3.7.7 Humidity Controls and Devices

General

Humidifier Type
Applicability	Optional humidifier
Definition	The type of humidifier employed. Choices include: Hot-Water Steam Electric Evaporative Humidification
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Maximum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Minimum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for humidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as proposed design

Desiccant

Desiccant Type
Applicability	Systems with desiccant dehumidification
Definition	Describes the configuration of desiccant cooling equipment The following configurations for desiccant systems are allowed: LIQ-VENT-AIR1 – a liquid desiccant dehumidifying unit LIQ-VENT-AIR2 – a liquid desiccant dehumidifying unit combined with a gas-fired absorption chiller SOL-VENT-AIR1 – a solid desiccant dehumidifying unit NO-DESICCANT – the default, which indicates that no desiccant system is present
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Control Mode
Applicability	Systems with desiccant dehumidification
Definition	The method of controlling the operation of the desiccant unit. For liquid-based systems this can be either: Dry-bulb – the desiccant unit is turned on whenever the outside air dry-bulb exceeds a set limit. Evaporative cooling– cycles the desiccant unit on when an evaporative cooler is on to maintain a dewpoint setpoint. Dewpoint – cycles the desiccant unit on and off to maintain the dewpoint temperature of the supply air. For solid-based systems the following configurations are possible: Dehumidification only – the desiccant unit cycles on and off to maintain indoor humidity levels Sensible heat exchanger plus regeneration – the desiccant unit includes a sensible heat exchanger to precool the hot, dry air leaving the desiccant unit. The air leaving the exhaust side of the heat exchanger is directed to the desiccant unit Sensible heat exchanger – the desiccant unit includes a heat exchanger, but the air leaving the exhaust side of the heat exchanger is exhausted to the outdoors
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Air Fraction
Applicability	Systems with desiccant dehumidification
Definition	The fraction of the supply air that passes through the desiccant unit. Typically either the minimum outside air fraction or all of the air passes through the desiccant system.
Units	Ratio
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Heat Source
Applicability	Systems with desiccant dehumidification
Definition	The source of heat that is used to dry out the desiccant. This can be either: Gas – Hydronic – the regeneration heat load is met with a gas-fired heater Hot water – the heat load is met with hot water from the plant
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Not applicable

Liquid Desiccant Performance Curves

Applicability

Systems with liquid-based desiccant dehumidification

Definition

A set of performance curves that apply to liquid desiccant systems.

(6.7.7-1)

$$ D\!ESC\!\!-\!\!T\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-2)

$$ D\!ESC\!\!-\!\!W\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-3)

$$ D\!ESC\!\!-\!\!Gas\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-4)

$$ D\!ESC\!\!-\!\!kW\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

where

DESC-T-FTW	temperature leaving desiccant unit
DESC-W-FTW	humidity ratio leaving desiccant unit
DESC-Gas-FTW	Gas usage of desiccant unit
DESC-kW-FTW	Electric usage of desiccant unit
T	entering air temperature
w	entering humidity ratio

[table title="Liquid Desiccant Unit Performance Curves" id="liquid-desiccant-unit-performance-curves"]

Coefficient	DESC-T-FTW	DESC-W-FTW	DESC-Gas-FTW	DESC-kW-FTW
a	11.5334997	11.8993998	58745.8007813	3.5179000
b	0.6586730	-0.2695580	-1134.4899902	-0.0059317
c	-0.0010280	0.0044549	-3.6676099	0.0000000
d	0.2950410	0.0830525	3874.5900879	0.0040401
e	-0.0001700	0.0006974	-1.6962700	0.0000000
f	-0.0008724	0.0015879	-13.0732002	0.0000000

Units

Data structure

Input Restrictions

As designed, default to values in [bookref id="liquid-desiccant-unit-performance-curves"]

Baseline Rules

Not applicable

Desiccant Dewpoint Temperature Setpoint
Applicability	Systems with desiccant dehumidification
Definition	The setpoint dewpoint temperature of the air leaving the desiccant system
Units	Degrees Fahrenheit (°F)
Input Restrictions	As designed. Defaults to 50°F.
Baseline Rules	Not applicable

