Tech Bulletin # 17-08-032
1 PSI = 27.68 Inches of Water Column
Gas-fired CEI heaters have an incoming gas pressure regulator in the fuel train. Incoming gas pressure should not exceed 27.68 IWC.
That’s Inches of Water Column, not Pounds per Square Inch. There’s a major difference.
Since 1 PSI is equivalent to 27.68 IWC, even a 0.5 PSI increase in gas pressure will over-shoot max pressure by 13.84 Inches of Water Column.