15
HEATING — The Staged Heating Control routine determines
the staging of the available heating system to maintain space
comfort conditions. The heating cycle is available during the
Occupied period (for all CV units, and for VAV units when en-
abled), during Optimal Start/Morning Warm-up routine, and
during the Unoccupied period. A modified Heating function is
also available during Dehumidification and Reheat functions.
This function provides control of two stages of factory-
installed gas or electric heat or two stages of field-installed
accessory electric heaters, via channels 17 and 18.
Occupied Heating is Mode 30. Unoccupied Heating is
Mode 23.
On VAV units, Heating control will maintain set point tem-
perature at the Return Air Temperature sensor. On CV units,
Heating Control will prevent the space temperature from fall-
ing below the Heating set point. Heating control definitions are
shown in Table 12.
NOTE: On VAV units, VAV terminals must be fully open dur-
ing heating operation. The HIR (heat interlock relay) function
provides a control signal to the VAV terminals to move to
Heating-Open positions. The HIR is energized whenever Heat-
ing mode is active.
For CV heating operation, a Space Temperature sensor
(T-55 factory-supplied, field-installed or T-56 field-supplied,
field-installed) is required.
NOTE: If heat type is electric, all compressor stages must be
off before Heating control is permitted.
Table 12 — Heating Control Operation Definitions
VAV Units Occupied Heating — Occupied Heat must be en-
abled for Heating control to operate during Occupied periods.
The supply fan must be ON before Heating control can start.
Fan Status is determined by closure of contacts at Fan Status
switch. The RAT must be less than Occupied Heat Set Point.
The Master Loop (ML) checks the RAT and OHSP, and then
issues a Heating Submaster Reference value (SHSR) to the
Heating Submaster Loop (HSL). The HSL compares SHSR to
actual SAT, then calculates number of heating stages required
to deliver the SHSR. Heating stages are initiated. Heat Inter-
lock Relays are energized, initiating signal to room terminals to
move to heating position. As RAT approaches OHSP, the HSL
will deactivate stages of heating.
Gas Heat Units — If the RAT decreases below OHSP, then the
heating cycle will be initiated immediately, even if the cooling
cycle is already operating (cooling stages at one or higher).
The ML will issue a forced value to the Cooling Submaster
Loop (CSL) (at high limit value). This will drive cooling
stages back to zero stages (at minimum time delay between
stages). Simultaneous operation of heating and cooling cycles
may be observed during transition. Once OHSP is satisfied by
RAT, heating will terminate and cooling cycle will restart. The
Reheat function will activate Heating control with concurrent
operation of compressor stages.
CV Units Occupied Heating — If Auto Fan mode has been
configured, the fan will be OFF when there is no demand for
heating. When space temperature falls below OHSP, the fol-
lowing conditions will occur:
1. If the fan is configured for AUTO, the fan relay will be
energized, and Air Switch contacts will close, confirm-
ing fan operation.
2. The ML compares SPT to OHSP, calculates SHSR
value and issues it to HSL.
3. The HSL compares SHSR to actual SAT, and calcu-
lates number of heating stages required to satisfy space
temperature.
4. The HSL initiates heating stages.
5. Heating stages are deactivated as SPT approaches,
then equals OHSP.
6. If the fan is configured for AUTO, the fan contactor
will be deenergized when SPT equals OHSP and the
fan is deenergized.
Unoccupied Heating (VAV and CV Units) — During unoc-
cupied heating:
1. The fan will be OFF when there is no demand for
heating.
2. Demand is initiated when the RAT falls below UHSP
(VAV units) or when space temperature falls below
UHSP (CV units).
3. The fan contactor will be energized, and Air Switch
contacts will close, confirming fan operation.
4. The ML compares RAT (VAV) or SPT (CV) to UHSP,
calculates SHSR value, and issues it to the HSL.
5. The HSL compares SHSR to actual SAT, and then cal-
culates number of heating stages required to satisfy
space temperature.
6. The HSL initiates the heating stages.
7. The heating stages are deactivated as SPT approaches,
then equals UHSP.
8. The fan contactor will deenergize when RAT (VAV) or
SPT (CV) equals UHSP, then the fan stops.
Configuration of Electric Heat — If accessory electric heat
has been installed (50FP,JP,NP only), the control configuration
must be reconfigured for electric heat. See Table 13.
NOTE: Electric heat is not available on 50FB,FPX,FPY,
JB,JPX,JPY,NB units.
Configuration of Heating Set Points — To configure heat-
ing set points, enter the Set Point function and the Set Point
subfunction by pressing
and
. To select the Occupied
Heating set point, scroll down to OHSP. The current set point
value will be displayed. The default is 68 F. The range of ac-
ceptable values is 55 to 80 F. To change the set point, press the
numbers of the new set point (example:
) and then
press
.
To select the Unoccupied Heating set point, scroll down to
UHSP. The current set point value will be displayed. The de-
fault is 55 F. The range of acceptable values is 40 to 80 F. To
change the set point, press the numbers of the new set point
(example:
) and then press
.
ITEM
DEFINITION
CV
Constant Volume
HD
Heat Demand (Degrees F for Staged Heat and
Percent for Modulating
HS
Heating Stages
HSL
Heating Submaster Loop
HSR
Heating Submaster Reference
OAT
Outdoor Air Temperature
OHEN
Occupied Heat Enable/Disable
OHSP
Occupied Heating Set Point (Space Set Point)
PID
Proportional, Integral, Derivative Controls
RAT
Return-Air Temperature
SAT
Supply-Air Temperature
SATRV
STO Reset Value (Based on 2 to 10 v Input)
SHSMG
Staged Heating Submaster Gain
SHSR
Staged Heating Submaster Reference
SPT
Space Temperature
STO
Space Temperature Offset (CV Only)
UHSP
Unoccupied Heating Set Point
VAV
Variable Air Volume
ENTER
ENTER