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EXHAUST HOODS
Conditions
may
exist
in
some
installations
where
exhaust vent
hoods
for the
355, 650,
652,
653
and 655 would
offer
an advantage
.
For
these
installations
IBM
has designed two
different
vent
hood arrangements
.
The
hoods and
duct
system become
a part
of the
customer's
air conditioning
system and
are
not
furnished
by IBM.
Figures
2
and
3 illustrate
a
machine
supported system.
When
this
system
is
used,
the
screens
in
the top of the
machine
units
are
removed
and
the
hoods are
fastened
in
their
place. Additional
exhaust-fan capacity
must
be provided
in
the duct
system
to
overcome
the air
resistance
of the
hoods and
duct
system
Exhaust
duct
and
fan
should
have
sufficient
capacity
to
prevent any
back pressure
at the
top
of
any
unit
Figures
_4
and
5_
illustrate
a
ceiling-
supported exhaust-hood system.
The
hoods
for
this
system
are
of a different
design and are
suspended
4
inches
above
the top
of the
machine
If
exhaust hoods are
used, the radiant portion
of the
total
heat dissipated
from
the
machine
will
not be
removed.
This heat load
must
be considered
in
designing
the
room
cooling
system
The
customer's
air
conditioning
engineer or
building
superintendent should be
consulted
to
determine
if
exhaust hoods should be used.
He
should also advise
which system
offers the
most
advantages
for the
customer.
49
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