3
Theory of operation
The VT76x7 uses a Viconics proprietary adaptive logic
algorithm to control the space temperature. This
algorithm controls the heating / air conditioning system
to minimize overshoots while still providing comfort. It
provides exceptional accuracy due to its unique PI
time proportioning control algorithm, which virtually
eliminates temperature offset associated with
traditional, differential-based on/off thermostats.
Fig.2 - On/Off mechanical control vs PI electronic control.
Features overview
•
7 day programmable models, 2 or 4 events
•
Gas/oil or electric system compatibility for all type
of applications
•
Internal RH sensor and remote RH input with
humidification and dehumidification sequence of
operation embedded
•
Remote outdoor sensing capability for added
flexibility
- System mode lock out
- Humidity setpoint reset
•
High limit input to prevent over-humidification
•
Lockable keypads for tamper proofing. No need for
thermostat guards
•
Automatic frost protection to prevents costly freeze
damage
•
Anti short cycle and minimum on/off run time
protection. Reduces wear and maximizes life span
of mechanical equipment.
•
Programmable digital input for added flexibility. The
input can be programmed as the following:
-
None:
No function will be associated with the
input
-
Service:
a backlit flashing
Service
alarm will be
displayed on the thermostat LCD screen when
the input is energized. It can be tied in to the AC
unit control card, which provides an alarm in
case of malfunction.
-
Filter:
a backlit flashing
Filter
alarm will be
displayed on the thermostat LCD screen when the
input is energized. It can be tied to a differential
pressure switch that monitor filters
-
Rem NSB:
remote NSB timer clock input. Will
disable the internal scheduling of the thermostat.
The scheduling will now be set as per the digital
input. The menu part related to scheduling is
disabled and no longer accessible. It provides low
cost setback operation via occupancy sensor or
from a dry contact
-
RemOVR:
temporary occupancy contact. Disables
all override menu function of the thermostat. . The
override function is now controlled by a manual
remote momentarily closed contact. When
configured in this mode, the input operates in a
toggle mode.
With this function enabled it is now possible to
toggle between unoccupied & occupied setpoints
for the amount of time set by parameter
(TOccTime) temporary occupancy time.
Fan lock:
used in conjunction with a local airflow
sensor connected to the input. Locks out the
thermostat heating and cooling action and displays
a local alarm if no air flow is detected 10 seconds
after the fan ( G terminal ) is energized.
•
Programmable smart fan operation saves
energy during night mode
•
Non volatile EEPROM memory prevents loss of
parameters during power shortage
•
Built in default profile set-up for easier start up
and commissioning
•
Configurable SPST output relay on
programmable models for lighting, exhaust fan
or fresh air control
•
6 hour typical reserve time for clock in case of
power loss
•
0 to 10 Vdc humidification output
- Built in proportional humidity controller
- Proportional humidity high limit when used
with the analog input for supply humidity
- Automatic humidity setpoint reset when
outside air temperature value is used.
Summary of Contents for VT7607B5x28(X)
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