York DM090 installation manual DRY Coil Delta P Supply AIR Drive Adjustment

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035-17311-003-A-0704

FIGURE 23 - DRY COIL DELTA P

SUPPLY AIR DRIVE ADJUSTMENT

Before making any blower speed changes review the installation for any installation errors, leaks or undesirable systems effects that can result in loss of airflow.

Even small changes in blower speed can result in substantial changes in static pressure and BHP. BHP and AMP draw of the blower motor will increase by the cube of the blower speed. Static pressure will increase by the square of the blower speed. Only qualified personnel should make blower speed changes, strictly adhering to the fan laws.

At unit start-up, the measured CFM may be higher or lower than the required CFM. To achieve the required CFM, the speed of the drive may have adjusted by changing the datum diameter (DD) of the variable pitch motor sheave as described below:

(	Required CFM
	Measured CFM ) • Existing DD = New DD

Use the following tables and the DD calculated per the above equation to adjust the motor variable pitch sheave.

EXAMPLE

A 12.5 ton unit was selected to deliver 4,000 CFM with a 3 HP motor, but the unit is delivering 3,800 CFM. The variable pitch motor sheave is set at 2 turns open.

Use the equation to determine the required DD for the new motor sheave,

(4,0003,800 CFMCFM ) • 4.0 in. = 4.21 in.

Use Table 31 to locate the DD nearest to 4.21 in. Close the sheave to 1 turn open.

New BHP

=(Speed increase)3 • BHP at 3,800 CFM

=(Speed increase)3 • Original BHP

=New BHP

New motor Amps

=(Speed increase)3 • Amps at 3,800 CFM

=(Speed increase)3 • Original Amps

=New Amps

32	Unitary Products Group

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Contents Installation Manual Table of Contents List of Figures List of Tables Safety Considerations GeneralInspection Reference½ 12½ Ton Predator Model Number Nomenclature NomenclatureNOMENCLATURE, Additonal Options Johnson UNT Controller, DFS, APS & Phase Monitor Technicoat Condenser Coil, Phase Monitor, & Coil Guard Preceding Installation InstallationInstallation Safety Information Rigging and Handling Unit Temperature LimitationsLocation Point Load Weight Length of Forks Must be a Minimum of 60 InchesDetail B Detail a Detail CBottom Duct Openings from Above Ductwork Duct CoversSide Panels with Hole Plugs Condensate Drain Thermostat Wiring Control Wire SizesPower and Control Wiring Power Wiring DetailElectronic Thermostat Field Wiring RLA Electrical Data DM120 10 TON with Power Convenience Outlet 380 11.5 75.0Minimum Supply AIR CFM OPTIONS/ACCESSORIESPhysical Data Economizer and Power Exhaust SET Point Adjustments and InformationEnthalpy SET Point Chart Phasing Blower RotationSupply AIR Limitations Belt Tension1/2 TON Standard Motor Down Shot Blower PERFORMANCE* † 1/2 TON Optional Motor Down Shot Blower PERFORMANCE* †10 TON Standard Motor Down Shot Blower PERFORMANCE* † 10 TON Optional Motor Down Shot Blower PERFORMANCE* †12-1/2 TON Standard Motor Down Shot Blower PERFORMANCE* † 12-1/2 TON Optional Motor Down Shot Blower PERFORMANCE* †1/2 TON Standard Motor Side Shot Blower PERFORMANCE* † 1/2 TON Optional Motor Side Shot Blower PERFORMANCE* †10 TON Standard Motor Down Shot Blower PERFORMANCE* † 12-1/2 TON Standard Motor Side Shot Blower PERFORMANCE* † 12-1/2 TON Optional Motor Side Shot Blower PERFORMANCE* †Indoor Blower Specifications AIR BalanceChecking AIR Quantity Method ONE Method TWODRY Coil Delta P Supply AIR Drive Adjustment Operation Additional Static ResistanceMotor Sheave Datum Diameters Sequence of Operations OverviewCooling Sequence of Operation Safety Controls Compressor ProtectionElectric Heating Operation Errors Electric Heat Limit SettingElectric Heating Sequence of Operations Electric Heat Antictpator SetpointsSTART-UP Cooling Charging the Unit10 TON Standard Efficiency Superheat Charging 12.5 TON Standard Efficiency Superheat ChargingPredator Flash Codes Normal Maintenance TroubleshootingGeneral Basic Troubleshooting Flowchart Unit Control Board Flash CodesCooling Troubleshooting Guide Unitary Products Group 035-17311-003-A-0704 Unitary 5005 Norman Products York Group Drive 73069