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Hersteller: Johnson Controls Dateigröße: 661.67 kb Dateiname: Unterrichtssprache:

If the blower or compressors rotate in the wrong direction at start-up, the electrical connection to the unit is misphased. Change the incoming line connection phasing to obtain proper rotation. (Scroll compressors operate in only one direction. If the scroll is drawing low amperage, has similar suction and discharge pressures, or producing a high noise level, the scroll is misphased). Scroll compressors require proper rotation to operate correctly. Do not change the internal wiring to make the blower, condenser fans, or compressor rotate correctly. Change the incoming power to the main terminal block to obtain proper rotation. SUPPLY AIR BLOWERS These blowers have either 3-speed direct drive motors, or single speed motors equipped with a belt drive. Belt drive units have a variable pitch motor pulley that allows the blower speed to be adjusted. CHECKING SUPPLY AIR CFM The RPM of the supply air blower will depend on the required CFM, the unit accessories or options and the static resistances of both the supply and the return air duct systems. With this information, the motor speed tap (direct drive) or the motor pulley number of turns open (belt drive) can be determined from the Blower Performance Data Tables. Note the following: 1. The supply air CFM must be within the limitations shown in the Unit Application Data Table 1. 2. Pulleys can be adjusted in half turn increments. 3. The tension on the belt should be adjusted as shown in the Belt Adjustment Figure 12. PROCEDURE FOR ADJUSTING BELT TENSION: 1. Loosen nuts (A) (top and bottom). 2. Adjust the tension by turning bolt (B). 3. Never loosen nuts (C) from each other. 4. Use a belt tension checker to apply a perpendicular force to be one belt at the midpoint of the span as shown. The deflection force should be applied until a specific deflection distance of 4mm (5/32") is obtained. To determine the deflection distance from normal position, use a straight edge from sheave to sheave as a reference line. The recommended deflection force is as follows: *NeverLoosen(B) SPANLENGTHDEFLFORCE (A) (C)* Tension new belts at the max. deflection force recommended for the belt section. Check the belt tension at least two times during the first 24 hours of operation. Any re-tensioning should fall between the min. and max. deflection force values. 5. After adjusting, re-tighten nuts (A). FIGURE 12 - BELT ADJUSTMENT Start the supply air blower motor. Adjust the resistances in both the supply and the return air duct systems to balance the air distribution throughout the conditioned space. The job specifications may require that this balancing be done by someone other than the equipment installer. To check the supply air CFM after the initial balancing has been completed: 1. Remove the two 5/16” dot plugs from the blower motor and the filter access panels shown in Figure 11. 2. Insert at least 8" of 1/4 inch tubing into each of these holes for sufficient penetration into the air flow on both sides of the indoor coil. NOTE: The tubes must be inserted and held in a position perpendicular to the air flow so that velocity pressure will not affect the static pressure readings. 3. Using an inclined manometer, determine the pressure drop across a dry evaporator coil. Since the moisture on an evaporator coil may vary greatly, measuring the pressure drop across a wet coil Johnson Controls Unitary Products 364985-XIM-B-0508 under field conditions would be inaccurate. To assure a dry coil, the compressors should be deactivated while the test is being run. 4. Knowing the pressure drop across a dry coil, the actual CFM through the unit can be determined from the curve in Pressure Drop vs. Supply Air CFM (Figure 13). Failure to properly adjust the total system air quantity and static pressure can result in extensive system damage. After readings have been obtained, remove the tubes and reinstall the two 5/16” dot plugs that were removed in Step 1. NOTE: De-energize the compressors before taking any test measurements to assure a dry indoor coil. 0 0.1 0.2 0.3 0.4 0.5 1000 1500 2000 2500 3000 036 048 060 PRESSURE DROP ( IWG) FIGURE 13 - PRESSURE DROP ACROSS COIL OPERATION SEQUENCE OF OPERATIONS OVERVIEW For these units, the thermostat makes a circuit between “R” and “Y1” for the cooling cycle. The call is passed to the unit control board (UCB), which then determines whether the requested operation is available and, if so, which components to energize. For heating, the thermostat makes a circuit between “R” and “W1”. The UCB energizes the compressor and condenser fan allowing the unit to run in heating mode. A time / temperature control operates the defrost cycle. If at any time a call for both heating and cooling are present, the heating operation will be performed. If operating, the cooling system is halted as with a completion of a call for cooling. Heating always takes priority. COOLING SEQUENCE OF OPERATION CONTINUOUS BLOWER By setting the room thermostat fan switch to “ON,” the supply...

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