Operating instructions

Restricted Air Flow
General
The clearances required for design-life operation of ACZ/AGZ air-cooled units are described in the
previous section. Occasionally, 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.
The McQuay ACZ/AGZ units have several features that can mitigate the problems attributable to
restricted airflow.
• The condenser section is configured as shown below. This configuration allows inlet air for
these coils to come in from either side. A vertical coil and its adjacent angled coil are
manifolded together to serve one refrigerant circuit.
• The MicroTech II™ 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 (possibly at reduced capacity) rather than allowing a shut-off on
high discharge pressure.
• The MicroTech II™ 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 #1 to be the lag circuit (last circuit to reach full load) during periods of high ambient
temperatures.
Figure 4, Coil and Fan Arrangement
Building
Circuit #1 Circuit #2
NOTE: Models ACZ 030 to 045 and AGZ 026 to 035 do not have an interior slanted coil.
The following sections discuss the most common situations of condenser air restriction and give
capacity and power adjustment factors for each. Note that in unusually severe conditions, the
MicroTech II™ controller would adjust the unit operation to remain online until a less severe
condition is reached.
6 ACZ / AGZ-BM IMM ACZ/AGZ-4