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Operation Manual
MicroTech Applied Rooftop Unit Controller:
CAV-ZTC Control
Programs ART5 and ART7
Dehumidification/Reheat Control Sequence
OM 109 Supp. #1
Group: Applied Systems
Part Number: 629960Y
Date: May, 1998
©1998 McQuay International
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Contents
Introduction .................................................................................................................................................. 3
Dehumidification Enable/Disabled .............................................................................................................. 3
Occupied Dehumidification ......................................................................................................................... 3
Dehumidify from Cooling/Economizer ................................................................................................ 3
Dehumidify from Heating ..................................................................................................................... 4
Dehumidify from Fan On/Fan On Heat ................................................................................................ 4
Unoccupied Dehumidification ..................................................................................................................... 4
Dehumidify from Unoccupied Cooling/Unoccupied Economizer ........................................................ 4
Dehumidify from Unoccupied Heating ................................................................................................. 5
Dehumidify from Off Unoccupied ........................................................................................................ 5
Dehumidification Unit Configuration ......................................................................................................... 6
Dehumidification Cooling With Compressors ............................................................................................ 8
Dehumidify from Cooling/Economizer ................................................................................................ 8
Dehumidify from Fan On/Fan On Heat/Heating ...................................................................................9
Dehumidify from Off Unoccupied/Unocc. Cooling/Unocc. Economizer/Unocc. Heating .................. 9
Dehumidification Cooing With Chilled Water .......................................................................................... 10
Dehumidify from All Possible States .................................................................................................. 10
Heat/Reheat Control ...................................................................................................................................10
Configuration #1 ..................................................................................................................................10
Dehumidify from Economizer/Unoccupied Economizer/Cooling/Unoccupied Cooling ............. 10
Dehumidify from Heating/Unoccupied Heating ........................................................................... 11
Dehumidify from Fan On/Fan On Heat ........................................................................................ 11
Dehumidify from Off Unoccupied ................................................................................................12
Configuration #2 ..................................................................................................................................12
Configuration #3 ..................................................................................................................................12
Dehumidification Menu items ................................................................................................................... 13
Inputs/Outputs ............................................................................................................................................ 14
CAV-Zone Temperature Control w/Return Air .................................................................................. 14
CAV-Zone Temperature Control w/100% Outside Air ...................................................................... 15
Dehumidification Compressorized Staging Sequences ............................................................................. 16
Input Schematic ......................................................................................................................................... 20
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INTRODUCTION
This document describes the sequence of operation of the dehumidification sequence incorporated into the
standard Constant Volume Zone Control (ART5 & ART7) software packages.
A DX or chilled water cooling coil is controlled to cool the air low enough to wring out moisture. Reheat is
then supplied as necessary to provide properly conditioned air to the space. Although the unit will most
likely have an optional space temperature installed, the dehumidification sequence does not require one. The
unit reheat is always controlled to maintain the Menu # 12 “Cntl Temp=” input at the reheat set point.
Generally the unit would have an optional space temperature sensor installed and this parameter would be set
to “Space”. From this point forward in this document it is assumed that “Cntl Temp=Space”. When
dehumidification is not required the unit operates as described in operation manual OM 109.
An humidity sensor is mounted in either the space or return air to sense relative humidity. The sensor is
wired to field terminals 101, 126 and 127 as shown on the attached input schematic. Terminals 126 and 127
are factory wired to analog input AI12 on the unit ADI board. This signal from the humidity sensor to the
ADI board varies from 0-5VDC as the humidity varies from 0-100% RH. Dew point is calculated using this
RH value and either the space or return air temperature depending on the location of the humidity sensor.
Relative humidity and dew point are both displayed on Menu # 10 of the keypad (“Humidity=” and “Dew
point=”). Dehumidification control parameters are located on Menu # 18. "Humidity" or "Dew point" can be
selected as the type of humidity control (“Control=“). "Space" or "Return" can be selected for the location of
the humidity sensor (“Sensor=”). Note: “Space” cannot be selected if the “Space Sensor=” parameter on
Menu 28 is set to “No”. A relative humidity set point and dead band (“Humidity Spt=” and “Humidity
DB=”) and dew point set point and a dead band (“Dewpt Spt =” and “Dewpt DB=”) are also adjustable
through Menu #18. Refer to the “Dehumidification Menu Items” section of this document for a listing of all
menu items added related to dehumidification operation.
DEHUMIDIFICATION ENABLE/DISABLED
The dehumidification function is enabled or disabled through Menu # 18 (“DehumidCntl=”). Setting this
parameter to “No” disables and “Yes” enables dehumidification. Caution: This parameter should never be
set to “Yes” unless the unit can be classified as one of the three configurations described in the
“Dehumidification Unit Configuration” section of this document.
Dehumidification is disabled if mechanical cooling is disabled for any reason. It also is disabled if heating is
disabled for any reason except outside air temperature lockout. Refer to Menu #7 (Cool Status) and Menu #8
(Heat Status). Dehumidification is allowed if heat is disabled due to high OAT since it may be required
during warm periods.
