paragraph will be edited to secure controls to match
existing controls and to properly integrate the
specified controls into the existing temperature
control system. Designer will be required to put a
sequence of control for each cooling tower fan,
chilled water pump, condenser water pump, etc. on
the contract drawings.
One control measure recommended for consideration by
the designer for solid desiccant units is a bypass
damper arrangement whereby desiccant unit components
are de-energized when the desiccant unit is not
performing dehumidification, and a damper in the
process air ductwork is closed. At the same time, a
(bypass) damper in the outside air ductwork is open
so that a central station air handling unit will not
have to draw minimum (or economizer cycle) outside
air quantities through the desiccant unit; i.e.,
outside air will bypass the desiccant unit on its
way to the central air handler. When
dehumidification is called for, the bypass damper
will close and the damper in the process air
ductwork will open, which will enable desiccant unit
components to be energized (the dampers can be near
one another and set to assume reversible and
opposite positions through mounting on a common
jackshaft). This control has numerous advantages:
it reduces aggregate flow through desiccant unit
filters and rotors, extending their useful lives; it
reduces fan head pressure loss from particulate
accumulation on filters and rotors, simultaneously
reducing desiccant fouling and accompanying loss of
dehumidification capacity; also, it reduces
electrical energy consumption since the desiccant
unit process air fan will not (and cannot) operate
to move air through the desiccant unit to the
central station air handler when dehumidification is
not called for. The differential on the controls
must be set; however, so that dampers and desiccant
unit components do not short cycle.
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Automatic controls for the specified desiccant system shall be provided
with the desiccant equipment. These controls shall operate automatically
to balance the equipment capacity with the load on the air conditioning
system, and shall be fully coordinated with and integrated into the
[temperature control system specified in Sections 15895 AIR SUPPLY,
DISTRIBUTION, VENTILATION, AND EXHAUST SYSTEM and 15951 DIRECT DIGITAL
CONTROL FOR HVAC AND OTHER LOCAL BUILDING SYSTEMS] [existing
air-conditioning system].
3.2.3
General Piping, Valves, and Duct Installation
All piping, valve, and duct installation shall be made in accordance with
the desiccant equipment manufacturers recommendation or in accordance with
Sections 15895 AIR SUPPLY, DISTRIBUTION, VENTILATION, AND EXHAUST SYSTEM, [
15181 CHILLED, CHILLED-HOT, AND CONDENSER WATER PIPING SYSTEMS] [15182
REFRIGERANT PIPING] [[_____]], and 15400A PLUMBING, GENERAL PURPOSE.
SECTION 15500A
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