Trane Gas Heat Exchanger Replacement Installation Guide

Quick guide from the manual

This document provides instructions for replacing the gas heat exchanger in Trane Precedent A cabinet units (3 to 5 tons). Only qualified personnel should perform this service. The procedure requires specific tools, including 5/16-inch nut drivers and high-temperature RTV silicone. Ensure all electrical and gas supplies are disconnected before starting.

Safety Warnings

• Qualified Personnel Only: Installation and servicing must be performed by trained professionals. Improper installation can result in death, serious injury, or equipment damage.
• Personal Protective Equipment (PPE): Technicians must wear appropriate PPE, including cut-resistant gloves, safety glasses, and arc flash clothing when working with energized electrical components.
• Flammable Refrigerant: This equipment uses R-454B (A2L) refrigerant. Use only R-454B rated service equipment and components.
• Hazardous Gases: Ensure proper installation to prevent flammable mixtures or carbon monoxide leaks.

Tools and Parts

Tools Required

• 5/16-inch Nut Driver
• 5/16-inch Nut Long Driver (12 to 15-inch)
• 5/16-inch Ratchet and Extension
• Blade/Cutter
• Tube of RTV (Maximum temperature rating of 500°F)

Parts List

• Gas Heat Exchanger
• Rear 0.88 ID Tube Foam Block Enclosure
• Tube Insulation (7/8 in. OD x 3/8 in. Thick x 18 in. Long)

Replacement Procedures

Removal

1. Shut off all electrical power and gas service to the unit.
2. Disconnect condensate drain piping.
3. Remove all access panels, front center posts, and the rear duct cover.
4. If configured for horizontal supply, remove the connecting ductwork.
5. Remove the condensate drain pan.
6. Disconnect wires from components in the gas heat compartment (TCO1, Pressure Switch, Gas Valve, etc.) and route them out through harness routing holes.
7. Remove the high voltage spark ignition wire from the igniter and the pressure switch orange silicone hose.
8. Open the control box access panel and remove the specified sheet metal parts.
9. Remove the gas valve, manifold tube, burner assembly, TCO1 limit, pressure switch, and inducer motor.
10. Remove the air orifice (retain for reinstallation).
11. Remove the ten screws from the vestibule to access the heat exchanger assembly.
12. Remove foam blocks covering refrigeration tubes to access top screws.
13. Remove the unit roof to access the fourth screw.
14. Remove the heat exchanger support rod if necessary.
15. Using two people, push the heat exchanger out from the rear supply duct through the front of the unit.

Installation

1. Install the new heat exchanger by feeding it through the front of the unit with two people.
2. Align the heat exchanger from the rear duct opening.
3. Verify the heat exchanger catches the support rod between the bottom primary tube and the tube directly above it.
4. Seal the heat exchanger with a bead of high-temperature silicone.
5. Use field-supplied tube insulation to cover exposed rear side refrigeration tubes and secure with cable ties.
6. Reinstall sheet metal parts.
7. Seal gaps using the rear foam block cut into 0.5-inch thick pieces to prevent air leakage.
8. Use the front foam block to cover front tubes.
9. Reassemble the unit by reversing the removal steps.