28
McQuay IM 987
Mechanical Installation
Phase III. Reconnect power and control wiring
Once the sections are physically reconnected, the ends of the
power harness are fed back through the unit base into the
junction box, per the unit’s electrical schematics.
1
Make electrical connections and reinstall inner raceway
cover as shown in
Figure 32
.
Figure 32: Electrical Connections and Raceway Cover
Installation
2
When power wire reconnection is complete, reinstall the
inner raceway cover in the blank or heat section.
Figure 32
shows a typical installation of the raceway
cover.
3
Run the control harnesses by removing the external
raceway covers on either side of the unit split.
4
Remove the excess harness length from the external
raceway on the downstream side of the split; then route
along the raceway, through the bushed hole in the fan
section and into the junction box where control wiring
terminal blocks are provided for reconnection.
5
Make all electrical connections per the unit’s electrical
schematics.
6
Reinstall the external raceway covers after routing of the
control wires is complete.
Field Refrigerant Piping and Charging of DX Coils
Units that ship from the factory with DX coils installed do not
include refrigerant piping or refrigerant controls. The coil
assembly is ready for field connections at the distributors and
at the suction headers. Piping kits that provide the necessary
liquid and hot gas piping and control components are available
for field installation. Field-installed refrigerant piping may exit
the unit cabinet at one of the following locations:
•
Through the floor of the unit.
•
Through the discharge and bulkhead of the unit.
•
Through a cabinet door near the DX coil that is not required
for service areas.
In preparing for field piping, remove the plastic plugs on the
distributors and unsweat the copper caps at the suction header
connections.
Follow piping design, sizing, and installation information
presented in ASHRAE handbooks in the design and
installation of interconnecting piping. The DX coil and
condensing unit are intended to be set at the same elevation, as
close as possible to each other to minimize refrigerant pressure
drop. Design piping to prevent liquid refrigerant carryover to
the compressor and to provide a continuous return of
compressor oil from the system.
CAUTION
Connect the power block correctly and maintain proper
phasing. Improper installation can cause severe equipment
damage.
If applicable, install as shown
with provided fasteners.
After routing wires,
install inner raceway
cover (see step 6).
3.72 ref.
(94 mm)
CAUTION
For any of the above cabinet penetrations, tightly seal the hole
to prevent water or air leakage.
CAUTION
The pounds of refrigerant in the system may exceed the
capacity of the condenser, depending on the amount of
refrigerant in the liquid lines between the DX coil and the
condensing unit.
Refer to condenser manufacturer for information about
refrigerant capacity. Suitable means of containing the
refrigerant is required.
CAUTION
To prevent liquid return and damage to the compressor on
systems with optional hot gas bypass, it is important to locate
the bypass solenoid valve at the condensing unit and not at the
DX coil.
