ASHRAE Journal - October 2013 - 45

2013 ASHRAE TEcHnology AwARd cASE STudiES

mostly separate times. In addition, the exhaust system
was downsized.
A variable speed chilled water system is usually
designed with a constant speed circulator pump,
which maintains a constant flow through the chiller,
and a variable speed building pump that supplies
cold water from the chiller loop to the coils that
demand it. Since there was only one cooling coil to
serve, the system could be designed with one pump.
Basically, a large circulator pump was used with
a three-way valve at the single cooling coil for the
building. The AHU, the pump, and the chiller are all
directly adjacent to each other. The pump cuts on
and off with the chiller. With one pump, there is less
energy used than the two-pump solution described
earlier. This design is only effective if there is only
one coil for the system to serve.
The design of the custom ERV makeup air unit was
innovative. Since caustic and acidic exhaust could not be
used in the ERV, a unique application of the ERV wheel
was selected. This ERV wheel will both pre-cool the hot
incoming fresh air, and reheat the very cold discharge
air off the cooling coil.
Reheating the air to 60°F (16°C) will provide plenty
of cooling in the lab environment because high airflow
rates were required due to high room turnover rate
requirements. But the real advantage is that less of
the final electric reheat at the air control valves will be
required (Figure 1, Page 43).

Operation and Maintenance
The operation and maintenance was greatly improved
with the new designs. All of the following items are
improvements over what was existing. Each new split
system heat pump is either located in a mechanical
room, hung overhead in the warehouse, or located on a
fully accessible mezzanine. The units in the old building
were mostly hung above the insulation above the ceiling. The custom AHU and chilled water piping system
is located in a dedicated mechanical room with double
door access and plenty of room. All of the piping components (buffer tank, expansion tank, pump, pot feeder,
etc.) are neatly lined up against the wall for easy access.
The air-cooled chiller is on a pad directly outside. The
DDC system allows centralized manipulation, scheduling, and automatic control. The chilled water makeup
AHU is a very simple machine. This simplicity was considered as another reason not to go with a much more
complicated DX system. Maintenance will be relatively
easy as a result. Finally, a cooling tower was considered
(with a water-cooled chiller), but ruled out due to cost
and maintenance. The air-cooled chiller will be significantly easier for maintenance operations.

Cost Effectiveness
The budget for the job (not including the new property)
was $1,000,000. I was able to convince the owner and architect that the HVAC budget would need to be at least 50% of
the total budget ($500,000). Even so, I was doubtful that we

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ASHRAE Journal - October 2013

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