Desiccant Heat Exchanger Effectiveness
Applicability	Systems with desiccant dehumidification
Definition	The effectiveness of a sensible heat exchanger used with a desiccant system
Units	Ratio
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Heat Exchanger Pressure Drop
Applicability	Systems with desiccant dehumidification
Definition	The pressure drop across a sensible heat exchanger used with a desiccant system
Units	in. H2O
Input Restrictions	As designed. Defaults to 1.0 in. H₂O
Baseline Rules	Not applicable

Minimum volume setpoint shall be 50% of the maximum design airflow rate, the minimum ventilation outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards, whichever is larger. Fan volume shall be reset from 100% airflow at 100% cooling load to minimum airflow at 50% cooling load. Supply air temperature setpoint shall be reset from minimum supply air temperature at 50% cooling load and above to space temperature at 0% cooling load. In heating mode supply air temperature shall be modulated to maintain space temperature, and fan volume shall be fixed at the minimum airflow.

General

Humidifier Type
Applicability	Optional humidifier
Definition	The type of humidifier employed. Choices include1 : Isothermal Humidification. the water vapor is dispersed in the air after having been created by boiling water. Isothermal humidification requires an external source of energy to change the state of the water. In the commercial HVAC world Isothermal Humidification has been used for years in nearly all applications. Types include: Direct Steam Injection Steam-To-Steam Gas-To-Steam Electric Steam Infra-Red Adiabatic Humidification. finely atomized water is introduced into the air. The adiabatic process does not involve the contribution of thermal energy from an external source. There is no heat added. Types include: High Pressure Atomizing Air/Water Atomizing Ultrasonic Wetted Media Evaporative
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	The baseline building shall have humidification if the proposed design does, but the system shall be non-adiabatic. For systems serving computer rooms, the baseline shall nt have reheat for the purpose of humidification.

Humidistat Maximum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Minimum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for humidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as proposed design

Desiccant

Desiccant Type
Applicability	Systems with desiccant dehumidification
Definition	Describes the configuration of desiccant cooling equipment The following configurations for desiccant systems are allowed: LIQ-VENT-AIR1 – a liquid desiccant dehumidifying unit LIQ-VENT-AIR2 – a liquid desiccant dehumidifying unit combined with a gas-fired absorption chiller SOL-VENT-AIR1 – a solid desiccant dehumidifying unit NO-DESICCANT – the default, which indicates that no desiccant system is present
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Control Mode
Applicability	Systems with desiccant dehumidification
Definition	The method of controlling the operation of the desiccant unit. For liquid-based systems this can be either: Dry-bulb – the desiccant unit is turned on whenever the outside air dry-bulb exceeds a set limit. Evaporative cooling– cycles the desiccant unit on when an evaporative cooler is on to maintain a dewpoint setpoint. Dewpoint – cycles the desiccant unit on and off to maintain the dew point temperature of the supply air. For solid-based systems the following configurations are possible: Dehumidification only – the desiccant unit cycles on and off to maintain indoor humidity levels Sensible heat exchanger plus regeneration – the desiccant unit includes a sensible heat exchanger to precool the hot, dry air leaving the desiccant unit. The air leaving the exhaust side of the heat exchanger is directed to the desiccant unit Sensible heat exchanger – the desiccant unit includes a heat exchanger, but the air leaving the exhaust side of the heat exchanger is exhausted to the outdoors
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Air Fraction
Applicability	Systems with desiccant dehumidification
Definition	The fraction of the supply air that passes through the desiccant unit. Typically either the minimum outside air fraction or all of the air passes through the desiccant system.
Units	Ratio
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Heat Source
Applicability	Systems with desiccant dehumidification
Definition	The source of heat that is used to dry out the desiccant. This can be either: Gas – Hydronic – the regeneration heat load is met with a gas-fired heater Hot water – the heat load is met with hot water from the plant
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Not applicable

Liquid Desiccant Performance Curves

Applicability

Systems with liquid-based desiccant dehumidification

Definition

A set of performance curves that apply to liquid desiccant systems.

