Page 17 - HVAC Pump Handbook

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Physical Data for HVAC System Design

14 The Basic Tools

2.2 Standard Operating Conditions

Every piece of HVAC equipment available is based on some particular
operating conditions such as maximum temperature or pressure; usu-
ally, these conditions are spelled out by the manufacturer. It is the re-
sponsibility of the design engineer to check these conditions and to
ensure that they are compatible with the system conditions. It is very
important that variations in electrical service as well as maximum
ambient air temperature be verified for all operating equipment.

2.2.1 Standard air conditions
Standard air conditions must be defined for ambient and ventilation
air. Ambient air is the surrounding air in which all HVAC equipment
must operate. Standard ambient air is usually listed as 70°F, while
maximum ambient air temperature is normally listed at 104°F. This
temperature is the industry standard for electrical and electronic
equipment. For some boiler room work, the ambient air may be listed
as high as 140°F. It is incumbent on the designer to ensure that his or
her equipment is compatible with such ambient air conditions.
Along with ambient air temperature, the designer must be con-
cerned with the quality of ventilation air. This is the air that is used
to cool the operating equipment as well as provide ventilation for the
building. The designer must ensure that the equipment rooms are not
affected by surrounding processes that contain harmful substances.
This includes chemicals in the form of gases or particulate matter.
Hydrogen sulfide is particularly dangerous to copper-bearing equip-
ment such as electronics. Many sewage treatment operations gener-
ate this gas, so it is very important that any HVAC equipment in-
stalled in sewage treatment facilities be protected from ambient air
that can include this chemical. Dusty industrial processes must be
separate from equipment rooms to keep equipment clean. Dust that
coats heating or cooling coil surfaces or electronics will have a sub-
stantial effect on the performance and useful life of that equipment.
The designer must be aware of the presence of any such substances
that will harm the HVAC equipment.
Ventilation air does not bother the operation of the pump itself, but it
does affect the pump motor or variable-speed drive. This is the air that
is used to cool this electrical equipment. Evaluating ventilation air is
part of the design process for the selection of such equipment and is
therefore very important in equipment selection. Outdoor air data in-
cluding maximum wet bulb and dry bulb temperatures is listed in the
American Society of Heating, Refrigerating, and Air-Conditioning
Engineers’ (ASHRAE’s) Systems and Equipment Handbook for most of

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