Product Manual ALR2-3 ALR 110F – 150F 31
Restricted Air Flow
General
The clearances required for penalty-free operation of ALR air-cooled condensers are described in the
previous section. Inevitably there are situations where these clearances cannot be maintained due to
site restrictions such as units being too close together or a fence or wall restricting airflow, or both.
Fortunately the McQuay ALR chillers have several features that mitigate the penalties attributed to
restricted airflow.
• The condenser section is “U” shaped, as shown below. This allows inlet air for these coils to
come in from either side. A vertical coil and its adjacent horizontal coil are manifolded together to
serve one circuit.
• The optional MicroTech control is proactive in response to “off-design conditions”. In the case
of single or compounded influences restricting airflow to the unit, the microprocessor will act to
keep the compressor(s) running (at reduced capacity) rather than allowing a shut-off on high
discharge pressure.
• The optional MicroTech control can be programmed to sequence the compressors in the most
advantageous way. For example, in the diagram shown below, it might be desirable to program
circuit 2 to be the lag circuit (last circuit to reach full load) during periods of high ambient
temperatures.
Figure 12, Coil and Fan Arrangement
The following sections discuss the most common situations of condenser air restriction and give
capacity and power adjustment factors for each. It should be noted that in unusually severe
conditions the optional MicroTech controller would adjust the unit operation to remain online until a
safe condition is reached.
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