Kohler Generator Sets 20--2800 kW User Manual download pdf (Page 35)

TP-5700 7/93 23Section 5 Exhaust System

5.4 Double-Sleeve Thimbles

If the exhaust pipe should need to pass through a wall or

roof, an exhaust thimble must be used to prevent

exhaust pipe heat from being transmitted to the

combustible material. Construction details for a typical

double-sleeve thimble to be used where exhaust piping

passes through a combustible roof or wall are shown in

Figure 5-4. They are usually fabricated at a local sheet

metal shop to the specifications furnished by the

installation engineer.

The thimbles should be constructed so that they extend

at least 10 inches (25.40 cm) both ways from the surface

of the wall or roof. Holes are provided at both ends to

allow cooling air to circulate through the thimble. If

screening is used on the outer end to keep birds,

rodents, etc., from entering the thimble, make sure that

the mesh is large enough so that it doesn’t impair air

circulation through the thimble. If the exhaust pipe must

exit through a roof, a rain shield must be included above

the thimble as shown in Figure 5-4. The rain cap as

shown on the end of the exhaust pipe is recommended

only in areas not subject to freezing temperatures. In an

area where freezing is common, extend the exhaust

piping well beyond the roof and use a gradual “U” bend

at the end to direct the exhaust outlet downward which

will keep rain, snow, etc., out of the pipe. The outlet of the

pipe should be far enough from the roof to prevent

ignition of the roof material from hot exhaust.

TP-5700-5

1. Rain cap (or gradual U bend)

2. Rain shield

3. 10 in. (254 mm) minimum

4. 1 in. (25 mm) minimum

5. Exhaust pipe

6. Ventilation holes at both ends

7. 10 in. (254 mm) minimum

8. 1 in. (25 mm) minimum

9. Flashing

10. Inner sleeve

11. Outer sleeve

12. Thimble outer diameter

13. 10 in. (254 mm) minimum outside

14. 10 in. (254 mm) minimum inside

15. Exhaust pipe diameter

Figure 5-4 Double-Sleeved Thimbles and Rain Cap

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 55 56

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Kohler Generator Sets 20--2800 kW User Manual Page 35

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