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 In-Series, T, Fork or Herringbone. Please refer to Page 31, Section 9.6.1 through Page 35, Section 9.6.3 for explanation of manifold rules and basic diagrams of each layout type. The diagrams show very simple examples of each layout type. Actual layouts will vary in total number of burners in the system as well as the overall shape of the system. Additional pieces such as elbows may change the overall layout appearance but are usually considered a variant of one of the five multiburner layout types.
9.6.1Flag and Modified In-Series Layouts and Manifold Tube Length Rules
See Page 32, Figure 19 through Page 32, Figure 20 for diagrams of Flag and Modified In-Series layouts. Minimum and maximum manifold tube length applies to all tubing between the end of a radiant tube run and a tee or cross; all tubing between any tees and/ or crosses; and all tubing between the last tee or cross and the pump. See Page 30, Table 10.
Example: Consider a Flag or Modified In-Series layout with five CTHN-100 burners. Page 30, Table 10 shows a minimum of 6' (2 m) and a maximum of 45' (13.5 m) of manifold tube required per burner. Therefore the entire five-burner system must have between 30' (10 m) and 225' (69 m) of manifold tubing. The manifold tubing is in addition to the 40' (12 m) of radiant tube per burner. Radiant tube may end at a tee, or runs may be lengthened by adding some manifold tube between the end of the radiant tube and a tee. Each burner in the system (except for the burner furthest from the pump) must use a damper coupling to properly adjust the vacuum at each burner. The damper coupling may be placed anywhere between the end of the radiant pipe and the tee.
