Trane AM4A0A18S11SA Series, Installation, Operation And Maintenance Manual

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82 CLCH-SVX07C-EN
Coil Piping and Connections
NOTICE:
Vacuum Breaker Cracking Pressure!
The 1/2-inch NPT, 15 degree swing check valve vacuum breaker is recommended because other
vacuum breakers, such as spring-loaded ball-check breakers, have cracking pressures as high as
1.25 inches Hg (17 inches of water). Vacuum breakers with fitting sizes smaller than 1/2 inch NPT
are too small to relieve vacuum quick enough to ensure complete condensate drainage. Other
types of swing check valve vacuum breakers are acceptable if the fittings size is not smaller than
1/2-inch NPT and the cracking pressure is not larger than 0.25 inches Hg (3.4 inches of water).
Failure to follow these instructions could result in equipment damage.
To prevent coil damage, complete the following recommendations:
• Install a 1/2-inch NPT, 15 degree swing check valve vacuum breaker with cracking pressure of
0.25 inches Hg (3.4 inches water) or lower at the top of the coil. This vacuum breaker should be
installed as close to the coil as possible.
• For coil type NS, install the vacuum breaker in the unused condensate return tapping at the top
of the coil.
• Vent the vacuum breaker line to atmosphere or connect it into the return main at the discharge
side of the steam trap
Note: Vacuum breaker relief is mandatory when the coil is controlled by a modulating steam
supply or automatic two position (ON-OFF) steam supply valve. Vacuum breaker relief is
also recommended when face-and-bypass control is used.
NOTICE:
Coil Condensate!
Condensate must flow freely from the coil at all times to prevent coil damage from water
hammer, unequal thermal stresses, freeze-up and/or corrosion. In all steam coil installations, the
condensate return connections must be at the low point of the coil. Failure to follow these
instructions could result in equipment damage.
Proper steam trap installation is necessary for satisfactory coil performance and service life. For
steam trap installation:
1. Install the steam trap discharge 12 inches below the condensate return connection. Twelve
inches provides sufficient hydrostatic head pressure to overcome trap losses and ensures
complete condensate removal.
a. Use float and thermostatic traps with atmospheric pressure gravity condensate return, with
automatic controls, or where the possibility of low-pressure supply steam exists. (Float and
thermostatic traps are recommended because of gravity drain and continuous discharge
operation.)
b. Use bucket traps only when the supply steam is not modulated and is 25 psig or higher.
Note: Trane steam coils require a minimum of 2 psi of pressure to assure even heat distribution.
2. Trap each coil separately to prevent holding up condensate in one or more of the coils.
3. Install strainers as close as possible to the inlet side of the trap.
4. If installing coils in series airflow, control each coil bank independently with an automatic
steam-control valve. Size the traps for each coil using the capacity of the first coil in direction
of airflow.
5. Use a modulating valve that has linear flow characteristics to obtain gradual modulation of the
coil steam supply.
Note: Do not modulate systems with overhead or pressurized returns unless the condensate is
drained by gravity into a receiver, vented to atmosphere, and returned to the condensate
pump.