Cooling System; Leveled Operation; Poor Cooling; Low Propane Pressure - Norcold 121X Series Service Manual

The cooling system is a sealed gas absorption
refrigeration system charged with R 707
refrigerant.

R 707 refrigerant contains
water, and hydrogen. The refrigerant also
contains sodium chromate, a corrosion
inhibitor.
Optimal cooling system efficiency requires
controlled heat application, sufficient air flow
to remove heat and for combustion air, and

leveled operation.

Leveled Operation
Cooling system efficiency is not affected when
the vehicle is in motion. When parked, off-level
operation should not exceed three (3) degrees
from side-to-side and/or six (6) degrees front-
to-back at the refrigerator.

Poor cooling

Poor cooling may be the result of one or a
combination of the following:
 Insufficient or obstructed ventilation.
 Low AC voltage.
 AC heater failure.
 Low propane pressure.
 Dirty burner.
 Fan failure
 Dirty flue.
 Blocked or jammed heat deflector cap.
 Operation over maximum off-level limits.
 Inadequate repairs.
 Unauthorized modifications.
s
ection
NOTE
anhydrous ammonia,
8 —c s
ooling
Insufficient or obstructed ventilation
Insufficient or obstructed ventilation reduces
cooling efficiency because the heat load
generated and dissipated by the system is not
efficiently removed.
To maintain cooling efficiency cooling air has
to flow freely over the external walls of the
absorber coils and over the condenser fins.
When ventilation is suspected of being the
cause of poor cooling, make sure that:
 Air intake vent and exhaust vent are clear.
 Vents have are not covered with insect
screen, plastic sheeting, leaves or a birds
nest.
 Loose insulation is not blocking air flow
over the condenser or absorber or the flue
opening.
 Both fans are working.
 DC voltage is 10.5 VDC or higher.
Low AC voltage
Two 225 Watt AC heaters generate the heat
load required to turn liquid ammonia into
vapor. To accomplish this task voltage has to
be maintained between 108 and 132 volts..
AC heater failure
One AC heater failure causes the system to
operate at half the heat input required. The
heat output of one heater is insufficient to
generate the ammonia vapor required.

Low propane pressure

Propane pressure of 10.5 to 11.5 in. w. c. is
needed to generate the required heat output
required for proper gas mode operation.
Dirty burner
A dirty burner affects the heat output. Under
normal conditions the burner and flue need to
be checked and cleaned annually.
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ection