Assessments - 3, GPA: 4.7
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The performance tables for blower models are shown on pages 18 and 19. As an example, a model BD 350 unit, operating with no external static pressure, that is, no duct work, nozzles, etc., and is to deliver an air volume of 6481 cfm (cfm = cubic feet of air per minute) requires that the unit be supplied with a 5 hp motor, a C207 drive, and the drive sheave must be set at 2.5 turns open to achieve a blower speed of 960 rpm (see performance table for units with or without blower enclosure, page 18). See "Blower Adjustments" on page 8 for setting of drive pulley turns open. If a blower unit is to be used with ductwork or nozzles, etc., the total external static pressure under which the unit is to operate, and the required air flow must be known before the unit can be properly adjusted. Any device added externally to the unit, and which the air must pass through, causes a resistance to air flow. This resistance is called pressure loss. The total of the pressure losses must be determined before adjusting the blower speed. If Modine filters are used, the expected pressure loss through the filters is included in the performance data on page 19. If Modine supplied discharge nozzles are used, the expected pressure drop of the nozzles can be found footnoted at the bottom of page 14. If filters, nozzles or ductwork are to be used with the unit, and they are not supplied by Modine, the design engineer or installing contractor must determine the pressure loss for the externally added devices or ductwork to arrive at the total external static pressure under which the unit is to operate. Once the total static pressure and the required air flow are known, the operating speed of the blower can be determined and the correct motor sheave adjustments made. As an example, let's say, a model BD 350 is to be used with a Modine supplied blower enclosure and Modine supplied filters attached to someone else's ductwork. The unit is to move 6481 cfm or air flow against an external static pressure of 0.2" W.C. Also, 0.2" W.C. must be added for the filter pressure drop for a total of 0.4" W.C. total pressure drop. Entering the performance table on page 18 for a BD 350, at 6481 cfm and 0.4" W.C. static pressure, it is seen that the unit will require a 5 hp motor using a C207 drive, and the motor sheave should be set at .5 turns open to achieve a blower speed of 1050 rpm. You can see this example differs from similar conditions in paragraph 2 by the number of turns open and a higher rpm, which is needed to overcome the added external static pressure from the filters. 7 Heater Parts from ACF Greenhouses To Install (Figure 5) 1. Remove and discard the motor tie down strap and the shipping block beneath the belt tension adjusting screw (Not used on all models.) 2. Adjust motor adjusting screw for a belt deflection of approximately 3/4" with five pounds of force applied midway between the sheaves (refer to Figure 6a). Since the belt tension will decrease dramatically after an initial run-in period, it is necessary to periodically re-check the tension. Excessive tension will cause bearing wear and noise. 3. The blower bearings are lubricated for life; however, before initial unit operation the blower shaft should be lubricated at the bearings with SAE 20 oil. This will reduce initial friction and start the plastic lubricant flowing. 4. Make electrical connections according to the wiring diagram. 5. Check rotation of the blower. Motor should be in clockwise rotation when facing motor pulley. If rotation is incorrect, correction should be made by interchanging wiring within the motor. See wiring diagram on the motor. 6. The actual current draw of the motor should be determined. Under no condition should the current draw exceed that shown on the motor rating plate. 7. It is the installers responsibility to adjust the motor sheave to provide the specified blower performance as listed on pages 18 & 19 for blower settings different from the factory set performance. The drive number on the unit may be identified by referring to the Power Code number on the serial plate of the unit (see page 26 for model number nomenclature) and matching that number with those shown on page 25. From the listing, the drive number can be determined. 8. Blower sheave and motor sheave should be measured to assure correct drive is on unit. Refer to page 26 for drive sizes. Blower Adjustments Following electrical connections, check blower rotation to assure blow-through heating. If necessary interchange wiring to reverse blower rotation. Start fan motor and check blower sheave RPM with a hand-held or strobe-type tachometer. RPM should check out with the speeds listed in Performance Data shown on pages 18 and 19. A single-speed motor with an adjustable motor sheave is supplied with these units. If blower fan speed changes are required, adjust motor sheave as follows: NOTE: Do not fire unit until blower adjustment has been made or unit may cycle on limit (overheat) control. 1...
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