Johnson Controls BQ 060, BQ 036, BQ 048 Phasing, Supply AIR Blowers, Checking Supply AIR CFM

PHASING

Check for proper compressor rotation. 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 pro- ducing 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.

PROCEDUREFORADJUSTINGBELTTENSION:364985-XIM-B-0508
1	Loosennu	(A)(topandbottom).
2	Adjustthet		byturningbolt(B).
3	Neverloosennuts(C)fromeachother.
4.Usebelttensioncheckertoapplyaperpendicularforcetobeonebeltatthe
	midpointofthespanasshown.Thedeflectionforceshouldbeapplied
	untilaspecificdeflectiondistanceof4mm(5/32")is			.Todetermine
	thedeflection		fromnormalposition,useastraight	dgefrom
	sheavetosheavedistanascereferenceline.herecommendedobtainedflectionforce
	isasfollows:		DEFLFORCE

(A) (C)**Never(B)Loosen Tnsionnewbeltsatthemax.deflectionbetweenforcerecomendminandeforthebelt sdeflectionoperati.Check.forceAnyrethevalues-tenioningbelt.tensionshouldatleastfalltwotimestheduring.thfirstmax24.hoursof

5.Afteradjusting,re-tightennuts(A).

FIGURE 12 - BELT ADJUSTMENT

Start the supply air blower motor. Adjust the resis- tances in both the supply and the return air duct sys- tems 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 posi- tion perpendicular to the air flow so that veloc- ity pressure will not affect the static pressure readings.

3.Using an inclined manometer, determine the pres- sure drop across a dry evaporator coil. Since the moisture on an evaporator coil may vary greatly, measuring the pressure drop across a wet coil

30 Johnson Controls Unitary Products