52
Table 50 — Heat/Cool Setpoint Offsets
Demand Level High Heat on Offset (H.H.ON)
This is the heating setpoint offset below the heating setpoint
minus
L.H.ON
at which point high heat starts.
Demand Level Low Heat Off Offset (L.H.OF)
This is the heating setpoint offset above the heating setpoint
minus
L.H.ON
at which point the Low Heat mode ends.
See Fig. 10 for an example of offsets.
To enter into a LOW HEAT mode, if the controlling tempera-
ture falls below the heating setpoint minus
L.H.ON
, then
HVAC mode = LOW HEAT.
To enter into a HIGH HEAT mode, if the controlling tempera-
ture falls below the heating setpoint minus
L.H.ON
minus
H.H.ON
, then HVAC mode = HIGH HEAT.
To get out of a LOW HEAT mode, the controlling temperature
must rise above the heating setpoint minus
L.H.ON
plus
L.H.OF
.
To get out of a HIGH HEAT mode, the controlling temperature
must rise above the heating setpoint 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 con-
trol types (
C.TYP
=1 and 2) in the occupied period. This method
of operation 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 setpoints
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 De-
mand Level section for more details.
HEAT MODE DIAGNOSTIC HELP
To quickly determine 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 51 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.
Table 51 — Mode Trip Helper 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 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
)*
*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 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
)
ITEM
EXPANSION
RANGE
UNITS
CCN POINT
DEFAULT
D.LV.T
COOL/HEAT SETPT. OFFSETS
L.H.ON
Dmd Level Lo Heat On
-1 to 2
^F
DMDLHON
1.5
H.H.ON
Dmd Level(+) Hi Heat On
0.5 to 20.0
^F
DMDHHON
0.5
L.H.OF
Dmd Level(-) Lo Heat Off
0.5 to 2
^F
DMDLHOFF
1
L.C.ON
Dmd Level Lo Cool On
-1 to 2
^F
DMDLCON
1.5
H.C.ON
Dmd Level(+) Hi Cool On
0.5 to 20.0
^F
DMDHCON
0.5
L.C.OF
Dmd Level(-) Lo Cool Off
0.5 to 2
^F
DMDLCOFF
1
C.T.LV
Cool Trend Demand Level
0.1 to 5
^F
CTRENDLV
0.1
H.T.LV
Heat Trend Demand Level
0.1 to 5
^F
HTRENDLV
0.1
C.T.TM
Cool Trend Time
30 to 600
sec
CTRENDTM
120
H.T.TM
Heat Trend Time
30 to 600
sec
HTRENDTM
120
Fig. 10 — Heating Offsets
H.H.ON
L.H.OF
L.H.OF/2
L.H.ON
the "Heating Setpoint"
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
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...