Owner:
Richmond County Schools
Hamlet, NC
Architectural
Firm:
Wash Hatem Nelson Architects PA
Charlotte, NC
|
Engineering Firm:
United Engineering Group
Charlotte, NC
Greenheck
Representative:
Hoffman & Hoffman, Inc.
Charlotte, NC |
The
Ventilation Challenge
- Design
a new HVAC system for a new three story classroom
addition that complements and supports existing
HVAC equipment.
- Design
and install an economical system with low first
cost and operating costs.
- Improve
indoor air quality and comfort in a hot, humid
climate.
Richmond County Schools wanted to replace a 1920
classroom building with a new, three-story junior
high classroom building in Rockingham, North Carolina,where
hot and humid weather is common in spring, summer
and fall. To simplify maintenance, the school district
preferred to use an HVAC system in the new building
that would be similar to the system already in place
in other buildings on the campus, but wanted to
avoid indoor air quality issues other new school
buildings in the area were experiencing. In Richmond
County, newly constructed schools with tighter,
more advanced window systems have been experiencing
severe mold and mildew problems because mechanical
ventilation systems did not treat outdoor air independently.
Existing buildings on the Rockingham Junior High
campus were heated and air conditioned with unit
ventilators and fan coil units connected to a two-pipe
hot water or chilled water piping system. An air-cooled
chiller produces chilled water during the cooling
season, and a gas-fired, cast iron boiler produces
hot water in the heating season. All ventilation
is provided through the unit ventilators that are
connected to the outdoors.
Greenheck's
Solution
-
Greenheck
Energy Recovery Unit (Model ERCH)
-
Fan
coil units, exhaust fans and unit ventilators
as part of McQuay air- cooled chiller and Weil-
McLain hot water boiler.
 At
the beginning of the design phase of this project,
Doug Simpson, P.E. of United Engineering Group,
Charlotte, NC and Steve Woodrow of Hoffman &
Hoffman, Greenheck’s manufacturing rep in
Charlotte, suggested the owner install dedicated
outdoor air systems to prevent the potential IAQ
problems that could be caused by mold and mildew.
However, the owner was very concerned that the first
cost of such a system and future operating costs
might
|
be more than their budget could handle. Simpson
and Woodrow explained that Greenheck’s energy
recovery units could help reduce first costs of
a newchiller and boiler by requiring smaller units
and also help lower overall system operating costs.
Ultimately, two Greenheck Energy Recovery Units
(Model ERCH) sized at 7500 cfm and 7900 cfm capacity
were recommended which allowed a 36 ton reduction
in chiller capacity and a 129 Mbh reduction
in boiler capacity. In addition, a unit ventilator
serving a typical classroom was downsized to 1000
cfm of supply air, whereas a classroom unit ventilator
which conditions outdoor air directly would have
had to been sized at 1500 cfm. By using the two
Greenheck ERCH units, the cooling load requirement
of a typical classroom was reduced by more than
1.5 tons. And finally, more cost savings were achieved
by installing a smaller hydronic piping system (which
supplies water to the classroom units in the new
school). This was possible because the use of the
energy recovery units reduced system gallons per
minute by an estimated 25 percent.
The
Results
Although specific energy savings have not yet been
calculated, atypical payback period for Greenheck’s
energy recovery ventilator units in this climate
is less than three years. After one year of operation,
the school’s principal has said that he and
everyone else are very pleased with the new building
and the indoor air quality provided by the HVAC
system
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