Daikin RDT Installation And Maintenance Manual page 36

Figure 37: Hot Water Heat Section (Shown with Factory
Valve and Piping)
Figure 38: Hot Water Valve Package
Steam Coil Piping
Steam coils are provided without valves for field piping, or
piped with two-way valves and actuator motors.
The steam heat coil is pitched at 1/8ʺ (3 mm) per foot (305
mm) to provide positive condensate removal. When no factory
piping or valve is included, the coil connections are 2.5ʺ male
NPT iron pipe.
With the factory piping and valve package, the field supply
connection is the same NPT size as the valve with female
threading (see Figure 40).
Refer to the certified drawings for the recommended piping
entrance locations. All piping penetrations must be sealed to
prevent air and water leakage.
NOTE: The valve actuator spring returns to a stem up
position upon power failure. This allows full flow
through the coil.
IM 893-10 • ROOFPAK SINGLEZONE UNITS
Figure 39: Steam Heat Section (Shown with Factory Valve
and Piping)
Steam Piping Recommendations
1. Be certain that adequate piping flexibility is provided.
Stresses resulting from expansion of closely coupled
piping and coil arrangement can cause serious damage.
2. Do not reduce pipe size at the coil return connection.
Carry return connection size through the dirt pocket,
making the reduction at the branch leading to the trap.
3. Install vacuum breakers on all applications to prevent
retaining condensate in the coil. Generally, the vacuum
breaker is to be connected between the coil inlet and the
return main. However, if the system has a flooded return
main, the vacuum breaker to the atmosphere; the trap
design should allow venting of the large quantities of air.
4. Do not drain steam mains or takeoffs through coils. Drain
mains ahead of coils through a steam trap to the return
line.
5. Do not attempt to lift condensate.
6. Pitch all supply and return steam piping down a minimum
of 1ʺ (25 mm) per 10 feet (3 m) of direction of flow.
Steam Trap Recommendations
1. Size traps in accordance with manufacturers'
recommendations. Be certain that the required pressure
differential will always be available. Do not undersize.
2. Float and thermostatic or bucket traps are recommended
for low pressure steam. Use bucket traps on systems
with onoff control only.
3. Locate traps at least 12ʺ (305 mm) below the coil return
connection.
4. Always install strainers as close as possible to the inlet
side of the trap.
5. A single tap may generally be used for coils piped in
parallel, but an individual trap for each coil is preferred.
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