21
Heating Operation
The 48/50PG and 48/50PM unit’s heating operation consists of:
demand, mode determination, staging request to satisfy the
demand, and handling a request with the unit’s resources. These
resources can be gas heat or electric heat. This section covers both
gas heat units and electric heat units. The Type of Heat Installed
(
Configuration
→
HEAT
→
HT.TY
) configuration will be factory
set to 1 for gas units, 2 for electric heat units with heaters installed,
and 0 for electric heat units without heat installed. The unit enters
a heating mode based on a demand, decides how to satisfy the
demand, executes its plan, and then leaves the heating mode.
Heating Mode Control
The heating HVAC mode (
Run Status
→
MODE
→
HVAC=4
),
represents both types of heating (gas or electric) under all types of
control. For the unit to be allowed to enter the heat mode, heat
must be enabled (
HT.TY = 1 or 2
), and the Outdoor Air
Temperature (
Temperatures
→
AIR.T
→
OA
T) must be less than the
Heating Lockout Temp (
Configuration
→
HEAT
→
HT.LO
). Heat
OAT Lockout (
Run Status
→
MODE
→
H.LOC
) displays when
heat is locked out on outdoor temperature and therefore can not
allow heat mode. The control will display if it is ok to select the
heating mode (
Operating Modes
→
HEAT
→
OK.HT= Yes
).
Thermostat Control
For the unit to enter heating mode, three additional things must be
true: the indoor fan must be ok to use, the mode changeover time
guard must be expired, and there must be a heating demand (W1,
W2). The unit will remain in heating until the heating demand is
dropped or if any of the above conditions turn false. The heating
mode can not officially end until all heat stages are off and the IGC
fan request is dropped (on gas units without Humidi--MiZer
t
).
Space Sensor Control
For the unit to enter heating mode, five additional things must be
true: the indoor fan must be ok to use, the mode changeover time
guard must be expired, the unit must have a valid space
temperature, the W1 jumper must be installed, and there must be a
heating demand. The unit will remain in heating for at least one
minute and until the heat demand drops below --0.5
_
F or if any of
the above conditions turn false.
The heating mode can not
officially end until all heat stages are off and the IGC fan request is
dropped (on gas units without Humidi--MiZer).
Supply--Air Temperature Sensor (SAT)
The
SAT
Heat
Mode
Sensing
(
Configuration
→
HEAT
→
SAT
→
SAT.H
) informs the unit if the supply air sensor
has been relocated downstream of the heat section.
This
configuration affects the Supply Air Temperature (
Temperatures
→
AIR.T
→
SAT
) value displayed as listed below.
When SAT.H = DSBL, the Supply Air Temperature (
Temperatures
→
AIR.T
→
SAT
) value on the Scrolling Marquee and the CCN
tables will be forced to zero when heat outputs come ON and for 5
minutes after. The default Supply Air Temperature location is at
the fan inlet, upstream of the heat section.
When SAT.H = ENBL, the Supply Air Temperature (
Temperatures
→
AIR.T
→
SAT
) sensor reading is displayed at the Scrolling
Marquee and the CCN tables during heating mode. This setting
should only be used if the original SAT sensor wires are removed
from the Main Base Board (MBB) and replaced by an accessory
SAT sensor located in the supply duct downstream of the heat
section. There are then two supply air temperature limits that
become active, the Maximum SAT Lower Level (
Configuration
→
HEAT
→
SAT
→
SAM.L
) the Maximum SAT Upper Level
(
Configuration
→
HEAT
→
SAT
→
SAM.U
). Any time the supply
air temperature rises above SAM.L the heat staging will be limited
to what is currently on and no additional stages can be added until
the supply air temperature falls back below SAM.L. If the supply
air temperature rises above SAM.U, then heating will be reduced
by removing a heat stage. That stage can not be added again until
the Supply Air Temperature falls below SAM.L. If the supply air
temperature stays above SAM.U, then another stage will be
removed after the Heat Stage Decrease Time (
Configuration
→
HEAT
→
H.DEC
). If SAM.L and SAM.U are configured so that
they are close together, the last stage of heat might cycle rapidly,
slowed only by its minimum on and off--time requirements.
Staging Control
Once the unit is in a heating mode, it must decide what the demand
is and how to satisfy. Based on the unit control configuration,
requested heating stages (
Run Status
→
HEAT
→
REQ.H
) will be
determined then passed to heat control to actually add the heating
stages.
Thermostat Control
There are two ways of requesting stages when thermostat control is
enabled:
Traditional Thermostat control or Adaptive control.
Traditional Thermostat control is used if the Thermostat Control
Type (T.CTL) is set to 1, 2, or 3. Adaptive control is used if
Thermostat Control (T.CTL) is set for 0.
T.CTL = 0 (Adaptive Control)
Stage timers and supply air temperature limits apply when
determining the request for stages. The first request (REQ.C=1)
comes immediately when the W1 input is active. The Heat Stage
Increase Time (
Configuration
→
HEAT
→
H.INC
) or the Heat
Stage Decrease Time (
Configuration
→
HEAT
→
H.DEC
) has to
expire before another stage can be added or a stage can be
subtracted. If at any time the Supply--Air Temperature (SAT) rises
above the Maximum Supply Air Temperature Lower Level
(
Configuration
→
HEAT
→
SAT
→
SAM.L
), the requested stages
will not be allowed to increase. If at any time the SAT rises above
the
Maximum
Supply
Air
Temperature
Upper
Level
(
Configuration
→
HEAT
→
SAT
→
SAM.U
), the requested stages
will be reduced by one without honoring H.DEC.
T.CTL = 1, 2 or 3 (Traditional thermostat control)
Stage timers and supply air temperature limits do not apply when
determining the request for stages. Request staging will follow the
thermostat inputs directly. W1 will request one stage. W2 will
request all stages.
48/
50P
G
and
P
M
Summary of Contents for 48/50PG Series
Page 32: ...32 C07009 Fig 20 Air Baffle Dimensions 48 50PG03 16 48 50PG and PM...
Page 33: ...33 C08077 Fig 21 Air Baffle Dimensions 48 50PG20 28 and 48 50PM16 28 48 50PG and PM...
Page 58: ...58 C08549 Fig 28 48PG03 16 Control Wiring Schematic 48 50PG and PM...
Page 59: ...59 C08550 Fig 29 50PG03 16 Control Wiring Schematic 48 50PG and PM...
Page 64: ...64 C08471 Fig 34 Typical 48PG and PM16 28 Control Schematic 48PM16 28 Shown 48 50PG and PM...
Page 66: ...66 C08557 Fig 36 Typical 50PG and PM16 28 Control Schematic 50PG20 28 Shown 48 50PG and PM...
Page 68: ...68 C08558 Fig 38 Typical 48 50PG and PM16 28 Power Schematic 48 50PM16 28 Shown 48 50PG and PM...
Page 72: ...72 C08565 Fig 42 Typical 48 50PG20 28 Component Arrangement 48 50PG20 24 Shown 48 50PG and PM...
Page 73: ...73 C08067 Fig 43 48 50PM16 28 Component Arrangement 48 50PG and PM...
Page 74: ...74 C08562 Fig 44 48 50PM16 28 with Humidi MiZert Component Arrangement 48 50PG and PM...
Page 208: ...208 48 50PG and PM...