(Equation 3.7.7-1)

$$DESC\_T\_FTW = a + b \cdot T + c \cdot T^{2} + d \cdot w + e \cdot w^{2} + f \cdot T \cdot w$$

(Equation 3.7.7-2)

$$DESC\_W\_FTW = a + b \cdot T + c \cdot T^{2} + d \cdot w + e \cdot w^{2} + f \cdot T \cdot w$$

(Equation 3.7.7-3)

$$DESC\_Gas\_FTW = a + b \cdot T + c \cdot T^{2} + d \cdot w + e \cdot w^{2} + f \cdot T \cdot w$$

(Equation 3.7.7-4)

$$DESC\_kW\_FTW = a + b \cdot T + c \cdot T^{2} + d \cdot w + e \cdot w^{2} + f \cdot T \cdot w$$

where

DESC-T-FTW	temperature leaving desiccant unit
DESC-W-FTW	humidity ratio leaving desiccant unit
DESC-Gas-FTW	Gas usage of desiccant unit
DESC-kW-FTW	Electric usage of desiccant unit
T	entering air temperature
w	entering humidity ratio
a, b, c, d, e, f	Coefficients taken from Appendix H

Units

Data structure

Input Restrictions

As designed, default to values in Appendix H

Baseline Rules

Not applicable

Desiccant Dewpoint Temperature Setpoint
Applicability	Systems with desiccant dehumidification
Definition	The setpoint dewpoint temperature of the air leaving the desiccant system
Units	Degrees Fahrenheit (°F)
Input Restrictions	As designed. Defaults to 50°F.
Baseline Rules	Not applicable

Desiccant Heat Exchanger Effectiveness
Applicability	Systems with desiccant dehumidification
Definition	The effectiveness of a sensible heat exchanger used with a desiccant system
Units	Ratio
Input Restrictions	As designed
Baseline Rules	Not applicable

Desiccant Heat Exchanger Pressure Drop
Applicability	Systems with desiccant dehumidification
Definition	The pressure drop across a sensible heat exchanger used with a desiccant system
Units	in. H₂O
Input Restrictions	As designed. Defaults to 1.0 in. H₂O
Baseline Rules	Not applicable

1This information is taken from http://www.dac-hvac.com/ask-rick-what-is-adiabatic-humidification/. The biggest advantages of Adiabatic Humidifiers are: energy savings, precise humidity control, simple technology. The disadvantages are longer absorption distances (more length need in an air handling unit), requires preheat of supply air, typically requires RO water, compressed air required on air/water systems.

90.1-2019

Humidity control, devices, and sources are not represented fully in many simulation program, but humidification and dehumidification can result in significant energy consumption. A simulation program should be chosen that most adequately represents the components, or has adequate workarounds implemented, or supplemental calculations employed to determine the associated energy use. These methods should be documented in the manner required for “exceptional calculations.”

3.7.7.1 General

Humidifier Type
Applicability	Optional humidifier
Definition	The type of humidifier employed. Choices include: Hot water Steam Electric Evaporative humidification Adiabatic humidification
Units	List (see above)
Input Restrictions	As designed
Baseline Building	For systems serving zones where humidification is included in the proposed design, the baseline shall include the same humidifier type unless the proposed humidifier does not include automatic shutoff valves and insulated dispersion tubes meeting the requirements of 90.1-2019 Section 6.5.2.4. In that case, adiabatic humidification shall be used in the baseline. In either case, the baseline humidification system uses the same schedule and setpoints as the proposed building.

