2.7.2
Coils
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NOTE: Research local conditions to determine the
effect of corrosive atmosphere on dissimilar metals.
Where condenser or evaporator coils are to be
installed in corrosive atmospheres, rewrite the
specification for coils and fins for these specific
conditions. Consider the following coil and fin
combinations based on past experience with the
suitability of these materials in dealing with the
local conditions.
a.
Copper coil and aluminum fins, coated.
b.
Copper coil and copper fins, coated.
c.
Aluminum coil and aluminum fins, coated.
d.
Aluminum coil and aluminum fins, uncoated.
e.
Copper coil and copper fins, uncoated.
Coating may be either phenolic, vinyl or
epoxy[slsh]electrodeposition. For coils with
relatively close fin spacing such as those found in
most unitary equipment, the phenolic or
epoxy[slsh]electrodeposition coating is preferred,
as these have less tendency to bridge across the
fins than vinyl, better thermal conductivity than
vinyl and in many conditions weathers better than
vinyl.
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Coils shall be fin-and-tube type constructed of seamless [copper] [red
brass] tubes and [aluminum] [or] [copper] fins mechanically bonded or
soldered to the tubes. [Copper tube wall thickness shall be a minimum of
[0.406] [0.508] [0.6096] mm [0.016] [0.020] [0.024] inches]. [Red brass
tube wall thickness shall be a minimum of [0.89] [1.24] mm [0.035] [0.049]
inches]. [Aluminum fins shall be [0.14] [0.19] mm [0.0055] [0.0075] inch
minimum thickness.] [Copper fins shall be 0.114 mm 0.0045 inch minimum
thickness.] Casing and tube support sheets 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.
Each coil shall be tested at the factory under water at not less than 2.76
MPa 400 psi air pressure and shall be suitable for 1.38 MPa 200 psi working
pressure. Mount coils for counterflow service. Coils shall be rated and
certified and meet the requirements of ARI 410.
2.7.2.1
Direct-Expansion Coils
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NOTE: Use this paragraph for Army and Air Force
projects only.
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Direct-expansion coils shall be suitable for the refrigerant involved.
Refrigerant piping shall conform to ASTM B 280 and shall be cleaned,
dehydrated and sealed. Suction headers shall be seamless copper tubing or
SECTION 15895
Page 31
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