Dometic DM2652 Refrigerator overview, Absorption cooling system, Leveling the refrigerator

refrigerator overview

Absorption cooling system

In an absorption refrigerator system, ammonia is liquefied in the finned condenser coil at the top rear of the refrigerator. The liquid ammonia then flows into the evaporator (inside the freezer section) and is exposed to a circulating flow of hydro- gen gas, which causes the ammonia to evaporate, creating a cold condition in the freezer.

When starting this refrigerator for the very first time, the cooling cycle may require up to four hours of running time before the cooling unit is fully operational.

The tubing in the evaporator section is specifically sloped to provide a continuous movement of liquid ammonia, flowing downward by gravity through this section.

Sodium chromate is used for corrosion protection (less than 2 weight % of the coolant).

Leveling the refrigerator

Leveling is one of the requirements for proper operation with absorption refrigerators. to ensure proper leveling the vehicle needs to be leveled only so it is comfortable to live in (no no- ticeable sloping of floor or walls).

Any time the vehicle is parked for several hours with the refrig- erator operating, the vehicle should be leveled to prevent this loss of cooling.

If the refrigerator is operated when it is not level and the vehicle is not moving, liquid ammonia will accumulate in sec- tions of the evaporator tubing. This will slow the circulation of hydrogen and ammonia gas, or in severe cases, completely block it, resulting in a loss of cooling.

When the vehicle is moving, the leveling is not critical, as the rolling and pitching movement of the vehicle will pass to either side of level, keeping the liquid ammonia from accumulating in the evaporator tubing.

automatic energy selector system

The refrigerator is equipped with an automatic energy selector system. The user turns the refrigerator on and then, the refriger- ator automatically selects the most suitable energy source avail- able, either 120 V AC or LP gas operation. The system can be set by the user to be fully automatic (AUTO mode is selected) or to operate on LP gas only (AUTO mode is off).

On 3-way models, the control system can manually be set to DC mode (DC operation). The DC mode overrides all other operating modes.

The refrigerator controls will work down to 9.6 V DC.

Modes of operation

AUTO mode - AES/AUTO mode

When operating in AUTO - AES/AUTO mode, the AUTO - AES/AUTO mode indicator lamp is illuminated. The control sys- tem will automatically select between AC and GAS operation. AC has priority over GAS. Should AC become unavailable, the system automatically switches to GAS. As soon as AC becomes available again, the control will switch back to AC regardless of the status of the GAS operation.

If the CHECK indicator lamp is illuminated the controls have failed to ignite the burner in the GAS mode. To restart an igni- tion attempt with the CHECK lamp illuminated (or to turn off the CHECK lamp), press the ON/OFF button OFF and back ON again. The control system activates the ignition system and makes three attempts to light the burner for a period of approx. 45 sec. at two minutes interval. Should 120 V AC become available while the CHECK indicator lamp is on, the CHECK lamp will not turn off until the ON/OFF button is pressed OFF and then ON again.

GAS mode

The GAS mode indictor lamp is illuminated. This mode pro- vides LP gas only. The control system activates the ignition system and attempts to light the burner for a period of approx. 45 sec. at two minutes interval. If unsuccessful, the CHECK indicator lamp will illuminate.

To restart GAS operation, press the ON/OFF button to OFF and then back ON. The control system attempts a new ignition sequence.

Purging air from the lines

If the refrigerator has not been used for a long time - or -

the LP tanks have just been refilled, air may be trapped in the supply lines. To purge the air from the lines, turn the refrigera- tor off and on by pressing the ON/OFF button. If the flame is not lit within 45 seconds, turn the refrigerator off and back on again. This procedure can be repeated 3 to 4 times. If repeated attempts fail to start the LP gas operation, check to make sure that the LP gas supply tanks are not empty and that all manual shutoff valves in the lines are open.

! WARNING

FIRE OR EXPLOSION HAZARD. When refu- eling or parked near gasoline pumps, shut off all LP gas appliances. Failure to heed this warning could cause a fire or explosion resulting in death or severe personal injury.

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