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<br />SECTION IV - SYSTEM DESIGN <br />UL EX. 3470 ULC CEx747 Page 4-4 <br />REV. 5 q-1-04 <br /> <br />Transition Protection <br /> <br />Transitions are protected at a point in the transition where the <br />.. pel:imeter or, the diameter is equal to or less than the maximum <br />.. size duct that can be protected. The nozzle must be located in the <br />center of the transition opening where the maximum perimeter or <br />diameter begins. See Figure 4. <br /> <br /> <br />FIGURE 4 <br />D001n <br /> <br />Electrostatic Precipitator Protection <br /> <br />Some restaurant ventilating ducts have an electrostatic precipita- <br />tor installed at or near the base. These precipitators are used to <br />aid in the cleaning of exhaust air. <br /> <br />Normally electrostatic precipitators do not require protection but <br />should the "authority having jurisdiction" require protection, use <br />the following guidelines. <br /> <br />Ducts with precipitators located at or near the base can be pro- <br />tected using duct nozzle(s) above the precipitator and 1/2N noz- <br />zle(s) (Part No. 419334) for the precipitator. One 1/2N nozzle must <br />be used for each cell being protected. This nozzle tip is stamped <br />with 1/2N, indicating that it is a 1/2-f1ow nozzle and must be count- <br />ed as 1/2 flow number. <br /> <br />When protecting ducts equipped with precipitators, the duct noz- <br />zle(s) must be installed above the precipitator and aimed to dis- <br />charge downstream. If the area above the precipitator is a duct, <br />the nozzle(s) must be positioned according to duct protection <br />guidelines. If the area above the precipitator is a transition, the <br />transition guidelines must be followed. <br /> <br />The 1/2N nozzle (Part No. 419334) must be centered 10 to 26 in. <br />(25 to 66 em) below the precipitator and aimed to discharge at the <br />center of each precipitator cell. However, if it is physically impos- <br />sible to mount the nozzle at 10 to 26 in. (25 to 66 em) due to pre- <br />cipitator placement, the nozzle may be mounted closer than 10 in. <br />(25 cm). See Figure 5. <br /> <br />DUCT <br />NOZZLE <br /> <br />r <br /> <br />PRECIPITATOR <br /> <br /> <br />NOZZLE FOR <br />PRECIPITATOR <br />PROTECTION <br /> <br />. IF PHYSICALLY IMPOSSIBLE AT 10 TO 26 IN. (25 TO 66 em), NOZZLE MAY BE MOUNT- <br />ED CLOSER THAN 10 IN. (25 em). <br /> <br />FIGURE 5 <br />000'96 <br />