![9.4 Radiant Tube Length](/images/new-backgrounds/35182/3518273x1.webp)
SECTION 9: MULTIBURNER HEATER INSTALLATION
9.4 Radiant Tube Length
The radiant tube length fixed for each burner is shown on Page 30, Table 10.
9.5 Manifold Tube
Any tube beyond the radiant tube length is considered manifold. Manifold tube can be used to lengthen tube runs beyond the radiant tube length; to connect multiple runs of tubing and connect the system to the pump. Minimum and maximum manifold tube lengths are shown on Page 30, Table 10. The table must be used in conjunction with the additional rules for the diameter and length of manifold in a system, as described on Page 31, Section 9.5.1 through Page 35, Section 9.6.3.
9.5.1 Manifold Diameter
1.Manifold diameter for systems containing less than 320,000 Btu/h input can be 4" (10 cm) or 6" (15 cm).
2.Manifold diameter for systems containing 320,000 Btu/h input and greater must be 6" (15 cm).
Exception: If total manifold tube length is 70' (21 m) or less, 4" (10 cm) diameter manifold tube can be used for systems up to 800,000 Btu/h.
9.6Multiburner System Layouts and Manifold Tube Length Rules
Most CTHN multiburner layouts can be classified as one of the following five layout types:
Flag, Modified
9.6.1Flag and Modified
See Page 32, Figure 19 through Page 32, Figure 20 for diagrams of Flag and Modified
Example: Consider a Flag or Modified
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