23
Table 7 — Switch Functions
*Not required on 48FM and 50FM,FS units (units with high capacity power exhaust).
LEGEND
Air Pressure Tubing — Before options such as inlet
guide vanes (IGV), variable frequency drive (VFD), and/or
modulating power exhaust can operate properly, the pneumatic
tubing for pressure sensing must be installed. Use fire-retardant
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
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.
SUPPLY FAN 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 pres-
sure 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 control 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.
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 (48FK,JK and 50FK,JK Units) Force Power Exhaust VFD
to Maximum Speed (48FM and 50FM,FS Units)
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)
BP — Building Pressure
DPS — Differential Pressure Switch
EOR— Economizer Open Relay
HIR — Heat Interlock Relay
IFC — Indoor F an 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
OPTION UNITS NOMINAL TUBE
SIZE (in.)
Inlet Guide Vanes (IGV) ALL 3/8
Supply Fan Variable
Frequency Drive (VFD) ALL 1/4
Modulating Power Exhaust FK,FKX,JK,JKX 3/8
FM,FS 1/4