valutazioni - 1, GPA: 3
(
)
)
|
Facilità d'uso
1 operates either fully loaded or at one step of unloading depending on the suction pressure, which in turn is dependent on the evaporator load conditions. As cooling demand increases, TC2 of the 2-stage thermostat energizes control relay no. 2. CR2 deenergizes the crankcase heater at compressor no. 2 and brings on compressor no. 2 after one second. The LLSV for solenoid drop refrigerant control (circuit no. 2) opens as soon as CR2 is energized. On standard units, compressor no. 2 operates fully loaded. As cooling demand is satisfied, thermostat contacts TC2 break and deenergize CR2 which then deenergizes compressor no. 2 and energizes its crankcase heater. The LLSV on circuit no. 2 closes, preventing refrigerant migration back to compressor no. 2 during the off cycle. If the space temperature continues to decrease, stage 1 thermostat contacts TCI break and deenergize CR1. Immediately after CR1 is deenergized, compressor no. 1 shuts off and its crankcase heater is energized. The LLSV on circuit no. 1 closes, preventing refrigerant migration back to compressor no. 1 during the off cycle. Outdoor-fan motors no. 1 and 2 deenergize as soon as CR1 is deenergized. NOTE: If thermostat fan switch is in the auto position, the indoor fan will cycle on and off as the thermostat calls for cooling (or heating). If the fan switch is in the continuous position, the fan will run as long as the outdoor unit is powered up. Two Air Handlers — Two 2-Stage Cool Thermostats (One Per Air Handler) — At start-up of circuit no. 1, the thermostat controlling circuit no. 1 calls for first stage of cooling when thermostat contact TCI closes. If all safety devices are satisfied, circuit no. 1 control relay CR1 energizes which deenergizes the crankcase heater inside compressor no. 1. The indoor-fan motor on the circuit no. 1 fan coil starts immediately, and the main liquid line solenoid valve (LLSV) for solenoid drop refrigerant control on circuit no. 1 opens. Outdoor-fan motor no. 1 and compressor no. 1 start after one second. Fan no. 2 starts if the outdoor ambient is above 60 F (15.6 C). On standard units, compressor no. 1 operates either fully loaded or at one step of unloading depending on the suction pressure, which in turn is dependent on the evaporator load conditions. As cooling demand increases, TC2 of the 2-stage thermostat energizes the capacity control LLSV resulting in full activity of the evaporator surface. The fully active evaporator surface will raise the suction pressure until the pressure-operated capacity control valve setting is exceeded, so that the compressor becomes fully loaded. The thermostat controlling circuit no. 2 calls for first stage of cooling when thermostat contact TC2 closes. Assuming all safety devices are satisfied, circuit no.2 control relay CR2 energizes, which deenergizes the crankcase heater inside compressor no. 2. The indoor-fan motor on circuit no. 2 fan coil starts immediately, and the main LLSV for solenoid drop refrigerant control on circuit no. 2 opens. Compressor no. 2 starts after one second. The outdoor fans are already running if circuit no. 1 is running. If circuit no. 1 is not running when thermostat no. 2 calls for cooling, the outdoor fans are off. In this situation, outdoor-fan motor no. 1 starts when compressor no. 2 starts. Outdoor-fan motor no. 2 comes on if the outdoor ambient is above 60 F (15.6 C). As cooling demand is satisfied at thermostat no. 1 or 2 (whichever comes first), contacts TC2 break, and the capacity control LLSV on that circuit is deenergized. This prevents refrigerant flow through the upper (circuit no. 1 or 2) evaporator section causing the suction pressure to drop and the compressor on that circuit to unload. NOTE: Circuit no. 2 does not have a factory-installed unloader. If desired, one must be added in the field. As the space temperature drops further, the space thermostat contacts TCI open which will deenergize control relay CR1 or CR2. Immediately after CR1 or CR2 is deenergized, the compressor CR1 or CR2 control is shut off and its crankcase heater is energized. The LLSV on that circuit closes, preventing refrigeration migration back to the compressor during the off cycle. Outdoor-fan motors no. 1 and 2 are deenergized only if the space thermostats for both circuits no. 1 and 2 are not calling for cooling. NOTE: If thermostat fan switch is in the auto position, the indoor fan will cycle on and off as the thermostat calls for cooling (or heating). If the fan switch is in the continuous position, the fan will run as long as the outdoor unit is powered up. Restart — Manual reset of the 24-v control circuit is necessary if unit shutdown is caused by automatic reset devices (including COTP [compressor overcurrent protection] and HPS [high-pressure switch]) or if shutdown is caused by manual reset devices (including OPS [oil pressure switch] and compressor circuit breaker protection). To restart the unit when COTP or HPS has tripped (after COTP ...