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.

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Fridge Trailers and Boxes

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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.

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.

How It Works -
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.
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 - Example

Large compartment, (2 cages wide), might carry chilled food at +3 deg. C. Small compartment, (1 cage wide), might carry frozen food at -25 deg. C.
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.

The Control Box

1. The Display Panel Shows the both the set point and the current box temperatures.
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. NB: Some fridges use '=' sign instead of 'Enter'.
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.
MAN. DEFROST There is automatic defrost every three hours. This button starts the process manually: Takes about 11 minutes.	BUZZER OFF Shut Up button.	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.

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.