Cooling Unit; Description; Heat Absorption; Leveled Operation - Norcold N61X Service Manual

COOLING UNIT

Description

The cooling unit is a self-contained gravity flow
absorption refrigeration system. The refrigerant charge
is a solution of water, ammonia, sodium hydroxide,
and sodium chromate (a corrosion inhibitor).
Refrigeration is accomplished by applying heat energy
and venting the heat extracted from the freezer and
fresh food cabinet while maintaining the unit leveled.

Heat Absorption

The refrigerant transfers the heat from the freezer and
the food cabinet to the absorber coils. At the absorber
coils the metal surface absorbs the heat and air flow
over the external surfaces of the coils and carries
away the heat. A thermal air current created by the
rising hot air flows out of the enclosure through the
roof exhaust vent or sidewall exhaust vent (depending
on installation). The flowing air mass passes over the
surface of the condenser fins where it absorbs heat
transferred from the ammonia vapors flowing through
the condenser.
The thermal airflow process creates a "chimney
effect". The "chimney effect" creates a continuous
draft of cooling and combustion air. The fresh air
drafted by the "chimney effect" though the intake vent
removes rejected heat, support combustion, and
expels the exhaust gases produced by the combustion
process. Obstructions, restrictions, or modifications to
vents or the enclosure will affect the heat absorption
cycle. Poor cooling unit performance may be due to:
n
Loose insulation interfering with the ventilation
process.
n
Construction material or debris left in the
enclosure.
n
Insect screen covering vents.
n
Plastic sheeting covering vents.
n
Items stored in the enclosure.
n
Modifications to vents or enclosure.
n
No roof or sidewall exhaust vent opening.
Information pertaining to ventilation and enclosure
requirements appears on page 22.

Leveled Operation

The circulation of the refrigerant through the cooling
unit is accomplished by gravity flow; therefore, the
refrigerator must be operated leveled. Off-level
operation affects the flow of the refrigerant through the
cooling system. The maximum off-level operation limits
are:
n
3 degrees from side-to-side.
n
6 degrees from front-to-back.
Exceeding the maximum off-level limits can
permanently damage the cooling unit.
The cooling unit or its performance are not affected
when the vehicle is in motion
Refrigerator Service Manual

Gradual Decrease in Cooling Efficiency

A gradual decrease in cooling efficiency is not a clear
indication of cooling system failure. Other factors that
affect cooling efficiency include ventilation, the heat
input, off-level operation, lack of service and
maintenance, inadequate repairs, or unauthorized field
modifications. If any of these factors exist and are not
corrected, a replacement cooling unit will also perform
inefficiently or fail.
Step-by-step troubleshooting is the best approach
when dealing with a gradual decrease in cooling. It is
important to consider is that, though not efficiently, the
cooling unit is working. Troubleshooting should always
begin by checking ventilation, then thoroughly
checking the cooling unit, and heat sources. In the
majority of reported case, the problem has been
related to the installation, which in turn hindered
cooling unit ventilation.
Additionally, ambient air temperature plays a
significant role if the unit was not installed correctly.
Incorrect installation lead to poor ventilation, which in
turn relates to poor cooling performance.
The unit's service and maintenance history should be
considered when checking a cooling unit for poor
cooling performance. The service history and the
scope of service work performed may lead directly to
cause and resolution of a cooling problem.
The cooling unit has to reach normal operating
temperatures before troubleshooting can take place. It
takes an average of four hours for the refrigerant to
reach normal operating temperatures. The time frame
to reach operating temperatures depends on ambient
air temperature.

Cooling System Monitoring

The controls monitor cooling system performance
when a heat source is active. If the controls sense that
.
the system is not cooling, it displays a fault code ("n"/
"no" "co") and locks out all heat energy sources.

First "No Cooling" Fault Occurrence

Users can reset the controls by turning the refrigerator
off then back on. The user resetting option can only be
accomplished when the controls record the first "no
cooling" ("n"/"no" "co") fault occurrence. The
completion of a full cooling cycle will remove the
recorded first "n"/"no" "co" fault from memory and
returns the controls to normal monitoring operation.

Two Recorded "No Cooling" Fault Occurrences

If the controls detect two consecutive recorded "no
cooling" faults , the "n"/"no" "co" fault code displays
and the controls will lock out all heat sources (AC/LP/
DC). The power board can then only be reset by an
authorized service center after troubleshooting and
testing cooling system operation. See Page 21.
www.norcold.com/cda
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N6XX/N8XX Models