34
piping.
Refer
to
Figure
3
‐
6.5.
Air
vents
should
not
be
installed
too
close
to
indoor
unit
lift
pumps.
Figure
3
‐
6.5:
Drain
piping
air
vents
Air
conditioner
drain
piping
should
be
installed
separately
from
waste,
rainwater
and
other
drain
piping
and
should
not
come
into
direct
contact
with
the
ground.
Drain
piping
diameter
should
be
not
less
than
the
indoor
units’
drain
piping
connection.
To
allow
inspection
and
maintenance,
the
piping
clamps
shipped
with
units
should
be
used
to
attach
drain
piping
to
indoor
units
–
adhesive
should
not
be
used.
Thermal
insulation
should
be
added
to
drain
piping
to
prevent
condensation
forming.
Thermal
insulation
should
extend
all
the
way
to
the
connection
with
the
indoor
unit.
Units
with
drain
pumps
should
have
separate
drain
piping
systems
from
systems
that
use
natural
drainage.
6.2
Water
Traps
For
indoor
units
with
a
high
negative
pressure
differential
at
the
outlet
of
the
drainage
pan,
a
trap
should
be
fitted
to
the
drain
piping
to
prevent
poor
drainage
and/or
water
being
blown
back
into
the
drainage
pan.
Traps
should
be
arranged
as
in
Figure
3
‐
6.6.
The
vertical
separation
H
should
be
in
excess
of
50mm.
A
plug
may
be
fitted
to
allow
cleaning
or
inspection.
6.3
Selecting
Piping
Diameters
Select
branch
drainage
piping
(the
drain
piping
connection
to
each
unit)
diameters
according
to
indoor
unit
flow
volume
and
select
main
drainage
piping
diameters
according
to
the
combined
flow
volume
of
the
upstream
indoor
units.
Use
a
design
assumption
of
2
liters
of
condensate
per
horsepower
per
hour.
For
example,
the
combined
flow
volume
of
three
2HP
units
and
two
1.5HP
units
would
be
calculated
as
follows:
Combined
flow
volume
=
3
x
2
L/HP/h
×
2HP
=
18
L/h
+
2
x
2
L/HP/h
×
1.5HP
Tables
3
‐
6.1
and
3
‐
6.2
specify
the
required
piping
diameters
for
horizontal
and
vertical
branch
piping
and
for
main
piping.
Note
that
main
piping
should
use
PVC40
or
larger.
Table
3
‐
6.1:
Horizontal
drain
piping
diameters
PVC
piping
Nominal
diameter
(mm)
Capacity
(L/h)
Remarks
Slope
1:50
Slope
1:100
PVC25
25
39
27
Branch
piping
only
PVC32
32
70
50
PVC40
40
125
88
Branch
or
main
piping
PVC50
50
247
175
PVC63
63
473
334
Figure
3
‐
6.6:
Drain
piping
water
traps
p l u g
H / 2
H
i n d o o r u n i t
Vent
