LCBS CONNECT SOLUTION
31-00118EFS—01
8
minimum on and off times for compressor operation and lockouts based on low sensed ambient or outdoor air
temperature. Freeze stat operation protects HVAC system from being damaged as systems are cycled off if system
freezing conditions are detected.
Cooling Operation
LCBS Connect controllers support control of compressor stages and DX refrigeration circuits. Up to three stages of
cooling can be controlled by LCBS Connect controllers. There is a freeze stat sensor control input that monitors potential
freezing temperatures and serves as a low limit. The sensor is typically mounted against the cooling coil and protects it
from freezing, resulting in coil damage and can also make sure that unheated outdoor compressors aren't "slugged." The
LCBS Connect controller shuts off the supply fan, the compressor and closes the outdoor air damper if a frozen coil
condition is detected. Also the discharge air sensor utilizes a control tactic called a "low limit", where if the discharge air
temperature falls below the low limit, compressor stages will be turned off until the condition goes away or all stages are
off.
Dehumidification
Dehumidification Theory and Operation
Dehumidification is an important part of control operation in many parts of the United States. High humidity can result in
two major problems. First, high relative humidity can result in uncomfortable conditions for building occupants. Second,
relative humidity is destructive to architectural elements like carpeting, wallpaper, paint, and art work.
How does LCBS Connect dehumidification work?
Three (3) dehumidification strategies for dehumidification control are supported. First, cooling and heating can be
programmed to operate in a reheat sequence to provide precise dehumidification operation. Second, dehumidification
equipment can be controlled through a direct LCBS Connect output to provide dehumidification. Third, extended cooling
extended runtime can be selected that can enhance and augment the dehumidification process. These are described in
detail below.
Method #1. Cooling On, Cycle Heating
The reheat dehumidification control algorithm works only when system in in cooling mode. The call for dehumidification
occurs as a result of humidity level rising above the dehumidification limit. If cooling is not operating, it becomes
energized. A single stage of heating is energized in conjunction with the call for dehumidification. When humidity drops
below set point less differential, hysteresis, the heating stage is cycled off and cooling cycles off. If a call for cooling
continues, cooling remains on and cycles per temperature control algorithm. Method #1 can be augmented with Method
#3, described below.
NOTE:
It's important to observe the configuration of heating and cooling coils in the constant volume that you intend to
apply the dehumidification algorithm. The heating coil must be downstream of the supply fan and cooling coil for
the dehumidification algorithm to work properly.
Fig. 2.
Method #2: Simple Humidification
In the "simple dehumidification method," the algorithm simply senses space or return air humidity and energizes a
designated digital output until the call for dehumidification abates. Method #2 can be augmented with Method #3,
described below.
ON
OFF
ON
OFF
ON
OFF
DEHUMIDIFICATION CONTROL
WORKS IN “COOLING MODE” ONLY, DOES NOT WORK IN “HEATING MODE”
TIME
HUMIDITY LIMIT,
SETPOINT EXCEEDED
HUMIDITY LIMIT,
SETPOINT ABATES
FAN
COOLING
HEATING
FAN ON CONTINUOUSLY (OCCUPIED, STANDBY PERIOD)
COOLING CYCLING, LOCKED ON, CYCLING
HEATING OFF, CYCLING, OFF
MCR36697