Carrier 48SS018-060 Maintenance, Wet Coil Pressure Drop, Unit Size Airflow Pressure Drop

Table 17 Ð Wet Coil Pressure Drop

UNIT SIZE	AIRFLOW	PRESSURE DROP
	(cfm)	(in. wg)
	600	0.069
018*	700	0.082
	800	0.102
	900	0.116
	600	0.039
024	700	0.058
	800	0.075
	900	0.088
	900	0.088
030	1000	0.095
	1200	0.123
	1000	0.068
036	1200	0.088
	1400	0.108
	1600	0.123
	1000	0.048
042	1200	0.069
	1400	0.088
	1600	0.102
	1400	0.068
048	1600	0.075
	1800	0.088
	1700	0.082
060	1900	0.095
	2100	0.108
	2300	0.123

*Unit 48SS only.

COOLING SEQUENCE OF OPERATION Ð With the room thermostat SYSTEM switch in the COOL position and the FAN switch in the AUTO. position, the cooling sequence of operation is as follows:

When the room temperature rises to a point that is slightly above the cooling control setting of the thermostat, the ther- mostat completes the circuit between thermostat terminal R to terminals Y and G. These completed circuits through the thermostat connect contactor coil (C) (through unit wire Y) and blower relay coil (BR) (through unit wire G) across the 24-v secondary of transformer (TRAN).

NOTE: The blower relay coil (BR) is used on standard non- ICM units, ICM units use evaporator (indoor) fan on (IFO) connection.

The normally-open contacts of energized contactor (C) close and complete the circuit through compressor motor (COMP) to condenser (outdoor) fan motor (OFM). Both motors start instantly.

On standard non-ICM units, the set of normally-open con- tacts of energized relay BR close and complete the circuit through evaporator blower (indoor) fan motor (IFM). On ICM units, the IFO completes the circuit through evaporator blower IFM. The blower motor starts instantly.

NOTE: Once the compressor has started and then has stopped, it should not be started again until 5 minutes have elapsed.

The cooling cycle remains ``on'' until the room tempera- ture drops to point that is slightly below the cooling control setting of the room thermostat. At this point, the thermostat ``breaks'' the circuit between thermostat terminal R to ter- minals Y and G. These open circuits deenergize contactor coil C and relay coil BR. The condenser and compressor mo- tors stop. After a 30-second delay, the blower motor stops. The unit is in a ``standby'' condition, waiting for the next ``call for cooling'' from the room thermostat.

MAINTENANCE

To ensure continuing high performance, and to minimize the possibility of premature equipment failure, periodic main- tenance must be performed on this equipment. This combi- nation heating/cooling unit should be inspected at least once each year by a quali®ed service person. To troubleshoot heat- ing or cooling of units, refer to tables at the back of the book.

NOTE TO EQUIPMENT OWNER: Consult your local dealer about the availability of a maintenance contract.

The ability to properly perform maintenance on this equip- ment requires certain expertise, mechanical skills, tools, and equipment. If you do not possess these, do not at- tempt to perform any maintenance on this equipment other than those procedures recommended in the User's Manual. FAILURE TO HEED THIS WARNING COULD RESULT IN SERIOUS PERSONAL INJURY AND POSSIBLE DAMAGE TO THIS EQUIPMENT.

Failure to follow these warnings could result in serious personal injury:

1.Turn off gas supply, then turn off electrical power to the unit before performing any maintenance or serv- ice on the unit.

2.Use extreme caution when removing panels and parts. As with any mechanical equipment, personal injury can result from sharp edges, etc.

3.Never place anything combustible either on, or in con- tact with, the unit.

4.Should overheating occur, or the gas supply fail to shut off, shut off the external main manual gas valve to the unit, then shut off the electrical supply.

Errors made when reconnecting wires may cause im- proper and dangerous operation. Label all wires prior to disconnection when servicing.

The minimum maintenance requirements for this equip- ment are as follows:

1.Inspect air ®lter(s) each month. Clean or replace when necessary.

2.Inspect indoor coil, drain pan, and condensate drain each cooling season for cleanliness. Clean when necessary.

3.Inspect blower motor and wheel for cleanliness and check lubrication each heating and cooling season. Clean and lubricate (if required) when necessary. For ®rst heating season, inspect blower wheel bimonthly to determine proper cleaning frequency.

4.Check electrical connections for tightness and controls for proper operation each heating and cooling season. Serv- ice when necessary.

5.Check and inspect heating section before each heating sea- son. Clean and adjust when necessary.

6.Check ¯ue hood screen and remove any obstructions if necessary.

7.Check vent screen and clean if necessary.

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