Piper SENECA III - Heating, Ventilating and Defrosting System

SECTION 7
PIPER
AIRCRAFT CORPORATION
DESCRIPTION &
OPERATION
PA-34-220T,
SENECA
IH
7.25
HEATING,
VENTILATING AND
DEFROSTING SYSTEM
Heated
air
for
cabin
heat
and
windshield
defrosting is provided by
a
Janitrol
combustion heater
located
in
the
aft
fuselage behind
the
cabin
baggage
compartment
close-out
panel
(refer
to
Figure 7-23). Air
from the
heater
is
ducted
forward
along
the
cabin
floor
to
outlets
at
each
seat
and
to
the
windshield
area.
Operation
of
the
combustion
heater is
controlled
by
a
three-position
switch
located
on
the
control
console
(Figure 7-25)
between
thefront
seats
and
labeled
FAN, OFF
and HEATER.
Airflow
and
temperature
are
regu-
lated by
the
two
levers
on
the
console. The
right-hand
lever
regulates
air
intake
and
the
left-hand lever
regulates
cabin
temperature.
Cabin comfort
can
be
maintained
as
desired through
various
combinations
of
lever
positions. Passengers
have
secondary control
over
heat
output
by
individ-
ually
adjustable
outlets
at
each
seat
location.
For
cabin
heat, the
air intake
lever
on
the heater
control
console
must
be
partially
or
fully
open
and
the three-position switch
set
to
the
HEATER
position. This
simultaneously
starts
fuel
flow
and
ignites the heater;
and,
during
ground
operation,
it also
activates
the
ventilation
blower
which
is
an
integral
part
of
the
combustion
heater.
With
instant
starting
and
no
need
for
priming, heat
should
be felt
within
a
few
seconds. When
cabin
air
reaches
the
temperature
selected
on
the
cabin
temperature
lever,
ignition
of
the
heater
cycles
automatically
to
maintain the
selected
temperature.
Two
safety
switches
activated by
the
intake
valve and
located
aft
of
the heater
unit
prevent
both
fan.and
heater
operation
when the
air intake lever
is
in
the
closed
position.
A
micro
switch,
which
actuates
when
the
landing
gear
is
retracted,
turns
off
the
ventilation
blower
so
that
in
flight the
cabin
air
is
circulated by
ram
air
pressure
only.
When
the
three-position
switch
is in
the FAN
position during
ground
operation,
the
ventilation
fan blows
fresh
air
through
the
heater
ductwork
for
cabin
ventilation
and
windshield
defogging when heat
is
not
desired.
When
the
heater
controls
are
used
either
for
cabin
heat
or
for
ventilation, air
is automatically
ducted
to
the
windshield
area
for
defrosting.
The
flow
of
defroster
air
to
the
windshield
area
can
be
increased by
the
activation
of
a
defroster
fan.
The
fan is
controlled
by
a
defroster
switch
located
on
the
control
console
between
the
two
front
seats.
REPORT:
VB-1110 ISSUED:
JANUARY
8,
1981
30