www.DaikinApplied.com 49 IM 1287-6 • REBEL APPLIED ROOFTOP
Steam Piping Recommendations
1. Be certain that adequate piping exibility 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 ooded 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 takeos 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 ow.
Steam Trap Recommendations
1. Size traps in accordance with manufacturers’
recommendations. Be certain that the required pressure
dierential 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 ON/OFF 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.
Steam Coil Freeze Conditions
If the air entering the steam coil is below 35°F (2°C), note the
following recommendations:
1. Supply 5 psi (34.5 kPa) steam to coils at all times.
2. Modulating valves are not recommended. Control should
be by means of face and bypass dampers.
3. As additional protection against freeze-up, install the
tap suciently far below the coil to provide an adequate
hydrostatic head to ensure removal of condensate during
an interruption on the steam pressure. Estimate 3 ft. (914
mm) for each 1 psi (7 kPa) of trap dierential required.
4. If the unit is to be operated in environments with
possible freezing temperatures, an optional freezestat is
recommended.
Chilled Water
CAUTION
Coil freeze possible when the ambient temperature is below 35°F and can
result in poor equipment operation or damage to the equipment. Follow
instructions for mixing antifreeze solution used. Some products have
higher freezing points in their natural state than when mixed with water.
The freezing of coils is not the responsibility of Daikin Applied.
Cold water coils are not normally recommended for use with
entering air temperatures below 35°F (1.6°C). No control
system can guarantee a 100% safeguard against coil freeze-
up. Glycol solutions or brines are the only freeze-safe media
for operation of water coils at low entering air temperature
conditions.
NOTE: All coils have vents and drains factory installed.
Cold water coils are provided without valves as a standard
unit, requiring eld installation of valves and piping. As an
option, the cold water coil is supplied with either a two-way or
three-way valve and actuator motor from the factory. Refer to
the submittal drawings to determine unit conguration. The
submittal drawing will also have information about the line size
connections.
NOTE: All eld installed piping should be insulated to prevent
condensation from dripping into the cabinet.
NOTE: Factory-installed water valves and piping are bronze,
brass, and copper. Dissimilar metals within the
plumbing system can cause galvanic corrosion. To
avoid corrosion, provide proper dielectric ttings as
well as appropriate water treatment when making
a connection to a pipe that is not copper, bronze or
brass.
A factory provided oor knockout location is provided on every
unit equipped with a cold water coil. Refer to the certied
drawings for the recommended piping entrance locations. Seal
all piping penetrations to prevent air and water leakage.
Table 6 shows the connection piping sizes based on the coil
selection. Valve package connections will require a straight
pipe connection and connections to the header pipe will require
a coupling.
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