54
If the economizer is able to provide free cooling at the start
of a cooling session, the mechanical cooling algorithm
(SumZ), checks the economizer’s current position (Run Status
→
ECON
→
ECN.P) and compares it to the economizer’s
maximum position (Configuration
→
ECON
→
EC.MX) – 5%.
Once the economizer has opened beyond this point a 150 sec-
ond timer starts. If the economizer stays beyond this point for
2.5 minutes continuously, the mechanical cooling algorithm is
allowed to start computing demand and stage compressors and
unloaders.
2-Stage Cooling Economizer Mechanical Cooling Delay —
This type of mechanical cooling delay is relevant to the follow-
ing machine control types:
C.TYP = 4 TSTAT-2 STG
C.TYP = 6 SPT-2 STG
If the economizer is able to provide free cooling at the start
of a cooling session (for either a low cool or a high cool mode),
the 2-stage cooling algorithm will start a 10-minute hold off
timer on staging. Once this timer has expired, the 2-stage
cooling algorithm will qualify both the temperature of the
evaporator discharge temperature (EDT) and the outside-air
temperature (OAT).
If either of these temperatures are less than the current cool-
ing control point (Run Status
→
VIEW
→
CL.C.P) plus 1.5° F,
mechanical cooling will be held off. But if both of these
temperatures are above CL.C.P + 1.5° F, the first compressor
will be requested and a 5-minute hold off timer will be started
that will give the first compressor time to run before the second
compressor may be started.
At this point, if the 5-minute timer expires and the cooling
mode request is high or the cooling mode request is low and
dehumidification is active (Operating Modes
→
MODE
→
DEHU=ON), the 2-stage cooling algorithm checks whether
EDT is 1.5° F greater than the current cooling control point
(CL.C.P) and if it is, the second compressor will be requested.
Heating Control — The Z Series ComfortLink™ con-
trols offers control for four different types of heating systems to
satisfy general space heating requirements: 2-stage gas heat,
2-stage electric heat, multiple-stage gas heat and hydronic heat.
Heating control also provides tempering and reheat functions.
These functions are discussed in separate sections. Reheat is dis-
cussed under Dehumidification function on page 77.
Variable air volume (VAV) type applications (C.TYP = 1, 2,
3, or 5) require that the space terminal positions be commanded
to open to minimum heating positions when gas or electric heat
systems are active, to provide for the unit heating system’s
Minimum Heating Airflow rate.
Also, for VAV applications, the heat interlock relay (HIR)
function provides the switching of a control signal intended for
use by the VAV terminals. This signal must be used to com-
mand the terminals to open to their Heating Open positions.
The HIR is energized whenever the Heating mode is active, an
IAQ pre-occupied force is active, or if fire smoke modes, pres-
surization, or smoke purge modes are active.
Hydronic heating applications that use the unit’s control
require the installation of a Local Equipment Network (LEN)
communicating actuator on the hydronic heating coil’s control
valve. This actuator (with or without matching control valve)
may be separately shipped for field installation.
All heating systems are available as factory-installed
options. The hydronic heating coil may also be field-supplied
and field-installed; the LEN actuator is still required if unit
control will be used to manage this heating sequence.
SETTING UP THE SYSTEM — The essential heating con-
figurations located at the local display under Configuration
→
HEAT. See Table 42.
Table 42 — Heating Configuration
*Some defaults are model number dependent.
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
HEAT HEATING CONFIGURATION
HT.CF Heating Control Type 0 - 4 HEATTYPE 0*
HT.SP Heating Supply Air Setpt 80 - 120 dF SASPHEAT 85
OC.EN Occupied Heating Enabled Yes/No HTOCCENA No
LAT.M MBB Sensor Heat Relocate Yes/No HTLATMON No
SG.CF STAGED GAS CONFIGS
HT.ST Staged Gas Heat Type 0 - 4 HTSTGTYP 0*
CAP.M Max Cap Change per Cycle 5 - 45 HTCAPMAX 45*
M.R.DB S.Gas DB min.dF/PID Rate 0 - 5 HT_MR_DB 0.5
S.G.DB St.Gas Temp. Dead Band 0 - 5 ^F HT_SG_DB 2
RISE Heat Rise dF/sec Clamp 0.05 - 0.2 HTSGRISE 0.06
LAT.L LAT Limit Config 0 - 20 ^F HTLATLIM 10
LIM.M Limit Switch Monitoring? Yes/No HTLIMMON Yes
SW.H.T Limit Switch High Temp 110 - 180 dF HT_LIMHI 170*
SW.L.T Limit Switch Low Temp 100 - 170 dF HT_LIMLO 160*
HT.P Heat Control Prop. Gain 0 - 1.5 HT_PGAIN 1
HT.D Heat Control Derv. Gain 0 - 1.5 HT_DGAIN 1
HT.TM Heat PID Rate Config 60 - 300 sec HTSGPIDR 90
HH.CF HYDRONIC HEAT CONFIGS
HW.P Hydronic Ctl.Prop. Gain 0 - 1.5 HW_PGAIN 1
HW.I Hydronic Ctl.Integ. Gain 0 - 1.5 HW_IGAIN 1
HW.D Hydronic Ctl.Derv. Gain 0 - 1.5 HW_DGAIN 1
HW.TM Hydronic PID Rate Config 15 - 300 sec HOTWPIDR 90
ACT.C HYDR.HEAT ACTUATOR CFGS.
SN.1 Hydronic Ht.Serial Num.1 0 - 255 HTCL_SN1 0
SN.2 Hydronic Ht.Serial Num.2 0 - 255 HTCL_SN2 0
SN.3 Hydronic Ht.Serial Num.3 0 - 255 HTCL_SN3 0
SN.4 Hydronic Ht.Serial Num.4 0 - 255 HTCL_SN4 0
SN.5 Hydronic Ht.Serial Num.5 0 - 255 HTCL_SN5 0
C.A.LM Hydr.Ht.Ctl.Ang.Lo Limit 0-90 HTCLCALM 85