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Transport fridges, (as used on trailers and rigids), a basic guide.
If you have
had no, or little experience, with fridges, then this simple fridge
tutorial may be of use to you.
This outline is limited to one type of popular Control Panel as used on many fridge trailers and rigid box vans.
Feedback about other types, advice on operation, etc., for inclusion on this page, would be welcome:
Contact
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Fridges are controlled by
a Control Panel.
On trailers, this is fitted to the front of the fridge housing.
On rigids, it may be in the cab.
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How It Works
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Simple explanation of the Fridge Control Cycle. |
FUEL: Fridge units
use a separate fuel tank, and run on gas oil, (red diesel). |
Most fridge trailers, or rigid box fridges, are just
one large compartment with the fridge unit fitted to the front.
The simplest way to provide additional compartments is by using a tight
fitting insulating partition, or buffer, which can be moved forwards, or
backwards, in the trailer, as required.
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One should be aware, however, that trailers,
and rigids, are often constructed with partitions running front to
back, forming two or three compartments.
Compartments can be set to run at different temperatures: This is achieved
by the use of separate evaporators for each compartment. You will see these
fitted at the front of each compartment. |
| Hardware - Interior
of a 2 compartment box |
Large compartment, (2 cages wide), carries chilled
food at c +3 deg. C.
Small compartment, (1 cage wide), carries frozen food at c -25 deg.
C.
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| Loading / Unloading |
Protective
gloves must always be worn when handling cages.
These are essential in the frozen compartment. |
| Touching
metal cages, at -25 deg. C., with your bare hands will cause
pain and injury. |
| NEVER touch
the evaporator. |
| Buffer |
When the frozen compartment is fully loaded,
a thick flexible insulating pad, (buffer), is secured against
the last cage.
NB: The buffer should not
be placed nearer than 10' from the front of the
compartment, (restricts airflow).
Cage retaining bars should be fitted before the buffer is pushed
in. |
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| The Control Box |
1. The Display Panel
Shows the both the set point and the current box temperatures. |
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| 2. The Main ON/OFF Switch |
3. The Compartment
Switches
If the control box does not have these switches, then it is a single
compartment box.
In a two compartment box, only the first two switches are used. |
Fascia Cover
Hides set point buttons.
Lift to change set point. |
Set Point Buttons
These will alter the set point: You will see it change on the Display
Panel.
To SAVE any changes, press 'Enter' button. |
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CITY
SPEED
Press once to reduce fridge motor noise when running in town or
city.
You MUST remember to press again when you leave the town/city.
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MAN. DEFROST
There is automatic defrost every three hours.
This button starts the process manually: Takes about 11 minutes. |
BUZZER
OFF
Shut Up button.
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ALARM
Fault data displayed on Display Panel. |
UNIT DATA
Press twice to retrieve engine running data, etc. |
Continuous
Running.
You may encounter this where a company has lost produce because a
fridge failed to restart.
They may require you to set the mode to 'Continuous Running'. |
AUTO
START/STOP
Normal Stop/Start Mode.
Press twice to change to Continuous Running. |
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Chill Down
With the frozen compartments in particular, you may need to chill down
before loading can start.
You may, for instance, need to start the fridge whilst on route to the
loading point.
The time needed to chill down, is directly affected by the outside temperature.
On hot summer days, you will need much longer than on cold winter days. |
| How it works.. |
Temperature control works around the Set
Point: This is the temperature the box or compartment is
set to run at.
The fridge may be switched on, but the cooling action itself is only
switched on and off when compartment temperature deviates too much
from the set point, (usually activated at plus or minus 2 deg. C
from the set point).
You will hear the diesel engine, (which drives the pump* that circulates
the coolant through the fridge system), start or stop running.
* Not technically correct, probably a compressor:
Compression and expansion are used in the refrigeration cycle. |
When the temperature in the compartment reaches 2 deg.s C. above
the set point, the fridge motor will start up.
The fridge is now running
and cooling the compartment.
When the compartment temperature drops to 2 deg. below the set point,
the fridge will stop running / cooling.
The fridge is still switched on, but
is not running / cooling. You should hear it stop.
The cycle continues until the fridge is switched off. |
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