are already in existence or are scheduled for installation, consider their use
for monitoring only (not control) to insure the HVAC system is not increased
at the expense of reliability. Use the following guidelines.
a) Base minimum outside ventilation air flow rate for air
conditioned areas on average expected building occupancy rather than on a
simple percentage of total air circulated. Where occupancy will vary
or CO2 sensor system to control the outside fresh air
damper should be considered for keeping outside air ventilation rates at the
minimum required level.
b) Avoid conflict between components within the systems, such as
excessive latent cooling that must be offset with humidification during
temperature control or excessive sensible cooling that must be offset with
reheat during humidity control. System designs that properly match the
sensible-to-total load ratio performance of the equipment to that of the
application are necessary.
c) Avoid conflict or cross-control between units when multiple
units are used, as in computer rooms with multiple units.
d) Use capacity increments for improved part-load performance.
e) Features such as economizer cycles (except when provided and
used only as emergency ventilation), night setback and wide-throttling-range
or dual-setpoint thermostats are incompatible with electronic equipment spaces
that require close control.
f) For areas not containing electronic equipment, use proper
zoning to permit economizers, night setback and other energy conservation
g) Use simple but adequate controls. Electric controls are more
than adequate for most applications and are simple to understand and easy to
maintain by station forces. Electronic controls are more complicated and
sometimes subject to error due to the proximity of heavy currents or RF
interference. Although the trend is toward more sophisticated electronic type
controls, consideration should be given to the fact that outside contract
maintenance would probably be needed to maintain them. Pneumatic controls
Unless constant and proper maintenance is given this type system it may become
contaminated with moisture and will be erratic in operation thereafter. This
type system is not recommended.
Applications. For spaces not containing electronic equipment, the
requirements of NAVFAC DM-3.03 shall apply. Requirements for specific
electronic facilities are described in Section 8. Requirements which apply to
more than one facility type are described herein.
Computer Rooms and Spaces with Similar Equipment. Specific
requirements for computer rooms, receiver rooms, telephone and switchgear
rooms, and electronic equipment maintenance shops will be indicated in the