OCCUPIED DEHUMIDIFICATION
The unit is allowed to enter the Dehumidify state from the following “occupied” operating states: Fan On,
Fan On Heat, Economizer, Mechanical Cooling or Heating. Dehumidification operation is initiated when the
humidity/dew point rises above the set point by more than the dead band. Refer to Figure 4 (ART5) and
Figure 5 (ART7) for sequence charts showing the possible transitions in and out of the Dehumidify state.
Dehumidify from Cooling/Economizer
If the humidity/dew point rises above the set point by more than the dead band while the unit is in either the
Economizer or Mechanical Cooling state, the unit enters the Dehumidify state in which dehumidification
cooling is turned on and reheat is controlled to maintain the space temperature at the reheat set point (Menu
14 “Reheat Spt=”). This set point is not adjustable from the keypad but is set equal to the zone cooling set
point (Menu 12 “Cooling Spt=” ) by the controller. When both the humidity/dew point set point and the
reheat set point are satisfied, the unit will leave the Dehumidify and enter the Fan On state. Note: The unit
can leave the Dehumidify and enter the Mechanical Cooling state under certain conditions if the unit has DX
cooling (refer to the “Dehumidification Cooling With Compressors” section of this document). While in the
OM 109 Supplement #1 / Page 3
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Dehumidify state, the outside air dampers are driven fully open if the outside air enthalpy is suitable for free
cooling. Otherwise the dampers are driven to minimum position.
Dehumidify from Heating
If the humidity/dew point rises above the set point by more than the dead band while the unit is in the
Heating state, the unit enters the Dehumidify state in which dehumidification cooling is turned on and reheat
is controlled to maintain the space temperature at the reheat set point (Menu 14 “Reheat Spt=”). This set
point is not adjustable from the keypad but is set equal to the zone heating set point (Menu 12 “Heating
Spt=” ) by the controller. When both the humidity/dew point set point and the reheat set point are satisfied,
the unit will leave the Dehumidify and enter the Fan On state. While in the Dehumidify state, the outside air
dampers are driven to minimum position.
Dehumidify from Fan On/Fan On Heat
If the humidity/dew point rises above the set point by more than the dead band while the unit is in the Fan On
or Fan On Heat state, the unit enters the Dehumidify state in which dehumidification cooling is turned on and
reheat is controlled to maintain the unit discharge temperature at the reheat set point (Menu 14 “Reheat
Spt=”). This set point is not adjustable from the keypad but is set equal to the fan on heating set point (Menu
14 “Fan On Htg=” ) by the controller. When the humidity/dew point set point is satisfied, the unit will leave
the Dehumidify and enter the Fan On state. While in the Dehumidify state, the outside air dampers are
driven to minimum position.
If the space temperature should rise above the zone cooling set point (Menu 12 “Cooling Spt=”) while the
unit is in this “Dehumidify from Fan On/Fan On Heat” operating mode, the unit will change to the
“Dehumidify from Cooling/Economizer” operating mode.
If the space temperature should fall below the zone heating set point (Menu 12 “Heating Spt=”) while the
unit is in this “Dehumidify from Fan On/Fan On Heat” operating mode, the unit will change to the
“Dehumidify from Heating” operating mode.
UNOCCUPIED DEHUMIDIFICATION
The default dehumidification parameters on Menu # 18 are set so that the unit will not provide
dehumidification during unoccupied time periods. If unoccupied dehumidification is desired, the Menu # 18
parameter “UnocDehumid=” must be set to “Yes”.
When unoccupied dehumidification is enabled, the unit is allowed to enter the Dehumidify state from the
following “unoccupied” operating states: Off Unoccupied, Unoccupied Heating, Unoccupied Economizer or
Unoccupied Cooling. The unit enters the Dehumidify state if the humidity/dew point rises above the set
point by more than the dead band. If the unit is in the Off Unoccupied state, it will start up and enter the
Dehumidify state. Unoccupied dehumidification operation is the same as occupied dehumidification except
that dehumidification cooling is cycled off and the unit leaves the Dehumidify state as soon as the
humidity/dew point set point is satisfied even if the reheat set point is not yet satisfied.
Dehumidify from Unoccupied Cooling/Unoccupied Economizer
If the unit is in the Unoccupied Economizer or Unoccupied Cooling state and the humidity/dew point rises
above the set point by more than the dead band, the unit enters the Dehumidify state. Unoccupied
dehumidification operation is then similar to that describe above for occupied “Dehumidify from
Economizer/Cooling” except the outside air dampers are fully closed if the outside air enthalpy is high rather
than driven to minimum position.
When the humidity/dew point set point is satisfied, dehumidification cooling is cycled off and the unit leaves
the Dehumidify state and enters the Off Unoccupied state even if the reheat set point is not satisfied.
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Dehumidify from Unoccupied Heating
If the unit is in the Unoccupied Heating state and the humidity/dew point rises above the set point by more
than the dead band, the unit enters the Dehumidify state. Unoccupied dehumidification operation is then
similar to that describe above for occupied “Dehumidify from Heating” except the outside air dampers are
fully closed rather than driven to minimum position.
