D. Inspect Firebox
Surface cracking or crazing of firebrick material is normal and expected. The following types of cracks are acceptable and do not require replacement of the unit or the firebox:
•Cracks that do not propagate entirely through the material.
•Light fracture lines or
•Cracks that are less than 1/32 in. wide and less than 3 in. long.
•If cosmetically unacceptable, such cracks may be repaired with the
Cracks that are unacceptable:
•Cracks greater than 1/32 in. wide and 3 in. long are at risk of growing.
•Cracks that penetrate entirely through the firebrick material.
Inspection for cracking should be run when the appliance is cool. Cracks tend to close as the appliance heats up.
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