Humidistat Maximum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Building	If the proposed design HVAC system(s) have humidistatic controls, then the baseline building design shall use mechanical cooling for dehumidification and shall have reheat available to avoid overcooling. Systems serving computer rooms shall not have reheat for dehumidification. The reheat type shall be the same as the system heating type. Only 25% of the system reheat energy shall be included in the baseline building performance, when the baseline building doesn’t comply with any of the exceptions listed below (Standard 90.1-2019 Section 6.5.2.3). The requirements and exceptions to the same are listed below- Humidity controls shall prevent reheating, mixing of hot and cold airstreams, or other means of simultaneous heating and cooling of the same airstream. Exceptions : The system is capable of and configured to reduce supply air volume to 50% or less of the design airflow rate or the minimum outdoor air ventilation rate specified in ASHRAE Standard 62.1 or other applicable federal, state, or local code or recognized standard, whichever is larger, before simultaneous heating and cooling takes place. The individual fan cooling unit has a design cooling capacity of 65,000 Btu/h or less and is capable of and configured to unload to 50% capacity before simultaneous heating and cooling takes place. The individual mechanical cooling unit has a design cooling capacity of 40,000 Btu/h or less. An individual mechanical cooling unit is a single system comprising a fan or fans and a cooling coil capable of providing mechanical cooling. Systems serving spaces where specific humidity levels are required to satisfy process needs, such as vivariums; museums; surgical suites; pharmacies; and buildings with refrigerating systems, such as supermarkets, refrigerated warehouses, and ice arenas, and where the building includes site-recovered energy or site-solar energy that provide energy equal to at least 75% of the annual energy for reheating or for providing warm air in mixing systems. This exception does not apply to computer rooms. At least 90% of the annual energy for reheating or for providing warm air in mixing systems is provided from site-recovered energy (including condenser heat) or site-solar energy. Systems where the heat added to the airstream is the result of the use of a desiccant system, and 75% of the heat added by the desiccant system is removed by a heat exchanger, either before or after the desiccant system, with energy recovery.

Humidistat Minimum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Building	Same as proposed

3.7.7.2 Desiccant

Desiccant Type
Applicability	Systems with desiccant dehumidification
Definition	Describes the configuration of desiccant cooling equipment The following configurations for desiccant systems are allowed: A liquid desiccant dehumidifying unit A liquid desiccant dehumidifying unit combined with a gas-fired absorption chiller A solid desiccant dehumidifying unit No desiccant – the default, which indicates that no desiccant system is present
Units	List (see above)
Input Restrictions	As designed
Baseline Building	Not applicable

Desiccant Control Mode
Applicability	Systems with desiccant dehumidification
Definition	The method of controlling the operation of the desiccant unit. For liquid-based systems this can be either: Dry-bulb: The desiccant unit is turned on whenever the outside air dry-bulb exceeds a set limit. Evaporative cooling: Cycles the desiccant unit on when an evaporative cooler is on to maintain a dewpoint setpoint. Dewpoint: Cycles the desiccant unit on and off to maintain the dewpoint temperature of the supply air. For solid-based systems the following configurations are possible: Dehumidification only: The desiccant unit cycles on and off to maintain indoor humidity levels. Sensible heat exchanger plus regeneration: The desiccant unit includes a sensible heat exchanger to precool the hot, dry air leaving the desiccant unit. The air leaving the exhaust side of the heat exchanger is directed to the desiccant unit. Sensible heat exchanger: The desiccant unit includes a heat exchanger, but the air leaving the exhaust side of the heat exchanger is exhausted to the outdoors.
Units	List (see above)
Input Restrictions	As designed
Baseline Building	Not applicable

Desiccant Air Fraction
Applicability	Systems with desiccant dehumidification
Definition	The fraction of the supply air that passes through the desiccant unit. Typically either the minimum outside air fraction or all of the air passes through the desiccant system.
Units	Fraction (between 0 and 1)
Input Restrictions	As designed
Baseline Building	Not applicable

Desiccant Heat Source
Applicability	Systems with desiccant dehumidification
Definition	The source of heat that is used to dry out the desiccant. This can be either: Gas – hydronic: The regeneration heat load is met with a gas-fired heater. Hot water: The heat load is met with hot water from the plant.
Units	List (see above)
Input Restrictions	As designed
Baseline Building	Not applicable

