There are two basic types of refrigerator
: Absorption (Gas or Electric
heated) and Compression
(Mechanical or Electric
I don’t recommend propane-powered refrigerators on boats.
Absorption refrigerators operate on a heat cycle, normally powered by gas (LPG) burner. A flame or heat element powers the heating
cycle, which creates the cooling affect.
As indicated, absorption fridges must be kept level
. Different models have different requirements, but in general, 3 - 6 degrees of tilt (in BOTH pitch
& roll axis*) is the maximum. A simple gimbal will only level the fridge on one axis.
* Some manufacturers specify 3 deg.of roll (sideways) & 6 deg. (front to back) of Fridge pitch
(if oriented bow to stern in the boat).
The combustion products from most propane
refrigerators are discharged inside of the cabin
. If the burner is not adjusted properly, it can produce deadly carbon monoxide (CO) emissions. Propane-fueled refrigerators must be equipped with a fuel
solenoid (operated by a CO detector). Propane
fridges require an adequate supply of combustion air.
Compressor refrigerators will work effectively above 50 deg C ambient, and at all temperatures will pull the fridge temperature down more quickly than absorption fridges, which are generally limited to maximum ambient temperatures of about 40 deg C.
The cycle works like this:
The gas absorption refrigerator cools by evaporating liquid ammonia in a hydrogen environment
. The gaseous ammonia is then absorbed (dissolved) into water
, and then later separated (boiled off from the water) by a small source of heat. This drives off the dissolved ammonia gas which is then condensed into a liquid. The liquid ammonia then enters the hydrogen-charged evaporator to repeat the cycle.
1. Heat is applied to the generator
. The heat comes from burning something like liweuid propane gas, or kerosene.
2. In the generator
is a solution of ammonia and water
. The heat raises the temperature of the solution to the boiling point of the ammonia.
3. The boiling solution flows to the separator. In the separator, the water separates from the ammonia gas.
4. The ammonia gas flows upward to the condenser. The condenser is composed of metal coils and fins that allow the ammonia gas to dissipate its heat and condensed into a liquid.
5. The liquid ammonia makes its way to the evaporator, where it mixes with hydrogen gas and evaporates, producing cold temperatures inside the refrigerator.
6. The ammonia and hydrogen gases flow (by gravity) to the absorber. Here, the water that has collected in the separator is mixed with the ammonia and hydrogen gases.
7. The ammonia forms a solution with the water and releases the hydrogen gas, which flows back to the evaporator. The ammonia-and-water solution flows toward the generator to repeat the cycle.
How Propane Fridges Work: