Carrier 48LJD - Manual (Page 29)

Table 21 — Economizer Service Analysis
PROBLEM CAUSE REMEDY
Damper does not
open. Evaporator fan not on. Check wiring between G on connection board and indoor fan
contactor
No power to economizer motor. 1. Check that SW3 is making proper contact with the damper blade,
2. Check continuity across R1 coil. If not connected, replace relay
R1.
3. Check diode D1. If diode is not functioning properly, replace D1.
4 Check wiring in economizer relay pack (See unit label
diagram.)
Economizer motor failure If there is 24 vac power at the motor terminals, but motor is not oper­
ating, replace motor
Economizer opera­
tion limited to mini­
mum position.
OAT or EC set too high. 1 Set at correct temperature (3 F below indoor space temperature).
2. Check OAT or EC by setting set point above outdoor temperature
or humidity level. If switch does not close, replace OAT or EC.
Check wiring of economizer relay packs 1 Check continuity across relay R2 coil. If not connected, replace R2
relay.
2. Check continuity across relay R3 coil If not connected, replace R3
relay.
Check SAT If supply-air temperature is over 57 F, switch T2 should be closed. If
not, replace SAT.
Damper does not
close. Incorrect wiring or wiring defects. 1. Check switch 2 and 4. If non-operational, replace.
2. Check diode D2. If diode D2 is not functioning properly, replace.
3. Check wiring on economizer and on economizer relay pack (see
unit label diagram).
Check SAT If supply air thermostat is below 52 F, switch T1 should be closed If
not, replace SAT.
Economizer motor failure. If there is 24 vac power at motor terminals, but motor is not operating,
replace motor.
LEGEND
EC — Enthalpy Control
OAT — Outdoor-Air Thermostat
SAT — Supply-Air Thermostat
Legend for Fig. 39 — Typical Component Arrangement
and Fig. 40 — Typical Wiring Schematic
IMPORTANT: Refer to unit wiring label for actual unit wiring.
AHA — Adjustable Heat Anticipator
C — Contactor, Compressor
CAP — Capacitor
CC — Cooling Compensator
CH — Crankcase Heater
COMP — Compressor Motor
D — Diode
EC — Enthalpy Control
ECON — Economizer
EPS — Emergency Power Supply
EQUIP — Equipment
ER — Economizer Relay
FPT — Freeze-Up Protection Thermostat
GND — Ground
HPS — High-Pressure Switch
HS — Hall Effect Sensor
I — Ignitor
IDM — Induced-Draft Motor
IFC — Indoor-Fan Contactor
IFM — Indoor-Fan Motor
IGC — Integrated Gas Unit Controller
LED — Light-Emitting Diode
LPS — Low-Pressure Switch
LS — Limit Switch
MGV — Main Gas Valve
MTR — Motor
OAT — Outdoor-Air Thermostat
OFM — Outdoor-Fan Motor
P — Plug
PL — Plug Assembly
QT — Quadruple Terminal
R — Relay
NOTES
1 If any of the original wire furnished must be replaced, it must be re­
placed with Type 90 C wire or its equivaient
Number(s) indicates the line location of contacts A bracket over 2
numbers signifies single-pole, double-throw contacts. An underlined
number signifies a normally closed contact. Plain numbers (no lines)
signifies a normally open contact
RS — Rollout Switch
SAT — Supply-Air Thermostat
SEN — Sensor
SW1 — Switch Fully Open
SW2 — Switch Fully Closed
SW3 — Switch Min. Vent Position
SW4 — Switch Max Vent Position
TO — Thermostat-Cooling
TH — Thermostat-Heating
TRAN — Transformer
Field Splice
______ Marked Wire
Terminal (Marked)
O Terminal (Unmarked)
I X I Terminal Block
9 Splice
<( y* Splice (Marked)
---------- Factory Wiring
----------Field Control Wiring
—— — — Field Power Wiring
--------- Accessory or Optional Wiring
To indicate common potential only;
not to represent wiring
Three-phase motors are protected under primary single phasing con­
ditions
Thermostat: HH07AT170, 172, 174 and P272-2783
Subbase: HH93AZ176, 178 and P272-1882, 1883
Set heat anticipator at 14 amp For units with 2 stages of heating, set
stage 2 anticipator at 14 amp.
Use copper conductors only.
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