Specifications

51
Table 61 — Economizer Configuration Table
Economizer Trim for Sum Z? (
E.TRM) — Sum Z is the
adaptive cooling control algorithm used for multiple stages
of mechanical cooling capacity. The configuration option,
E.TRM is typically set to Yes, and allows the economizer to
modulate to the same control point (Sum Z) that is used to
control capacity staging. The advantage is lower compressor
cycling coupled with tighter temperature control. Setting this
option to No will cause the economizer, if it is able to provide
free cooling, to open to the Economizer Max. Position
(EC.MX) during mechanical cooling.
ECONOMIZER OPERATION — There are four potential
elements which are considered concurrently which determine
whether the economizer is able to provide free cooling:
1. Dry bulb changeover (outside-air temperature qualification)
2. Economizer switch (discrete control input monitoring)
3. Economizer changeover select (E.SEL economizer
changeover select configuration option)
4. Outdoor dewpoint limit check (requires an installed out-
door relative humidity sensor installed)
Dry Bulb Changeover
— Outside-air temperature may be
viewed under Temperatures → AIR.T → OAT. The control
constantly compares its outside-air temperature reading against
the high temperature OAT lockout (OAT.L). If the temperature
reads above OAT.L, the economizer will not be allowed to per-
form free cooling.
Economizer Switch
— The state of the economizer switch can
be viewed under Inputs → GEN.I → E.SW. The function of this
input is determined by Configuration
→ ECON → EC.SW.
When set to EC.SW =0, the switch is disabled. When set to
EC.SW =1, the economizer switch functions to enable/disable
the economizer. When set to EC.SW =2, the switch functions
as an IAQ override switch. This functions just like the discrete
IAQ input Inputs
→ AIR.Q → IAQ.I when Configuration
→ IAQ → AQ.CF → IQ.I.C=2 (IAQ Discrete Override). See the
Indoor Air Quality Control section for more information.
When Configuration
→ ECON → EC.SW=1 and Inputs →
GEN.I → E.SW =No, free cooling will not be allowed.
ECONOMIZER CHANGEOVER SELECT (E.SEL)—The
control is capable of performing any one of the following
changeover types in addition to both the dry bulb lockout and
the external switch enable input:
E.SEL = 0 none
E.SEL = 1 Differential Dry Bulb Changeover
E.SEL = 2 Outdoor Enthalpy Changeover
E.SEL = 3 Differential Enthalpy Changeover
Differential Dry Bulb Changeover
— As both return air and
outside air temperature sensors are installed as standard on
these units, the user may select this option, E.SEL =1,to
perform a qualification of return and outside air in the enabling/
disabling of free cooling. If this option is selected and outside-
air temperature is greater than return-air temperature, free
cooling will not be allowed.
Outdoor Enthalpy Changeover
— This option should be used
in climates with higher humidity conditions. The A Series
control can use an enthalpy switch or enthalpy sensor, or the
standard installed outdoor dry bulb sensor and an accessory
relative humidity sensor to calculate the enthalpy of the air.
Setting Configuration
→ ECON → E.SEL = 2 requires that
the user configure Configuration
→ ECON → OA.E.C,the
Outdoor Enthalpy Changeover Select, and install an outdoor
relative humidity sensor. Once the sensor is installed, enable
Configuration
→ ECON → ORH.S, the outdoor relative humid-
ity sensor configuration option.
If the user selects one of the Honeywell curves, A,B,C or D,
then OA.E.C options 1-4 should be selected. See Fig. 8 for a
diagram of these curves on a psychrometric chart.
OA.E.C = 1 Honeywell A Curve
OA.E.C = 2 Honeywell B Curve
OA.E.C = 3 Honeywell C Curve
OA.E.C = 4 Honeywell D Curve
OA.E.C = 5 custom enthalpy curve
If the user selects OA.E.C = 5, a direct compare of outdoor
enthalpy versus an enthalpy set point is done. This outdoor
enthalpy set point limit is configurable, and is called
Configuration
→ ECON → OA.EN.
Depending on what Configuration
→ ECON → OA.E.C is
configured for, if the outdoor enthalpy exceeds the Honeywell
curves or the outdoor enthalpy compare value (Configuration
→ ECON → OA.EN), then free cooling will not be allowed.
Differential Enthalpy Changeover
— This option compares
the outdoor-air enthalpy to the return air enthalpy and chooses
the option with the lowest enthalpy. This option should be
used in climates with high humidity conditions. This option
uses both humidity sensors and dry bulb sensors to calculate
the enthalpy of the outdoor and return air. An accessory
outdoor air humidity sensor (ORH.S) and return air humidity
sensor (RRH.S) are used. The outdoor air relative humidity
sensor config (ORH.S) and return air humidity sensor config
(Configuration
→ SENS → RRH.S) must be enabled.
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
EC.EN Economizer Installed? Yes/No ECON_ENA Yes
EC.MN Economizer Min.Position 0 - 100 % ECONOMIN 5
EC.MX Economizer Max.Position 0 - 100 % ECONOMAX 98
E.TRM Economzr Trim For SumZ ? Yes/No ECONTRIM Yes
E.SEL Econ ChangeOver Select 0 - 3 ECON_SEL 0
OA.E.C OA Enthalpy ChgOvr Selct 1 - 5 OAEC_SEL 4
OA.EN Outdr.Enth Compare Value 18 - 28 OAEN_CFG 24
OAT.L High OAT Lockout Temp -40 - 120 dF OAT_LOCK 60
O.DEW OA Dewpoint Temp Limit 50 - 62 dF OADEWCFG 55
ORH.S Outside Air RH Sensor Enable/Disable OARHSENS Disable
E.TYP Economizer Control Type 1 - 3 ECON_CTL 1
E.SW Economizer Switch Config 0 - 2 ECOSWCFG 0
E.CFG ECON.OPERATION CONFIGS
E.P.GN Economizer Prop.Gain 0.7 - 3.0 EC_PGAIN 1
E.RNG Economizer Range Adjust 0.5 - 5 ^F EC_RANGE 2.5
E.SPD Economizer Speed Adjust 0.1 - 10 EC_SPEED 0.75
E.DBD Economizer Deadband 0.1 - 2 ^F EC_DBAND 0.5
UEFC UNOCC.ECON.FREE COOLING
FC.CF Unoc Econ Free Cool Cfg 0-2 UEFC_CFG 0
FC.TM Unoc Econ Free Cool Time 0 - 720 min UEFCTIME 120
FC.L.O Un.Ec.Free Cool OAT Lock 40 - 70 dF UEFCNTLO 50