World Class RV Refrigeration Incorporated

Heating Elements

An often overlooked component on an rv refrigerator, and one that causes as many problems as anything else on the cooling system, is the 110 volt heating element. Too much heat, and you will ruin your cooling unit. Too little heat, and your cooling unit will not work.

A cooling unit is designed with a specific liquid capacity based on the physical size of the cooling unit itself. As such, different cooling units require a different wattage heating element to boil the ammonia...smaller units require less heat than larger units. If your heating element does not get hot enough, it will not boil the ammonia and the unit will not cool. If your heating element gets too hot, you will boil the unit dry and damage the coolant itself by separating the sodium chromate out of solution with the ammonia. This causes a blockage inside the unit.

A heating element is simply a ceramic filled stainless steel sleeve with 2 wires running through it that conducts electricity. This electricity causes the element to heat up. The amount of heat is controlled by varying the resistance of the electricity. This resistance is measured in ohms. If the ceramic inside the element becomes cracked or damaged, the element's resistance will vary.

The easiest way to test a heating element is to measure the ohms resistance with a digital test meter. Some of the more common ohms readings are below:

Dometic:

325 watt element...44 ohms +/- 10%

This is the most common Dometic element and is used on all 6 and 8 cubic foot Americana series ( RM2652, RM3662, RM2852, RM3862, etc.) refrigerators, and all RM2800 series refrigerators.

Norcold:

300 watt element...38 ohms +/- 10%.

This element is used on 90% of all double door Norcold refrigerators.

If you are unsure or want more information on your particular element, call us at 501-977-0833.

Sodium Chromate

The ammonia used in absorption refrigeration is almost 70% water. As such, if left untreated inside the steel tubes of a cooling unit, it can rust the unit from the inside out. To prevent this, we add sodium chromate to the cooling unit to act as a corrosion inhibitor.

Sodium chromate is a yellow powder that dissolves when mixed with the ammonia. It stays dissolved unless the boiler assembly overheats, either by running the unit out of level or by a faulty heating element. When the boiler overheats, sodium chromate forms crystals (almost like small pebbles) that will circulate inside the unit and block the internal perk tubes. This causes the cooling unit to stop functioning. Once this happens, the sodium chromate will not dissolve back into the ammonia...the cooling unit is ruined.

This is why it is important to level your refrigerator and provide periodic preventative maintenance on the heating element(s).

Sodium chromate crystals

DOMETIC

OR

NORCOLD

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1-501-977-0833