Installation Configuration Operating Sequence Demand Limit - Carrier 48FK Controls Operation And Troubleshooting

SIZES 034-048
TB3
RED
12
BLK
15
TO ACCESSORY SPACE
TEMPERATURE RESET
CONTROL BOARD
SIZES 054-104
TB4
12
15
SPACE TEMPERATURE RESET — 4 SENSOR AVERAGING APPLICATION
SIZES 034-048
TB3
RED
12
BLK
15
TO ACCESSORY SPACE
TEMPERATURE RESET
CONTROL BOARD
SIZES 054-104
TB4
12
15
NOTE: Sensor part number is HH79NZ014.
SPACE TEMPERATURE RESET — 9 SENSOR AVERAGING APPLICATION
Demand Limit —
The demand limit function provides
a means to limit the cooling capacity of the VAV unit using
an external discrete switch function. When enabled by the
closure of the external switch, the control will limit the avail-
able compressor staging capacity according to user set points
established at demand limit potentiometer(s).
The unit controls support two types of demand limit: single-
step and 2-step control.
SINGLE-STEP DEMAND LIMIT — This function will limit
the total compressor staging based on the ratio of the set point
potentiometer's wiper arm position to the full scale resis-
tance of the potentiometer. The exact percentage of capacity
reduction differs depending on the number of capacity steps.
A field-supplied potentiometer and control switch are re-
quired for this function. See installation section for speci-
fication on potentiometer and field wiring.
TWO-STEP DEMAND LIMIT — Two-step demand limit is
provided with the installation of the accessory Demand Limit
RED
BLK
RED
BLK
SENSOR 1
SENSOR 1
SENSOR 4
SENSOR 7
Fig. 26 — Space Temperature Sensor Averaging
RED
BLK
SENSOR 2
RED
BLK
SENSOR 2
RED
BLK
SENSOR 5
RED
BLK
SENSOR 8
Control Module kit plus installation of 2 field-supplied con-
trol switches (SPST-NO each). This accessory control pro-
vides for a first step reduction of 50% to 100% of the maxi-
mum compressor staging; the second step provides for reduction
between 0% and 49%. The exact percentage of capacity re-
duction differs depending on the number of capacity steps.
When demand limit is active, the LED display will show
22
code .
INSTALLATION
Single-Step Demand Limit — A 3-wire 5 to 20 K-ohm po-
tentiometer must be field-supplied and installed. A single-
pole normally open switch is also required (field-supplied
and -installed). Locate the potentiometer (designated P4) and
the switch in a suitable location (external from the unit or in
the unit control box).
18
RED
BLK
SENSOR 3
RED
BLK
SENSOR 3
RED
BLK
SENSOR 6
RED
BLK
SENSOR 9
SENSOR 4