• Use proper electrostatic discharge (ESD) precautions during installation and servicing to avoid
damaging the electronic circuits of the device.
PSHC-QREV application wiring
QREV and PSHC technical specifications
table for power requirements.
Power supply usage and application
When you install the QREV and PSHC, observe the following guidelines when you wire the application.
Grounding
PSHCs that you network with non-isolated instrumentation must share only one single-point
earth ground, or you must fully isolate them from each other. The single-point ground location
can be either the communication ground or at one of multiple power supplies, if in use, but
not both. If multiple power supplies are in use, and all must be earth ground, then isolated
communication is required.
Incompatible power supply topologies
Make sure that the 3rd-party instrumentation uses either a full-wave rectifier, or a two-diode
half-wave rectifier topology if PSHCs are networked with non-isolated 3rd-party instrumentation
and both share the same power supply. Most 1/2 wave implementations use a single diode only,
which can result in a high-current ground loop.
Wiring a PSHC-QREV application
1. Choose a QREV model that is rated for your application’s supply power.
Note:
The PSHCs operate on 12 VDC, 24 VDC, or 24 VAC. The QREVs are voltage specific. See
Table 1 for more information.
Important:
Do not apply 24 V supply power to 12 VDC QREV models. 24 V supply power
damages the 12 VDC QREV models and voids the warranty. Do not apply 12 V supply power to
24 V QREV models. 24 V QREV models do not operate properly on 12 V supply power.
Figure 16: Class 2 AC and DC power sources
Note:
Never connect a green data Ground (Gnd) wire to earth ground. Run the wire only to
RS-485 data ground. If you are unsure, do not attach a wire but just cap it off.
Do not ground any of the power leads to the PSHC if possible. If this is not possible, never
ground the data Gnd wire or the RS-485 data wires because this damages the PSHC.
Quick Response Expansion Valve and Precision Superheat Controller Installation Guide
12