When the humidity/dew point set point is satisfied, dehumidification cooling is cycled off and the unit leaves
the Dehumidify state and enters the Off Unoccupied state even if the reheat set point is not satisfied.
Dehumidify from Off Unoccupied
1) If the unit is in the Off Unoccupied state and the space temperature is above the occupied zone cooling
set point (Menu 12 “Heating Spt=” ) at the time the humidity/dew point rises above the set point by more
than the dead band, the unit starts up and enters the Dehumidify state. Unoccupied dehumidification
operation is then similar to that describe above for occupied “Dehumidify from Economizer/Cooling”
except the outside air dampers are fully closed if the outside air enthalpy is high rather than driven to
minimum position.
When the humidity/dew point set point is satisfied, dehumidification cooling is cycled off and the unit
leaves the Dehumidify state and enters the Off Unoccupied state even if the reheat set point is not
satisfied.
2) If the unit is in the Off Unoccupied state and the space temperature is below the occupied zone heating
set point (Menu 12 “Heating Spt=” ) at the time the humidity/dew point rises above the set point by more
than the dead band, the unit starts up and enters the Dehumidify state. Unoccupied dehumidification
operation is then similar to that describe above for occupied “Dehumidify from Heating” except the
outside air dampers are fully closed rather than driven to minimum position.
When the humidity/dew point set point is satisfied, dehumidification cooling is cycled off and the unit
leaves the Dehumidify state and enters the Off Unoccupied state even if the reheat set point is not
satisfied
3) If the unit is in the Off Unoccupied state and the space temperature is between the occupied zone cooling
and heating set points (Menu 12 “Cooling Spt=” and “Heating Spt=” ) at the time the humidity/dew point
rises above the set point by more than the dead band, the unit starts up and enters the Dehumidify state.
Unoccupied dehumidification operation is then similar to that describe above for occupied “Dehumidify
from Fan On/Fan On Heat” except the outside air dampers are fully closed rather than driven to minimum
position.
When the humidity/dew point set point is satisfied, dehumidification cooling is cycled off and the unit
leaves the Dehumidify state and enters the Off Unoccupied state even if the reheat set point is not
satisfied.
OM 109 Supplement #1 / Page 5
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DEHUMIDIFICATION UNIT CONFIGURATION
The dehumidification function can be configured to control one of three different heat/reheat/cooling unit
arrangements:
Configuration # 1 Unit has one heat source downstream of cooling coil. This heat source functions as
both the primary unit heat and the dehumidification reheat (refer to Figure 1).
Configuration # 2 Unit has a primary heat source upstream of the cooling coil and a dedicated
dehumidification reheat source downstream of cooling coil (refer to Figure 2).
Configuration # 3 Unit has a primary heat source and a dedicated dehumidification reheat source
downstream of cooling coil (refer to Figure 3).
This configuration is set up through two parameters in Menu #18.
1) “DedRHCfg=” defines whether or not the unit has a source of heat that is dedicated to reheat. If the unit
is Configuration # 1, this parameter is set to “None”. If the unit is either Configuration # 2 or
Configuration # 3, this parameter is set to indicate the type of dedicated reheat. If the dedicated reheat is
modulating, this parameter is set to “Modulating”. If the dedicated reheat is staged, this parameter is set
to Stage 1, Stage 2, Stage 3, Stage 4, Stage 5, Stage 6, Stage 7 or Stage 8, depending on the number of
dedicated reheat stages. Note: More than 2 stages of dedicated reheat requires reheat staging board
hardware. In order to change this parameter in the field, the user is prompted to enter a password before
the value can be changed. To enter the password, the user must press “ENTER”, “ENTER”, “-“, “-“ on
the unit keypad. This password is different than the standard keypad password.
2) “Supplmntl RH=” defines whether or not the standard unit heat should supplement the dedicated reheat
during dehumidification if the reheat source is insufficient to meet the reheat requirements. If the unit is
Configuration # 1 or Configuration # 2, this parameter should be set to “No”. If the unit is Configuration
# 3, this parameter can be set to “Yes” and the standard heat will supplement the reheat in the event that
the reheat source cannot meet the reheat requirements.
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Cool
Primary Heat/
Figure 1: Configuration # 1
Reheat
Primary Heat Cool
Figure 2: Configuration # 2
Cool
Dedicated
Reheat
Figure 3: Configuration # 3
Dedicated
Reheat
Primary Heat
OM 109 Supplement #1 / Page 7
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DEHUMIDIFICATION COOLING WITH COMPRESSORS
When dehumidification operation is enabled through Menu # 18 (“DehumidCntl=Yes”), the
compressor/unloader staging sequence of a two circuit unit is changed. In lieu of the standard “crossloading” of the circuits, the first circuit is loaded fully before the second circuit is energized. This lowers the
suction temperature and improves dehumidification. Tables 1 through 4 show the dehumidification
compressor staging sequences for the possible unit compressor/unloader configurations. Note: When
dehumidification operation is enabled, the dehumidification compressor staging sequences are also followed
when the unit is the Mechanical Cooling or Unoccupied Cooling state.
