Heat Mode Diagnostic Help; Two-Stage Gas And Electric Heat Control; Hydronic Heating Control - Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

67.5 F
L.H.ON
L.H.OF
H.H.ON
66.0 F
Fig. 14 — Heating 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.
Demand Level Low Heat Off Offset (L.H.OF) — This is the
heating set point offset above [the heating set point minus
L.H.ON] at which point the Low Heat mode ends.
To enter into a LOW HEAT mode, if the controlling temper-
ature falls below [the heating set point minus L.H.ON], then
HVAC mode = LOW HEAT.
To enter into a HIGH HEAT mode, if the controlling tem-
perature falls below [the heating set point minus L.H.ON mi-
nus H.H.ON], then HVAC mode = HIGH HEAT.
To get out of a LOW HEAT mode, the controlling tempera-
ture must rise above [the heating set point minus L.H.ON plus
L.H.OF].
To get out of a HIGH HEAT mode, the controlling tempera-
ture must rise above [the heating set point minus L.H.ON plus
L.H.OF/2].
The Run Status table in the local display allows the user to
see the exact trip points for both the heating and cooling modes
without doing the calculations.
Heat Trend Demand Level (H.T.LV) — This is the change in
demand that must be seen within the time period specified by
H.T.TM in order to hold off a HIGH HEAT mode regardless of
demand. This is not applicable to VAV control types (C.TYP=1
and 2) in the occupied period. This technique has been referred
to as "Comfort Trending." As long as a LOW HEAT mode is
making progress in warming the space, the control will hold off
on a HIGH HEAT mode. This is relevant for the space sensor
machine control types (C.TYP = 4) because the unit may tran-
sition into the occupied mode and see an immediate and large
heating demand when the set points change.
Heat Trend Time (H.T.TM) — This is the time period upon
which the heat trend demand level (H.T.LV) operates and may
work to hold off staging or a HIGH HEAT mode. This is not
applicable to VAV control types (C.TYP=1 and 2) in the
occupied period. See "Heat Trend Demand Level" section for
more details.
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
HEATING SET POINT
68.0 F
L.H.OF/2
66.5 F
a48-8407
Table 35 — Heat/Cool Set Point Offsets
EXPANSION
Lo Heat On
Lo Cool On
HEAT MODE DIAGNOSTIC HELP — To quickly deter-
mine the current trip points for the low and high heat modes,
there is a menu in the local display which lets the user quickly
view the state of the system. This menu also contains the cool
trip points as well. See Table 31 at the local display under Run

Status TRIP.
The controlling temperature is "TEMP" and is in the middle
of the table for easy reference. Also, the "HVAC" mode can be
viewed at the bottom of the table.

TWO-STAGE GAS AND ELECTRIC HEAT CONTROL

(HT.CF = 1,2) — If the HVAC mode is LOW HEAT:
• If electric heat is configured, then the control will request
the supply fan ON
• If gas heat is configured, then the IGC and IFO (IGC fan
output) controls the supply fan request
• The control will turn on Heat Relay 1 (HS1)
• If evaporator discharge temperature is less than 50 F,
then the control will turn on Heat Relay 2 (HS2)*
*The logic for this "low heat" override is that one stage of
heating will not be able to raise the temperature of the supply
airstream sufficient to heat the space.
If the HVAC mode is HIGH HEAT:
• If electric heat is configured, then the control will request
the supply fan ON
• If gas heat is configured, then the IGC and IFO output
controls the supply fan request
• The control will turn on Heat Relay 1 (HS1)
• The control will turn on Heat Relay 2 (HS2)
HYDRONIC HEATING CONTROL (HT.CF = 4) — Hy-
dronic heating in N Series units refers to a hot water or steam
coil controlled by an actuator. This actuator is a communicating
actuator and may be field supplied. When Configuration
 
HEAT HT.CF=4, there is a thermistor array called Tem-
 
peratures AIR.T CCT, that is connected to the RXB, that
serves as the evaporator discharge temperature (EDT). The
leaving-air temperature (LAT) is assigned the thermistor that is
normally assigned to EDT and is located at the supply fan
housing (Temperatures
The configurations for hydronic heating are located at
the local displays under Configuration
See Table 36.
Hydronic Heating Control Proportional Gain (HW.P) — This
configuration is the proportional term for the PID which runs in
the HVAC mode LOW HEAT.
Hydronic Heating Control Integral Gain (HW.I)
configuration is the integral term for the PID which runs in the
HVAC mode LOW HEAT.
Hydronic Heating Control Derivative Gain (HW.D) — This
configuration is the derivative term for the PID which runs in
the HVAC mode LOW HEAT.
Hydronic Heating Control Run Time Rate (HW.TM) —
This configuration is the PID run time rate which runs in the
HVAC mode LOW HEAT.
RANGE UNITS
-1 - 2 ^F
0.5 - 2.0 ^F
0.5 - 2 ^F
-1 - 2 ^F
0.5 - 2 ^F
0.5 - 2 ^F
0.1 - 5 ^F
0.1 - 5 ^F
30 - 600 sec
30 - 600 sec
63
 
AIR.T SAT).

HEAT
CCN POINT DEFAULT
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

HH.CF.
— This