55
Heating Control Type (HT.CF) — The heating control types
available are selected/configured with this variable.
0 = No Heat
1 = Electric Heat
2 = 2 Stage Gas Heat
3 = Staged Gas Heat
4 = Hydronic Heat
Heating Supply Air Set Point (HT.SP) — In a low heat mode
for either staged gas or hydronic heat, this is the supply air set
point for heating.
Occupied Heating Enable (OC.EN) — This configuration
only applies when the unit’s control type (Configuration
→
UNIT
→
C.TYP) is configured for 1 (VAV-RAT) or 2 (VAV-
SPT). If the user wants to have the capability of performing
heating throughout the entire occupied period, then this
configuration needs to be set to “YES”. Most installations do
not require this capability, and if heating is installed, it is used
to heat the building up in the morning. In this case set OC.EN
to “NO”.
NOTE: This unit des not support simultaneous heating and
cooling. If significant simultaneous heating and cooling
demand is expected, it may be necessary to provide additional
heating or cooling equipment and a control system to provide
occupants with proper comfort.
MBB Sensor Heat Relocate (LAT.M) — This option allows
the user additional performance benefit when under CCN
Linkage for the 2-stage electric and gas heating types. As two-
stage heating types do not “modulate” to a supply air set point,
no leaving air thermistor is required and none is provided. The
evaporator discharge thermistor, which is initially installed up-
stream of the heater, can be repositioned downstream and the
control can expect to sense this heat. While the control does not
need this to energize stages of heat, the control can wait for a
sufficient temperature rise before announcing a heating mode
to a CCN Linkage system (ComfortID™).
If the sensor is relocated, the user will now have the
capability to view the leaving-air temperature at all times at
Temperatures
→
AIR.T
→
CTRL
→
LAT.
NOTE: If the user does not relocate this sensor for the 2-stage
electric or gas heating types and is under CCN Linkage, then
the control will send a heating mode (if present) uncondition-
ally to the linkage coordinator in the CCN zoning system
regardless of the leaving-air temperature.
HEAT MODE SELECTION PROCESS — There are two
possible heat modes that the control will call out for heating
control: HVAC Mode = LOW HEAT and HVAC Mode =
HIGH HEAT. These modes will be called out based on control
type (C.TYP).
VAV- R AT ( C.TYP = 1) and VAV-SPT (C.TYP = 2) — There
is no difference in the selection of a heating mode for either
VAV-RAT or VAV-SPT, except that for VAV-SPT, space
temperature is used in the unoccupied period to turn on the
supply fan for 10 minutes before checking return-air tempera-
ture. The actual selection of a heat mode, LOW or HIGH for
both control types, will be based upon the controlling return-air
temperature.
With sufficient heating demand, there are still conditions
that will prevent the unit from selecting a heat mode. First, the
unit must be configured for a heat type (Configuration
→
HEAT
→
HT.CF not equal to “NONE”). Second, the unit has a
configuration which can enable or disable heating in the
occupied period except for a standard morning warmup cycle
(Configuration
→
HEAT
→
OC.EN). See descriptions above in
the Setting Up the System section for more information.
If the unit is allowed to select a heat mode, then the next
step is an evaluation of demand versus set point. At this point,
the logic is the same as for control types SPT Multi-Stage and
SPT-2 Stage, (C.TYP = 5,6) except for the actual temperature
compared against set point. See Temperature Driven Heat
Mode Evaluation section.
Tstat-Multi-Stage (C.TYP = 3) and Tstat-2 Stage (C.TYP =
4) — There is no difference to consider for selecting a heat
mode whether the control type is for TSTAT 2-stage or TSTAT
multi-stage as this only refers to how cooling will be handled.
With thermostat control the W1 and W2 inputs determine
whether the HVAC Mode is LOW or HIGH HEAT.
W1 = ON, W2 = OFF: HVAC MODE = LOW HEAT*
W2 = ON, W2 = ON: HVAC MODE = HIGH HEAT
*If the heating type is either 2-stage electric or 2-stage gas, the
unit may promote a low heat mode to a high heat mode.
NOTE: If W2 = ON and W1 is OFF, a “HIGH HEAT” HVAC
Mode will be called out but an alert (T422) will be generated.
See Alarms and Alerts section on page 94.
SPT Multi-Stage (C.TYP = 5) and SPT 2 Stage (C.TYP = 6)
— There is no difference to consider for selecting a heat mode
whether the control type is for SPT 2-stage or SPT multi-stage as
this only refers to how cooling will be handled. So, for a valid
heating type selected (HT.CF not equal to zero) the unit is free
to select a heating mode based on space temperature (SPT).
If the unit is allowed to select a heat mode, then the next
step is an evaluation of demand versus set point. At this point,
the logic is the same as for control types VAV-RAT and
VAV- S PT, ( C.TYP = 1,2) except for the actual temperature
compared against set point. See Temperature Driven Heat
Mode Evaluation section below.
TEMPERATURE DRIVEN HEAT MODE EVALUATION —
This section discusses the technique for selecting a heating
mode based on temperature. Regardless of whether the unit is
configured for return air or space temperature the logic is ex-
actly the same. For the rest of this discussion, the temperature
in question will be referred to as the “controlling temperature.”
First, the occupied and unoccupied heating set points under
Setpoints must be configured.
Then, the heat/cool set point offsets under Configuration
→
D.LV.T should be set. See Table 43.
Table 43 — Heat/Cool Set Point Offsets
ITEM EXPANSION RANGE UNITS CCN
POINT DEFAULT
OHSP Occupied Heat
Setpoint 55-80 dF OHSP 68
UHSP Unoccupied
Heat Setpoint 40-80 dF UHSP 55
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
D.LV.T COOL/HEAT SETPT. OFFSETS
L.H.ON Dmd Level Lo Heat On -1 - 2 ^F DMDLHON 1.5
H.H.ON Dmd Level(+) Hi Heat On 0.5 - 2.0 ^F DMDHHON 0.5
L.H.OF Dmd Level(-) Lo Heat Off 0.5 - 2 ^F DMDLHOFF 1
L.C.ON Dmd Level Lo Cool On -1 - 2 ^F DMDLCON 1.5
H.C.ON Dmd Level(+) Hi Cool On 0.5 - 2 ^F DMDHCON 0.5
L.C.OF Dmd Level(-) Lo Cool Off 0.5 - 2 ^F DMDLCOFF 1
C.T.LV Cool Trend Demand Level 0.1 - 5 ^F CTRENDLV 0.1
H.T.LV Heat Trend Demand Level 0.1 - 5 ^F HTRENDLV 0.1
C.T.TM Cool Trend Time 30 - 600 sec CTRENDTM 120
H.T.TM Heat Trend Time 30 - 600 sec HTRENDTM 120