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DEALER SERVICE BULLETIN

Number: DSB 09-0022 Date: 4/809 Supersedes: DSB 07-0049

Title: 90% Furnace Heat Exchanger

Inspection Procedure

PRODUCT CATEGORY:

90% furnaces

MODELS AFFECTED:

320A, 321A, 340A, 340M, 345M, 350A, 350M, 351D, 352A, 352M, 355A, 355B, 355C,

355M, 398A, 398B, 399A

58SX, SXA, SXB, SXC, DX, DXA, DXC, VCA, VUA, MCA, MCB, MXA, MXB, MSA,

UVB, MVP, MVB, MVC, MTA, MTB

490A, PG9MAA, PG9MAB

SITUATION

There are several furnace heat exchanger inspection methodologies that have been used in the field.

Improper or inadequate furnace heat exchanger inspection techniques can result in the misdiagnosis

of a heat exchanger failure when a failure has not occurred or is not imminent.

SOLUTION:

Attached is the official Carrier / Bryant / Payne 90% Furnace Heat Exchanger Inspection Procedure.

This procedure should be utilized to properly diagnose a heat exchanger failure once preliminary

service and troubleshooting techniques indicate the heat exchanger is suspected to have failed. This

bulletin may also be used as a reference to verify the furnace is installed properly. The maintenance

items section can be used to identify any existing or future service related issues.

This inspection procedure details significant installation, set-up, and maintenance items that can

impact furnace operation, combustion characteristics, and heat exchanger performance and

reliability. In general, if an initial check of combustion performance as detailed in Section 2 of this

procedure yields CO levels in the vent of 200 ppm or less, no further examination or inspection of the

heat exchanger is required. Installation, set-up, and maintenance items should still be reviewed

and corrected to resolve any remaining furnace operational concerns. An excess air measurement

can also help in diagnosis of heat exchanger failure. The combustion check procedure included in

this document details additional steps to include this diagnostic when possible.

This bulletin also includes a 90% Furnace Heat Exchanger Inspection Certificate that must be

completed, signed by the technician, and faxed or e-mailed to Warranty Administration as part of the

heat exchanger warranty claim approval process.

Warning: Do not perform any of the servicing instructions provided in this Service Bulletin unless you are a trained and

qualified technician. Observe all precautions in the instructions, equipment tags, labels, and observe all other safety

precautions that may apply. Failure to follow this warning could result in property damage, personal injury or death.

Summary of content (18 pages)

