Heat Mode Diagnostic Help - Carrier 48AJ Operating And Service Manual

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
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.
See Fig. 7 for an example of offsets.
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 = 5 and 6) because they may
transition 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.
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 61 at the local display under Run
→
Status TRIP.
Table 60 — Heat/Cool Set Point Offsets
EXPANSION
Lo Heat On
Lo Cool On
RANGE UNITS
-1 - 2 ^F
0.5 - 20.0 ^F
0.5 - 2 ^F
-1 - 2 ^F
0.5 - 20.0 ^F
0.5 - 2 ^F
0.1 - 5 ^F
0.1 - 5 ^F
30 - 600 sec
30 - 600 sec
Table 61 — Mode Trip Helper Table
ITEM EXPANSION
TRIP MODE TRIP HELPER
UN.C.S Unoccup. Cool Mode Start
UN.C.E Unoccup. Cool Mode End
OC.C.S Occupied Cool Mode Start
OC.C.E Occupied Cool Mode End
TEMP Ctl.Temp RAT,SPT or Zone
OC.H.E Occupied Heat Mode End
OC.H.S Occupied Heat Mode Start
UN.H.E Unoccup. Heat Mode End
UN.H.S Unoccup. Heat Mode Start
HVAC the current HVAC MODE
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.
HT.CF = 1,2 (Two-Stage Gas and Electric Heat Control)
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 indoor fan input
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)*
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 indoor fan input
controls the supply fan request
• The control will turn on Heat Relay 1 (HS1)
• 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.
L.H.ON
L.H.OF
H.H.ON
Fig. 7 — Heating Offsets
49
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
UNITS CCN POINT
dF UCCLSTRT
dF UCCL_END
dF OCCLSTRT
dF OCCL_END
dF CTRLTEMP
dF OCHT_END
dF OCHTSTRT
dF UCHT_END
dF UCHTSTRT
String
the "Heating Setpoint"
L.H.OF/2
A48-7702