Carrier 48FK, Controls Operation And Troubleshooting

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Table 7 — Switch Functions
SWITCH
NUMBER
CONFIGURATION VOLTAGE FUNCTION
SW-1 N.C. 115 Deenergize 115-v (OFC, Comp, IFC, Electric Heaters)
SW-2 N.C. 115 Deenergize TRAN7 (Process Board)
SW-3 N.O. 24 Energize EOR (Open Economizer Outside Air Dampers)
SW-4 N.O. 115 Energize IFC and CR-3 (IGV/VFD)
SW-5 N.C. 115 Isolate IFC and PEC for Separate Operation
SW-6 N.O. 115 Energize PEC (Power Exhaust)
SW-7 N.O. 24 Open PED at DPS
SW-8 N.C. 24 Block Auto-Close at DPS (Due to Low BP)
SW-9A/B
A: N.O.
B: N.C.
115 max Signal Room Terminals to Open (HIR1)
LEGEND
BP — Building Pressure
DPS — Differential Pressure Switch
EOR — Economizer Open Relay
HIR
— Heat Interlock Relay
IFC — Indoor Fan Contactor
IGV — Inlet Guide Vane
N.C. — Normally Closed
N.O. — Normally Open
PEC — Power Exhaust Contactor
PED — Power Exhaust Damper
OFC — Outdoor Fan Contactor
VFD — Variable Frequency Drive
Air Pressure Tubing —
Before options such as inlet
guide vanes (IGV), variable frequency drive (VFD), and/or
modulating power exhaust can operate properly, the pneu-
matic tubing for pressure sensing must be installed. Use fire-
retardent plenum tubing (field-supplied). Tubing size depends
on type of control device (see Table 8 below). Tubing must
be run from the appropriate sensing location (in the duct or
in the building space) to the control device location in the
unit.
Table 8 — Tubing Size
OPTION UNITS
NOMINAL TUBE
SIZE (in.)
Inlet Guide Vanes (IGV) ALL
3
⁄
8
Variable Frequency
Drive (VFD)
ALL 1 ⁄
4
Modulating Power Exhaust FK,FKX,JK,JKX 3 ⁄
8
INLET GUIDE VANES — The tubing for the duct pressure
(DP) control option should sample supply duct pressure about
2
⁄
3
of the way out from the unit in the main trunk duct, at a
location where a constant duct pressure is desired.
The inlet guide vanes are controlled by a differential pres-
sure switch (DPS). On sizes 034-048, the DPS is located in
the auxiliary control box at the economizer end of the unit
(see Fig. 33). On sizes 054-104, the DPS is located in the
supply fan section. See Fig. 34. Use a nominal
3
⁄
8
-in. plastic
tubing.
VARIABLE FREQUENCY DRIVE — The tubing for the
duct pressure (DP) control option should sample supply duct
pressure about
2 ⁄
3
of the way out from the unit in the main
trunk duct, at a location where a constant duct pressure is
desired.
The duct pressure is sensed by a pressure transducer. The
pressure transducer output is directed to the VFD. On 034-
048 units the DP transducer is located in the auxiliary con-
trol box. On 054-104 units, the DP transducer is located in
the supply fan section. See Fig. 34. Use a nominal
1 ⁄
4
-in.
plastic tubing.
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