McQuay IM 743 Installation Manual

IM 781-2 Page 31
Remote I/O Wiring
The remote I/O modules for the CSM allow for additional analog inputs, analog outputs, digital inputs, and digital outputs
for Cooling Load Pump Control and Cooling Tower Control. Since both cooling load pumping and cooling tower control
are optional features of the CSM, remote I/O modules will not be required on all jobs.
A remote I/O module communicates with the CSM on the same L
ONWORKS network as the chillers. This means the remote
I/O modules do not have to be mounted near the CSM (see the Communications with Chillers and Remote I/O Modules via
L
ONWORKS section on page 20 for network configuration and wire length data). This allows the pump control I/O module
to be mounted near the pumps or the cooling tower I/O modules to be mounted near the fan motor starters. For information
on mounting and power wiring for the remote I/O modules, refer to IM 783-Remote I/O Panel Installation Manual.
Each remote I/O module allows the user to add the following increments of I/O to the CSM:
a)
Four digital outputs
b)
Four digital inputs
c)
Two analog outputs
d)
Four analog inputs
Remote I/O module A, B, and C each provides two analog outputs for variable pump speed control of flow to the cooling
loads (see Figure 8). AO#1 and AO#2 are available for control of VFDs. Digital outputs are also available on these
modules to enable pumps or pump VFDs. If VFDs are not used, the module’s relay outputs are used for control of up to six
constant flow pumps. Digital inputs on these remote I/O modules are used for proving flow after a pump has been enabled.
Each module can control a maximum of two pumps.
Remote I/O module D provides an analog output to provide control of a loop bypass valve (see Figure 11). AO#1 is
available to be wired to a valve.
Remote I/O modules E, F, G, and/or H are used to provide multiple digital outputs for control of cooling tower fans. These
remote modules also provide analog outputs for control of a Cooling Tower Bypass Valve and/or VFDs which may be
controlling the cooling tower fan speeds. Digital Inputs on these remote I/O modules are used for optional cooling tower
alarm status feedback to the CSM. Analog Inputs on these remote I/O modules are used for optional cooling tower VFD
percent of speed feedback to the CSM.
When you receive a remote I/O module(s) in a remote I/O panel, it has not yet been assigned a designation (meaning it has
not yet been assigned to be hardwired, remote A, remote B, etc.). The module only becomes a remote I/O module A (or B,
or C, etc.) or a remote I/O module for hardwired chillers after it has been commissioned into the CSM’s L
ONWORKS
communications network. This assignment is accomplished at the Device Addressing screen of the CSM User Interface.
To designate a remote I/O module(s), go to the Device Addressing tab in the CSM User Interface. The Device Addressing
screen contains both a Chiller table and a Remote I/O table. To designate a remote I/O module, click on the Service Pin
button associated with the appropriate remote I/O device (e.g. Remote I/O - A) in the Remote I/O table. While the Service
Pin timer is counting down, (the timer appears as a pop-up box on the screen) press down on the Service Pin button located
on the remote I/O module. After you have assigned a module, label it for future reference. Labels are included with the
remote I/O panel for this purpose.
Note: All terminals on the remote I/O modules accept wire from a min size of 20 AWG (0.5 mm
2
) to a max of 14 AWG
(2.5 mm
2
).
Inputs
Analog Inputs
Each remote I/O module is equipped with four universal inputs. The CSM configures these universal inputs to be voltage
variable inputs. The CSM user can configure these inputs to display a percentage corresponding to 0-10 VDC or 2-10
VDC. A 4-20 mA signal can be converted to voltage for connection to the remote I/O module’s voltage variable input by
installing a 499 ohm, ¼ watt, 1%, metal film resistor across the analog input terminals.
The remote I/O module’s analog inputs are isolated from ground as long as the 24-volt power supply does not have its
common (terminal 2) tied to ground. Do not wire the secondary side of this 24-volt transformer to ground. The analog
input common terminals are tied to each other (and the analog output common terminals). Ground loops could occur
through the remote I/O module if it is connected to two or more external devices that are not isolated from ground.

McQuay IM 743 Specifications

General

Brand	McQuay
Model	IM 743
Category	Controller
Language	English