Carrier 48VT-A Maintenance and Service, Defrost Mode, Emergency Heat Mode, Routine Maintenance

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Fig. 8 - To Shut Off Unit Electric Cooling

Defrost Mode

When your heat pump is providing heat to your home or office and the outdoor temperature drops below 45°F (7.2°C), moisture may begin to freeze on the surface of the coil. If allowed to build up, this ice would impede airflow across the coil and reduce the amount of heat absorbed from the outside air. So, to maintain energy-efficient operation, your heat pump has an automatic defrost mode.

The defrost mode starts at a preset time interval of 60 minutes, although, it may be reset to 30, 90 or 120 minutes. Defrost will start at the preset time only if the ice is sufficient to interfere with normal heating operation.

After the ice is melted from the coil, or after a maximum of 10 minutes in defrost mode, the unit automatically switches back to normal heating operation.

Do not be alarmed if steam or fog appears at the outdoor unit during defrost mode. Water vapor from the melting ice may condense into a mist in the cold outside air.

During certain weather conditions such as heavy snow and freezing rain it is not uncommon for ice to build up on the unit grille. This is normal for these weather conditions. Do not attempt to remove the ice from the unit grille. This condition will not affect the proper function of the unit and will clear within a few days.

Emergency Heat Mode

If you should have problems with the heat pump portion of your system, this mode allows your supplemental gas heating source to keep your home or office warm until your heat pump can be serviced.

MAINTENANCE AND SERVICE

This section discusses maintenance that should be performed on your system. Most maintenance should be performed by your dealer. You, as the owner, may wish to handle some minor maintenance for your new unit.

Routine Maintenance

All routine maintenance should be handled by skilled, experienced personnel. Your dealer can help you establish a standard procedure.

For your safety, keep the unit area clear and free of combustible materials, gasoline, and other flammable liquids and vapors.

To assure proper functioning of the unit, flow of condenser air must not be obstructed from reaching the unit. Clearance from the top of the unit is 48 in. (1219 mm). Clearance of at least 36 in. (914 mm) is required on sides except the power entry side (42 in. [1067 mm] clearance) and the duct side (12 in. [305 mm] minimum clearance.

Maintenance and Care for the Equipment Owner

Before proceeding with those things you might want to maintain yourself, please carefully consider the following:

!WARNING

FIRE, EXPLOSION, ELECTRICAL SHOCK AND CUT HAZARD

Failure to follow this warning could result in personal injury, death or property damage.

1.Turn off gas supply first, then all electrical power to your unit and install lock-out tag before servicing or per- forming maintenance.

2.When removing access panels or performing maintenance functions inside your unit, be aware of sharp sheet metal parts and screws. Although special care is taken to reduce sharp edges to a minimum, be extremely careful when handling parts or reaching into the unit. Wear safety glasses, gloves, and appropriate protective clothing.

Air Filters

The air filter(s) should be checked every 3 or 4 weeks and changed or cleaned whenever it becomes dirty. Dirty filters produce excessive stress on the blower motor and can cause the motor to overheat and shut down.

This unit must have air filters in place before it can be operated. These filters can be located in one of at least two places. In many applications, the installer will provide return air filter grilles mounted on the wall or ceiling of the conditioned structure. In the instance of filter grilles, the filters can simply be removed from the grille and replaced.

The other typical application is an accessory filter rack installed inside the unit itself. The following information is given to assist in changing filters used in these internal filter racks.

Table 1 indicates the correct indoor filter size for your unit. Refer to Fig. 3 to access filters installed in the accessory filter rack. If using an Accessory Filter Rack, refer to the Installation Instructions provided with it for correct filter sizes and quantities.

Table 1 – Indoor Air Filter Data

Unit Size	Filter Size in. (mm)
24040	20x20x1 (508x508x25)
24060 and 30	20x24x1 (508x610x25)
36 --- 42	24x30x1 (610x762x25)
48 --- 60	24x36x1 (610x914x25)

To replace or inspect filters in accessory filter rack (See Fig. 3):

1.Remove the filter access panel using a 5/16-in. nut driver.

2.Remove the filter(s) by pulling it out of the unit. If the filter(s) is dirty, clean or replace with a new one.

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