Assessments - 1, GPA: 5
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mounted to a heavy gauge metal terminal box. Due to the various options and materials available, check the IMPORTANT — Observe at least one complete heating cycle nameplate attached to the heater terminal box with the catalog operation before leaving the installation. number designation system on page 7 before installing to insure the heater you received conforms to your specification. © 2010 Chromalox, Inc. Duct Heater4 Ft. Min. Air HandlerAirFlow GENERAL Limitations: Ductwork must be in accordance with one of the fol4. Installation near turns. (Refer to Figure 8). If heater must be lowing: Standards of the National Fire Protection Association for installed closer than 4 feet from the downstream side of a turn, the installation of Air Conditioning and Ventilating Systems of turning vanes must be installed in the turn. The turning vanes other than Resident Type (Pamphlet 90A) or Residential Type will straighten out the air flow so it will be uniform over the Warm Air Heating and Air Conditioning Systems (Pamphlet 90B). face of the heater. 2. Installation near air handler discharge. (Refer to Figure 6). Location: Chromalox Duct Heaters may be located anywhere in the duct system. NOTE: The minimum distances shown are limitations. Wherever possible, locate as far away from these limits as practical. In any case, this distance with any required airflow correction must be sufficient to accomplish even air flow at a velocity equal to, at least, the minimum stated on the heater nameplate. 1. Installation near heat pump, central air conditioner, filters or humidifier. (Refer to Figure 5). Figure 5 Figure 6 3. Installation in branch duct take-off. (Refer to Figure 7). Duct Heater4 Ft. Min. Straight SectionAir Flow Figure 7 4 Ft. Min. Duct HeaterHere or Here2 Ft. Min. Air FlowFigure 8 5.Installation with duct transitions in some air distribution sys- tems, the duct heater may be considerably larger than the duct- work and the duct area must be increased by a sheet metal tran- sition. The slope of the transformation piece on the upstream side of the equipment is limited to 30° as indicated in Figure 9. On the leaving side, the slope should not be more than 45°. AirFlow30" Max.45° 45°30° 4 Ft. Min.4 Ft. Min. Max. Duct HeaterFigure 9 6. Do not insulate control or terminal box. (Refer to Figure 10). Leave ControlBox UninsulatedExternalInsulationTop of DuctDuct HeaterFigure 10 -2 GENERAL 7. Installation in duct larger than heater. For installation where the duct dimensions exceed the insert type heater dimensions, the area beyond the heater dimensions must be filled with wire mesh, expanded or perforated sheet metal of 50% open area as shown in Figure 11. This will maintain a uniform air velocity across the face of the duct. Figure 11 8. Installation with flexible duct. Where a duct heater must be installed near a flexible duct connection, be certain that a 4’ minimum distance between the duct heater and the flexible connector exists and that the connector is suitable for 195°F temperature. (Refer to Figure 12). 9. Do not install duct heater outdoors. Duct heaters cannot be installed with rooftop equipment where they are exposed to the weather. 4 Ft. Min. AirFlowDuct HeaterFlexible Duct(Must be suitablefor 195°F) Figure 12 10. Installation with dampers or filters. Maintain at least 4’ dis- tance between duct heater and damper, filter frames, or other similar obstructions. (Refer to Figure 13). 4 Ft. Min. DamperAir FlowTop of DuctDuctHeaterFigure 13 Clearance: Zero clearance between duct heater and combustible materials such as wood is permissible. However, adequate clear- ance must be provided around terminal box for proper ventilation and future service accessibility. AIR FLOW Flow through duct heater must never drop below the minimum air velocity shown on duct heater nameplate. If the air handling system includes filters, they must be cleaned whenever necessary in order to maintain air flow above the minimum, otherwise poor temperature control and discomfort will result. If air flow is poorly distributed within the duct, deflector vanes must be added to provide correction. The minimum air velocities shown on the nameplate are not to be considered average readings. Do not add various velocities taken across the face of the duct, find an average value, and compare it to the minimum velocity shown on the heater nameplate. The minimum air velocity refers to any point along the face of the duct heater when checking duct velocities, no velocity can be below that sown on the heater nameplate (remembering inlet air temperature). Velocities are best checked with an anemometer, taking numerous readings along the horizontal and vertical centerline of the duct heater at the location prior to installation or slightly up stream from the heater after installation. (Refer to Figure 14). Large ducts will require additional readings taken at locations in addition to the centerline. Duct HeaterVelocityProfileAir FlowFigure 14 Incoming Air...