Control Circuit, 24-V; Premierlink Control; Rtu-Open Control System; Gas Heating System - Carrier WeatherMaster Puron 48HC D17 Service And Maintenance Instructions

static pressure in the unit-duct system increases and to IN-
CREASE when the static pressure in the unit-duct system de-
creases (and fan airflow rate increases). Motor overload condi-
tions typically develop when the unit is operated with an access
panel removed, with unfinished duct work, in an economizer-
open mode, or a leak develops in the duct system that allows a
bypass back to unit return opening.
Table 8 — Overcurrent Device Type
MOTOR SIZE (bhp) OVERLOAD DEVICE
Internal Linebreak
1.7
Internal Linebreak
2.4
2.9
3.7
4.7
(Circuit Breaker)
CONDENSER FAN MOTOR PROTECTION
The condenser fan motor is internally protected against over
temperature.

Control Circuit, 24-v

The control circuit is protected against overcurrent conditions
by a circuit breaker mounted on control transformer TRAN.
Reset is manual.
The factory-installed PremierLink Controller includes the sup-
ply-air temperature (SAT) sensor. The outdoor air temperature
(OAT) sensor is included in the FIOP/accessory EconoMi$er 2
package.
NOTE: Refer to PremierLink™ Installation, Start-Up and Config-
uration Instructions. Have a copy of this manual available at unit
startup.

PREMIERLINK CONTROL

For details on operating 48HC units equipped with the factory-
installed PremierLink controller option, refer to the Premier-
Link Retrofit Rooftop Controller Version 3.x Installation, Start-
Up, and Configuration Instructions manual.

RTU-OPEN CONTROL SYSTEM

For details on operating 48HC units equipped with the factory-
installed RTU Open controller, refer to the "Factory-Installed
RTU Open Multi-Protocol Controller Control, Start-Up, Oper-
ation and Troubleshooting" manual.

GAS HEATING SYSTEM

General

The heat exchanger system consists of a gas valve feeding mul-
tiple inshot burners off a manifold. The burners fire into match-
ing primary tubes. The tubes exit into the collector box, the
into the induced draft fan wheel inlet. The induced fan wheel
discharges into a flue passage and flue gases exit out a flue
hood on the side of the unit. The induced draft fan motor in-
cludes a Hall Effect sensor circuit that confirms adequate
wheel speed through the Integrated Gas Control (IGC) board.
Safety switches include a Rollout Switch mounted at the top of
the burner compartment. A limit switch is mounted through the
side of the fan deck over the tubes. The vestibule plate faces
the tubes. See Fig. 39-41.
RESET
Automatic
Automatic
Thermik Automatic
Thermik Automatic
External
Manual
GAS
VALVE
SPARK
IGNITER
FLAME
SENSOR
Fig. 39 — Burner Section Details
INDUCER
MOTOR
CAPACITOR
INDUCER
COOLING FAN
Fig. 40 — Inducer Assembly
LIMIT
SWITCH FOR
SIDESHOT
Fig. 41 — Limit Switch Locations

Fuel Types and Pressures

NATURAL GAS
The 48HC unit is factory-equipped for use with natural gas
(NG) fuel at elevation under 2000 ft (610 m). See section Ori-
fice Replacement on page 38 for information in modifying this
unit for installation at elevations above 2000 ft (610 m).
Gas line pressure entering the unit's main gas valve must be
within specified ranges. See Table 9. Adjust unit gas regulator
valve as required or consult local gas utility.
Manifold pressure is factory-adjusted for NG fuel use. Adjust
as required to obtain best flame characteristic. See Table 10.
33
ROLLOUT
SWITCH
INDUCER
WHEEL
INDUCER
HOUSING
LIMIT SWITCH
FOR DOWNSHOT