Carrier ZONE-MIZER 50ME - Manual (Page 42)

Method no. 3 — heating and cooling night setback and
indoor fan cycling — This system requires a remote
control panel, a heating and cooling thermostat with
subbase, a night setback relay and a 7-day timer.
Because cooling is not locked out, the clock switches that
close at night close the outdoor air dampers by connecting
across R and W on the remote panel accessory. The MUR
shuts down the unit (including the indoor fans). When the
NS thermostats reach their settings, the NS relay is
energized, opening the NC contacts and de-energizing
the MUR.
However, if a “wild” zone exists, it is allowed to cool
on heating NS or vice versa. This may be an advantage on
some applications between zones. When the day/night is
switched to “Day,” the NS is overridden and the unit
operates normally except the dampers remain closed at
night. The 2 jumper wires have to be removed from the
back of the remote panel to isolate the day/night switch.
Morning start-up — To conserve energy and lower total
operating costs, the outdoor dampers may be closed when
starting the system in the morning. During a warm-up
period, when the system is opeated for one or 2 hours
before occupancy, heat only building return air. The extra
load of cold outdoor air introduced uses extra heat energy.
Ventilation is unnecessary until space is occupied, so the air
introduced produces unnecessary heat waste.
This principle holds true on a cooling day, when outside
air transmits heat and moisture to the evaporator coil. This
extra load above the return air only load is an unnecessary
expense.
To offset this, wire a heating or cooling thermostat
across the “Short To Close Dampers” terminals on the
zone control board. The thermostat senses return air
temperature and the outdoor air damper does not open
until the building is at the required temperature.
A time clock can also be used and set as follows:
1. Occupied cycle; 8 a.m. to 6 p.m. Outdoor air damper is
open and the system is controlled by individual zone
thermostats.
2. Night setback cycle: 6 p.m. to 6 a.m. Individual zone
thermostats are on night setback (NS) cycle. The out­
door air damper is closed, the unit is reset down and
controlled by NS thermostat.
3. Warm-up (or cool-down) cycle: 6 a.m. to 8 a.m. Out­
side air damper is closed by time clock and the system
is controlled by indoor zone thermostats.
Using any method, increased economy is achieved and
building requirements are satisfied.
Sound and vibration
For maximum sound attenuation, locate roof-mounted
multizone units over unoccupied space (i.e. storage areas,
utility rooms, corridors) where slightly higher sound levels
are not objectionable. Line supply and return duct systems
with acoustic material to prevent sound transmission into
occupied space. If open plenum return air systems are used,
install an acoustical trap or fiberglass-lined chamber to
attenuate sound. Use simple return duct elbows and tees
with 5-ft minimum fiberglass-lined legs and low static pres­
sure on open plenum return air systems. A method of
forming an acoustical trap using the roof curb area under a
multizone unit is shown on Acoustical Trap Installation.
Special vibration isolating bases and curbs designed for
rooftop applications are available from some vibration
isolator manufacturers. This equipment virtually eliminates
vibration transmission on critical applications. However,
ACOUSTICAL TRAP INSTALLATION
MULTIZONE UNIT
NOTES:
1. Dimension A is approximately 7 in. for optimum performance.
2. Acoustical lining is 1-in. 1-ib density, neoprene-coated fiberglass.
3. Return air grille sbould be located at least 15 ft from return air opening.
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