Bypass Time (Tenant Override); Emergency Override; Scheduling - McQuay MicroTech II Operation Manual

Bypass Time (Tenant Override)

Table 13: Programmable Parameters
Keypad/Display ID
Menu Name Item Name
Occ Mode= Auto
Occupancy
Bypass Time= 0 min
Timer Settings Bypass= 120 min
There are two types of tenant override functions: timed and
non-timed. Timed override uses the Bypass Timer and
Bypass Time Increment to place the unit into bypass mode.
Non-timed override uses a simple field supplied SPST
switch to override unoccupied operation.
Timed Tenant Override
The tenant-override button provided with the optional zone
temperature sensor packages is used to override unoccupied
operation for a preprogrammed time period. This time period
is set with the Bypass Time Increment. This value can be
adjusted from 0 to 300 minutes (default is 120 minutes).
When an occupant presses and releases the tenant-override
button on the zone temperature sensor (ZNT1), the Bypass
Timer is set equal to the Bypass Time Increment. (The but-
ton must be held for at least 1 second but not more than 30
seconds.) The unit then starts and runs in the bypass mode
which is the same as occupied mode except that it is tempo-
1
rary. The Bypass Timer begins timing out and the unit runs
until the timer expires. If the tenant override button is
pressed again while the unit is operating in bypass mode, the
Bypass Timer is reset to the Bypass Time Increment and the
unit continues to operate. For example, assume that the
Bypass Time Increment is 120 minutes. One press of the
override button provides at 120 minutes of unit operation. If
the button is pressed again 60 minutes later, the Bypass
Timer is reset to 120 minutes, and a total of 180 minutes of
uninterrupted operation results.
Note: The same operation occurs if, instead of pressing
the override button on a zone temperature sensor,
the Occupancy Mode is set to "Bypass." Once set to
"Bypass", the Occupancy Mode automatically
reverts to the "Auto" setting once the Bypass Timer
is set to the Bypass Time Increment.
Non-Timed Tenant Override
If an field supplied external time clock or a tenant override
switch signal in the form of a set of dry contacts is closed
across terminals 101 and 102 on the unit field terminal block
TB2 (binary input MCB-BI1 on), the unit is placed into
occupied mode 1 . When this switch is open, the unit is con-
1. The unit will not start regardless of the occupancy mode
when the UnitStatus= parameter indicates "Off Sw", "Man
Ctrl", "Off Alm", "Off Net", or "Off Man". For a description of
these operating states, refer to "Operating State Descrip-
tions" on page 61.
48
Parameter Name
Occupancy Mode
Bypass Timer
Bypass Time Increment
trolled by any active scheduling function (internal time clock
schedule, optimal start function, one time event schedule, or
an optional network schedule). If there is no active schedul-
ing function, the unit remains in the unoccupied mode. For
detailed information refer to "External Time Clock or Tenant
Override (Non-Timed)" in IM 696, MicroTech Applied Roof-
top Unit Controller.
Operator Override
The Bypass Timer can be manually set. When the Bypass
Timer is set to a non-zero value, the unit starts and runs in
the bypass mode regardless of any scheduling features.
unit stops when the timer expires. The Bypass Timer can be
set from 0-300 minutes.
Note: If the Bypass Timer remaining time is larger than
the Bypass Time Increment, pressing the tenant
override button on the space sensor has no effect. If
the Bypass Timer remaining time is less than the
Bypass Time Increment, pressing the tenant over-
ride button resets the Bypass Timer to the Bypass
Time Increment value.

Emergency Override

Table 14: Programmable Parameters
Keypad/Display ID
Menu Name Item Name
Occupancy Emerg Override= Norm
The unit can be shutdown by setting the Emergency Over-
ride Mode Flag. When the Emergency Override Mode Flag
is set to "Off", the UnitStatus= parameter indicates "Off
Net" and the unit remains off regardless of any time schedule
or other occupied or unoccupied start commands. The only
way a unit can be restarted is to set Emergency Override
Mode Flag back to "Norm." The Emergency Override Mode
Flag can either be set manually at the unit keypad or via a
network signal.

Scheduling

The rooftop unit can be scheduled for operation by using the
following three methods:
1) Unit internal time scheduling functions
2) External time clock function
3) Network time scheduling function
Provided the unit is not locally or remotely disabled, the unit
operates when any of these scheduling functions is calling
for occupied operation. Conversely, the unit enters the unoc-
cupied mode when all of these scheduling functions are call-
ing for unoccupied operation. Therefore, any unused
scheduling functions should be set for continuous unoccu-
pied operation. Refer also to"Auto/Manual Operation" on
page 45.
1 The
Parameter Name
Emergency Override Mode
Flag
OM 138