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Carrier 38TN Service Manual

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SAFETY CONSIDERATIONS
Service and repair of these units should be attempted only by
trained service technicians familiar with Carrier standard service
instruction and training material.
All equipment should be installed in accordance with accepted
practices and unit Installation Instructions, and in compliance with
all national and local codes.
Power should be turned off when servicing or repairing electrical
components. Extreme caution should be observed when trouble-
shooting electrical components with power on. Observe all warn-
ing notices posted on equipment and in instructions or manuals.
Refrigeration system contains refrigerant under pressure. Extreme
caution should be observed when handling refrigerants. Wear
safety glasses and gloves to prevent personal injury. During
normal system operation, some components are hot and can cause
burns. Rotating fan blades can cause personal injury. Appropriate
safety considerations are posted throughout this manual where
potentially dangerous techniques are addressed.
INTRODUCTION
This Application Guideline and Service Manual provides the
required system information necessary to install equipment in
low-ambient conditions, and service, repair, and maintain the
family of 38TN Air Conditioners with nominal capacities ranging
from 24,000 to 48,000 Btu's. These air conditioners use R134A
refrigerant and operate at lower pressures than standard R22
systems.
TABLE OF CONTENTS
SECTION 1—INSTALLATION GUIDELINE ......................1
SECTION 2—LOW-AMBIENT GUIDELINE ......................1
• Applicable Systems
• Field-Installed Accessories
• Accessory Information
SECTION 3—SERVICE MANUAL ........................................3
UNIT IDENTIFICATION .........................................................3
• Product Number Stamped on Unit Rating Plate
• Serial Number Identification
CABINET ....................................................................................3
• Remove Top Cover
• Remove Fan Motor Assembly
• Information Plate
ELECTRICAL ............................................................................4
• Aluminum Wire
• Contactor
• Capacitor
• PTC Devices
• Cycle Protector
• Crankcase Heater
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book 1 1 2
PC 101
Tab 3a 5a 1a
Air Conditioner with R134A Refrigerant
Application Guideline
and Service Manual
Page
Catalog No. 513-829
Printed in U.S.A.
• Time-Delay Relay (TDR)
• Pressure Switches
• Fan Motor
• Compressor Plug
• Low-Voltage Terminals
MILLENNIUM SCROLL COMPRESSOR ............................9
• Mechanical Failures
• Electrical Failures
• System Clean-Up After Burnout
• Compressor Removal and Replacement
REFRIGERATION SYSTEM ................................................11
• Refrigeration Cycle
• Leak Detection
• Brazing
• Service Valves
• AccuRater® (Bypass Type) Components
• Thermostatic Expansion Valve (TXV)
• Coil Removal
• Accumulator
• Contaminant Removal
• R134A Refrigerant System Charging
• Checking Charge
• Care and Maintenance
TROUBLESHOOTING CHART ...........................................18
SECTION 1—INSTALLATION GUIDELINE
Specifications for this unit in the RNC market require the outdoor
section, indoor section, refrigerant tubing sets, metering device,
and filter drier listed in Product Data Digest (PDD.) There can be
no deviation.
Specifications for this unit in the AOR market require change-out
of the total system, including the outdoor section, indoor section,
refrigerant tubing sets, metering device, and filter drier listed in
PDD. There can be no deviation.
The system can be applied in low-ambient conditions when
installed following the guidelines in Section 2 of this manual.
For long-line applications over 50 ft, consult the 38TN (R134A)
Residential Application Bulletin available from your local dis-
tributor. The R134A long-line application differs from R22 long-
line application.
SECTION 2—LOW-AMBIENT GUIDELINE
This guideline is for 38TN split-system products only. For
applications involving standard R22 single-speed products, refer to
Low-Ambient Guideline Residential Split-System Application
Bulletin.
This guideline explains the system changes and accessories re-
quired for any 38TN application having operating requirements
below 55°F outdoor ambient temperatures.
Form 38TN-1XA
Pg 1
38TN
3-94
Replaces: New

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Summary of Contents for Carrier 38TN

  • Page 1: Section 1-Installation Guideline

    • Serial Number Identification installed following the guidelines in Section 2 of this manual. CABINET ..................3 For long-line applications over 50 ft, consult the 38TN (R134A) • Remove Top Cover Residential Application Bulletin available from your local dis- tributor. The R134A long-line application differs from R22 long- •...

  • Page 2: Baffle Assembly

    Some accessories may be standard features on Step 1—Applicable Systems certain outdoor units. Refer to the 38TN PDD. The 38TN outdoor unit with approved indoor combination listed in • Low-Ambient Controller the outdoor unit PDD can be modified for low-ambient operation.

