Controls, Start-Up, Operation, Service and ... - Climayoreo

The default sensor is the return air relative humidity sensor
(D.SEN = 1). Units ordered with the Humidi-MiZer option
will have factory-installed return air relative humidity sensors.
Economizer Disable in Humidi-MiZer Mode (D.EC.D) —
When D.SEL = 4 (DH – HUMDZR), this configuration is automatically
set to D.EC.D = YES (Economizer disabled during
dehumidification).
Vent Reheat Set Point Select (D.V.CF) — This configuration
determines how the vent reheat set point is selected. This set
point becomes the supply air set point when the Humidi-MiZer
function is initiated and the unit enters a Reheat Mode (relative
humidity above set point with no cooling demand).
D.V.CF = 0 — Reheat follows an offset subtracted from return
air temperature (D.V.RA).
D.V.CF = 1 — Reheat follows a dehumidification heat set
point (D.V.HT).
Vent Reheat RAT Offset (D.V.RA) — Set point offset used
only when the Humidi-MiZer function is initiated and the unit
enters a Reheat Mode. This occurs when the relative humidity
is above set point with no cooling demand. The air will be reheated
to return-air temperature less this offset.
Vent Reheat Set Point (D.V.HT) — Set point used only when
the Humidi-MiZer function is initiated and the unit enters a Reheat
Mode. This occurs when the relative humidity is above set
point with no cooling demand. When D.V.CF = 0, the supply
air will be reheated to D.V.HT minus D.V.RA. When D.V.CF =
1, the supply air will be reheated to D.V.HT.
Dehumidify Cool Set Point (D.C.SP) — This is the Humidi-
MiZer cooling set point used to determine the temperature the
air will be cooled to prior to it being reheated to the desired
supply air temperature. This set point is used during the Humidi-MiZer
dehumidification and reheat modes of operation
Dehumidify RH Set Point (D.RH.S) — This is the Humidi-
MiZer relative humidity trip point.
HumidiMiZer Adjust Rate (HZ.RT) — This is the rate (seconds)
at which corrections are made in the position of the modulating
valves (C.EXV and B.EXV) to maintain supply air set
point.
HumidiMiZer Proportional Gain (HZ.PG) — This is the
proportional gain used in calculating the required valve position
change for supply air temperature control. It is essentially
the percentage of total reheat capacity adjustment that will be
made per degree Fahrenheit of supply air temperature error.
OPERATION
Mode Qualifications — An HVAC: Off, Vent or Cool mode
must be in effect to launch a Humidi-MiZer mode.
Sensor Failure — If an associated sensor responsible for controlling
Humidi-MiZer fails, dehumidification will not be attempted
(SPRH, RARH).
Initiating a Humidi-MiZer Reheat or Dehumidification
Mode — To call out a Reheat mode in the “Vent” or the “Off”
HVAC mode, or to call out a Dehumidification mode in a
“Cool” HVAC mode, one of the following must be true:
• The space is occupied and the humidity is greater than
the relative humidity trip point (D.RH.S).
• The space is occupied and the discrete humidity input is
closed.
Ending a Humidi-MiZer Reheat or Dehumidification Mode
— When either the humidity sensor falls 5% below the set
point (ConfigurationDEHUD.RH.S) or the discrete input
reads “LOW”, the Humidi-MiZer mode will end.
Relevant Outputs — The Humidi-MiZer 3-way valve (reheat
valve) commanded output can be found in OutputsCOOLRHV.
The Humidi-MiZer Condenser Modulating Valve (Condenser
EXV) position output can be found in Outputs
81
COOLC.EXV. The condenser position will be provided
as percent open.
The Humidi-MiZer Bypass Modulating Valve (Bypass
EXV) position output can be found in OutputsCOOL.EXV.
The bypass position will be provided as
percent open.
HUMIDI-MIZER MODES
Dehumidification Mode (Subcooling) — This mode will be
engaged to satisfy part-load type conditions when there is a
space call for cooling and dehumidification. Although the temperature
may have dropped and decreased the sensible load in
the space, the outdoor and/or space humidity levels may have
risen. A typical scenario might be when the outside air is 85 F
and 70 to 80% relative humidity (RH). Desired SHR for equipment
in this scenario is typically from 0.4 to 0.7. The Humidi-
MiZer unit will initiate Dehumidification mode when the space
temperature and humidity are both above the temperature and
humidity set points, and attempt to meet both set point requirements.
Once the humidity requirement is met, the unit can continue
to operate in normal cooling mode to meet any remaining
sensible capacity load. Alternatively, if the sensible load is met
and humidity levels remain high the unit can switch to Hot Gas
Reheat mode to provide neutral, dehumidified air.
Reheat Mode — This mode is used when dehumidification is
required without a need for cooling, such as when the outside
air is at a neutral temperature but high humidity exists. This situation
requires the equipment to operate at a low SHR of 0.0 to
0.2. With no cooling requirement and a call for dehumidification,
the P-Series Humidi-MiZer adaptive dehumidification
system will cycle on enough compressors to meet the latent
load requirement, while simultaneously adjusting refrigerant
flow to the Humidi-MiZer coil to reheat the air to the desired
neutral air set point. The P-Series Humid-MiZer system controls
allow for the discharge air to be reheated to either the return
air temperature minus a configurable offset or to a configurable
Reheat set point (default 70 F). The hot gas reheat mode
will be initiated when only the humidity is above the humidity
set point, without a demand for cooling.
System Control — The essential difference between the Dehumidification
Mode and the Reheat mode is in the supply air
set point. In Dehumidification Mode, the supply air set point is
the temperature required to provide cooling to the space. This
temperature is whatever the cooling control point would have
been in a normal cooling mode. In Reheat Mode, the supply air
set point will be either an offset subtracted from return air temperature
(D.V.RA) or the Vent Reheat Set Point (D.V.HT).
Both values are configurable. For both Dehumidification mode
and Reheat mode, the unit compressor staging will decrease the
evaporator discharge temperature to the Dehumidify Cool Set
Point (D.C.SP COOL) in order to meet the latent load and reheat
the air to the required cooling or reheat set point. There is a
thermistor array called TemperaturesAIR.TCCT connected
to the RCB. This thermistor array serves as the evaporator
discharge temperature (EDT). See Fig. 15.
The P-Series Humid-MiZer ® system uses refrigerant flow
modulation valves that provide accurate control of the leaving
air temperature as the evaporator discharge temperature is decreased
to meet the latent load. As the refrigerant leaves the
compressor, the modulating valves vary the amount of refrigerant
that enters and/or bypasses the condenser coil. As the bypassed
and hot refrigerant liquid, gas or two-phase mixture
passes through the Humidi-MiZer coil, it is exposed to the cold
supply airflow coming from the evaporator coil. The refrigerant
is subcooled in this coil to a temperature approaching the
evaporator leaving air temperature. The liquid refrigerant then
enters a thermostatic expansion valve (TXV) where the refrigerant
pressure is decreased. The refrigerant enters the TXV and
evaporator coil at a temperature lower than in standard cooling
operation. This lower temperature increases the latent capacity
of the evaporator. The refrigerant passes through the evaporator