Carrier A Series - Cleaning Heat Exchanger

PG80VTLA: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
41
Cleaning Heat Exchanger
The following steps should be performed by a qualified service agency.
NOTE: If the heat exchangers get a heavy accumulation of soot and
carbon, they should be replaced rather than trying to clean them
thoroughly. A build-up of soot and carbon indicates that a problem exists
which needs to be corrected, such as improper adjustment of manifold
pressure, insufficient or poor quality combustion air, incorrect size or
damaged manifold orifice(s), improper gas, or a restricted heat
exchanger. Action must be taken to correct the problem.
If it becomes necessary to clean the heat exchangers because of dust or
corrosion, proceed as follows:
1. Turn OFF gas and electrical power to furnace.
2. Remove outer access door.
3. Disconnect vent connector from furnace vent elbow.
4. For downflow or horizontal furnace having an internal vent pipe,
remove internal vent pipe within the casing.
5. Disconnect wires to the following components. Mark wires to aid in
reconnection (be careful when disconnecting wires from switches
because damage may occur):
a. Draft safeguard switch.
b. Inducer motor.
c. Pressure switches.
d. Limit overtemperature switch.
e. Gas valve.
f. Hot surface igniter.
g. Flame-sensing electrode.
h. Flame rollout switches.
6. Remove screws that fasten the collector box assembly to the cell
panel. Be careful not to damage the collector box. Inducer assembly
and elbow need not be removed from collector box.
7. Disconnect gas line from gas manifold.
8. Remove the four screws that attach the burner assembly to the cell
panel. The gas valve and individual burners need not be removed
from support assembly. Remove NOx baffles, if installed.
NOTE: Be very careful when removing burner assembly to avoid
breaking igniter. See Fig. 56 and Fig. 57 for correct igniter location.
A05026
Fig. 56 – Igniter Position - Top View
A05025
Fig. 57 – Igniter Position - Side View
NOTE: The materials needed in item 9 can usually be purchased at local
hardware stores.
9. Using a field-provided 25-caliber rifle cleaning brush; a 36-in. (914
mm) long, 1/4-in. (6 mm) diameter steel spring cable; and a
variable speed drill, do the following:
a. Remove metal screw fitting from wire brush to allow insertion
into cable.
b. Insert the twisted wire end of brush into end of spring cable, and
crimp tight with crimping tool or crimp by striking with
ball-peen hammer. TIGHTNESS IS VERY IMPORTANT. After
crimping:
(1.) Attach variable-speed, reversible drill to the end of spring
cable (end opposite brush).
(2.) Insert brush end of cable into the outlet opening of cell and
slowly rotate with drill. DO NOT force cable. Gradually
insert cable into upper pass of cell. (See Fig. 58).
A91252
Fig. 58 – Cleaning Heat Exchanger Cell
(3.) Work cable in and out of cell 3 or 4 times to obtain
sufficient cleaning. DO NOT pull cable with great force.
Reverse drill and gradually work cable out.
(4.) Insert brush end of cable in burner inlet opening of cell, and
proceed to clean 2 lower passes of cell in same manner as
upper pass.
(5.) Repeat foregoing procedures until each cell in furnace has
been cleaned.
(6.) Using vacuum cleaner, remove residue from each cell.
(7.) Using vacuum cleaner with soft brush attachment, clean
burner assembly.
(8.) Clean flame sensor with fine steel wool.
1-7/8
(47.6 mm)
9/32”
7.1mm
5/16”
7.9mm