INTRODUCTION
The following pages provide information on the features,
in-
stallation, operation and problem analysis of the
McQuay
Microprocessor control for Centrifugal chillers.
Some discrepancy may exist between display statements,
or time Intervals on certain units, and published data. The
differences are minor and exist because of SnyderGeneral’s
avowed ntention to continually improve its products.
Figure 1.
MicroTech
Control Panel
-
GENERAL DESCRIPTION
The
MicroTech
Unit Controller is a
microprocessor
based con-
trol panel designed to initiate the step-by-step start functions
of its host centrifugal compressor unit, monitor and regulate
the compressor’s capacity, protect it, and sequence the com-
pressor shutdown on temperature demand or in response to
a pre-set time.
Visual display of the entire sequence of functions is pro-
vided in plain English on a 20 character vacuum fluorescent
display.
Communication ports permit control and/or status inquiry
through a telephone modem, or over a limited distance,
through a twisted pair, to an IBM PC compatible computer
using
MIcroTech
software.
In the event the compressors’ operation is interrupted by
the action of a safety trip, the cause of the trip condition is
displayed. To further assist the operator or service person-
nel, the cause of the preceeding eight trip conditions is also
recorded
in the non-volatile memory.
Information
about the units’ fault history, setpoints or
operating display values may be obtained by pressing any
of 24
touch
sensitive membrane key switches.
To protect the system from unauthorized or accidental
set-
point changes, the
MicroTech
panel also includes operator
password protection.
IM 403 / Page 3
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