74
Vent Reheat Setpoint Select (D.V.CF)
This configuration determines how the vent reheat setpoint is
selected.
•
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)
Setpoint offset used only during the vent mode. The air will be
reheated to return-air temperature less this offset. This configu-
ration will have a range of 0 to 8°F with default of 0°F.
Vent Reheat Setpoint (D.V.HT)
Setpoint used only during the vent mode. The air will be re-
heated to this setpoint. This configuration will have a range of
55 to 95°F with default of 70°F.
Dehumidify Cool Setpoint (D.C.SP)
This is the dehumidification cooling setpoint. This configura-
tion will have a range of 40 to 55°F with default of 45°F.
Dehumidify RH Setpoint (D.RH.S)
This is the dehumidification relative humidity trip point. This con-
figuration will have a range of 10 to 90°F with default of 55°F.
Enable Hmzr St Oil Ret (HZ.OR)
[ENHORTST] This configuration can enable or disable the
Humidi-MiZer oil return during service test. It is recommended
leaving this configuration enabled. This configuration will
have a range of DSLB/ENBL with default of ENBL.
OPERATION
Dehumidification and reheat can only occur if the unit is
equipped with staged gas, or hydronic heat, or Humidimizer, or
an external heat source via the alarm relay. Dehumidification
without reheat can be done on any unit but
Configuration
DEHU
D.SEL
must be set to 0 or 2.
If the machine’s control type is a TSTAT type (
Configuration
UNIT
C.TYP
=3 or 4) and the economizer is able to provide
cooling, a dehumidification mode may be called out, but the con-
trol will not request mechanical cooling and
D.EC.D
=NO.
NOTE:
• Configuring
Configuration
DEHU
D.SEN
to 1
(RARH or SPRH SENSOR) will enable the ECB1 board
along with the sensor selected for control.
• Configuring
Configuration
DEHU
D.SEN
to 2
(DISCR.INPUT) will enable the CEM board along with
the switch input for control.
• Configuring
Configuration
DEHU
D.SEL
to 3
(DH-HMZR) will enable the EXB2/RXB board with the
CCT input and three-way valve in addition to the EXV
board with the modulating valves.
If an associated RARH sensor responsible for dehumidification
fails, dehumidification will not be attempted; see Alert T078
Return Air Relative Humidity Sensor Fail.
Initiating a Dehumidification Mode
To call out a Dehumidification mode in any HVAC mode, one
of the following conditions 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.
Dehumidification Including Reheat Control
If a dehumidification mode is initiated, the rooftop will attempt
to lower humidity as follows:
• Economizer Cooling — The economizer, if allowed to per-
form free cooling, will have its control point (
Run Status
VIEW
EC.C.P
) set to
Configuration
DEHU
D.C.SP
.
If
Configuration
DEHU
D.EC.D
is disabled, the econ-
omizer will always be disabled during dehumidification.
• Cooling — For all cooling control types: A High Cool
HVAC mode will be requested internally to the control to
maintain diagnostics, although the end user will see a Dehu-
midification mode at the display (Cooling Dehum). In addi-
tion, for multi-stage cooling units the cooling control point
will be set to
Configuration
DEHU
D.C.SP
(no
SASP reset is applied).
• Reheat When Cooling Demand is Present — For reheat con-
trol during dehumidification: If reheat follows an offset sub-
tracted from return-air temperature (
Configuration
DEHU
D.SEL
= 2), then no heating will be initiated and
the alarm relay will be energized. If
Configuration
DEHU
D.SEL
= 1 and
Configuration
HEAT
HT.CF
=
staged gas or hot water valve, then the selected heating con-
trol type will operate in the low heat/modulating mode.
• The heating control point will be whatever the actual cool-
ing setpoint would have been (without any supply air reset
applied).
• Reheat During Vent Mode — If configured
(
Configura-
tion
DEHU
D.V.CF
= 0), the heating control point
will be equal to RAT –
D.V.RA
. If configured (
Configura-
tion
DEHU
D.V.CF
=1
), the heating control point
will be equal to the
D.V.HT
setpoint. (
VENTING DE-
HUM
) will be displayed for the MODE.
• Dehumidification and Reheat in a Heat Mode — If there is a
Dehum demand and the temperature demand requires heat,
the Heating Dehum will be displayed and in LO-Heat condi-
tions the reheat setpoint will be equal to the Heat Control
point HT.SP. In a High heat condition the Heat will stage up
fully or go to 100%.
Ending Dehumidification and Reheat Control
When either the humidity sensor fall 5% below the setpoint
(
Configuration
DEHU
D.RH.S
)
or the discrete input
reads “LOW”, the Dehumidification mode will end.
Table 69 — Dehumidification Configuration
ITEM
EXPANSION
RANGE
UNITS
CCN POINT
DEFAULT
DEHU
DEHUMIDIFICATION CONFIG.
D.SEL
Dehumidification Config
0 to 3
DHSELECT
0
D.SEN
Dehumidification Sensor
1 to 2
DHSENSOR
1
D.EC.D
Econ disable in DH mode?
Yes/No
DHECDISA
Yes
D.V.CF
Vent Reheat Setpt Select
0 to 1
DHVHTCFG
0
D.V.RA
Vent Reheat RAT offset
0 to 8
^F
DHVRAOFF
0
D.V.HT
Vent Reheat Setpoint
55 to 95
dF
DHVHT_SP
70
D.C.SP
Dehumidify Cool Setpoint
40 to 55
dF
DHCOOLSP
45
D.RH.S
Dehumidify RH Setpoint
10 to 90
%
DHRELHSP
55
DH.DB
Dehumidify RH Deadband
1 to 30
%
DHSENSDB
DH.TG
Dehum Discrete Timeguard
10 to 90
s
DHDISCTG
HZ.RT
Humidi-MiZer Adjust Rate
5 to 120
sec
HMZRRATE
30
HZ.PG
Humidi-MiZer Prop. Gain
0 to 10
HMZR_PG
0.8
HZ.OR
Enable HMZR St Oil Ret
Dsbl/Enbl
ENHORTST
Enbl
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...