Carrier Weathermaster 48P2030-100 Controls, Start-Up, Operation, Service, And Troubleshooting page 61

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-RAT (C.TYP = 1) and VAV-SPT (C.TYP = 2)
There is no difference in the selection of a heating mode for ei-
ther 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
HT.CF not equal to "NONE"). Second, the unit must have a
configuration which can enable or disable heating in the occu-
pied period except for a standard morning warmup cycle (Con-
 
figuration HEAT OC.EN). See descriptions in the Setting
Up the System section on page 60 for more information.
Tstat-Multi-Stage (C.TYP = 3)
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 118.
SPT Multi-Stage (C.TYP = 4)
The unit is free to select a heating mode based on space tem-
perature (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 log-
ic is the same as for control types VAV-RAT and VAV-SPT,
(C.TYP = 1,2) except for the actual temperature compared
against set point. See Temperature Driven Heat Mode Evalua-
tion section below.
ITEM
D.LV.T COOL/HEAT SETPT. OFFSETS
L.H.ON Dmd Level
H.H.ON Dmd Level(+) Hi Heat On
L.H.OF Dmd Level(-) Lo Heat Off
L.C.ON Dmd Level
H.C.ON Dmd Level(+) Hi Cool On
L.C.OF Dmd Level(-) Lo Cool Off
C.T.LV Cool Trend Demand Level
H.T.LV Heat Trend Demand Level
C.T.TM Cool Trend Time
H.T.TM Heat Trend Time

HEAT
Table 41 — Heat/Cool Set Point Offsets
EXPANSION
Lo Heat On
Lo Cool On
L.H.ON
L.H.OF
H.H.ON
66.0 F
Fig. 8 — Heating Offsets
TEMPERATURE DRIVEN HEAT MODE EVALUATION
This section discusses the technique for selecting a heating mode
based on temperature. Regardless of whether the unit is config-
ured for return air or space temperature, the logic is exactly 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.
ITEM EXPANSION
Occupied Heat
OHSP
Setpoint
Unoccupied
UHSP
Heat Setpoint
Then, the heat/cool set point offsets under Configuration

D.LV.T should be set. See Table 41.
Related operating modes are under Operating Modes
MODE.
.
ITEM
MODE MODES CONTROLLING UNIT
OCC Currently Occupied
T.C.ST Temp.Compensated Start
The first thing the control determines is whether the unit is in
the occupied mode (OCC) or in the temperature compensated
start mode (T.C.ST). If the unit is occupied or in temperature
compensated start mode, the occupied heating set point
(OHSP) is used. In all other cases, the unoccupied heating set
point (UHSP) is used.
The control will call out a low or high heat mode by comparing
the controlling temperature to the heating set point and the
heating set point offset. The set point offsets are used as addi-
tional help in customizing and tweaking comfort into the build-
ing space. See Fig. 8 for an example of offsets.
Demand Level Low Heat on Offset (L.H.ON)
This is the heating set point offset below the heating set point
at which point Low Heat starts.
Demand Level High Heat on Offset (H.H.ON)
This is the heating set point offset below [the heating set point
minus L.H.ON] at which point high heat starts.
RANGE UNITS
–1 to 2 ^F
0.5 to 20.0 ^F
0.5 to 2 ^F
–1 to 2 ^F
0.5 to 20.0 ^F
0.5 to 2 ^F
0.1 to 5 ^F
0.1 to 5 ^F
30 to 600 sec
30 to 600 sec
HEATING SET POINT
67.5 F
L.H.OF/2
66.5 F
61
CCN
RANGE UNITS
POINT
55-80 dF OHSP
40-80 dF UHSP
EXPANSION RANGE
ON/OFF
ON/OFF
CCN POINT
DMDLHON 1.5
DMDHHON 0.5
DMDLHOFF 1
DMDLCON 1.5
DMDHCON 0.5
DMDLCOFF 1
CTRENDLV 0.1
HTRENDLV 0.1
CTRENDTM 120
HTRENDTM 120
68.0 F
DEFAULT
68
55


CCN POINT
MODEOCCP
MODETCST
DEFAULT