Description Of Operation; Operating States And Sequences; About Operating States; Operating State Descriptions - McQuay MicroTech II Operation Manual

Description of Operation

The following sections describe how the various zone (or
space comfort) control unit processes function to maintain
temperature, ventilation and pressure control. The "Operat-
ing States and Sequences" section provides an overall
description of unit operation. The subsequent sections pro-
vide detailed descriptions of the various control processes
and how the related set points and parameters affect them.
The related set points and parameters are listed at the begin-
ning of each applicable sub-section. The default keypad pro-
grammable values are shown in italic letters.
Note: Not all the features covered in this section apply to
all units depending on the specific unit options. The
applicable items should be read and understood
before making set point or control parameter
changes.

Operating States and Sequences

About Operating States

Operating states define the current overall status of the roof-
top unit. The operating state can be displayed and the unit
operating condition can be quickly determined by viewing
the UnitStatus= parameter in the System menu. Each operat-
ing state summarizes the following information:
Discharge and return/exhaust fan status
l
Outdoor air damper status
l
Return/exhaust airflow capacity
l
Heating system status
l
Cooling system status
l
Fan Operation Output status (MCB-BO3)
l
Table 28: Operating States
Operating Discharge/ Exhaust
State Return Fans
Off Off
Startup Off
Recirc On
Fan Only On Cycling
Econo On Cycling
Cooling On Cycling
MWU On
Heating On Cycling
Min DAT On Cycling
UnocEcon On Cycling
UnocClg On Cycling
UnocHtg On
a. When the OA Ambient= parameter indicates "Low", the economizer outdoor air dampers is fully open; when the OA Ambient= parameter
indicates "High", the economizer outdoor air dampers are at Eff Min OA Pos= value.
When the OA Ambient= parameter indicates "Low", the outdoor air dampers are fully open; when the OA Ambient= parameter indicates
b.
"High", the outdoor air dampers are fully closed.
OM 138
Return
OA
Airflow
Fan Dampers
Capacity
Off Closed 0%
Off Closed 0%
Off Closed Modulating
Minimum Modulating
Modulating Modulating
Minimum or
Modulating
a
Open
Off Closed Modulating
Minimum Modulating
Minimum Modulating
Modulating Modulating
Closed or
Modulating
b
Open
Off Closed Modulating
Table 28 shows the all the normal operating states and the
status information they summarize

Operating State Descriptions

The following sections describe each of the unit operating
states.
Off
There are five different Off operating states. In any of the
Off operating states the unit is shut down. The fans are off
and the outdoor air dampers are closed, any fan inlet vanes
or VFD is driven to 0%. Cooling and heating are disabled.
The Fan Operation Output (MCB-BO3) is open.
The five different Off operating states are described in the
following sections:
Off Unoc . Generally, the unit operating state is Off Unoc
when it the unit is being scheduled on and off by a time clock
function and the time schedule indicates an unoccupied
period. Specifically, the operating state is Off Unoc when the
Occupancy= parameter indicates "Unocc" and none of the
unoccupied unit operation functions are active. For details
regarding the Occupancy= parameter refer to "Occupancy"
on page 46. For details regarding unoccupied unit operation
functions refer to "Unoccupied Control" on page 89.
Off Net . The unit operating state is Off Net when the Appl
Mode= parameter is set to "Off" via a network signal and the
Ctrl Mode= parameter is set to "Auto." For detailed infor-
mation regarding the Appl Mode= and Ctrl Mode= parame-
ter, refer to "Auto/Manual Operation" on page 45.
The unit operating state is also Off Net when the Emerg
Override= parameter in the Occupancy menu is set to "Off."
Refer to "Emergency Override" on page 48.
Exhaust Mechanical
Heat
Airflow Cooling
Enabled
Capacity Enabled
0% No No
0% No No
0% No No
Modulating No No
Modulating No No
Modulating No Yes
0% Yes No
Modulating Yes No
Modulating Yes No
Modulating No No
Modulating No Yes
0% Yes No
Fan Output
(MCB-BO3)
Open
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Closed
Closed
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