User's Manual

3300-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures
335B, Rev. 0 3-2
Now that the amount of heat that must
be removed is known, the next step is to
determine how to accomplish this. The
options are air conditioning, ventilation,
or a combination of the two. Air
conditioning is always the preferred
method and is the only way to create
anything close to an ideal environment.
Ventilation will work quite well if the
ambient air temperature is below 100° F,
or about 38° C, and the humidity is kept
at a reasonable level. In addition, the air
stream must be adequately filtered to
ensure that no airborne particulates of
any kind will be carried into the
transmitter. The combination of air
conditioning for summer and ventilation
during the cooler months is acceptable,
when the proper cooling cannot be
obtained through the use of ventilation
alone and using air conditioning
throughout the year is not feasible.
Caution: The use of air conditioning
and ventilation simultaneously is not
recommended. This can cause
condensation in transmitters.
The following precautions should be
observed regarding air conditioning
systems:
1. Air conditioners have an ARI
nominal cooling capacity rating.
In selecting an air conditioner, do
not assume that this number can
be equated to the requirements of
the site. Make certain that the
contractor uses the actual
conditions that are to be
maintained at the site in
determining the size of the air
conditioning unit. With the
desired conditioned room
temperature under 80° F, the unit
must be derated, possibly by a
substantial amount.
2. Do not have the air conditioner
blowing directly onto the
transmitter. Condensation may
occur on, or worse in, the
transmitter under certain
conditions.
3. Do not isolate the front of the
transmitter from the back with the
thought of air conditioning only
the front of the unit. Cooling air is
drawn in at the front of all
transmitters and in the front and
back of others. Any attempt to
isolate the front from the rear will
adversely affect the flow of cooling
air.
4. Interlocking the transmitter with
the air conditioner is
recommended to keep the
transmitter from operating without
the necessary cooling.
5. The periodic cleaning of all filters
is a must.
When using ventilation alone, the
following general statements apply:
1. The blower, with attendant filters,
should be on the inlet, thereby
pressurizing the room and
preventing dirt from entering the
transmitter.
2. The inlet and outlet vents should
be on the same side of the
building, preferably the leeward
side. As a result, the pressure
differential created by wind will be
minimized. Only the outlet vent
may be released through the roof.
3. The inlet and outlet vents should
be screened with 1/8-inch
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.