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49
Table 60 — Heat/Cool Set Point 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.
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 61 — Mode Trip Helper Table
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.
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 - 20.0
^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 - 20.0
^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
ITEM
EXPANSION
UNITS
CCN POINT
TRIP
MODE TRIP HELPER
UN.C.S
Unoccup. Cool Mode Start
dF
UCCLSTRT
UN.C.E
Unoccup. Cool Mode End
dF
UCCL_END
OC.C.S
Occupied Cool Mode Start
dF
OCCLSTRT
OC.C.E
Occupied Cool Mode End
dF
OCCL_END
TEMP
Ctl.Temp RAT,SPT or Zone
dF
CTRLTEMP
OC.H.E
Occupied Heat Mode End
dF
OCHT_END
OC.H.S
Occupied Heat Mode Start
dF
OCHTSTRT
UN.H.E
Unoccup. Heat Mode End
dF
UCHT_END
UN.H.S
Unoccup. Heat Mode Start
dF
UCHTSTRT
HVAC
the current HVAC MODE
String
H.H.ON
L.H.OF
L.H.OF/2
L.H.ON
the "Heating Setpoint"
Fig. 7 — Heating Offsets
A48-7702
Summary of Contents for WEATHERMAKER 48AJ020
Page 95: ...95 Fig 13 Typical Main Control Box Wiring Schematic A48 7787 ...
Page 96: ...96 TO NEXT PAGE Fig 14 Auxiliary Control Box Wiring Schematic A48 7294 ...
Page 98: ...98 Fig 15 Typical 2 Stage Gas Heat Wiring Schematic Size 051 and 060 Units Shown A48 6866 ...
Page 102: ...102 TO NEXT PAGE Fig 18 Typical Power Schematic Size 051 and 060 Units Shown A48 7298 ...
Page 104: ...104 Fig 19 Controls Option Wiring Schematic A48 7810 ...
Page 105: ...105 Fig 20 Small Chassis Component Location Size 020 035 Units A48 7301 ...
Page 106: ...106 Fig 21 Large Chassis Component Locations Size 036 060 Units A48 7302 ...