Dehumidify from Cooling/Economizer
The minimum and maximum number of dehumidification cooling stages are adjustable through Menu # 18 of
the keypad (“Min Stages=” and “Max Stages=”). When the unit first enters the Dehumidify state:
1) If the unit enters the Dehumidify state from the Economizer state or from the Mechanical Cooling state
and the number of cooling stages currently running is below the “Min Stages=” number, cooling will
stage up rapidly to the “Min Stages=” number. At the same time a dehumidification cooling timer starts
counting down. After the timer expires, and if there is still a call for dehumidification, the unit cooling
will stage rapidly up to the “Max Stages” number. The dehumidification cooling timer is adjustable
through Menu # 18 (“Clg Timer=”).
2) If the unit enters the Dehumidify state from the Mechanical Cooling state and the number of cooling
stages currently running is equal to or greater than the “Min Stages=” number but less than the “Max
Stages number, cooling will stage up rapidly to the “Max Stages=” number. At this time a
dehumidification cooling timer starts counting down. The dehumidification cooling timer is adjustable
through Menu # 18 (“Clg Timer=”).
3) If the unit is in the Mechanical Cooling state and the number of cooling stages currently running is equal
to or greater than the “Max Stages=” number when the humidity/dew point rises above the set point by
more than the dead band, the unit will not enter the Dehumidify state but will remain in the Mechanical
Cooling state.
The number of cooling stages currently operating is displayed on Menu # 10 (“Clg Stgs=”).
When the humidity/dew point is satisfied and reheat is not operating:
1) If the number of dehumidification cooling stages currently running is equal to the “Max Stages =”
number and the dehumidification cooling timer (“Clg Timer=”) has expired, cooling will stage down
rapidly to the “Min Stages =” number and the unit will leave the Dehumidify state and enter the
Mechanical Cooling state with the “Min Stages =” number of cooling stages operating.
2) If the number of dehumidification cooling stages currently running is equal to the “Min Stages=” number
and the dehumidification cooling timer (“Clg Timer=”) has expired, cooling will rapidly stage off
completely and the unit will leave the Dehumidify and enter the Fan On state.
When the humidity/dew point set point is satisfied while reheat is operating:
1) If the number of cooling stages currently running is equal to the “Max Stages=” number and the
dehumidification timer has expired, the cooling is staged down to the “Min Stages=” number. At this
time, the dehumidification timer is reset and begins to count down. When the timer expires and the
humidity/dew point is still satisfied, the cooling is staged of completely. The unit then leaves the
Dehumidify state and enters the Fan On state as soon as the reheat set point is satisfied and reheat is
cycled off.
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2) If the number of cooling stages currently running is equal to the “Min Stages=” number and the
dehumidification timer has expired, the cooling is staged of completely. The unit then leaves the
Dehumidify state and enters the Fan On state as soon as the reheat set point is satisfied and reheat is
cycled off.
Dehumidify from Fan On/Fan On Heat/Heating
The minimum and maximum number of dehumidification cooling stages are adjustable through Menu # 18 of
the keypad (“Min Stages=” and “Max Stages=”). When the unit first enters the Dehumidify state from the
Fan On, Fan On Heat or Heating state, cooling will stage up rapidly to the “Min Stages =” number. At the
same time a dehumidification cooling timer starts counting down. After the timer expires, and if there is still
a call for dehumidification, the unit cooling will stage up rapidly to the “Max Stages” number. The
dehumidification cooling timer is adjustable through Menu # 18 (“Clg Timer=”). The number of cooling
stages currently operating is displayed on Menu # 10 (“Clg Stgs=”).
When the humidity/dew point set point is satisfied:
1) If the number of cooling stages currently running is equal to the “Max Stages=” number and the
dehumidification timer has expired, the cooling is staged down rapidly to the “Min Stages=” number. At
this time, the dehumidification timer is reset and begins to count down. When the timer expires and if
the humidity/dew point is still satisfied, the cooling is rapidly staged off completely. If the unit had
entered the Dehumidify state from the Fan On or Fan On Heat state, the unit then leaves the Dehumidify
state and enters the Fan On state even if the reheat set point is not satisfied. If the unit had entered the
Dehumidify state from the Heating state, the unit then leaves the Dehumidify state and enters the Fan On
state as soon as the reheat set point is satisfied.
2) If the number of cooling stages currently running is equal to the “Min Stages=” number and the
dehumidification timer has expired, the cooling is rapidly staged off completely. The unit then leaves the
Dehumidify state and enters the Fan On state even if the reheat set point is not satisfied.
Dehumidify from Off Unoccupied/Unocc. Cooling/Unocc. Economizer/Unocc. Heating
The minimum and maximum number of dehumidification cooling stages are adjustable through Menu # 18
of the keypad (“Min Stages=” and “Max Stages=”).
