seamless or resistance welded steel tube with copper connections. Supply
headers shall consist of a distributor that shall distribute the
refrigerant through seamless copper tubing equally to all circuits in the
coil. Tubes shall be circuited to ensure minimum pressure drop and maximum
heat transfer. Circuiting shall permit refrigerant flow from inlet to
suction outlet without causing oil slugging or restricting refrigerant flow
in coil. Each coil to be field installed shall be completely dehydrated
and sealed at the factory upon completion of pressure tests.
2.7.2.2
Water Coils
Install water coils with a pitch of not less than 10 mm/m 1/8 inch/foot of
the tube length toward the drain end. Use headers constructed of cast
iron, welded steel or copper. Furnish each coil with a plugged vent and
drain connection extending through the unit casing. Water coils shall be
removable and have drain pans.
2.7.2.3
Steam Heating Coils
Construct steam coils from cast semisteel, welded steel or copper headers,
and [red brass] [copper] tubes. Construct headers from cast iron, welded
steel or copper. Fin tube and header section shall float within the casing
to allow free expansion of tubing for coils subject to high pressure steam
service. Provide each coil with a field or factory installed vacuum
breaker. Coils shall be single-tube type with tubes not less than 13 mm
1/2 inch outside diameter, except for steam preheat coils. Supply headers
shall distribute steam evenly to all tubes at the indicated steam pressure.
Coils shall be factory tested to ensure that, when supplied with a uniform
face velocity, temperature across the leaving side will be uniform with a
maximum variation of no more than 5 percent.
2.7.2.4
Steam Preheat (Nonfreeze) Coils
Steam (nonfreeze) coils shall be steam-distribution-tube type with
condensing tubes not less than 25 mm 1 inch outside diameter for tube
lengths 1.5 m 60 inches and over and 13 mm 1/2 inch outside diameter for
tube lengths under 1.5 m 60 inches. Construct headers from cast iron,
welded steel, or copper. Distribution tubes shall be not less than 15 mm
5/8 inch outside diameter for tube lengths 1.5 m 60 inches and over and 10
mm 3/8 inch outside diameter for tube lengths under 1.5 m 60 inches with
orifices to discharge steam to condensing tubes. Distribution tubes shall
be installed concentric inside of condensing tubes and shall be held
securely in alignment. Maximum length of a single coil shall be limited to
3.66 m 144 inches. Coils shall be factory tested to ensure that, when
supplied with a uniform face velocity, temperature across the leaving side
will be uniform with a maximum variation of no more than 5 percent.
2.7.2.5
Electric Heating Coil
**************************************************************************
NOTE: Use this paragraph for Navy projects only.
Choose the second set of brackets if an
air-conditioning unit for EDP is specified.
**************************************************************************
Coil shall be an electric duct heater in accordance with UL 1995 and NFPA 70.
Coil shall be duct- or unit-mounted. Coil shall be of the [nickel
chromium resistor, single stage, strip] [nickel chromium resistor, single
stage, strip or stainless steel, fin tubular] type. Coil shall be provided
SECTION 15895
Page 32
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