Goodman Mfg IO-354B installation instructions Heat Pump Operation, Air Flow Adjustments

de-energized (heating) position. After giving the unit time to settle out, make sure the unit is supplying heated air.

12.If the outdoor ambient is above 80°F, the unit may trip on its high pressure cut out when on heating. The compressor should stop. The heating cycle must be thoroughly checked, so postpone the test to another day when conditions are more suitable but-DO NOT FAIL TO TEST.

If the outdoor ambient is low and the unit operates properly on the heating cycle, you may check the pressure cutout operation by blocking off the indoor return air until the unit trips.

13.If unit operates properly in the heating cycle, raise the temperature setting until the heating second stage makes contact. Supplemental resistance heat, if installed should now come on. Make sure it operates properly.

NOTE: If outdoor thermostats are installed the outdoor ambient must be below the set point of these thermostats for the heaters to operate. It may be necessary to jumper these thermostats to check heater operation if outdoor ambient is mild.

14.For thermostats with emergency heat switch, return to step 11. The emergency heat switch is located at the bottom of the thermostat. Move the switch to emergency heat. The heat pump will stop, the blower will continue to run, all heaters will come on and the thermostat emergency heat light will come on.

15.If checking the unit in the wintertime, when the outdoor coil is cold enough to actuate the defrost control, observe at least one defrost cycle to make sure the unit defrosts completely.

FINAL SYSTEM CHECKS

16.Check to see if all supply and return air grilles are adjusted and the air distribution system is balanced for the best compromise between heating and cooling.

17.Check for air leaks in the ductwork. See Sections on

Air Flow Adjustments.

18.Make sure the unit is free of “rattles”, and the tubing in the unit is free from excessive vibration. Also make sure tubes or lines are not rubbing against each other or sheet metal surfaces or edges. If so, correct the trouble.

19.Set the thermostat at the appropriate setting for cooling and heating or automatic changeover for normal use.

20.Be sure the Owner is instructed on the unit operation, filter, servicing, correct thermostat operation, etc.

REFRIGERATION PERFORMANCE CHECK

Under normal summertime (full load) operating conditions, superheat should be between 8°F and 12°F and sub-cooling measured at the condenser outlet should be 15°F (nominal). A 25°F to 35°F temperature difference should exist between the entering condenser air and the temperature correspond- ing to the compressor saturated discharge pressure. Check

that compressor RLA corresponds to values shown in Ap- pendix C. RLA draw can be much lower than values listed at low load conditions and low ambient condensing tempera- tures. Values in Appendix C can slightly exceed at high load conditions and high ambient condensing temperatures.

HEAT PUMP OPERATION

COOLING CYCLE

When the heat pump is in the cooling cycle, it operates ex- actly as a Summer Air Conditioner unit. In this mode, all the charts and data for service that apply to summer air condi- tioning apply to the heat pump. Most apply on the heating cycle except that “condenser” becomes “evaporator”, “evapo- rator” becomes “condenser”, “cooling” becomes “heating”.

HEATING CYCLE

The heat pump operates in the heating cycle by redirecting refrigerant flow through the refrigerant circuit external to the compressor. This is accomplished with through the reversing valve. Hot discharge vapor from the compressor is directed to the indoor coil (evaporator on the cooling cycle) where the heat is removed, and the vapor condenses to liquid. It then goes through the expansion device to the outdoor coil (con- denser on the cooling cycle) where the liquid is evaporated, and the vapor goes to the compressor.

When the solenoid valve coil is operated either from heating to cooling or vice versa, the piston in the reversing valve to the low pressure (high pressure) reverse positions in the re- versing valve.

The following figures show a schematic of a heat pump on the cooling cycle and the heating cycle. In addition to a re- versing valve, a heat pump is equipped with an expansion device and check valve for the indoor coil, and similar equip- ment for the outdoor coil. It is also provided with a defrost control system.

The expansion devices are flowrator distributors and perform the same function on the heating cycle as on the cooling cycle. The flowrator distributors also act as check valves to allow for the reverse of refrigerant flow.

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