Liquid Desiccant Performance Curves

Applicability

Systems with liquid-based desiccant dehumidification

Definition

A set of performance curves apply to liquid desiccant systems:

DESC-T-FTW=a+b×T+c×T²+d×w+e×w²+f×T×w

(44)

DESC-W-FTW=a+b×T+c×T²+d×w+e×w²+f×T×w

(45)

DESC-Gas-FTW=a+b×T+c×T²+d×w+e×w²+f×T×w

(46)

DESC-kW-FTW=a+b×T+c×T²+d×w+e×w²+f×T×w

(47)

Where:

DESC-T-FTW = Temperature leaving desiccant unit

DESC-W-FTW = Humidity ratio leaving desiccant unit

DESC-Gas-FTW = Gas usage of desiccant unit

DESC-kW-FTW = Electric usage of desiccant unit

T = Entering air temperature

w = Entering humidity ratio

Table 78. Liquid Desiccant Unit Performance Curves

Coefficient	DESC-T-FTW	DESC-W-FTW	DESC-Gas-FTW	DESC-kW-FTW
a	11.5334997	11.8993998	58745.8007813	3.5179000
b	0.6586730	-0.2695580	-1134.4899902	-0.0059317
c	-0.0010280	0.0044549	-3.6676099	0.0000000
d	0.2950410	0.0830525	3874.5900879	0.0040401
e	-0.0001700	0.0006974	-1.6962700	0.0000000
f	-0.0008724	0.0015879	-13.0732002	0.0000000
Source: COMNET 2017

Units

Data structure

Input Restrictions

As designed, default to values in Table 78

Baseline Building

Not applicable

Desiccant Dewpoint Temperature Setpoint
Applicability	Systems with desiccant dehumidification
Definition	The setpoint dewpoint temperature of the air leaving the desiccant system
Units	Degrees Fahrenheit (°F)
Input Restrictions	As designed. Defaults to 50°F.
Baseline Building	Not applicable

Desiccant Heat Exchanger Effectiveness
Applicability	Systems with desiccant dehumidification
Definition	The effectiveness of a sensible heat exchanger used with a desiccant system
Units	Fraction (between 0 and 1)
Input Restrictions	As designed
Baseline Building	Not applicable

Desiccant Heat Exchanger Pressure Drop
Applicability	Systems with desiccant dehumidification
Definition	The pressure drop across a sensible heat exchanger used with a desiccant system
Units	in. H₂O
Input Restrictions	As designed. Defaults to 1.0 in. H₂O.
Baseline Building	Not applicable

General

Humidifier Type
Applicability	Optional humidifier
Definition	The type of humidifier employed. Choices include: Hot-Water Steam Electric Evaporative Humidification
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Maximum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Minimum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for humidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as proposed design

Desiccant

Desiccant Type
Applicability	Systems with desiccant dehumidification
Definition	Describes the configuration of desiccant cooling equipment The following configurations for desiccant systems are allowed: LIQ-VENT-AIR1 – a liquid desiccant dehumidifying unit LIQ-VENT-AIR2 – a liquid desiccant dehumidifying unit combined with a gas-fired absorption chiller SOL-VENT-AIR1 – a solid desiccant dehumidifying unit NO-DESICCANT – the default, which indicates that no desiccant system is present
Units	List (see above)
Input Restrictions	As designed

Desiccant Control Mode
Applicability	Systems with desiccant dehumidification
Definition	The method of controlling the operation of the desiccant unit. For liquid-based systems this can be either: Dry-bulb – the desiccant unit is turned on whenever the outside air dry-bulb exceeds a set limit. Evaporative cooling– cycles the desiccant unit on when an evaporative cooler is on to maintain a dewpoint setpoint. Dewpoint – cycles the desiccant unit on and off to maintain the dewpoint temperature of the supply air. For solid-based systems the following configurations are possible: Dehumidification only – the desiccant unit cycles on and off to maintain indoor humidity levels Sensible heat exchanger plus regeneration – the desiccant unit includes a sensible heat exchanger to precool the hot, dry air leaving the desiccant unit. The air leaving the exhaust side of the heat exchanger is directed to the desiccant unit Sensible heat exchanger – the desiccant unit includes a heat exchanger, but the air leaving the exhaust side of the heat exchanger is exhausted to the outdoors
Units	List (see above)
Input Restrictions	As designed

