Lockout Control, Checking Supply AIR CFM

LOCKOUT CONTROL

Any one of four conditions will put the system into a lock-out condition during the heating or cooling mode:

1.The discharge line temperature reaches 255° F (215° F reset) or,

2.The discharge pressure reaches 398 PSIG (310 PSIG reset) or,

3.The suction line freezestat equals 26° F (38° F reset) or,

4.The low-pressure cut-out equals 7 PSIG (22 PSIG reset).

Alock-out will energize the emergency heat light on the thermostat and the red LED light on the unit relay board.Turning the thermostat switch to "Off" then back to "On", will reset the system.

511.06-N5Y

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 8 for blower motor drive data. The tension on the belts should be adjusted as shown in Figure 9.

NOTICE TO OWNER:

If a lockout occurs, check for the following problems before calling a serviceman:

1.Dirty filters.

2.Snow accumulation.

3.Leaf or debris blockage.

After eliminating the problem, attempt to restart the system as follows:

•turn the system switch on the thermostat to its "OFF" position for 10 seconds.

•turn it back to its original position.

If the unit doesn’t start, call a serviceman.

NOTE: Models with an anti-recycle accessory will have a 5-minute delay before starting.

CHECKING SUPPLY AIR CFM

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

TABLE 11 - BELT-DRIVE SUPPLY AIR

MOTOR PULLEY ADJUSTMENT

TURNS	BLOWER DRIVE RANGE (RPM)
OPEN*	3 TON	4 TON	5 TON
5	780	790	850
4	842	856	924
3	904	922	998
2	966	988	1072
1	1028	1054	1246
0	1090	1120	1220

*Pulley can be adjusted in half-turn increments.

determined from the blower performance and static resistance data on Tables 4 through 7.

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 pulley can be determined from Table 11.

FIG. 9 - 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 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 indoor coil. Since the moisture on an indoor coil may vary greatly, measuring the pressure drop across a wet coil under field conditions would be inaccurate. To ensure a dry coil, the compressors should be de-energized 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 Figure 10.

Unitary Products Group

LOCKOUT CONTROL

OPTIONAL BELT-DRIVE BLOWER

CHECKING SUPPLY AIR CFM

TABLE 11 - BELT-DRIVE SUPPLY AIR

MOTOR PULLEY ADJUSTMENT

TURNS

BLOWER DRIVE RANGE (RPM)

OPEN*

3 TON

FIG. 9 - BELT ADJUSTMENT