Application Engineering |
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7.Using the appropriate lifting devices, carefully remove the compressor from the system.
The following steps should be followed to install the digital compressor into the system.
1.Before removing the rubber plugs, install the compressor in the unit on the mounting grommets using the appropriate lifting devices.
2.Install the compressor mounting bolts.
3.Connect the suction and discharge lines using standard brazing practices.
4.If the compressor has an external modulation valve and tubing (3 to 7.5 ton only) refer to Figure 8 for the correct valve orientation and position. Wrap a wet rag around the valve and complete the assembly by brazing the valve and tubing into place.
5.Check for leaks using nitrogen with a properly sized regulating and relief valve.
6.Connect conduits and wiring to the compressor. Inspect and/or replace the contactor. If the compressor is
NOTICE
The above procedures for changing the compressor are not comprehensive and additional steps/procedures may be necessary.
Refrigerant Flow Control
In the system with a digital compressor, the refrigerant flow control valve is required to control flow across a wide range of flow rates and varying pressure differentials. Most balanced port thermostatic expansion valves can control flow down to about 40% of their rated capacity. Excessive hunting and loss of superheat control can result when asking a thermostatic expansion valve to operate outside of its design range. For this reason, the expansion device needs to be evaluated to ensure reliable operation over the expected operating range. Limiting the minimum compressor modulation rate to a value that the expansion valve can tolerate should be considered. Electronic expansion valves should be considered if modulation over the entire range of the compressor’s modulation range is anticipated.
Evaporator Air Flow
For the highest level of energy savings, comfort, and efficiency the variable capacity system should be capable of varying the air flow. Variable frequency drives and tapped blowers are two means of reducing air flow. Reducing air flow in humid or maritime climates is important to maintain coil temperatures low enough to
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remove latent heat. In desert and arid climates, because of low or no latent loads, air flow is less critical.
The controls required for variable air flow are not provided by Emerson so the contractor may need to consult with controls experts in this field.
Condenser Air Flow
Modulating the condenser air flow is not critical to the success of the application. For the highest level of energy savings, condenser air flow will be reduced based on the compressor modulation rate, condensing temperature, ambient temperature, etc.
Modulation Control
The preferred modulation control for retrofit applications is the Commercial Comfort Controller. This controller is a closed loop controller that is installed in the conditioned space. The controller measures the space temperature and through an algorithm in the controller, controls the modulation of the digital scroll. The controller can be positioned up to 300 feet from the compressor/unit, is configurable for roof top unit or heat pump, and is wired like a commercial room thermostat. For more information on the Commercial Comfort Controller please refer to
ASSEMBLY LINE PROCEDURES
3 To 7.5 Ton Modulation Valve Brazing Procedure
The external modulation valve is purchased and shipped separately from the 3 to 7.5 ton digital scroll. Therefore, assembly is required in the OEM manufacturing plant. Figure 8 illustrates the correct position and orientation of the modulation valve. Please note the direction of the arrow on the valve, it must point to suction.
When brazing the modulation valve into the system, the valve must be wrapped with a wet rag to help keep the valve cool. The torch flame must be directed away from the valve and the brazing operation should be done quickly so the valve isn't overheated. The brazing operation should be performed with a nitrogen purge to prevent the
Pressure Testing
The pressure used on the OEM assembly line to meet the UL burst pressure requirement cannot be higher than 400 psig (27.6 bar) for
