mA signals. It can be located in or near the control room so that
the 4-20 wires do not have to be run from the plant floor. An RS-485 DeviceNet™ cable
runs from the distribution box to the transmitter box. (There are restrictions on how this
can be done, so check manual SECTION 6, or contact the factory.)
2.2 PROBE INSTALLATION
A. Hot Tap Installation
1. Check hardware. Verify that the probe slides easily through the hot tap assembly and
pipe penetration hole.
2. Verify there is a minimum probe insertion clearance of 4 feet (1.3m) between pipe
surface and any obstruction.
3. Install the mounting hardware. Drill a 1½” through-hole, center the thread-o-let over
the hole and weld it onto the condenser vacuum pipe (see Figure 3). Thread the hot
tap assembly into the thread-o-let. Use thread tape or pipe dope to seal the
connection. (Alternate: weld thread-o-let to pipe wall, then drill a 1¼" hole in pipe
wall using a hot tap drill.)
4. Make sure the probe is parallel to the floor (see Figure 3). Be sure location is
accessible for probe removal and maintenance.
B. Installing/Removing the Probe
1. It may be necessary to apply a force of about 23 lb (102 Newtons) to remove or
replace the probe under plant operating conditions.
2. Check proper installation direction. Each probe has a directional arrow on the
junction box. Before installing the unit, note proper flow direction. This is important
to instrument operation.