Optional Staged Gas Units; Step 8 - Install Supply-Air Thermistors; Modulating Gas Units Only); Step 9 - Make Electrical Connections - Carrier WeatherMaker 48A020 Installation Instructions Manual

OPTIONAL STAGED GAS UNITS

See Table 7 for staged gas information. Staging pattern is selected
during controls start-up. For complete information and service in-
structions for staged gas control units, see Controls, Start-Up, Op-
eration, Service and Troubleshooting literature.
Table 7 — 48A Series Staged Gas Control
MODEL NUMBER POSITION
NUMBER OF
STAGES
5
S
5 STAGES
T
7 STAGES T
9 STAGES T
11 STAGES S
Step 8 — Install Supply-Air Thermistors (Staged
and Modulating Gas Units Only)
Supply-air thermistors (SATs) are a field-installed, factory-provid-
ed component. Three supply-air thermistors are shipped with
staged and modulating gas units inside the unit control box.
Thermistor wires must be connected to the SGC (staged gas con-
troller) in the unit control box. See Table 8.
WARNING
SGC sensors are located in the heat section for shipping and
must be field installed for proper stage gas heat operation.
Failure to do so may cause improper operation leading to
future relocation of the sensors and possible system compo-
nent failure.
The supply-air thermistors should be located in the supply duct
with the following criteria:
• downstream of the heat exchanger cells
• equally spaced as far as possible from heat exchanger cells
• a duct location where none of the supply air thermistors
are within sight of the heat exchanger cells
• a duct location with good mixed supply air portion of the unit.
Table 8 — SGC Thermistor Designations
PIN
THERMISTOR CONNECT
POINT
SAT — Inserted into sup-
J8 – 1,2 ply section underneath the
SAT1
(SGC) gas heat section (factory-
provided, field-installed)
SAT — Inserted into sup-
J8 – 3,4 ply section underneath the
SAT2
(SGC) gas heat section (factory-
provided, field-installed)
SAT — Inserted into sup-
J8 – 5,6 ply section underneath the
SAT3
(SGC) gas heat section (factory-
provided, field-installed)
Limit Switch Thermistor
J8 – 15,16 (LIMTTEMP) — Inserted
LIMTTEMP
(SGC) next to the lower limit
switch (factory-installed)
SGC — Staged Gas Controller
HEAT SIZE
6,7,8
020
025
027
030 Low
035
040
050
035
040 High
050
020
025
High
027
030
060 High
060 Low
FUNCTION AND
LOCATION
PART NO.
Thermistors
HH79NZ034
Step 9 — Make Electrical Connections

POWER WIRING

Units are factory wired for the voltage shown on unit nameplate.
Provide a unit safety disconnect switch in the main power supply
to each unit. See Fig. 23. Select switch size and mounting location
in accordance with applicable local codes or National Electrical
Code (NEC). If combining the functions of safety disconnect with
maximum overcurrent protection (MOCP) fuses ("fused discon-
nect"), coordinate safety switch size with MOCP size data as
marked on unit informative plate.
Unit may be equipped with optional factory-installed non-fused
disconnect switch. See Fig. 23. Provide maximum overcurrent
protection devices (fuses or HACR breakers, per local codes) in
branch circuit wiring remote from unit. Observe requirements of
NEC Article 440. Install service switch upstream of remote fuses
if required.
The main power terminal block is suitable for use with aluminum
or copper wire. See Fig. 23. Units have circuit breakers for
compressors, fan motors, and control circuit. The unit must be
electrically grounded in accordance with local codes or, in absence
of local codes, with NEC, ANSI C1-latest year.
FIELD-INSTALLED DISCONNECT
FACTORY-INSTALLED DISCONNECT
LEGEND
GND — Ground
NEC — National Electrical Code
TB — Terminal Block
Fig. 23 — Field Power Wiring Connections

FIELD POWER SUPPLY

Unit is factory wired for voltage shown on unit nameplate.
Field wiring can be brought into the unit from bottom (through
basepan and roof curb) or through side of unit (corner post next to
control box).
A 3 / -in. NPT coupling for field power wiring and a
1
2
coupling for 24-v control wiring are provided in basepan. In the
side post, there are two 2
060) knockouts for the field power wiring. See Fig. 5-12. If con-
trol wiring is to be brought in through side of unit, a
ter hole is provided in the condenser side post next to control box.
24
TB1
FIELD
11
POWER
12
SUPPLY
13
EQUIP GND
OPTIONAL
FACTORY-INSTALLED
DISCONNECT
11
12
13
GND
/ -in. (sizes 020-035) or 3-in. (sizes 040-
1
2
7
21
22
23
21
22
23
/ -in. NPT
3
4
/ -in. diame-
8