  • Page 3: Section 3-Service Manual

    For construction details see Fig. 1. New units have 0. As major component variations occur, such as START COMPONENTS — The 38TN unit is equipped with a compressor, fan motor, coil circuiting changes, etc., the change is Millennium scroll compressor specifically designed for use with indicated by increasing this digit in increments of 1.
  • Page 4 1. Perform items 1 through 6 above. TROUBLESHOOTING. 2. Remove nuts holding fan motor top cover. Troubleshooting chart for the 38TN Air Conditioner units is 3. Remove motor and fan blade assembly. provided at the back of this manual. It will enable the service 4.
  • Page 5 SE FL JO SD J SE FL JO SE FL SD J JO SD J SE SE FL FL JO SE FL JO SD SD J JO SD J SE J SE FL JO FL JO SE FL SD J SD J JO SD J SE...
  • Page 6 Step 3—Capacitor 3. Remove any capacitor that shows signs of bulging, dents, or leaking. Do not apply power to a defective capacitor as it may explode. Capacitors can store electrical energy when power is off. Step 4—PTC Devices Electrical shock can result if you touch the capacitor termi- Sometimes under adverse conditions, a standard run capacitor in a nals and discharge the stored energy.
  • Page 7 OPERATING 5 MIN TIME BLK DENOTES CLOSED CONTACTS HN67ZA008 HN67ZA008 A94005 A94009 Fig. 8—Cycle Protector Device Fig. 9—Cycle Protector Sequence CUT YELLOW WIRE BETWEEN CONTACTOR AND LOW-PRESSURE SWITCH SAFETY CONTROL TERMINAL TERMINAL BOARD BOARD CONNECTION CONNECTION LOGIC A88415 Fig. 10—Cycle Protector Wiring Step 6—Crankcase Heater Crankcase heater is a device for keeping compressor oil warm.
  • Page 8 AUTO, the TDR is probably defective and must be replaced. INVIROFLOW TOP Step 8—Pressure Switches A94066 The low-pressure switch used on the 38TN unit is the switch Fig. 12—Fan Position normally used in heat pump applications. The standard air condi- provided. tioner low-pressure switch is NOT used.

  • Page 9: Millennium Scroll Compressor

    Y—Energizes contactor for cooling. Step 1—Mechanical Failures C—Common side of transformer (blk). A compressor is a mechanical pump driven by an electric motor contained in a welded or hermetic shell. In a mechanical failure, MILLENNIUM SCROLL COMPRESSOR motor or electrical circuit appears normal, but compressor does not (R134A REFRIGERANT) The compressor used in this product is specifically designed for function normally.
  • Page 10 (EXAMPLE) TO DETERMINE INTERNAL CONNECTIONS OF SINGLE- PHASE MOTORS (C,S,R) EXCEPT SHADED-POLE DEDUCTION: POWER OFF! (GREATEST RESISTANCE) RUN WINDING (R) 5.8Ω (OHM) START WINDING (S) OHMMETER (SMALLEST RESISTANCE) IS COMMON (C) 0-10Ω SCALE 0.6Ω BY ELIMINATION (REMAINING RESISTANCE) IS COMMON, 5.2Ω...

  • Page 11: Short Circuit

    Step 4—Compressor Removal and Replacement 230 volts X 1000 ohms/volt = 230,000 ohms minimum. Once it is determined that compressor has failed and the reason SHORT CIRCUIT established, compressor must be replaced. To determine if any wires within windings have broken through their insulation and made contact with other wires, thereby shorting all or part of the winding(s), be sure the following Wear safety glasses and gloves when handling refrigerants...
  • Page 12 In all instances when a leak is found, system charge must be bled down and leak repaired before final charging and operation. After leak testing or leak is repaired, evacuate system reclaiming refrigerant and recharge with correct refrigerant charge. Step 3—Brazing When brazing is required in the refrigeration system, certain basics should be remembered.
  • Page 13 AccuRater piston has a refrigerant metering hole through it. The 3. The needle valve on the pin carrier is spring loaded, which retainer forms a stop for piston in refrigerant bypass mode, and a exerts pressure on the underside of the diaphragm via the...
  • Page 14 This tends to cause the pin carrier The accumulator is a passive device which seldom needs replac- spring pressure to close the valve. The refrigerant flow is ing.

  • Page 15: Superheat Charging Method

    If system has lost all charge, weigh in charge using dial-a-charge or digital scale designed for R134A refrigerant. System charge should be fine tuned by using the superheat or subcooling method, whichever is appropriate. These methods are covered later in this manual. Step 11—Checking Charge Superheat charging is the process of charging refrigerant in a system until the temperature (superheat) of the suction gas entering...

  • Page 16: Outdoor Temp

    Table 1—Superheat Charging Table INDOOR COIL ENTERING AIR TEMP (°F WB) OUTDOOR TEMP (°F) — — — — — — — — — — — — — — — — — — — — — — — — — — —...

  • Page 17: Electrical Controls And Wiring

    Table 3—Required Liquid Tube Temperatures REQUIRED SUBCOOLING TEMPERATURE (°F) PRESSURE (PSIG) AT SERVICE FITTING 80.2 85.1 90.1 95.3 100.6 106.2 112.0 118.0 124.2 130.6 137.2 144.1 151.1 158.4 166.0 173.8 181.8 190.1 198.7 207.5 216.6 226.0 235.7 245.6 be burned or smokey, disassemble the connection, clean all parts and stripped wires, and reassemble.

  • Page 18: Air Conditioner Troubleshooting Chart

    1. Locate the unit on side of structure opposite the prevailing Maintenance winds. 1. Frequent inspection of coil and basepan especially after storms and/or high winds. 2. Elevate the unit to height where drifting sand cannot pile up 2. Clean coil by flushing out sand from between coil fins and out against coil.
  • Page 20 Copyright 1994 CARRIER Corp. • 7310 W. Morris St. • Indianapolis, IN 46231 33058c Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations. Book 1 1 2 PC 101 Catalog No.

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