Supply-Air Set Point Reset (External Signal) - Carrier 48FP Controls Operation And Troubleshooting

To set the Static Pressure set point, press
into the Set Point function and the Set Point subfunction. Scroll
down to SPSP. The current set point will be shown. The default
is 1.5 in. wg. The acceptable range of values is 0.0 to 5.0 in.
wg. To change the set point, enter the new number (example:
) and press . See Table 36.
ENTER
SUPPLY AIR SET POINT RESET FROM SPACE TEM-
PERATURE (VAV Units Only) — The SASP reset from
space temperature allows the Supply-Air Temperature set point
of a VAV system to be adjusted up as the space temperature
falls below the Occupied Set point, in order to maintain ventila-
tion to the occupied space and minimize cooling stage opera-
tion. Supply Air Temperature Reset is Mode 21. See Table 37.
As space temperature falls below the cooling set point, the
supply air set point control value will be reset upward as a
function of the Reset Ratio (RTIO).
RTIO = degrees change in SASP per degree of Space Tem-
perature change
The Reset Limit (LIMT) will limit maximum number of de-
grees the SASP may be raised.
Space Temperature (SPT) is compared to Occupied Cooling
set point (OCSP). If the SPT is below OCSP, the reset value is
calculated. If the reset value is greater than Reset Limit, then
Reset Limit will be used as the reset value. The CSL uses an
adjusted control value for determining stages of cooling control
during the reset function.
SRV Formula: RESET = (OCSP – SPT) x RTIO
To enable Supply Air Set Point Reset, press
the password. Press
tion subfunction. Scroll down to RSEN (Reset Enable). The
current configuration will be displayed (0 = disabled, 1 = en-
abled). The default is disabled. To change the configuration,
press the number of the new configuration (example:
then press .
ENTER
To configure the Supply Air Set Point Reset Ratio, press
to enter into the Space Temperature Reset Config-
uration subfunction. Scroll down to RTIO (Reset Ratio). The
current configuration will be displayed.
The default is 3 F. The range of acceptable values is 0 to
10 F. To change the set point, press the number of the new con-
figuration (example: ) and then press
Table 36 — Configuring Supply Fan Duct Pressure Control (IGV/VFD)
DESCRIPTION
Enable Duct Pressure Function
Select Duct Pressure Set Point
to enter
. Enter
to enter into the User Configura-
) and
.
ENTER
HOW TO CONFIGURE AT HSIO
To configure the Supply Air Temperature Reset Limit, press
to enter into the Space Temperature Reset Config-
uration subfunction. Scroll down to LMIT (Reset Limit). The
current configuration will be displayed.
The default is 10 F. The range of acceptable values is 0 to
20 F. To change the set point, press the number of the new
configuration (example:
Table 11.
Table 37 — Space Temperature Reset Definitions
ITEM
CSL Cooling Submaster Loop
LIMT Reset Limit
OCSP Occupied Cooling Set Point
Reset Enable
RSEN
RTIO Reset Ratio
SASP Supply-Air Set Point
SAT Supply-Air Temperature
SPT Space Temperature
SRV Submaster Reference Value
SUPPLY AIR SET POINT RESET (External Signal) —
Building/energy management systems can initiate a reset of the
unit Supply-Air set point temperature by up to 20 F, based on
external space or energy control system requirements.
An external source analog signal, 2 to 10 vdc, is required.
Connect signal leads at PSIO2, Channel 42 (control options
module is available as a factory-installed option or field-in-
stalled accessory on size 034-074 units and is standard on 078-
104 units).
Sequence of Operation
VAV Units — An input signal at Channel 42 will be scaled to
0º to 20 F range, representing reset value. The reset value will
be added to the cooling set points and subtracted from heating
set points. If (internal) Space Temperature Reset is enabled, the
reset value will be the higher of the external reset and the
Space Temperature Reset value.
CV Units — The input signal at Channel 42 will be scaled to 0º
to 20 F range, representing reset value. The reset value will be
added to the cooling set points and subtracted from heating set
points. If unit is equipped with a T-56 Space Sensor and is
using the Space Temperature Offset function, SASP Reset
from remote signal is NOT AVAILABLE.
Configuration — To configure, connect the external signal in-
put to Channel 42.
SET POINT
DPEN
SPSP
30
) and then press
ENTER
DEFINITION
RANGE
Enable = 1; Disable = 0
0.0 to 5.0 in. wg (0 to 1246 Pa)
. See