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Electric Heat (50PG Units)
For 50PG units with factory installed electric heat, the heat type
configuration
Configuration
→
HEAT
→
HT.TY
will be factory
set to a value of 2 and the number of heat stages configuration
Configuration
→
HEAT
→
N.HTR
will be factory set to match the
installed heater. If electric heat is installed in the field, the value of
HT.TY
must be changed.
Heat will not operate if the outdoor temperature is greater than the
value
configured
for
the
heat
lockout
temperature,
Configuration
→
HEAT
→
HT.LO
.
Minimum
on-time,
Configuration
→
HEAT
→
MRT.H
, and
minimum off-time,
Configuration
→
HEAT
→
MOT.H
, timeguards apply to both
stages of heating. Factory default values are 2 minutes On and 2
minutes Off.
If the indoor fan control is configured to cycle with the heating
demand (
Configuration
→
UNIT
→
OC.FN =
No
) the
fan will
stop
after
a
configured
delay
(
Configuration
→
HEAT
→
FOD.E
). The factory default value is 30 seconds.
Thermostat Control
The first stage of electric heat (HT.1) will follow the W1 input
and the second stage (HT.2) of heat will follow the W2 input.
During auto fan, the indoor fan will follow the HT.1 output.
During continuous fan, the indoor fan will follow the G input.
If the user has selected Adaptive (see Cooling section) for
thermostat mode, the algorithm will follow the configurable
delays for adding and removing stages. When adding additional
heat stages, the delay is measured from when the last stage was
added (
Configuration
→
HEAT
→
H.INC
). When removing
stages, the delay is measured from when the last stage was
removed (
Configuration
→
HEAT
→
H.DEC
). Therefore, if W1
and W2 turn on simultaneously, the second stage will turn on
after a
H.INC
delay.
NOTE
: If the mode is not Adaptive, then there are no delays for
adding and removing stages.
Space Sensor Control
During Space Sensor control, the electronic control uses
information from the space
sensor to determine the number of
heat stages. Once the number of stages needed for heating is
determined, either HT.1 or HT.1 and HT.2 outputs will be turned
on. See Space Sensor Control section for gas heat units for more
information.
NOTE
: The jumper wire in the installer’s packer must be
connected between R and W1 when using a T-55, T-56, or T-58
device. See Major System Components section.
Supply--Air Temperature (SAT) Sensor
The SAT Heat Sensing Configuration affects the SAT value
displayed. SAT Heat Sensing (
SAT.H
) Configuration is accessible
via the Scrolling Marquee at
Configuration
→
Unit
→
SAT.H
.
Configuration
→
HEAT
→
SAT.H = DSBL
When
SAT.H = DSBL
, the SAT value on the Scrolling Marquee
and CCN tables will be forced to zero when heat outputs come
ON and for 5 minutes after. The default SAT sensor location is at
the fan inlet, upstream of the heat section.
Configuration
→
HEAT
→
SAT.H = ENBL
When
SAT.H = ENBL
, the supply-air temperature measured by
the SAT sensor is displayed at the scrolling marquee and the CCN
tables during heating mode. This setting should only be used if
the original SAT sensor is replaced by an accessory SAT sensor
located in the supply duct, downstream of the heat section.
Economizer
If an economizer is installed, then Economizer Installed
configuration (
Configuration
→
UNIT
→
EC.EN
) should be set
to YES. The economizer is controlled by the economizer output
signal (
Outputs
→
ECON
→
EC.CP
) on the ECB control. If the
indoor fan is off or the building is unoccupied, the economizer
position is zero. If in Occupied mode and the unit is heating or
cooling and the economizer cannot provide free cooling, the
economizer position is the configured economizer minimum
position (
Configuration
→
ECON
→
EC.MN
) or the position
specified by the IAQ algorithm. If in Unoccupied mode, the
position is 0% open.
The economizer will be allowed to help with cooling if the
outdoor-air temperature (
Temperature
→
AIR.T
→
OAT
) is less
than the configured economizer high temperature lockout
(
Setpoints
→
EH.LO
) and greater than the configured economizer
low temperature lockout (
Setpoints
→
EL.LO
). If an
enthalpy
sensor is installed, the outdoor temperature must be below the
economizer high temperature lockout and the enthalpy
(
Inputs
→
GEN.I
→
ENTH
) must be LOW. For cooling, the
economizer position can vary between the configured economizer
minimum position (
Configuration
→
ECON
→
EC.MN
) and the
economizer
maximum
cooling
position
(
Configuration
→
ECON
→
EC.MX
).
Thermostat Control
If the unit is in cooling, operating under thermostat control, Y1 =
ON, and the economizer is available for cooling, the economizer
will control the supply-air temperature to the low cool set point
(
Setpoints
→
LCSP
). When Y2 = ON, the economizer will control
the
supply-air
temperature
to
high
cool
set
point
(
Setpoints
→
HCSP
).
Space Sensor Control
If the unit is in cooling, operating under space temperature
control, the economizer is available for cooling, and no
compressors are operating, the economizer will control the SAT
to either
Setpoints
→
LCSP
or
Setpoints
→
HCSP
(See Table 91).
If a compressor is ON, the economizer will try to position itself at
the
economizer
maximum
cooling
position
(
Configuration
→
ECON
→
EC.MX
).
If the control senses low suction pressure for any active
refrigerant circuit when the economizer is also providing cooling,
the maximum allowable economizer position will be reduced.
Factory default configurations have been qualified over a large
range of conditions and should only be changed with care. For
unit troubleshooting, factory default maximum economizer limits
for this condition are provided in Table 90.
Table 89—LCSP and HCSP Transitions for
Space Temperature Mode
CURRENT SAT
SET POINT
COOL DEMAND
(
∆
F)
NEXT SAT
SET POINT
LCSP
>0.5
HCSP
HCSP
<0
LCSP
LCSP
<–0.5
Exit Cooling
LEGEND
HCSP
--- High Cool Set Point
LCSP
--- Low Cool Set Point
SAT
--- Supply---Air Temperature
Table 90—Maximum Economizer Limits During Low
Suction Pressure
COOLING
STAGE
SIZES 03-07
SIZES 08-14
SIZE 16
Bottom
50
50
50
Middle
—
—
35
Top
—
25
25
48/
50P
G
C
03
--
16