Carrier 39LA-25 Installation, Start-Up And Service Instructions Manual page 37

Note 1
1/4 in. Pet Cock for
Unit
Continuous vent
12"
Min.
Dirt Leg (6 in.)
15° Check Valve
Float or
Bucket Trap
(Note 2)
* When end of supply main, see Fig. 34.
NOTES:
1. Flange or union is located to facilitate coil removal.
2. Flash trap may be used if pressure differential between steam and
condensate return exceeds 5 psi.
3. When a bypass with control is required.
4. Dirt leg may be replaced with a strainer. If so, tee on drop can be
replaced by a reducing ell.
5. The petcock is not necessary with a bucket trap or any trap which
has provision for passing air. The great majority of high or medium
pressure returns end in hot wells or deaerators which vent the air.
Fig. 33 — Low, Medium or High Pressure Coil Piping
Gate
Steam
Valve
Supply
to Unit
Dirt Leg
Globe Valve
(Plug Type) Drip
Line
Condensate
Return
From Unit
Gate Valve
NOTES:
1. A bypass is necessary around trap and valves when continuous
operation is necessary.
2. Bypass to be the same size as trap orifice but never less than
1/2 inch.
Fig. 34 — Dripping Steam Supply to Condensate
Control Valve (Note 3)
Strainer
Gate Valve
Steam Supply
Main
*
15° Check Valve for
Breaking Vacuum
1/2 in. Line
Note 1
Gate Valve
Condensate
Return Main
Steam Supply Main
Float and Thermostatic
Trap
Gate Valve
Open Air Relief to
Atmosphere Close
to Unit. Required on
Low Pressure Gravity
Return Systems
Condensate
Return Main
Return
Note 1
Unit
Unit
Dirt Leg (6")
Float or Bucket
Trap (Note 3 and 4)
NOTES:
1. Flange or union is located to facilitate coil removal.
2. When a bypass with control is required.
3. Flash trap can be used if pressure differential between supply
and condensate return exceeds 5 psi.
4. Coils with different pressure drops require individual traps. This
is often caused by varying air velocities across the coil bank.
5. Dirt leg may be replaced with a strainer. If so, tee on drop can be
replaced by a reducing ell.
6. The petcock is not necessary with a bucket trap or any trap
which has provision for passing air. The great majority of high
pressure return mains terminate in hot wells or deaerators which
vent the air.
7. When dripping steam supply main to condensate return, refer to
Dripping Steam Supply to Condensate Return figure.
Fig. 35 — Multiple Coil High Pressure Piping
37
Control Valve (Note 2)
Strainer
Gate Valve
1/4" Pet Cock Steam
for Continuous Supply
Vent Main
See Note 7
15° Check Valve
for Breaking Vacuum
1/4" Pet Cock for
Continuous Vent
12" Min.
15° Check Valve
Gate Valve
Condensate
Return Main