1) When the unit enters the Dehumidify state from the Off Unoccupied, Unoccupied Heating or Unoccupied
Economizer state, cooling will first stage up rapidly to the “Min Stages =” number. At the same time a
dehumidification cooling timer starts counting down. After the timer expires, and if there is still a call
for dehumidification, the unit cooling will stage up to the “Max Stages” number. The dehumidification
cooling timer is adjustable through Menu # 18 (“Clg Timer=”). The number of stages currently operating
is displayed on Menu # 10 (“Clg Stgs=”).
2) When the unit enters the Dehumidify state from the Unoccupied Cooling state and the number of cooling
stages currently running is below the “Min Stages=” number, cooling will stage up rapidly to the “Min
Stages=” number. At the same time a dehumidification cooling timer starts counting down. After the
timer expires, and if there is still a call for dehumidification, the unit cooling will stage up rapidly to the
“Max Stages” number. The dehumidification cooling timer is adjustable through Menu # 18 (“Clg
Timer=”). The number of stages currently operating is displayed on Menu # 10 (“Clg Stgs=”).
When the unit enters the Dehumidify state from the Unoccupied Cooling state and the number of cooling
stages currently running is equal to or greater than the “Min Stages=” number but less that the “Max
Stages number, cooling will stage up rapidly to the “Max Stages=” number. At this time a
dehumidification cooling timer starts counting down. The dehumidification cooling timer is adjustable
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through Menu # 18 (“Clg Timer=”). The number of stages currently operating is displayed on Menu # 10
(“Clg Stgs=”).
When the unit is in the Unoccupied Cooling state and the number of cooling stages currently running is
equal to or greater than the “Max Stages=” number when the humidity/dew point rises above the set point
by more that the dead band, the unit will not enter the Dehumidify state but will remain in the
Unoccupied Cooling state.
When the humidity/dew point set point is satisfied:
1) If the number of dehumidification cooling stages currently running is equal to the “Max Stages=” number
and the dehumidification timer has expired, the cooling is staged down rapidly to the “Min Stages=”
number. At this time, the dehumidification timer is reset and begins to count down. When the timer
expires and the humidity/dew point set point is still satisfied, the cooling is rapidly staged of completely.
The unit then leaves the Dehumidify state and enters the Off Unoccupied state even if the reheat set point
is not satisfied.
2) If the number of dehumidification cooling stages currently running is equal to the “Min Stages=” number
and the dehumidification cooling timer (“Clg Timer=”) has expired, cooling will rapidly stage off
completely. The unit then leaves the Dehumidify state and enters the Off Unoccupied state even if the
reheat set point is not satisfied.
DEHUMIDIFICATION COOLING WITH CHILLED WATER
Dehumidify from All Possible States
The unit chilled water valve is driven fully open when the unit enters the Dehumidify state. The chilled
water valve is driven closed when the humidity/dew point set point is satisfied.
HEAT/REHEAT CONTROL
Configuration #1 (One heat source downstream of cooling coil - refer to Figure 1)
Heat is controlled as described in OM 109 when dehumidification is not required. Heat is controlled as
reheat as described below when dehumidification is required. The heat may be modulating or staged.
Dehumidify from Economizer/Unoccupied Economizer/Cooling/Unoccupied Cooling
When the unit enters the Dehumidify state from the Economizer, Unoccupied Economizer, Mechanical
Cooling or Unoccupied Cooling state, the heat in the unit is controlled to maintain the space temperature at
the reheat set point (Menu 14 “Reheat Spt=”). This set point is not adjustable from the keypad but is set
equal to the zone cooling set point (Menu 12 “Cooling Spt=” ) by the controller. The heat is controlled in the
same manner as when the unit is in the standard Heating state except the space temperature is compared to
the zone cooling set point instead of the zone heating set point. Refer to OM109 for details regarding the
standard Heating state operation. Note: The number of heat or reheat stages currently operating is displayed
on Menu # 10 (“Htg Stgs=” or “RHtg Stgs= ”).
When the humidity/dew point set point is satisfied:
1) If the unit is in an occupied mode, the heat will cycle off rapidly as soon as the space temperature is
equal to or greater than the reheat set point and the dehumidification cooling is cycled off (refer to the
"Dehumidification Cooling with Compressors" or "Dehumidification Cooling with Chilled Water"
section of this document). The unit will then leave the Dehumidify state and enter the Fan On state.
2) If the unit is in an unoccupied mode, the heat will cycle off rapidly as soon as the humidity set point is
satisfied and the dehumidification cooling is cycled off even if the reheat set point is not satisfied (refer
to the “Dehumidification Cooling with Compressors” or “Dehumidification Cooling with Chilled Water”
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section of this document). The unit will then leave the Dehumidify state and enter the Off Unoccupied
state.
