McQuay RAH 047C Installation And Maintenance Manual page 32

Mechanical Installation
Piping for Steam, Hot Water/ChIlled Water Coils
Factory-installed chilled water coils are installed in a coil
section that can be designed to accept a factory-installed
heating coil immediately upstream. The coil section can be
ordered in either the draw-through or blow-through position.
All chilled water piping can be done internal to the unit
without requiring a piping vestibule (except on sizes 800–802
when heating coils are included in the cooling coil section).
Steam and hot water coils can be factory installed in either a
heat section, or in the combination coil section. These sections
can be located either in the draw-through or blow-through
position. When a steam or hot water coil is installed in the heat
section, all piping can be done internal to the unit without
requiring a piping vestibule. Refer to
Figure 37, page 34
When a steam or hot water coil is installed in the combination
coil section, the coil connections project to the inside surface
of the door panel. Holes can be cut in the door panels to
connect the piping to the coils, or an accessory piping
vestibule can be added to the unit to provide piping space.
Refer to the section on vestibule assembly instructions. The
piping can then be routed back within the unit as shown in
Figure 35, page 33.
To avoid piping penetrations through the roof external to the
curb, holes can be cut through the floor of the unit at the
locations specified on the certified drawings.
Seal all holes in the unit floor to prevent water leakage into the
building.
Hot Water Piping
Hot water coils are provided without valves for field piping or
piped with three-way valves and actuator motors.With the
factory piping and valve package, the two coils are piped in
parallel and controlled through a single three-way valve. Field
piping connections are of the same NPT size as the valve-male
threads at the supply connection, female threads at the return
connection.
Hot water coils are not normally recommended for use with
entering air temperatures below 40°F (4°C). No control system
can guarantee a 100% safeguard against coil freeze-up. Glycol
solutions or brines are the only freeze-safe media for operation
of water coils at low entering air temperature conditions. Refer
to the "Maintenance" section of this manual for more on
winterizing coils. The hot water section consists of two
stacked soils, as shown in Figure 34.
32
Figure 35, page 33
CAUTION
When no factory piping or valve is included, the coil
connections are 1.625" ODM copper on 800 and 802C, and
2.125" ODM copper on 047 and 077C.
With the factory piping and valve package, the two coils are
piped in parallel and controlled through a single three-way
valve. Field piping connections are of the same NPT size as
the valve-male threads at the supply connection, female
threads at the return connection.
Figure 34: Hot Water Heat Section (Shown with Factory
Valve and Piping)
and
Lower
Coil
Bypass
The valve actuator spring returns to a stem up position upon
power failure. This allows full flow through the coil.
Refer to the certified drawings for the recommended piping
entrance locations. Seal all piping penetrations to prevent air
and water leakage.
Note: Factory-installed water valves and piping are bronze,
brass, and copper. Dissimilar metals within the plumbing
system can cause galvanic corrosion. To avoid
corrosion, provide proper di-electric fittings as well as
appropriate water treatment.
Coil freeze possible. Can damage equipment.
Follow instructions for mixing antifreeze solution used. Some
products have higher freezing points in their natural state than
when mixed with water. The freezing of coils is not the
responsibility of McQuay International. Refer to
Water Coils"‚ page
2.12 " ODM
Upper
Copper Coil
Coil
Connections
Air Flow
Supply
CAUTION
111.
"Winterizing
McQuay IM 987