Amana GSH13024 Installation Manual download pdf (Page 10)

supplementary heat for all heat pump installations in areas where

the temperature drops below 45° F. It is also a good practice to

provide sufficient supplementary heat to handle the entire heating

requirement should there be a component failure of the heat pump,

such as a compressor, or refrigerant leak, etc.

Since the temperature of the refrigerant in the outdoor coil on the

heating cycle is generally below freezing point, frost forms on the

surfaces of the outdoor coil under certain weather conditions of

temperature and relative humidity. Therefore, it is necessary to

reverse the flow of the refrigerant to provide hot gas in the outdoor

coil to melt the frost accumulation. This is accomplished by re-

versing the heat pump to the cooling cycle. At the same time, the

outdoor fan stops to hasten the temperature rise of the outdoor

coil and lessen the time required for defrosting. The indoor blower

continues to run and the supplementary heaters are energized.

DEFROST C ONTROL

During operation the power to the circuit board is controlled by a

temperature sensor, which is clamped to a feeder tube entering

the outdoor coil. Defrost timing periods of 30,60 and 90 minutes

may be selected by setting the circuit board jumper to 30, 60 and

90 respectively. Accumulation of time for the timing period selected

starts when the sensor closes (approximately 31° F), and when

the wall thermostat calls for heat. At the end of the timing period,

the unit’s defrost cycle will be initiated provided the sensor re-

mains closed. When the sensor opens (approximately 75° F), the

defrost cycle is terminated and the timing period is reset. If the

defrost cycle is not terminated due to the sensor temperature, a

twelve minute override interrupts the unit’s defrost period.

SUGGESTED FIELD TESTING/TROUBLE SHOOTING

1. Run unit in the heating mode (room thermostat calling for

heat).

2. Check unit for proper charge. Note: Bands of frost on the

condenser coil indicate low refrigerant charge.

3. Shut off power to unit.

4. Disconnect outdoor fan by removing the outdoor fan motor

wire from “DF2” on defrost control.

5. Restart unit and allow frost to accumulate.

6. After a few minutes of operation, the unit’s defrost

thermostat should close. To verify this, check for 24 volts

between “DFT” and “C” on board. If the temperature at the

thermostat is less than 28° F and the thermostat is open,

replace the unit’s defrost thermostat, as it is defective.

7. When the unit’s defrost thermostat has closed, short the

test pins on the defrost board until the reversing valve

shifts, indicating defrost. This should take up to 21

seconds depending on what timing period the control is

set on. After defrost initiation, the short must instantly be

removed or the unit’s defrost period will only last 2.3

seconds.

8. The control is shipped from the factory with the compressor

delay option selected. This will de-energize the

compressor contactor for 30 seconds on defrost initiation

and defrost termination. If the jumper is set to Normal, the

compressor will continue to run during defrost initiation

and defrost termination. The control will also ignore the

low pressure switch connected to R-PS1 and PS2 for 5

minutes upon defrost initiation and 5 minutes after defrost

termination.

9. After the unit’s defrost thermostat has terminated, check

the defrost thermostat for 24 volts between “DFT” and “C”.

The reading should indicate 0 volts (open sensor).

10.Shut off power to unit.

11. Replace outdoor fan motor lead to terminal “DF2” on defrost

board and turn on power.

AIRFLOW M EASUREMENT AND A DJUSTMENT

After reviewing Duct Work section, proceed with airflow measure-

ments and adjustments. The unit blower curves (see Specifica-

tion Sheets) are based on external static pressure (ESP per in/wc).

The duct openings on the unit are considered internal static pres-

sure. As long as ESP is maintained, the unit will deliver the proper

air up to the maximum static pressure listed for the CFM required

by the application (i.e. home, building, etc.)

In general, 400 CFM per ton of cooling capacity is a rule of thumb.

Some applications depending on the sensible and latent capacity

requirements may need only 350 CFM or up to 425 CFM per ton.

Check condition space load requirements (from load calculations)

and equipment expanded ratings data to match CFM and capacity.

After unit is set and duct work completed, verify the ESP with a

1-inch inclined manometer with pitot tubes or a Magnahelic gauge

and confirm CFM to blower curves in the Specification Sheets. All

units have three-speed blower motors. If low speed is not utilized,

the speed tap can be changed to medium or high speed.

NOTE: Never run CFM below 350 CFM per ton, evaporator freezing

or poor unit performance is possible.

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Amana GSH13024 Installation Manual Page 10

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