New Buck Corporation 20 Room Heater Installation And Operation Manual page 46

Problem
6. Substrate Cracking—
Mechanical
7. Substrate Crumbling
8. Color Variations
Possible Cause
1. Mishandling or abuse
1. Extreme thermal shock
2. High draft
1. Variation in color from
combustor to combustor or
within a combustor can
occur (new combustors)
Solution
1. Handle with care
1. Combustor being contin-
ually overfired. Reduce burn
rate.
2. Do not exceed .06" of water
draft. Install a manual
damper and draft gauge, or a
barometric damper with
free-standing units
1. These color variations are
normal and do not affect
combustor performance