TM 5-852-9/AFR 88-19, Vol. IX
(1) If the outdoor thermostat to the steam control valve is set below 35EF, freezing of the steam coil
(2) If the bypass damper does not close the steam valve when in the full bypass position, the building
(3) When the low limit discharge control is set too low, uncomfortable cold drafts will result. If the
low limit is set too high, the buildings will overheat.
a. System operation. The heating and ventilating unit also provides building ventilation. Ventilation is
required to provide building ventilation. Ventilation is required to provide a clean healthful atmosphere and
to prevent accumulation of excess humidity. Ventilation is provided by mixing outside air with return in a
mixing box. The mixing box dampers are controlled by a thermostat which maintains mixed air within the
mixing box at a constant 42EF. Thus as the outside temperature rises, the percentage of outside air increases
to maintain comfortable conditions in the building. An auxiliary thermostat overrides the mixing box control
and shuts off all outside air whenever the return temperature falls below 68EF. Whenever outside air is
introduced, an equal amount of room air must be exhausted to prevent excess pressure accumulation inside
the building. This is accomplished by means of a relief damper located at the end of the gym. As the outside
air damper opens, the relief damper opens the same amount.
(1) If the mixing box control is set below 42EF, the heating coil may lack the capacity to maintain
the room temperature at 70EF.
(2) If the mixing box control is set above 42EF, the building will not be adequately ventilated and
damage may result from excess accumulation of moisture. The excess moisture condenses on cold surfaces
and "rain" occurs inside the building during certain weather conditions.
(3) If the override is set above 68EF, the building will not be properly ventilated and the same results
noted in paragraph (2) above may occur.
a. System operation. During cold weather, outside air is very dry. When the outside air is brought into
the building and warmed, its relative humidity drops to uncomfortable levels. To offset this, a steam
humidifier is installed in the duct downstream of the heating and ventilating unit. A room humidistat controls
an automatic valve in the steam supply line to the humidifier. The room humidistat should be set at 20 percent
to 30 percent.
(1) If the humidistat is set above 30 percent, excess humidity will condense on the building walls with
the undesirable results noted in paragraph 3-3.
(2) If the humidistat is set too low, the air will dry out, causing human discomfort and causing
shrinkage of the wood floors of the gym and bowling alley.
(3) Whenever the heating and ventilating unit fan is stopped, the manual valve on the steam supply
to the humidifier should be closed to prevent serious accumulations of water in the ductwork.
4 -- ELECTRICAL
4-1. General. The electrical system consists of power and lighting system and a fire detection and alarm
4-2. Power system. The 480 volt, 3 phase, 60 hertz power to the building is supplied from a feeder which
is tapped from Feeder F-15 inside the Operations Building through a 50 ampere, 600 volt circuit breaker. The
feeder is routed through P-5 raceway to the Recreation, Multipurpose building. Inside the Recreation,
Multipurpose building, the feeder branches, supplying the main building power through a 50 ampere, 600 volt
circuit breaker and a 30 KVA, 420-120/208 volt, 3 phase dry type transformer. The other branch supplies
the fire alarm and exit lights through a 20 ampere, 600 volt circuit breaker and a 250 VA, 480-120 volt single
a. Heating and ventilating. The power for the heating and ventilating unit
is supplied from Panel "P".
The control of the unit is described in the Mechanical Section.
b. Lighting. The power for the lighting power Panel "A" is supplied from Panel "P".
4-3. Fire detection and alarm system. The fire detection and alarm system consists of fixed temperature
type detectors, alarm stations, alarm bells and a control unit. The system is connected to the base system. A
local alarm will shut down all ventilating and exhaust fans through an interlocking relay.
4-4. Electrical system. The electrical system does not have any unusual maintenance requirements.