Allied Air A97USMV Installation Instructions Manual page 21

Field Supplied Wall Terminator or
(15F74) Wall Ring Termination Kit
See venting Table 5 for maximum venting lengths with this
arrangement.
* Use wall support every 24" (610 mm). Use two wall supports if
extension is greater than 24" (610 mm) but less than 48" (1219 mm).
NOTE: One wall support must be 6" (152 mm) from top of each pipe
(intake and exhaust).
Figure 24
507028-03 Issue 1622 Page 21 of 74