Dehumidify from Heating/Unoccupied Heating
When the unit enters the Dehumidify state from the Heating or Unoccupied Heating state, the heat in the unit
is controlled to maintain the space temperature at the reheat set point (Menu 14 “Reheat Spt=”). This set
point is not adjustable from the keypad but is set equal to the zone heating set point (Menu 12 “Heating
Spt=” ) by the controller. The heat is controlled in the same manner as when the unit is in the standard
Heating state. Refer to OM109 for details regarding the standard Heating state operation. Note: The number
of heat or reheat stages currently operating is displayed on Menu # 10 (“Htg Stgs=” or “RHtg Stgs= ”).
When the humidity/dew point set point is satisfied:
1) If the unit is in an occupied mode, the heat will cycle off rapidly as soon as the space temperature rises
above the reheat set point by more than the dead band and the dehumidification cooling is cycled off
(refer to the “Dehumidification Cooling with Compressors” or “Dehumidification Cooling with Chilled
Water” section of this document). The unit will then leave the Dehumidify state and enter the Fan On
state.
2) If the unit is in an unoccupied mode, the heat will cycle off rapidly as soon as the humidity set point is
satisfied and the dehumidification cooling is cycled off even if the reheat set point is not satisfied (refer
to the “Dehumidification Cooling with Compressors” or “Dehumidification Cooling with Chilled Water”
section of this document). The unit will then leave the Dehumidify state and enter the Off Unoccupied
state.
Dehumidify from Fan On/Fan On Heat
When the unit enters the Dehumidify state from the Fan On or Fan On Heat state, the heat in the unit is
controlled to maintain the supply air temperature at the reheat set point (Menu 14 “Reheat Spt=”). This set
point is not adjustable from the keypad but is set equal to the fan only heating set point (Menu 14 “Fan On
Htg=” ) by the controller. The heat is controlled in the same manner as when the unit is in the standard Fan
On Heat state. Refer to OM109 for details regarding the standard Fan On Heat state operation. Note: The
number of heat or reheat stages currently operating is displayed on Menu # 10 (“Htg Stgs=” or “RHtg Stgs=
”).
When the humidity/dew point set point is satisfied, the reheat will cycle off rapidly as soon as the
dehumidification cooling is cycled off even if the reheat set point is not satisfied (refer to the
“Dehumidification Cooling with Compressors” or “Dehumidification Cooling with Chilled Water” section of
this document). The unit will then leave the Dehumidify state and enter the Fan On state.
Dehumidify from Off Unoccupied
When the unit enters the Dehumidify state from the Off Unoccupied state:
1) If the space temperature is above the occupied zone cooling set point (Menu 12 “Cooling Spt=” ) at the
time, the reheat is controlled as described above for “Dehumidify from Economizer/Unoccupied
Economizer/Cooling/Unoccupied Cooling”.
2) If the space temperature is below the occupied zone heating set point (Menu 12 “Heating Spt=” ) at the
time, the reheat is controlled as described above for “Dehumidify from Heating/Unoccupied Heating”.
3) If the space temperature is in between the occupied zone cooling set point (Menu 12 “Cooling Spt=” )
and the occupied zone heating set point (Menu 12 “Heating Spt=” ) at the time, the reheat is controlled as
described above for “Dehumidify from Fan On/Fan On Heat”.
OM 109 Supplement #1 / Page 11
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Configuration #2 (Primary heat upstream and dedicated reheat downstream of cooling coil - refer to Fig. 2)
The primary heat upstream of the cooling coil is controlled as described in OM 109 when dehumidification is
not required. When dehumidification is required, the heat downstream of the cooling coil is controlled as
reheat as described above for Configuration # 1. The heat upstream of the cooling coil remains off while the
unit is in the Dehumidify state. Either heat source may be either modulating or staged.
Configuration # 3 (Primary heat and dedicated reheat source downstream of cooling coil - refer to Fig. 3)
The primary heat downstream of the cooling coil is controlled as described in OM 109 when
dehumidification is not required. When dehumidification is required, the dedicated reheat downstream of the
cooling coil is controlled as reheat as described above for Configuration # 1. The difference between
Configuration # 3 and Configuration # 2 is that the primary heat source can be allowed to supplement the
dedicated reheat source in the event that the dedicated reheat cannot meet the reheat requirements. To
activate this supplement reheat feature the Menu # 18 “Supplmntl RH =” parameter is set to “Yes”.
Page 12 / OM 109 Supplement #1
Page 13
DEHUMIDIFICATION MENU ITEMS (Additions to Table 4 & Table 5 of OM 109)
Menu # 10 - Misc Status
Menu Item Description
Humidity = Displays the current space (or return) air relative humidity % input from the sensor.
Dewpoint = Displays the calculated space (or return) air dew point in °F.
Clg Stgs= Displays the current number of operating cooling stages.
Htg Stgs= Displays the current number of operating heating stages.
RHtg Stgs= Displays the current number of operating dedicated reheat stages.