Desiccant Air Fraction
Applicability	Systems with desiccant dehumidification
Definition	The fraction of the supply air that passes through the desiccant unit. Typically either the minimum outside air fraction or all of the air passes through the desiccant system.
Units	Ratio
Input Restrictions	As designed

Desiccant Heat Source
Applicability	Systems with desiccant dehumidification
Definition	The source of heat that is used to dry out the desiccant. This can be either: Gas – Hydronic – the regeneration heat load is met with a gas-fired heater Hot water – the heat load is met with hot water from the plant
Units	List (see above)
Input Restrictions	As designed

Liquid Desiccant Performance Curves

Applicability

Systems with liquid-based desiccant dehumidification

Definition

A set of performance curves that apply to liquid desiccant systems.

(6.7.7-1)

$$ D\!ESC\!\!-\!\!T\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-2)

$$ D\!ESC\!\!-\!\!W\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-3)

$$ D\!ESC\!\!-\!\!Gas\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-4)

$$ D\!ESC\!\!-\!\!kW\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

where

DESC-T-FTW	temperature leaving desiccant unit
DESC-W-FTW	humidity ratio leaving desiccant unit
DESC-Gas-FTW	Gas usage of desiccant unit
DESC-kW-FTW	Electric usage of desiccant unit
T	entering air temperature
w	entering humidity ratio

[table title="Liquid Desiccant Unit Performance Curves" id="liquid-desiccant-unit-performance-curves"]

Coefficient	DESC-T-FTW	DESC-W-FTW	DESC-Gas-FTW	DESC-kW-FTW
a	11.5334997	11.8993998	58745.8007813	3.5179000
b	0.6586730	-0.2695580	-1134.4899902	-0.0059317
c	-0.0010280	0.0044549	-3.6676099	0.0000000
d	0.2950410	0.0830525	3874.5900879	0.0040401
e	-0.0001700	0.0006974	-1.6962700	0.0000000
f	-0.0008724	0.0015879	-13.0732002	0.0000000

Units

Data structure

Input Restrictions

As designed, default to values in [bookref id="liquid-desiccant-unit-performance-curves"]

Desiccant Dewpoint Temperature Setpoint
Applicability	Systems with desiccant dehumidification
Definition	The setpoint dewpoint temperature of the air leaving the desiccant system
Units	Degrees Fahrenheit (°F)
Input Restrictions	As designed. Defaults to 50°F.

Desiccant Heat Exchanger Effectiveness
Applicability	Systems with desiccant dehumidification
Definition	The effectiveness of a sensible heat exchanger used with a desiccant system
Units	Ratio
Input Restrictions	As designed

Desiccant Heat Exchanger Pressure Drop
Applicability	Systems with desiccant dehumidification
Definition	The pressure drop across a sensible heat exchanger used with a desiccant system
Units	in. H2O
Input Restrictions	As designed. Defaults to 1.0 in. H₂O

General

Humidifier Type
Applicability	Optional humidifier
Definition	The type of humidifier employed. Choices include: Hot-Water Steam Electric Evaporative Humidification
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Maximum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Humidistat Minimum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for humidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Rules	Same as proposed design

Desiccant

Desiccant Type
Applicability	Systems with desiccant dehumidification
Definition	Describes the configuration of desiccant cooling equipment The following configurations for desiccant systems are allowed: LIQ-VENT-AIR1 – a liquid desiccant dehumidifying unit LIQ-VENT-AIR2 – a liquid desiccant dehumidifying unit combined with a gas-fired absorption chiller SOL-VENT-AIR1 – a solid desiccant dehumidifying unit NO-DESICCANT – the default, which indicates that no desiccant system is present
Units	List (see above)
Input Restrictions	As designed

