Assembly Instructions Chapter 3
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures
835-3, Rev. 0 3-3
3.
The inlet and outlet vents should be screened with 1/8" hardware cloth
(preferred) or galvanized hardware cloth (acceptable).
4.
Cooling air should enter the room as low as practical but in no case higher than
four feet above the floor. The inlet must be located where dirt, leaves, snow, etc.,
will not be carried in with the cooling air.
5.
The exhaust should be located as high as possible. Some ducting is usually
required to insure the complete flushing of heated air with no stagnant areas.
6.
The filter area must be adequate to insure a maximum air velocity of 300 feet per
minute through the filter. This is not a conservative 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 should be used 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 when the transmitter is operating.
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 1 kW transmitter and to 15" for a 10-
kW transmitter. 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 ADC for comments before
installation commences.
To calculate 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 outlet for 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