5
Theory
of
Operation
Steamix
203
produces
hot
water
by
mixing
steam
with
cold
water.
The
hot
water
temperature
is
variable
from
cold
to
almost
boiling
by
rotating
the
temperature
regulating
lever
counter-clockwise.
If
desired,
the
temperature
can
be
locked
at
a
pre-selected
level
by
removing
the
temperature
regulating
lever
and
further
secured
by
installing
Part
No.
042
tamper
resistant
locking
Set.
(See
page
22.)
Inlet
water
pressure
activates
the
mixing
valve
allowing
steam
to
heat
the
water.
The
valve
requires
a
minimum
inlet
water
pressure
of
20
psig
(1.4
bar)
to
open
the
steam
inlet.
This
method
of
operation
provides
a
built-in
safety
feature
where
the
mixing
valve
automatically
shuts
off
the
steam
supply
when
a
water
supply
failure
or
a
pressure
reduction
below
20
psi
(1.4
bar)
occurs.
The
following
diagrams
illustrate
the
mixing
valveís
method
of
operation.
Figure
5-1.
With
the
outlet
closed
and
no
flow,
the
water
pressures
on
either
side
of
the
diaphragm
are
equal.
This
allows
the
spring
to
hold
the
poppet
valve
on
its
seat
thereby
preventing
steam
flow.
Figure
5-2.
Opening
the
outlet
allows
water
to
begin
to
flow.
When
a
minimum
differential
pressure
of
7
psi
(.5
bar)
develops
across
the
diaphragm*,
the
diaphragm
lifts
from
its
resting
position
and
pushes
the
poppet
valve
off
the
steam
seat
allowing
steam
to
flow.
By
allowing
steam
to
flow
only
when
inlet
water
flow
is
present,
the
operator
is
protected
from
accidental
exposure
to
live
steam
should
the
water
supply
fail.
The
poppet
valve
is
resisted
by
the
temperature
control
lever
which
allows
more
or
less
steam
into
the
mix
for
higher
or
lower
outlet
temperatures
as
adjusted.
*a
minimum
of
20
psi
(14.4
bar)
water
pressure
is
required
to
lift
the
diaphragm.
Figure
5-3.
Closing
the
outlet
valve
increases
back
pressure.
When
the
differential
pressure
across
the
diaphragm
becomes
less
than
7
psi
(.5
bar)
or
the
water
pressure
is
reduced
below
20
psi
(1.4
bar)
the
spring
pushes
the
poppet
valve
closed,
shutting
off
the
steam
flow
and
the
diaphragm
returns
to
its
resting
position.
