to provide structural strength. Tubes shall be correctly
circuited for proper water velocity without excessive pressure
drop and they shall be drainable where required or indicated. At
the factory, each coil shall be tested at not less than 1700 kPa
250 psi air pressure and shall be suitable for 1400 kPa 200 psi
working pressure. Install drainable coils in the air handling
units with a pitch of not less than 10 mm per m 1/8 inch per foot
of tube length toward the drain end. Coils shall conform to the
provisions of ARI 410.
b. Steam Coils: Steam coils shall be constructed of cast
semisteel, welded steel, or copper headers, red-brass or copper
tubes, and copper or aluminum fins mechanically bonded or soldered
to the tubes. Tubes shall be rolled and bushed, brazed or welded
into headers. Coil casings and tube support sheets, with collars
of ample width, shall be not lighter than 1.6 mm 16 gauge
galvanized steel formed to provide structural strength. When
required, multiple tube supports shall be provided to prevent tube
sag. The fin tube and header section shall float within the
casing to allow free expansion of tubing for coils subject to high
pressure steam service. Coils shall be factory pressure tested
and capable of withstanding 1700 kPa 250 psi hydrostatic test
pressure or 1400 kPa 250 psi air pressure, and shall be for [700]
[1400] kPa [100] [200] psi steam working pressure. Preheat coils
shall be steam-distribution tube type with condensing tubes having
not less than 15 mm 5/8 inch outside diameters. Distribution
tubes shall have not less than 10 mm 3/8 inch outside diameter,
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. The
maximum length of a single coil shall be limited to 120 times the
diameter of the outside tube. Other heating coils shall be single
tube type with not less than 13 mm 1/2 inch outside diameter.
Supply headers shall distribute steam evenly to all tubes at the
indicated steam pressure. Coils shall conform to the provisions
of ARI 410.
c. Electric Resistance Heaters: Electric resistance heaters
shall be of the duct-mounting type consisting of a nickel-chromium
resistor mounted on refractory material and a steel or aluminum
frame for attachment to ductwork. Electric duct heater shall meet
the requirement of Underwriters Laboratories and NFPA 70 and shall
be provided with a built-in or surface-mounted high-limit
thermostat. Interlock electric duct heaters electrically so that
they cannot be energized unless the fan is running.
2.9.4
Unit Ventilators
Unit ventilators shall include an enclosure, [galvanized casing,]
[cold-rolled steel casing with corrosion resistant coating,] coil assembly,
[resistance heating coil assembly,] [valve and piping package,] drain pan,
air filters, fan assembly, fan drive, motor, motor controller, dampers, and
damper operators. Sound power level shall be as indicated. Obtain sound
power level data or values for these units according to test procedures
based on ARI 350. Sound power values apply to units provided with factory
fabricated cabinet enclosures and standard grilles, when handling standard
flow for which the unit air capacity is rated. Secure each unit to the
building structure. Capacity of the unit ventilators shall be as
indicated. Unit ventilators shall be of the year-round classroom type with
SECTION 15895
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