14
Double Wall Adjustable Duct, Chimney Standard Installation
Adjustable duct lengths are used to make up variable lengths in the duct system(s). Adjustable sections
should always be installed with the overlap to the inside of the standard duct section. Overlap should
always be opposite the direction of airflow. This will allow grease/water to run back to the hood/appliance
when the system is shut down. If the inner adjustable section is too long to fit into the adjacent section of
duct without interfering with the flow path, it should be trimmed to the desired flange to flange length.
Flange to flange length of adjustment can range from 4” to 26”. When a Model 2R Type HT chimney
system is used in positive pressure applications, it must be fitted with an internal joint collar and sealed as
shown in Figure 3. When a chimney system is used in a negative or neutral pressure application, it does
not need to be sealed per the listing report; although, sealing the system is recommended for commercial
cooking appliances where grease is present.
1. The 7” standard duct section in the adjustable assembly is installed the same as the “Grease Duct
and Chimney Joint Assembly” on page 11.
2. The adjustable collar is slipped onto the adjustable duct section. Make sure the adjustable collar
flanges are opposite the adjustable duct section flange.
3. The adjustable section is pushed inside the 7” standard duct section. Verify the minimum overlap is set
correctly, refer to Table 3.
4. If the protruding section interferes with mating parts in the duct run, you will need to cut the adjustable
section that is interfering with mating parts, refer to Figure 5.
5. Once the overlap is set correctly, apply 3M Fire Barrier 2000+ Silicone to the flanges of the duct
section and the adjustable collar.
NOTE: For Positive Pressure Applications - If the adjustable section is used in a positive pressure
chimney application, the adjustable section may need to be cut to length. This will prevent
interference with the internal joint collar. Refer to Figure 6 for adjustable section installation.
6. Apply 3M Fire Barrier 2000+ Silicone to the single V-band groove. Install single V-band around
adjustable collar flange and standard duct flange. Tighten the single V-band hardware to 40-60 in-lbs.
7. Once the single V-band has been installed, tighten the adjustable collar hardware to 40-60 in-lbs.
8. Measure the distance between mating duct flanges prior to installing insulation and outer shell cover.
9. Subtract 1” from the measured distance and cut the pre-rolled shell to this dimension.
10. After the single wall adjustable section has been installed, wrap the assembly using blanket insulation
provided. Make sure all voids are adequately filled.
11. Wrap the pre-rolled outer shell cover around the insulation. Ratchet strap(s) may be used around outer
shell to aid in compressing insulation.
12. Install the double wall V-band on either end of the assembly. Make sure the double wall V-band is
secured onto the mating duct flange and overlapping onto the shell before tightening hardware.
13. The double wall V-band will close the pre-rolled shell as they are tightened. Once closed, secure the
outer shell cover along the seam using the 1” sheet metal screws that have been provided.
14. Use 3M Fire Barrier 2000+ Silicone to seal the outer shell, if required or installed outside.
NOTE: Outer Shell Must Extend Behind the Double Wall V-band.
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