Heavy Duty Balanced Opposed Compressors - Ariel Corporation

FOR MODELS: JGZ AND JGU SECTION 1 - DESIGN SPECIFICATIONS & DATA
Resistance Temperature Devices (RTDs)
An RTD is a resistor type sensor, in which the electrical
resistance accurately varies with temperature change.
When connected to the proper electronics, the resistance is
interpreted as temperature. When RTDs are ordered for the
main bearings, Ariel supplies dual-element RTD instrument
assemblies, consisting of two RTDs in each instrument for
each main bearing. Each element is a three-wire,
100 ohms (at 0°C), Alpha = 0.00385 ohms/ohm/°C,
platinum thin film type sensors.
Dual element RTDs are provided to allow for rewiring
instead of replacing the sensor in the event of an element
failure. The advantage of the dual-element RTD assembly
is that the redundancy saves time by allowing the operator
an opportunity to restore bearing temperature monitoring
without entering the crankcase for each RTD failure.
Wire: The dual element RTDs use 24 AWG (American Wire Gage) instrumentation wire
from the junction box mounted on the side of the compressor frame to the sensor wiring.
An RTD three wire set may be wired using a two, three, or four wire system. More wires
increases accuracy. Ariel recommends using standard foil shielded instrumentation
cable runs from the compressor frame to the control panel. Shields should be grounded
in the control panel.
Sensor Accuracy: 100 + 0.12 ohms at 0°C = 1.1°F (0.6°C), or 0.6 percent.
Terminals: Can use any standard terminals.
Element 1
Element 2
For each instrument, a single RTD three-wire set is used to connect to the monitoring circuit.
If the connected RTD fails, it can be disconnected and the remaining RTD three-wire set can
be used to connect to the circuit. Unused wire ends should be insulated from each other and
conduit ground.
RTD's are furnished with two red wires and one white wire for the one element, and two
black wires and one green wire for the other element to simplify the wiring requirements.
Main Bearing Temperature Alarm and Shutdown Limits
One of the following, minimum, is to be provided for main bearing temperature alarm and
shutdown to Ariel compressors:
1. Main bearing temperature high alarm and shutdown. - The alarm and
shutdown should be set as close as practical above the normal operating
temperature. Ariel recommends 20°F (12°C) over normal operating temperature
for alarm and 30°F (18°C) for shutdown. Maximum values of 220°F (104°C) for
alarm and 230°F (110°C) for shutdown apply. Normal operating temperature is the
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White
Red
Red
Green
Black
Black
FIGURE 1-14 DUAL ELEMENT
RTD WIRING DIAGRAM