Desiccant Control Mode
Applicability	Systems with desiccant dehumidification
Definition	The method of controlling the operation of the desiccant unit. For liquid-based systems this can be either: Dry-bulb – the desiccant unit is turned on whenever the outside air dry-bulb exceeds a set limit. Evaporative cooling– cycles the desiccant unit on when an evaporative cooler is on to maintain a dewpoint setpoint. Dewpoint – cycles the desiccant unit on and off to maintain the dewpoint temperature of the supply air. For solid-based systems the following configurations are possible: Dehumidification only – the desiccant unit cycles on and off to maintain indoor humidity levels Sensible heat exchanger plus regeneration – the desiccant unit includes a sensible heat exchanger to precool the hot, dry air leaving the desiccant unit. The air leaving the exhaust side of the heat exchanger is directed to the desiccant unit Sensible heat exchanger – the desiccant unit includes a heat exchanger, but the air leaving the exhaust side of the heat exchanger is exhausted to the outdoors
Units	List (see above)
Input Restrictions	As designed

Desiccant Air Fraction
Applicability	Systems with desiccant dehumidification
Definition	The fraction of the supply air that passes through the desiccant unit. Typically either the minimum outside air fraction or all of the air passes through the desiccant system.
Units	Ratio
Input Restrictions	As designed

Desiccant Heat Source
Applicability	Systems with desiccant dehumidification
Definition	The source of heat that is used to dry out the desiccant. This can be either: Gas – Hydronic – the regeneration heat load is met with a gas-fired heater Hot water – the heat load is met with hot water from the plant
Units	List (see above)
Input Restrictions	As designed

Liquid Desiccant Performance Curves

Applicability

Systems with liquid-based desiccant dehumidification

Definition

A set of performance curves that apply to liquid desiccant systems.

(6.7.7-1)

$$ D\!ESC\!\!-\!\!T\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-2)

$$ D\!ESC\!\!-\!\!W\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-3)

$$ D\!ESC\!\!-\!\!Gas\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

(6.7.7-4)

$$ D\!ESC\!\!-\!\!kW\!\!-\!\!FTW = a + b \times T + c \times T^2 + d \times w + e \times w^2 + f \times T \times w$$

where

DESC-T-FTW	temperature leaving desiccant unit
DESC-W-FTW	humidity ratio leaving desiccant unit
DESC-Gas-FTW	Gas usage of desiccant unit
DESC-kW-FTW	Electric usage of desiccant unit
T	entering air temperature
w	entering humidity ratio

[table title="Liquid Desiccant Unit Performance Curves" id="liquid-desiccant-unit-performance-curves"]

Coefficient	DESC-T-FTW	DESC-W-FTW	DESC-Gas-FTW	DESC-kW-FTW
a	11.5334997	11.8993998	58745.8007813	3.5179000
b	0.6586730	-0.2695580	-1134.4899902	-0.0059317
c	-0.0010280	0.0044549	-3.6676099	0.0000000
d	0.2950410	0.0830525	3874.5900879	0.0040401
e	-0.0001700	0.0006974	-1.6962700	0.0000000
f	-0.0008724	0.0015879	-13.0732002	0.0000000

Units

Data structure

Input Restrictions

As designed, default to values in [bookref id="liquid-desiccant-unit-performance-curves"]

Desiccant Dewpoint Temperature Setpoint
Applicability	Systems with desiccant dehumidification
Definition	The setpoint dewpoint temperature of the air leaving the desiccant system
Units	Degrees Fahrenheit (°F)
Input Restrictions	As designed. Defaults to 50°F.

Desiccant Heat Exchanger Effectiveness
Applicability	Systems with desiccant dehumidification
Definition	The effectiveness of a sensible heat exchanger used with a desiccant system
Units	Ratio
Input Restrictions	As designed

Desiccant Heat Exchanger Pressure Drop
Applicability	Systems with desiccant dehumidification
Definition	The pressure drop across a sensible heat exchanger used with a desiccant system
Units	in. H2O
Input Restrictions	As designed. Defaults to 1.0 in. H₂O