JOHNSON CONTROLS
78
FORM 102.20-N1
ISSUE DATE: 7/06/2016
SECTION 3 - HANDLING, STORAGE, AND INSTALLATION
• Use the actual operating conditions (coil pressure 
vs. return pressure) to select a trap.
• It is preferable to provide an individual trap for 
each coil, but a single trap may be used for coils 
operating in parallel with respect to the airow.
Coilsinserieswithrespecttoairowmustbesup-
plied with individual traps. 
• Locate the trap at least 12 in. below the coil return 
connection, and lower it when freeze protection is 
required. Do not attempt to lift condensate modu-
lated steam supply.
FIGURE 121 - STEAM COIL PIPING ARRANGEMENTS
LD04887a
SUPPLY MAIN
DRIP TRAP 
FOR END OR 
LOW POINT 
OF SUPPLY 
MAIN
RETURN 
MAIN
SUPPLY MAIN
SUPPLY 
MAIN
SUPPLY MAIN
VENT TO
ATMOSPHERE 
CLOSE TO 
UNIT (NOT ON 
VACUUM
SYSTEMS)
AIR FLOW
AIR FLOW
RETURN MAIN
RETURN MAIN
PITCHED IN CASING
STEAM COIL
STEAM COIL 
PITCHED IN CASING
12" MIN.
12" MIN.
SINGLE COIL
VERTICAL AIR FLOW
12" MIN.
12" MIN.
12" MIN.
COILS IN PARALLEL AIR 
FLOW MAY HAVE COMMON 
SUPPLY AND SINGLE TRAP 
(INDIVIDUAL COIL TRAP 
PREFERRED)
COILS IN SERIES AIR FLOW 
MUST HAVE INDIVIDUAL 
TRAPS AND CONTROL 
VALVES
RETURN MAIN
DIRT POCKET (FULL 
SIZE OF COIL CONN.)
F & T TRAP
VACCUM 
BREAKER 
1/2" CHECK 
VALVE
(OPTIONAL)
DIRT 
POCKET 
(FULL SIZE 
OF COIL 
CONN.)
VACUUM 
BRAKER 
1/2" CHECK 
VALVE
(OPTIONAL)
SYMBOLS FOR "SS" STEAM 
COIL PIPING ARRANGEMENTS
GATE VALVE
STRAINER
CONTROL VALVE 
(MODULATING OR 
TWO POSITION)
CHECK VALVE
FLOAT AND 
THERMOSTATIC 
TRAP