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Steam Coils
Piping
(see
Figure 33 on page
19)
• All steam coils in units are pitched toward return
connection.
• Steam supply and steam return connections typically are
male NPT iron pipe and are labeled on the end panel of
coil section. Connections extend through the coil section
end panel.
• When installing couplings, do not apply undue stress
to the connection extending through unit panel. Use a
backup pipe wrench to avoid breaking the weld between
coil connection and header.
• Support piping independently of coils and provide
adequate piping flexibility. Stresses resulting from
expansion of closely coupled piping can cause serious
damage.
• 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.
Coils
• Install vacuum breakers on all application to prevent
retaining condensate in the coil. Generally, the vacuum
breaker is connected between the coil inlet and the
return main. The vacuum breaker should be open to the
atmosphere, and the trap design should allow venting of
large quantities of air.
• Do not drip supply mains through the coil.
• Do not attempt to lift condensate when using modulating
or ON/OFF control.
Traps
• Size traps in accordance with the manufacturers'
recommendations. Make sure that the required pressure
differential is always available. Do not undersize.
• Use float and thermostatic or bucket traps for low
pressure steam. On high pressure steam, use bucket
traps. Use thermostatic traps only for air venting.
• Use bucket traps for ON/OFF control only.
• Locate traps at least 12 inches below the coil return
connection.
• Multiple coil installation:
• Individually trap each coil or group of coils that is
controlled individually trapped.
• Coils in series—use separate traps for each coil, or bank
of coils.
• Coils in parallel—a single trap can be used, but an
individual trap for each coil is preferred.
• Do not attempt to lift condensate when using modulating
or ON/OFF control.
• With coils arranged for series airflow, use a separate
control on each bank or coil in the direction of airflow.
www.DaikinApplied.com
Valves
• Do not use modulating steam valves on high pressure
systems.
• Properly size modulating valves. Do not undersize.
• Freezing conditions (entering air temperatures below
35°F).
— Daikin Applied strongly recommends 5JA, 8JA, 5RA
and 8RA coils.
— Supply 5 psi steam to coils at all times.
• Do not use modulating valves. Provide control by face
and bypass dampers:
— Consider using two or three coils in series with two
position steam control valves on the coil or coils that
handle 35°F or colder air. Use a modulating valve on
the downstream coil to provide the desired degree of
control.
— Thoroughly mix fresh air and return air before it enters
the coil. Also, to obtain true air mixture temperatures,
properly locate temperature control elements.
— For additional protection against freeze-up, install the
trap sufficiently below the coil to provide an adequate
hydrostatic head to remove condensate during an
interruption in the steam pressure. Estimate three feet
for each 1 psi of trap differential required.
— On startup, admit steam to coil ten minutes before
admitting outdoor air.
— Close fresh air dampers if steam supply pressure falls
below the minimum specified.
17
Installation Guidelines
IM 915-13 • VISION - EXTENDED SIZES
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