There is no specific limit on either length or elevation for Outdoor Units. The compressors will operate safely if the pressures, temperatures, oil and voltage are maintained at normal approved levels.
The accumulator that should be used on the Copeland Scroll Digital™ system is no different from the standard accumulator used on fixed speed systems. The size of the oil return hole should be in the range of 1.0 – 1.5 mm. This hole should be protected by a screen size of 30 mesh. It is important to ensure the cleanliness of the accumulator during its manufacturing as it can introduce debris inside the system that can be extremely harmful to the compressor.
The discharge pressure continuously fluctuates during loading and unloading. In order to ensure that a continuous flow of liquid is supplied to the electronic expansion valve, the receiver is required. The receiver acts as a buffer to the store the liquid refrigerant and also evens out the pressure fluctuation that is happening upstream in the condenser coil. A bi-flow receiver is only required for the heat pump system; for the cooling-only system, there is no need for a bi-flow receiver. The bi-flow receiver is required because during the heating mode the liquid has to flow to the condenser in the opposite direction.
It is important to fit sight glasses in the receiver and in the liquid line during the testing of the system. During full load cooling operation, the receiver outlet sight glass should be free from bubbles. This ensures that the amount of refrigerant in the system is adequate. For heat pumps refrigerant flows in both directions so sight glasses are required on both receiver inlet and outlet. On full load heating operation the receiver sight glass should also be free from bubbles. Please see separate detailed guidelines on refrigerant charging and receiver sizing for multi-evaporative systems.
In cooling mode operation, the liquid refrigerant from the condenser flows freely through the check valve. The outdoor electronic expansion valve is closed. When the compressor is loaded, condenser and receiver pressure increases. During the unloaded cycle, the check valve prevents the refrigerant in the receiver from losing pressure back to the condenser. This reduces power consumption. During the heating mode, the refrigerant flows in the opposite direction through the outdoor electronic expansion valve which controls the superheat of the outdoor coil. The check valve directs all of the liquid passing through the electronic expansion valve during the heating mode.
It is important to ensure the following checkpoints during prototype testing: - The receiver is of the correct size and is fitted with a sight tube or multiple sight glasses. - The liquid line has two sight glasses – one on each side of the receiver. - The sight tube is fitted to the accumulator. - Pressure ports are fitted in convenient locations around the system to allow the engineer to understand sub-cooling, superheating and pressure drops. - The expansion device for each indoor is of the right size. - The temperature sensors are located at approximately the right places. - The dip switch setting on each indoor unit and outdoor unit is set correctly. - The capacity setting in the dip switch on the board has been set correctly. - The discharge thermistor from the compressor is plugged in correctly to the outdoor board - High Pressure and Low Pressure switches are connected - There is enough refrigerant in the system before start up.
Equal distribution of refrigerant in the different circuits of the condenser is an important design consideration. Sometimes, the distribution is not even and some circuits receive more refrigerant than others. This unequal distribution results in uneven heat transfer and can result in coil freezing. Also, if the airflow over the coil is not evenly distributed, some parts of the coil may have insufficient energy transfer, which can result in frost formation.
During the loading and unloading of the scrolls, there is no fluctuation in the light bulbs. During the startup of any compressor, there is an inrush of current, the locked rotor ampere (LRA) . The locked rotor ampere can cause the dimming of lights if it is too high. But once the compressor starts loading and unloading, the fluctuation of the current is much smaller than the locked rotor ampere. Consequently, there is no effect on any other electrical appliances.
No. In a Copeland Scroll Digital multi system, there is a liquid receiver after the condenser coil. There is a pressure fluctuation at the entry to the condenser coil and also at the exit of the condenser coil. But the liquid receiver acts like a buffer tank and evens out the pressure fluctuations at the exit. In fact, at the liquid receiver outlet, the pressure is very constant.
The electronic expansion valves are located near the indoor unit. If there are any issues in fitting the electronic expansion valve inside the indoor unit due to size, the electronic expansion valve can be placed outside. Even though the electronic expansion valve is bi-flow, it is recommended that the inlet to the electronic expansion valve (cooling cycle) be the one that is inline with the coil. The perpendicular outlet is the outlet for the electronic expansion valve. Note: Changing the flow direction through electronic expansion valves can reduce refrigerant flow noise.
It is important to follow the right pipe sizes, as smaller or larger sizes can cause problems. This is particularly true in long pipe systems where small pipes cause excessive pressure drops that can lead to a loss of sub-cooling and/or low suction pressure. Please refer to Copeland Application Engineer to get more details on the piping sizes.
A multiple split system will normally have high quantity of refrigerant and so it is necessary to use a receiver and accumulator. The receiver for 3-4 HP systems should be about 2.5 liters. For 5-6 HP systems, it should be about 6 liters. For the tandem configuration, it should be about 12 liters. The accumulator is very much dependent on the system design and tests should be done to determine the optimum size. Please contact the Emerson Climate Technologies
The Copeland Scroll Digital is just like the standard Copeland scroll compressor as far as oil is concerned. The quantity of refrigerant in the system determines if there is any need to add oil to the system. Normally for a compressor up to 6HP, there is no need to add oil for up to 10kg of refrigerant.
In a tandem configuration, the crankcase pressures are different in the Copeland Scroll Digital and the standard scroll. Since the Copeland Scroll Digital is in a state of loading and unloading, the average suction pressure is higher compared to that of the standard scroll. Since the crankcase pressure is higher in the Copeland Scroll Digital, there is movement of oil from the digital to the standard scroll. However, the gas balance pipe is supposed to smooth this pressure fluctuation and there should not be a large difference in oil levels between the two compressors.
There is some imbalance in the flow distribution in the suction line. When the suction gas is returning to the compressor, at one point near the compressor, the gas gets distributed through a Y joint. If only gas is returning, then the distribution between the two compressors is fairly even. However, if there is some small amount of liquid entering the compressor, there in uneven distribution between the two compressors. Uneven distribution of liquid refrigerant causes uneven sump temperatures. Also, the amount of oil lost by the two compressors is not equal on a real time basis. Lastly, the amount of oil in the compressor also affects the sump temperature.
The noise from the electronic expansion valve happens mostly during part load operation, when gas is moving through the valve. There are no standard methods to eliminate this sound. Consider moving the expansion device from the evaporator to a junction box outside the conditioned space or use insulation to cover the body of the expansion valve or fit the expansion device in the outdoor unit.
Systems up to 6HP capacity do not normally need an oil separator. However, for tandem configurations above 8HP, an oil separator is recommended. There are two options for fitting the oil separator. Option1: Fit an oil separator to each of the compressor discharge lines. Return the oil to the accumulator inlet. If this configuration is used, check valves should be fitted to the discharge lines after the oil separator and before the Y joint. The check valves prevent the “off” oil separator from filling with liquid. Option2: Fit one oil separator on the common discharge line. Return the oil to the accumulator inlet.