Capacity
and Dimensions Table
Proper selection
of the APR Control is essential to the success of an application. For
each system with an APR Control applied, the following information must
be gathered:
- Total Capacity
of each individual system
- Number of compressors
- Number of circuits
- Compressor staging/steps
of unloading
- Split or package
system
- Routing of refrigeration
piping in split systems (particularly suction line)
- Suction line
sizing, including any risers in the routing from evaporator to condenser
APR Control selection will be determined by all the above factors
to provide the maximum capacity control, but still provide proper
protection of the compressor(s) by assuring the return of oil to the
compressor with the refrigerant
We encourage you
to call us to discuss any application questions that you might have.
We are available to review and evaluate applications with the APR Control,
to ensure proper selection and application with your specific systems.
Single
Compressor Package Systems
Selection is simply
the amount of capacity control required. Total system capacity minus
APR Control modulation capacity provides the lowest point to which the
system will modulate. We strongly recommend modulation of no more than
75 - 80% on any system. 80% capacity control provides for a minimum
condition at which the thermostat will shut the system off. This also
allows a minimum of refrigerant flow even at consistently low load conditions
to provide oil entrainment back to the compressor(s).
Multiple
or Unloading Compressor Package Systems
Selection is based
on the last or lowest stage at which the air conditioning system would
operate without the inclusion of the APR Control. The APR Control is
sized for that "last" stage, as selection had been made in
a single compressor package system. The APR Control will always be installed
on the first on/last off (or lead/lag) circuit.
Split
Systems
Selection is still
based on the amount of capacity control required, but has the additional
limitations of proper suction line sizing. We stress the importance
of proper refrigerant flow for oil entrainment at all times, to assure
oil returns to the compressor to maintain its lubrication. The total
capacity of the system, minus the modulation capacity of the APR Control
must be greater than the minimum tonnage for proper oil entrainment
– as shown in the chart on this page.
The design of suction
lines with regard to their distance, size and total rise should be undertaken
with the greatest care. Without proper refrigerant velocity up any suction
risers, oil attaches to the walls of the suction pipe and drains to
the low point, reducing the amount of oil returning to the compressor.
| Pipe OD |
1/2"
|
5/8"
|
3/4"
|
7/8"
|
1-1/8"
|
1-3/8"
|
1-5/8"
|
2-1/8"
|
2-5/8"
|
| Min. tonnage |
.2
|
.35
|
.55
|
.85
|
1.6
|
2.8
|
4.15
|
8.2
|
14.2
|
Please select conservatively.
If there is any doubt about the proper selection of the APR Control
and suction line sizing, Please call us to discuss your application.
We want to ensure a proper installation and solution for your customer.
Remember, when
the velocity in a suction riser is insufficient to lift the oil up the
riser and back to the compressor, a double suction riser or alternative
piping configuration may be required. Please call Rawal Devices Engineers
to consult.
Fast
Selection Table
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©2002
Rawal Devices. All rights reserved.
