Installation manual

34 McQuay IM 487-4
Introduction
Steam Coil Freeze Conditions
If the air entering the steam coil is below 35°F (2°C), note the
following recommendations:
1 Supply 5 psi (34.5 kPa) steam to coils at all times.
2 Modulating valves are not recommended. Control should
be by means of face and bypass dampers.
3 As additional protection against freeze-up, install the tap
sufficiently far below the coil to provide an adequate
hydrostatic head to ensure removal of condensate during an
interruption on the steam pressure. Estimate 3 ft. (914 mm)
for each 1 psi (7 kPa) of trap differential required.
4 If the unit is to be operated in environments with possible
freezing temperatures, an optional freezestat is
recommended. See “Freeze Protection” on page 85 for
additional information.
Figure 38. Valve assembly
Figure 39. Steam valve package
Chilled Water Piping
Chilled water coils are provided without valves for field
piping, or piped with three-way valves with motor actuators.
Table 11 provides information on units with factory installed
piping and valve packages. The table also provides field sweat
connection information for units not furnished with factory
installed piping and valve packages.
With the factory piping and valve package, the coil assembly is
controlled through a single three-way valve. When two coils
are included in the assembly, they are piped in parallel. Field
connections are male NPT, sized as shown in Table 11. Refer
to Figure 40 for a typical cooling coil with factory valve and
piping.
Figure 40. Chilled water coil (shown with factory valve and
piping
S t e m
S e t s c r e w s
S t e m C l i p
R e t u r n
S u p p l y
Air Flow
Bypass
Supply
Return