Menu # 14 - Htg Control
Menu Item Description
Reheat Spt = Reheat is controlled to maintain this setting. (Not Adjustable)
Reheat DB = Reheat set point dead band. (Range: 1-10 °F)
Menu # 18 - Humidity Ctrl
Menu Item Description
Dehumid Cntl = Enables or disables dehumidification function. (Range: No/Yes)
UnocDehumid = Enables or disables unoccupied dehumidification operation. (Range: No/Yes)
Control = Selects the type of humidity control. (Range: Humidity/Dewpoint)
Sensor = Selects the location of the humidity sensor. (Range: Return/Space)
Humidity Spt = Relative humidity set point. (Range: 0 - 99%)
Humidity DB = Relative humidity dead band. (Range: 0 - 10%)
Dewpt Spt = Dew point set point. (Range: 0 - 87 °F)
Dewpt DB = Dew point dead band. (Range: 0 - 10 °F)
Min Stages = Minimum number of dehumidification cooling stages. (Range: 1 - “Max Stages=”)
Max Stages = Maximum number of dehumidification cooling stages. (Range: “Min Stages=” - unit
maximum stages)
Clg Timer= Adjustable timer between “Min Stages=” and “Max Stages=” during dehumidification.
(Range: 1 - 60 min)
Supplmntl RH = Enables standard unit heat to supplement dedicated reheat during dehumidification.
(Range: No/Yes)
DedRHCfg = Configures dedicated reheat type if any. (Range: None/Staged 1 - 8/Modulating)
OM 109 Supplement #1 / Page 13
Page 14
INPUTS/OUTPUTS
CAV-Zone Temperature Control w/Return Air: 950163-XX-X (ART5)
Digital Inputs Analog Inputs
DI 0 Enthalpy Switch AI 0 Supply Air Temperature
DI 1 Remote Time Clock AI 1 Return Air Temperature
DI 2 Spare AI 2 Outdoor Air Temperature
DI 3 Cool Enable Switch AI 3 Space Temperature
DI 4 Heat Enable Switch AI 4 Mixed Air Temperature
DI 5 Refrigerant Circuit #1 Alarm AI 5 Misc Temperature
DI 6 Refrigerant Circuit #2 Alarm AI 6 Misc Temperature
DI 7 Spare AI 7 Spare 0-5 VDC
DI 8 Airflow Switch AI 8 Spare 0-5 VDC
DI 9 Flame Failure Alarm AI 9 Remote Heating Setpoint Adjust
DI 10 Freezestat Alarm AI10 Remote Cooling Setpoint Adjust
DI 11 Smoke Detector Alarm AI 11 OA Damper Position
DI 12 First Filter Dirty AI 12 Space or Return Air Humidity
DI 13 Final Filter Dirty AI 13 Building Static Pressure
DI 14 Spare AI 14 Remote Econo. Min. Position Spt. Adjust
DI 15 Spare AI 15 Spare 0-5 VDC
Digital Outputs
DO 0 Alarm
DO 1 Cooling Stage #1/Stag ing B oard/Cooling Valve Close (1)
DO 2 Cooling Stage #2/Stag ing B oard/Cooling Valve Open (1)
DO 3 Heating Stage #1/Stag ing B oard/G as Burner O ff-On/F&BP Valve Close- O pen (2)
DO 4 Heating Stage #2/Stag ing B oard/H tg . Vlv Close/F& BP Dmprs Open Face (2)
DO 5 Heating Stage #3/ /Htg . Vlv O pen/F&B P Dmprs Close Face (2)
DO 6 Heating Stage #4
DO 7 Outdoor Air Dampers Close
DO 8 Outdoor Air Dampers Open
DO 9 Cooling Stage #3
DO 10 Cooling Stage #4
DO 11 Cooling Stage #5/Return Fan Vanes Close/VFD Decrease/R H Stag ing B oard/Reheat Vlv C lose/Reheat
Stage #1 (3)
DO 12 Cooling Stage #6/Return Fan Vanes O pen/VFD Increase/ RH Staging Board/R eheat Vlv O pen/Reheat
Stage #2 (3)
DO 13 Supply Fan Off-On
DO 14 Return Fan Off-On
DO 15 Unoccupied-Occupied
Page 14 / OM 109 Supplement #1
Page 15
CAV-Zone Temperature Control w/100% Outside Air: 950166-XX-X (ART7)
Digital Inputs Analog Inputs
DI 0 Spare AI 0 Supply Air Temperature
DI 1 Remote Time Clock AI 1 Spare Temperature
DI 2 Spare AI 2 Outdoor Air Temperature
DI 3 Cool Enable Switch AI 3 Space Temperature
DI 4 Heat Enable Switch AI 4 Mixed Air Temperature
DI 5 Refrigerant Circuit #1 Alarm AI 5 Misc Temperature
DI 6 Refrigerant Circuit #2 Alarm AI 6 Misc Temperature
DI 7 Spare AI 7 Spare 0-5 VDC
DI 8 Airflow Switch AI 8 Spare 0-5 VDC
