10 - 2 RTHC-IOM-1C
Operating Mode at Time of Last Diagnostic
When <Enter> is pressed, the “Chiller Operating
Mode” at the time of the “Last” diagnostic will be
momentarily indicated. This is useful in
understanding what might have caused or
contributed to the diagnostic. More specific
information about the last diagnostic (and other
active diagnostics) is available by pressing <Next>.
Active Diagnostics
If there is at least one diagnostic present, information
about each diagnostic will be presented on the
following screens. (Since the information on each
diagnostic spans a pair of screens, the sequence
number [sn] gives order of occurrence and serves as
a “tag” for the diagnostic. The first pair of diagnostic
screens display the “Last” diagnostic (sn = 01) to
have occurred.
The “diagnostic type” is discussed in the paragraphs
following this. The “help message” identifies specific
checks to be initiated to solve the problem. For a
detailed list of all diagnostics, help messages, and
causes, see
Table 32
.
Diagnostic Types
Warning Only - Reset Not Reqd (IFW) - This type of
diagnostic, also known as an Informational Warning
diagnostic, suggests that while the condition is not
normal, it is not a serious enough to warrant a chiller
shutdown. Certain IFW diagnostics will substitute
safe values for detected erroneous inputs or settings,
to keep the chiller operating. The IFW diagnostics
are logged in the historic diagnostic list for reference.
Unit Shutdown - Reset Reqd (MMR) - This type of
diagnostic, also known as Machine Shutdown or
Manual Reset, causes either an immediate or
“friendly”
1
shutdown of the chiller to prevent system
damage. Generally conditions that cause this type of
diagnostic will not correct themselves, and thus the
root problem must be identified and corrected. For
this reason, these “latching” diagnostics require the
operator to perform a manual reset to restore normal
operation. The reset is accomplished via screens at
the end of the diagnostics menu. See “Clearing
Diagnostics.”
Unit Shutdown - Automatic Reset (MAR) - This
type of diagnostic, also known as Machine Shutdown
or Automatic Reset, causes either an “immediate”
2
or
friendly shutdown of the chiller to prevent system
damage. However, the conditions that cause this
type of diagnostic may correct themselves without
operator action (e.g., low voltage on the incoming
power). For this reason, these diagnostics are non-
latching and, once the condition causing them has
returned to normal, the chiller will restart
automatically. Attempting to manually reset an active
MAR diagnostic is usually both unnecessary and
ineffective.
Other Active Diagnostics
Other active diagnostics will be presented in order of
occurrence as <Next> is pressed. Note that the
Operating Mode of the chiller at the time of the
occurrence of a diagnostic is only given for the “Last”
diagnostic.
Historic Diagnostics
Historic diagnostics follow active diagnostics in the
display with their own sequence number and time
date stamp shown.
Press (Enter) To Display Operating Mode
At Time Of Last Diag Or (Next) For More
[sn] [diagnostic]
(Next) [diagnostic type]
[sn] occurred at HH:MM xm Mon xx, 199x
[help message]
1. A friendly shutdown allows the chiller to go
through a Run Unload period, (lasting about 40
seconds) in which the compressor is allowed
to fully unload prior to shutdown. A post-shut-
down unload, as well as a pre-start unload
period, are also performed, which will usually
allow the compressor to start unloaded on the
next start.
2. An immediate shutdown, does not
allow for an
unload period and will shut down the chiller
immediately. A post-shutdown unload, as well
as a pre-start unload period, however, are per-
formed, which will usually allow the compres-
sor to start unloaded on the next start.
[sn] [Diagnostic]
Historic Only, Press (Next) For More
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