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Inspecting the Air Distribution System
• Is there unobstructed airflow from the return air grill to the
coil?
• Is there a lint screen or filter in the return air path where it
is accessible for regular cleaning?
• Have flexible ducts been pulled tight to remove bends and
constrictions?
• Are grills correctly sized for the system?
Inspecting the Control and Electrical Wiring
• Is the thermostat sensor or thermistor properly located
and secured in the return air path and not in direct contact
with any metal objects?
• Are all wiring harnesses properly secured?
• Are wiring connections made, color-to-color, correctly at
terminal strips?
• Are all components properly grounded and bonded?
• Are proper sized circuit breakers installed?
• Are terminal strips located in a dry, safe place and
properly covered?
Charging the System with Refrigerant
Special considerations when charging the
Modulating system
All cooling units must be turned on and running (solenoid
valve open) in the cool mode before evacuating the system
or adjusting the refrigerant charge. To ensure that all
evaporators are on in the cooling mode, and the solenoid
valves are open, set each cabin control's set point down to
the lowest temperature setting. There is no need for the
compressor to run while evacuating the system, so turn the
condensing unit's circuit breaker off before turning the
cooling units on.
The modulating unit is different from a standard DX condens-
ing unit in that it has two special refrigerant valves that allow
partial loads to run safely: the hot gas bypass valve and the
"de-superheat" valve. These valves are factory set and do
not require any field adjustment. Any field adjustments could
cause the valves to operate incorrectly, causing damage to
the compressor or compromising the performance of the
system.
As cooling units in the system shut down, the suction
pressure at the modulating condensing unit will drop. The hot
gas bypass valve senses the suction pressure and will open
to allow discharge gas to flow into the accumulator if the
suction pressure drops below 55 psi. This will raise the
suction pressure and prevent liquid refrigerant from reaching
the compressor.
L-0952 Installation
As more hot (high-pressure) gas is dumped into the suction
line (due to cooling units shutting down), the superheat
(suction gas temperature going into the compressor) can rise
to unsafe levels. A thermal expansion (TX) valve is installed
which acts as a "de-superheat" valve. It senses the super-
heat and will flash liquid refrigerant into the accumulator to
cool the suction gas.
This process automatically balances the system as the load
from the evaporators changes. This is why it is important to
have all cooling units on and operating while charging the
system. If one or two are off line, it will cause the refrigerant
circuit to alter and make it impossible to correctly charge the
system.
The following instructions should be followed in evacuating
and charging a Cruisair modulating condensing system with
R-22. Some special-order units may contain refrigerant other
than R-22. Please follow the special charging procedures
included with the unit.
Notice
US federal law prohibits the intentional release of refrigerant
gases into the environment, including the R-22 refrigerant
used in most Cruisair systems. Special care must be taken
when installing, charging, and servicing Cruisair equipment
to prevent any loss of refrigerant. Only EPA certified techni-
cians with the proper equipment should perform service on
the refrigerant circuit.
Initial Charging, New System
There are three refrigerant circuit components in a Cruisair
Modulating System: the condensing unit, the cooling/heating
unit (evaporator) and the copper refrigerant line-sets. The
condensing unit is shipped from the factory charged with
refrigerant gas.
It will be necessary to properly evacuate the cooling units
and line-sets before releasing the refrigerant from the
condensing unit into the system. To facilitate this evacuation
procedure, there is a special vacuum port (aka: purge port,
access port, evacuation port or service port) located on the
condensing unit's discharge base valve. This vacuum port
has a red cap and a schrader valve, and is located at the
2:00 position on the base valve.
Required tools to charge a modulating system:
1. R-22 container (typically the disposable-type container
color-coded green for R-22).
2. Gauge manifold with self-closing fittings on the charging
hoses.
3. Vacuum pump.
4. Base valve wrench and hand tools.
14
English
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