PAGE 1
DEALER SERVICE BULLETIN Number: DSB 09-0022 Date: 4/809 Supersedes: DSB 07-0049 Title: 90% Furnace Heat Exchanger Inspection Procedure PRODUCT CATEGORY: 90% furnaces MODELS AFFECTED: 320A, 321A, 340A, 340M, 345M, 350A, 350M, 351D, 352A, 352M, 355A, 355B, 355C, 355M, 398A, 398B, 399A 58SX, SXA, SXB, SXC, DX, DXA, DXC, VCA, VUA, MCA, MCB, MXA, MXB, MSA, UVB, MVP, MVB, MVC, MTA, MTB 490A, PG9MAA, PG9MAB SITUATION: There are several furnace heat exchanger inspection methodologies that have been used in the f
PAGE 2
SMB 09-0022 90% Furnace Inspection Instruction 2 This procedure and the 90% Furnace Heat Exchanger Inspection Certificate will be posted in HVACPartners under the post-sale support service area. Field Action: All dealers and service contractors should use this procedure to properly troubleshoot and inspect 90% furnace heat exchangers. .
PAGE 3
SMB 09-0022 90% Furnace Inspection Instruction Follow all Local Codes. In the absence of local codes, consult the current edition of the National Fuel Gas Code and the current edition of the National Electric Code. Section 2- Combustion Check Prior to performing the Combustion Check, the furnace should already have been generally inspected and any installation, service, and/or maintenance related issues resolved. The unit should already have been set to the correct firing rate and temperature rise.
PAGE 4
SMB 09-0022 90% Furnace Inspection Instruction These conditions indicate a possible: Split heat exchanger seam Open crack Heat exchanger deterioration/restriction Gasket material failure Physical separation of the connected parts Chemical impurities in the fuel supply Flame disturbance (i.e. significant change in flame appearance) after the blower comes on is a good indication that further inspection of the heat exchanger is required.
PAGE 5
SMB 09-0022 90% Furnace Inspection Instruction Take a flue gas reading and record the CO value Is the CO level in high fire less than 200 ppm? YES NO IF Go to: “Is the excess air level above 30%?” YES IF Complete review of installation and maintenance items (Sections 3 and 4) Identify NO and correct any related issues. Return to this check list to complete the procedure. Is the excess air level above 30%? If unable to YES NO accurately measure excess air follow “YES” response path and proceed.
PAGE 6
SMB 09-0022 90% Furnace Inspection Instruction Place an “X” in the box next to each item as you inspect the system.
PAGE 7
SMB 09-0022 90% Furnace Inspection Instruction Temperature rise adjusted to mid-range per installation instructions Return air temperature maintained between 60° F (min) and 80° F (max)? Check for excess amounts of outside air. Check furnace for correct heating blower speed. Allow building temperature to increase above 60 degrees. Thermostat Set-up Anticipator setting adjusted or Electronic thermostat cycle rate (3-4 cycles per Hr.
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SMB 09-0022 90% Furnace Inspection Instruction b) Conversion Rating Plate Label c) Gas Control Conversion Label to gas valve Check for correct normal operation sequence of the ignition system as described in furnace Installation, Start-Up, and Operating Instructions 8 Section 4-Maintenance Items Important! Refer to the Service and Maintenance Instructions for the furnace model you are servicing. The steps outlined in this section are general steps used for servicing a 90% condensing furnace.
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SMB 09-0022 90% Furnace Inspection Instruction To clean the blower assembly: Disconnect power from furnace Remove blower access panel Disconnect blower motor wiring from furnace control board Remove the control box from the furnace and set aside Note: Before you begin the next step, the condensate trap and tubing will have water in it.
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SMB 09-0022 90% Furnace Inspection Instruction 10 Remove and clean the flame sensor with fine steel wool Blow out any dust, lint or corrosion products in the burners. If the burners are rinsed out with hot water, they should be thoroughly dried before installing in the burner box Check the flame retainers for distortion, corrosion products, damage, or blockage from corrosion If corrosion cannot be adequately removed by cleaning, replace burners.
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SMB 09-0022 90% Furnace Inspection Instruction Restricted heat exchanger (primary or secondary) 11 Action must be taken to correct these problems Clean heat exchanger openings with a vacuum and a soft brush. Check the screws where the primary heat exchanger attaches to the cell panel.
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SMB 09-0022 90% Furnace Inspection Instruction 12 F. Re-install the burner box Note: The burner box should be fully assembled and ready to attach to the furnace cell inlet panel Install a new burner box gasket on the burner box Use small dabs of RTV to hold the gasket in place.
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SMB 09-0022 90% Furnace Inspection Instruction 13 Repair or replace as necessary I. Check vent termination Vent termination damaged Evidence of water staining on building surfaces Evidence of leaves or debris getting into intake Correct level above anticipated snow/ ice level Repair or replace as necessary Section 5- Inspecting the heat exchanger Any crack or hole that is big enough to affect combustion will be visible to the naked eye.
PAGE 14
SMB 09-0022 90% Furnace Inspection Instruction If an evaporator coil is installed and the delta plate on the coil cannot be removed, drill a 7/8” hole in the sheet metal delta plate. Use a bore scope to inspect the individual primary heat exchanger cells. Is there evidence of: Split seams Improperly crimped seams Cracks Perforations or pitting Corrosion If any abnormalities are noted, remove the heat exchanger assembly for further inspection.
PAGE 15
SMB 09-0022 90% Furnace Inspection Instruction 15 Coupling Box Cover Failed If soot is present on all parts (primary heat exchanger outlet, coupling box and secondary heat exchanger inlet), replace the entire heat exchanger assembly. Failed Failed If the coupling box or cold spot baffle has significant corrosion and debris, replace the coupling box. A new cold spot baffle is included in the coupling box kit. Remove the cold spot baffle to reveal the secondary heat exchanger inlets.
PAGE 16
SMB 09-0022 90% Furnace Inspection Instruction Not a Failure 16 Failed Inspect the inlets of the secondary heat exchanger. If the inlets are significantly obstructed by corrosion or there is significant corrosion and delamination of the polypropylene laminate, replace the secondary heat exchanger.
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SMB 09-0022 90% Furnace Inspection Instruction Not a failure Not a failure After the heat exchanger is inspected and serviced, re-install the heat exchanger assembly in the furnace. Test the furnace for air leakage around the cell inlet panel area where the heat exchanger assembly attaches to the furnace casing. Seal any air leaks with foil tape or silicone sealant. Re-test the unit to verify the CO level in the vent is less than 200 ppm and the excess air is greater than 30%.
PAGE 18
SMB 09-0022 90% Furnace Inspection Instruction 90% Furnace Secondary Heat Exchanger Inspection Certificate Fax to Warranty Administration at (860) 998-2941 or e-mail to admin.sams@carrier.utc.com with SMB09-0022 in subject line. A copy of this certificate must also be attached to or held with the part.