62
SETTING UP THE SYSTEM
The economizer configuration options are under the Local Dis-
play Mode Configuration
ECON. See Table 63.
Economizer Installed? (EC.EN)
If an economizer is not installed or is to be completely disabled
then the configuration option EC.EN should be set to No. Oth-
erwise in the case of an installed economizer, this value must
be set to Yes.
Economizer Minimum Position (EC.MN)
The configuration option EC.MN is the economizer minimum
position. See the section on indoor air quality for further infor-
mation on how to reset the economizer further to gain energy
savings and to more carefully monitor IAQ problems.
Economizer Maximum Position (EC.MX)
The upper limit of the economizer may be limited by setting
EC.MX. This value defaults to 98% to avoid problems associated
with slight changes in the economizer damper’s end stop over
time. Typically this will not need to be adjusted.
Economizer Position at Minimum VFD Speed (EP.MS)
The configuration option EP.MS is the economizer command-
ed position at SP.MN (STATPMIN), which is the minimum
speed for the supply fan VFD. Typically the value is chosen to
maintain a minimum level of ventilation. See the section on in-
door air quality for further information on how to reset the
economizer further to gain energy savings and to more careful-
ly monitor IAQ problems.
Economizer Position at Maximum VFD Speed (EP.XS)
The configuration option EP.XS is the economizer commanded
position at SP.MX (STATPMAX), which is the maximum
speed for the supply fan VFD. This is usually set to 100%
when CV.FD = Yes, the range is 33 to 67% with the default set-
ting of 67%. See the section on indoor air quality for further in-
formation on how to reset the economizer further to gain ener-
gy savings and to more carefully monitor IAQ problems.
Economizer Trim for Sum Z? (E.TRM)
Sum Z is the adaptive cooling control algorithm used for multi-
ple stages of mechanical cooling capacity. The configuration
option, E.TRM is typically set to Yes, and allows the econo-
mizer to modulate to the same control point (Sum Z) that is
used to control capacity staging. The advantage is lower com-
pressor cycling coupled with tighter temperature control. Set-
ting 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 concur-
rently which determine whether the economizer is able to pro-
vide free cooling:
1. Dry bulb changeover (outside-air temperature qualification)
2. Economizer switch (discrete control input monitoring)
3. Economizer changeover select (E.SEL economizer change-
over select configuration option)
4. Outdoor dewpoint limit check (requires an installed outdoor
relative humidity sensor installed)
Dry Bulb Changeover (OAT.L)
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 perform free cooling.
Economizer Switch (EC.SW)
The function of this switch is determined by Configuration
ECON
EC.SW. The state of the corresponding economizer
input can be viewed under Inputs
GEN.I
E.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 Control Type (E.TYP)
This configuration should not be changed.
Table 63 — Economizer Configuration Table
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
EC.EN Economizer Installed? Yes/No ECON_ENA Yes
EC.MN Economizer Min.Position 0 to 100 % ECONOMIN 5
EC.MX Economizer Max.Position 0 to 100 % ECONOMAX 98
EP.MS Economizer Position at Minimum VFD Speed 0 to 100 % EPOSMNFS 5
EP.XS Economizer Position at Maximum VFD Speed 0 to 100 % EPOSMXFS 5
E.TRM Economzr Trim For SumZ ? Yes/No ECONTRIM Yes
E.SEL
Econ ChangeOver Select 0 to 3 ECON_SEL 0
DDB.C
Diff Dry Bulb RAT Offset 0 to 3
dF
EC_DDBCO 0
OA.E.C OA Enthalpy ChgOvr Selct 1 to 5 OAEC_SEL 4
OA.EN Outdr.Enth Compare Value 18 to 32 OAEN_CFG 24
OAT.L High OAT Lockout Temp -40 to 120 dF OAT_LOCK 60
O.DEW OA Dewpoint Temp Limit 50 to 62 dF OADEWCFG 55
ORH.S Outside Air RH Sensor Enable/Disable OARHSENS Disable
E.TYP Economizer Control Type 1 to 3 ECON_CTL 1
EC.SW Economizer Switch Config 0 to 2 ECOSWCFG 0
E.CFG ECON.OPERATION CONFIGS
E.P.GN Economizer Prop.Gain 0.7 to 3.0 EC_PGAIN 1
E.RNG Economizer Range Adjust 0.5 to 5 ^F EC_RANGE 2.5
E.SPD Economizer Speed Adjust 0.1 to 10 EC_SPEED 0.75
E.DBD Economizer Deadband 0.1 to 2 ^F EC_DBAND 0.5
UEFC UNOCC.ECON.FREE COOLING
FC.CF Unoc Econ Free Cool Cfg 0 to 2 UEFC_CFG 0
FC.TM Unoc Econ Free Cool Time 0 to 720 min UEFCTIME 120
FC.L.O Un.Ec.Free Cool OAT Lock 40 to 70 dF UEFCNTLO 50
T.24.C TITLE 24 FDD
LOG.F Log Title 24 Faults Yes/No T24LOGFL No
EC.MD T24 Econ Move Detect 1 to 10 dF T24ECMDB 1
EC.ST T24 Econ Move SAT Test 10 to 20 % T24ECSTS 10
S.CHG T24 Econ Move SAT Change 0 to 5 dF T24SATMD 0.2
E.SOD T24 Econ RAT-OAT Diff 5 to 20 dF T24RATDF 15
E.CHD T24 Heat/Cool End Delay 0 to 60 min T24CHDLY 25
ET.MN T24 Test Minimum Pos. 0 to 50 % T24TSTMN 15
ET.MX T24 Test Maximum Pos. 50 to 100 % T24TSTMX 85
SAT.T SAT Settling Time 10 to 900 sec SAT_SET 240
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