77
Table 60 — Humidity Configuration
Table 61 — Related Humidity Points
OPERATION — For operation, PID control will be utilized.
The process will run at the rate defined by the Configuration
→
HUMD
→
H.PID
→
HM.TM. The first part of humidity
control tests the humidity control configuration and will turn
on corresponding configurations to read space or return air rel-
ative humidity. If the supply fan has been ON for 30 seconds
and the space is occupied, then the humidification is started.
Actuator Control — Control is performed with a generic PID
loop where:
Error = HM.SP – humidity sensor value (SP.RH or RA.RH,
depending on configuration).
The PID terms are calculated as follows:
P = K * HM.P * error
I = K * HM.I * error + “I” last time through
D = K * HM.D * (error – error last time through)
Where K = HM.TM/60 to normalize the effect of changing the
run time rate
Relay Output Control — If the humidity sensor reading is
greater than the humidity set point then the humidity relay
(Outputs
→
GEN.O
→
HUM.R) is closed. The relay will open
when the humidity is 2% less than the humidity set point.
CONFIGURING THE HUMIDIFIER ACTUATOR —
Every actuator used in the Z Series control system has its own
unique serial number. The rooftop control uses this serial
number to communicate with the actuator over the local equip-
ment network (LEN). The actuator serial number is located on
a two-part sticker affixed to the side of the actuator housing.
Remove one of the actuator’s serial number labels and paste it
onto the actuator serial number records label located inside
the left-hand access panel at the unit’s control panel. Five
individual numbers make up this serial number. Program the
serial number of the actuator in its Humidifier Actuator
Configurations group, ACT.C (SN.1, SN.2, SN.3, SN.4, SN.5)
NOTE: The serial numbers for all LEN actuators can be found
inside the control doors of the unit as well as on the actuator
itself. If an actuator is replaced in the field, it is a good idea to
remove the additional peel-off serial number sticker on the
actuator and cover up the old one inside the control doors.
Control Angle Alarm (Configuration
→
HUMD
→
ACTC
→
C.A.LM) — The humidifier actuator learns what its end stops
are though a calibration at the factory. Field-installed actuators
may be calibrated in the Service Test mode. When an actuator
learns its end stops through calibration, it determines its control
angle. The actuator will resolve this control angle and express
its operation in a percent (%) of this learned range.
If the humidifier actuator has not learned a sufficient control
angle during calibration, the actuator will be unable to control
humidity. For this reason, the humidifier actuator has a config-
urable control angle alarm low limit (C.A.LM). If the control
angle learned through calibration is less than C.A.LM, an alert
will occur and the actuator will not function.
NOTE: This configuration does not typically need adjustment.
It is configurable for the small number of jobs which may
require a custom solution or workaround.
Dehumidification and Reheat — The Dehumidifi-
cation function will override comfort condition set points
based on dry bulb temperature and deliver cooler air to the
space in order to satisfy a humidity set point at the space or
return air humidity sensor. The Reheat function will energize a
suitable heating system concurrent with dehumidification
sequence should the dehumidification operation result in
excessive cooling of the space condition.
The dehumidification sequence requires the installation of a
space or return air humidity sensor or a discrete switch input. A
CEM (option or accessory) is required to accommodate an RH
(relative humidity) sensor connection. Reheat is possible when
multiple-step staged gas control option or hydronic heat (op-
tion or field-installed coil) is installed. Reheat is also possible
using a heat reclaim coil (field-supplied and installed) or a hot
gas reheat coil (special order, factory-installed).
Dehumidification and reheat control are allowed during
Cooling and Vent modes in the Occupied period.
On constant volume units using thermostat inputs (C.TYP =
3 or 4), the discrete switch input must be used as the dehumidi-
fication control input. The commercial Thermidistat™ device
is the recommended accessory device.
SETTING UP THE SYSTEM — The settings for dehumidi-
fication can be found at the local display at Configuration
→
DEHU. See Table 62.
Dehumidification Configuration (D.SEL) — The dehumidi-
fication configuration can be set for the following settings:
•D.SEL = 0 — No dehumidification and reheat.
ITEM EXPANSION CCN POINT RANGE UNITS DEFAULT
HUMD HUMIDITY CONFIGURATION
HM.CF Humidifier Control Cfg. HUMD_CFG 0 - 4 0
HM.SP Humidifier Setpoint HUSP 0 - 100 % 40
H.PID HUMIDIFIER PID CONFIGS
HM.TM Humidifier PID Run Rate HUMDRATE 10 - 120 sec 30
HM.P Humidifier Prop. Gain HUMID_PG 0 - 5 1
HM.I Humidifier Integral Gain HUMID_IG 0 - 5 0.3
HM.D Humidifier Deriv. Gain HUMID_DG 0 - 5 0.3
ACT.C HUMIDIFIER ACTUATOR CFGS
SN.1 Humd Serial Number 1 HUMD_SN1 0 - 255 0
SN.2 Humd Serial Number 2 HUMD_SN2 0 - 255 0
SN.3 Humd Serial Number 3 HUMD_SN3 0 - 255 0
SN.4 Humd Serial Number 4 HUMD_SN4 0 - 255 0
SN.5 Humd Serial Number 5 HUMD_SN5 0 - 255 0
C.A.LM Humd Ctrl Angle Lo Limit HUMDCALM 0-90 85
ITEM EXPANSION UNITS CCN POINT WRITE STATUS
Config→UNIT→SENS→SRH.S Space Air RH Sensor SPRHSENS
Config→UNIT→SENS→RRH.S Return Air RH Sensor RARHSENS
Inputs→REL.H→RA.RH Return Air Rel. Humidity % RARH forcible
Inputs→REL.H→SP.RH Space Relative Humidity % SPRH forcible
Outputs→ACTU→HMD.P Humidifier Act.Curr.Pos. % HUMDRPOS
Outputs→ACTU→HMD.C Humidifier Command Pos. % HUMDCPOS
Outputs→GEN.O→HUM.R Humidifier Relay HUMIDRLY