Water And Steam Coil Piping Recommendations; Mixing Box/Filter Mixing Box, Sizes 32-92 - Carrier 39T Installation, Start-Up And Service Instructions Manual

Water and Steam Coil Piping
Recommendations
GENERAL — Use straps around the coil casing or the lift-
ing holes (see Fig. 41) to lift and place the coil.
To prevent damage to the coil or coil headers: Do not
use the headers to lift the coil. Support the piping and
coil connections independently. Do not use the coil con-
nections to support piping. When tightening coil con-
nections, use a backup wrench on the nozzles.
Piping practices are outlined in the Carrier System De-
sign Manual, Part 3, Piping Design.
WATER COILS — Pipe all water coils for counterflow by
connecting the inlet at the bottom and the outlet at the top.
See Fig. 41. This arrangement ensures that for chilled water
coils the coldest water meets the coldest air and that for hot
water coils the warmest water meets the warmest air.
STEAM COILS — Position the steam supply connection at
the top of the coil, and the return (condensate) connection at
the bottom. The coil tubes must incline downwards toward
the return header connection for condensate drainage. See
Fig. 42.
Following the piping diagram in Fig. 42, make all con-
nections while observing the following precautions:
• Install a drip line and trap on the pressure side of the inlet
control valve. Connect the drip line to the return line down-
stream of the return line trap.
Fig. 40 — Mixing Box/Filter Mixing Box, Sizes 32-92 —
Typical Damper Arrangement (Top and Bottom)
• To prevent scale or foreign matter from entering the con-
trol valve and coil, install a
steam supply line upstream from the control valve.
• Provide air vents for the coils to eliminate noncon-
densable gases.
• Select a control valve according to the steam load, not the
coil's supply connection size. Do not use an oversized con-
trol valve.
• Do not use bushings that reduce the size of the header re-
turn connection. The return connection should be the same
size as the return line and reduced only at the downstream
trap.
• To lift condensate above the coil return line into overhead
steam mains, or pressurized mains, install a pump and re-
ceiver between the condensate trap and the pressurized main.
Do not try to lift condensate with modulating or on-and-
off steam control valves.
• Use only 15-degree check valves, as they open with a lower
water head. Do not use 45-degree or vertical-lift check valves.
• Use float and thermostatic traps. Select the trap size ac-
cording to the pressure difference between the steam sup-
ply main and the return main.
• Load variations can be caused by uneven inlet air distri-
bution or temperature stratification.
• Drain condensate out of coils completely at the end of the
heating season to prevent the formation of acid.
48
3 ⁄ -in. mesh strainer in the
32