York BCH 036 Static Resistances, Phasing, Belt Adjustment, Afteradjusting,re-tightennutsA

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.

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177820-YIM-A-0506

TABLE 20: STATIC RESISTANCES

						RESISTANCE, IWG
DESCRIPTION
							CFM
		1000	1200	1400	1600		1800	2000	2200	2400	2600
ECONOMIZER1, 2		0.07	0.08	0.09	0.11		0.13	0.15	0.17	0.20	0.23
ELECTRIC	5-15KW	0.04	0.05	0.06	0.07		0.08	0.10	0.12	0.14	0.16
HEATERS1
	20-30KW	0.06	0.07	0.08	0.09		0.11	0.13	0.15	0.17	0.20
BOTTOM DUCT CONNECTIONS1		0.06	0.07	0.08	0.09		0.10	0.11	0.12	0.14	0.16

1. Deduct these resistance values from the available external static pressure shown in SUPPLY AIR BLOWER PERFORMANCE Tables.

2. The pressure through the economizer is greater for 100% outdoor air than for 100% return air. If the resistance of the return air duct system is less than 0.25 IWG, the unit will deliver less CFM during full economizer operation.

PHASING	PROCEDUREFORADJUSTINGBELTTENSION:
Check for proper compressor rotation. If the blower or
	1	Loosennu	(A)(topandbottom).
compressors rotate in the wrong direction at start-up,	2	Adjustthet		byturningbolt(B).
the electrical connection to the unit is misphased.	3	Neverloosennuts(C)fromeachother.
	4.Usebelttensioncheckertoapplyaperpendicularforcetobeonebeltatthe
Change the incoming line connection phasing to obtain		midpointofthespanasshown.Thedeflectionforceshouldbeapplied
		untilaspecificdeflectiondistanceof4mm(5/32")is			.Todetermine
proper rotation. (Scroll compressors operate in only		thedeflection		fromnormalposition,useastraight	dgefrom
		sheavetosheavedistanascereferenceline.herecommendedobtainedflectionforce
one direction. If the scroll is drawing low amperage,		isasfollows:		DEFLFORCE
has similar suction and discharge pressures, or pro-
ducing a high noise level, the scroll is misphased).

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

5.Afteradjusting,re-tightennuts(A).

FIGURE 12 - BELT ADJUSTMENT

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.

Unitary Products Group