DI 9 Flame Failure Alarm A I 9 Remote Heating S et Point A djust
DI 10 Freezestat Alarm AI10 Remote Cooling Set Point Adjust
DI 11 Smoke Detector Alarm AI 11 OA Damper Position
DI 12 First Filter Dirty AI 12 Space or Return Air Humidity
DI 13 Final Filter Dirty AI 13 Spare 0-5 VDC
DI 14 Spare AI 14 Spare 0-5 VDC
DI 15 Spare AI 15 Spare 0-5 VDC
Digital Outputs
DO 0 Alarm
DO 1 Cooling Stage #1/Stag ing B oard/Cooling Valve Close (1)
DO 2 Cooling Stage #2/Stag ing B oard/Cooling Valve Open (1)
DO 3 Heating Stage #1/Stag ing B oard/G as Burner O n-Off/F&BP Valve Close Open (2)
DO 4 Heating Stage #2/Stag ing B oard/H tg . Vlv Close/F& BP Dmprs Open Face (2)
DO 5 Heating Stage #3/ /Htg . Vlv O pen/F& BP D mprs Close Face (2)
DO 6 Heating Stage #4/G as Blower O ff-On (3)
DO 7 Outdoor Air Dampers Close
DO 8 Outdoor Air Dampers Open
DO 9 Cooling Stage #3
DO 10 Cooling Stage #4
DO 11 Cooling Stage #5/RH Stag ing Bo ard/Reheat Vlv C lose/Reheat Stag e #1 (4)
DO 12 Cooling Stage #6/RH Stag ing Bo ard/Reheat Vlv O pen/R eheat Stag e #2 (4)
DO 13 Supply Fan Off-On
DO 14 Spare
DO 15 Unoccupied-Occupied
OM 109 Supplement #1 / Page 15
Page 16
DEHUMIDIFICATION COMPRESSORIZED STAGING SEQUENCES
Table 1. Dehumidification Compressor Stag ing : 2- C ompressor/4-Stage
Output
Relay
Output Description Lit LED
Indication
STAGING
# 1 Lead # 2 Lead
0123401234
OBA1 Compressor # 1 S/S Start XXXX XX
OBA2 Compressor # 2 S/S Start X X XXXX
OBA9 Comp. #1 UL On/Off Unloaded X X
OBA10 Comp. #2 UL On/Off Unloaded X X
Table 2. Dehumidification Compressor Stag ing : 4- C ompressor/4-Stage
Output
Relay
Output Description Lit LED
Indication
STAGING
# 1 Lead # 2 Lead
0123401234
OBA1 Compressor # 1 S/S Start XXXX XX
OBA2 Compressor # 2 S/S Start X X XXXX
OBA9 Compressor # 3 S/S Start X X X X
OBA10 Compressor # 4 S/S Start X X X X
Table 3. Dehumidification Compressor Stag ing : 2- C ompressor/6-Stage
Output
Relay
Output Description Lit LED
Indication
STAGING
# 1 Lead # 2 Lead
01234560123456
OBA1 Compressor # 1 S/S Start XXXXXX XXX
OBA2 Compressor # 2 S/S Start X X X XXXXXX
OBA9 Comp. #1 UL1 On/Off Unloaded X X
OBA10 Com p. #2 UL1 On/Off Unloaded X X
OBA11 Com p. #1 UL2 On/Off Unloaded X X X X
OBA12 Com p. #2 UL2 On/Off Unloaded X X X X
Table 4. Dehumidification Compressor Stag ing : 4- C ompressor/8-Stage
Output
Relay
Output Description Lit LED
Indication
STAGING
# 1 Lead # 2 Lead
012345678012345678
OBA1 Compressor # 1 S/S Start XXXXXXXX XXXX
OBA2 Compressor # 2 S/S Start X X X X XXXXXXXX
OBA9 Comp. #1 UL On/Off Unloaded X X X X
OBA10 Comp. #2 UL On/Off Unloaded X X X X
OBA11 Compressor # 3 S/S Start X X X X X X X X
OBA12 Compressor # 4 S/S Start X X XXXXXX
Page 16 / OM 109 Supplement #1
Page 17
Figure 4. Sequence Chart for Program ART5: Mixed Air or 100% Return Air
Off
Start-up
Initialization
Unoccupied Heating
Unoccupied
Cooling
Cooling
Unoccupied
Economizer
Economizer
Recirculate
Morning
Warm-up
Fan Only
Heating
Fan On
Heating
Dehumidification
State Transitions Related to Dehumidification Operation
OM 109 Supplement #1 / Page 17
Page 18
Figure 5. Sequence Chart for Program ART7: 100% Outdoor Air
Off
Unoccupied Heating
Unoccupied Cooling
Cooling
Start-up Initialization
Fan Only
Dehumidification
Fan On
Heating
Heating
State Transitions Related to Dehumidification Operation
Page 18 / OM 109 Supplement #1
Page 19
INPUT SCHEMATIC: CAV-ZTC UNITS (ANALOG)
OM 109 Supplement #1 / Page 19
Page 20
13600 Industrial Park Boulevard, P.O. Box 1551, Minneapolis, MN 55440 USA (612) 553-5330
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