York Official Manual for D7CG Air Conditioner Models

PILOT CHECKOUT

The pilot flame should envelope 3/8 inches of the end of the flame sensor. Refer to Figure 12. To adjust pilot flame, (1) remove pilot adjustment cover screw, (2) adjust the screw for the proper pilot flame, (3) be sure to replace cover screw after adjustment to prevent possible gas leakage.

FIG. 12 - PROPER FLAME ADJUSTMENT

Put the system into operation and observe through complete cycle to be sure all controls function properly.

BURNER INSTRUCTIONS

To check or change burners, pilot or orifices, CLOSE MAIN MANUAL SHUT-OFF VALVE AND SHUT OFF ALL POWER TO THE UNIT.

1.	Remove the two screws holding either end of the manifold
	to the burner supports.
2.	Open the union fitting in the gas supply line just upstream of the unit
	gas valve and downstream from the main manual shut-off valve.
3.	Remove the gas piping patch plate.

					530.18-N8Y
TABLE 17 - BELT-DRIVE SUPPLY AIR
	MOTOR PULLEY ADJUSTMENT
TURNS		BLOWER DRIVE RANGE (RPM)
OPEN*	3 TON		4 TON	5 TON	6 TON
5	780		790	850	900
4	842		856	924	970
3	904		922	998	1040
2	966		988	1072	1110
1	1028		1054	1246	1180
0	1090		1120	1220	1250

*Pulley can be adjusted in half-turn increments.

OPTIONAL BELT-DRIVE BLOWER

All units with belt-drive blowers have single-speed motors. The variable pitch pulley on the blower motor can be adjusted to obtain the desired supply air CFM. Refer to Table 7 for blower motor and drive data. The tension on the belts should be adjusted as shown in Figure 14.

CAUTION

Procedure for adjusting belt tension:

1.Loosen nut (D) from the motor mount.

2.Never loosen nuts (C) from each other while loosening nut (D).

3.Adjust the tension by turning bolt (B).

4.Do not loosen the four nuts (top and bottom) (A); unless additional tensioning distance is required; immediately re-tighten these bolts if loosened.

5.Use a belt tension checker to apply a perpendicular force to 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:

4. Disconnect wiring to the gas valve and spark ignitor.

Remove the manifold-burner gas valve assembly by lifting

up and pulling back.

Burners are now accessible for service.

Reverse the above procedure to replace the assembly. Make sure that burners are level and seat at the rear of the heat exchanger.

BURNER AIR SHUTTER ADJUSTMENT

SPAN	LENGTH
DEFL		FORCE

(D)

(A)(C)*

(B)

Adjust burner shutters so that a distinct, sharp, blue flame is obtained. Refer to Figure 13.

FIG. 13 - TYPICAL FLAME APPEARANCE

SUPPLY AIR BLOWER AND TEMPERATURE RISE ADJUSTMENTS

The speed of the supply air blower will depend on the required CFM, the unit accessories and the static resistances of both the supply and the return air duct systems. With this information, the speed for the supply air blower can be determined from the blower performance and accessory static resistance data in Tables 4,6,8 and 9.

Knowing the required blower RPM and the blower motor HP, the speed setting for the supply air motor can be determined.

The setting (turns open) for the optional belt-drive supply air motor pulley can be determined from Table 17.

* NEVER LOOSEN

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.

6.After adjusting, re-tighten nut (D) against the motor mount taking care not to loosen nuts (C).

FIG. 14 - 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 holes located on the filter access panel side of the unit.

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 evaporator coil.

NOTE: The tubes must be inserted and held in a position perpendicular to the air flow so that velocity pres- sure 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

Unitary Products Group 17