350-Watt Digital VHF LB Transmitter
Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0
3-3
number but a never-exceed
number. In a dusty or remote
location, this number should be
reduced to 150 CFM.
7.
The inlet and outlet(s) must have
automatic dampers that close any
time the ventilation blower is off.
8.
In those cases in which
transmitters are regularly off for a
portion of each day, a
temperature-differential sensor
that controls a small heater must
be installed. This sensor will
monitor inside and outside
temperatures simultaneously. If
the inside temperature falls to
within 5° F of the outside
temperature, the heater will come
on. This will prevent condensation
when the ventilation blower comes
on and applies even in the
summer.
9.
A controlled-air bypass system
must be installed to prevent the
temperature in the room from
falling below 40° F during
transmitter operation.
10.
The blower should have two
speeds, which are thermostatically
controlled, and interlocked with
the transmitter.
11.
The blower on high speed must be
capable of moving the required
volume of air into a half inch of
water pressure at the required
elevation. The free air delivery
method must not be used.
12.
Regular maintenance of the filters,
if used, can not be
overemphasized.
13.
Tube transmitters should not rely
on the internal blower to exhaust
cooling air at elevations above
4000 feet. For external venting,
the air vent on the cabinet top
must be increased to an 8"
diameter for a 50-W, 100-W and
1-kW transmitter and to 10" for 5-
kW and 10-kW transmitters. An
equivalent rectangular duct may
be used but, in all cases, the
outlet must be increased in area
by 50% through the outlet screen.
14.
It is recommended that a site plan
be submitted to Axcera for
comments before installation
commences.
In calculating the blower requirements,
filter size, and exhaust size, if the total
load is known in watts, 2000 CFM into
1/2" of water will be required for each
5000 watts. If the load is known in BTUs,
2000 CFM into 1/2" of water will be
required for each 17,000 BTUs. The inlet
filter must be a minimum of seven
square feet, larger for dusty and remote
locations, for each 5000 watts or 17,000
BTUs. The exhaust must be at least four
square feet at the exhaust screen for
each 5000 watts or 17,000 BTUs.
The information presented in this section
is intended to serve only as a general
guide and may need to be modified for
unusually severe conditions. A
combination of air conditioning and
ventilation should not be difficult to
design (see Figure 3-1). System
interlocking and thermostat settings
should be reviewed with Axcera. As with
any equipment installation, it is always
good practice to consult the
manufacturer when questions arise.
Axcera can be contacted at 1-724-873-
8100.