RV Furnace Basics

Importance of Routine Maintenance

Your rv furnace may be the most tempermental appliance in your rv. The ignition system can perform flawlessly and then out of the blue it can totally fail. It can run quiet and purr like a well oiled machine and then start screeching and vibrating as though it's been possessed and wants "out" of your rv. Challenges for any rv, motorhome, or fifth wheel owner, and even greater challenge for the RV technician.

The solution? Simple periodic inspection of your rv furnace will go a long way in averting future problems. Just because your rv furnace runs and blows warm air doesn not mean some attention may be in order. The older the rv or motorhome is routine maintenance only becomes more important and if it is more than five years old your safety depends on it.

Warm beer from a poor cooling refrigerator will not kill you (its really true!) but an inadequately maintained furnace could. While there are, numerous safety features built into recreational vehicle furnaces their longevity and operating efficiency rest squarely on you, the rv owner.

Rv furnaces are referred to as forced draft furnaces and are different than the forced air furnaces in our homes in that the rv furnace untilizes a separate combustion air blower which provides a predetermined volume of air to the burner chamber to achieve ignition of the main burner. Once lit the flame is sustained by air supplied by the blower. Adequate return air then is crucial in order for the furnace to operate at proper temperature.


The above photo will give you an idea of where the furnace blowers are. This is a late model Atwood furnace (late model Suburban furnaces are of the same basic design)

The blowers are a squirrel cage design.

The main furnace blower sits behind the blower shroud on which the furnace data plate is attached. (The white square at upper left portion of photo) The furnace motor is also housed here. Slightly to the right is a narrow black vertical metal separator and to the right of it is a galvanized vertical metal strip. The combustion air blower (about l 1/2" wide)is housed directly behind this.

The motor has a shaft running through the center of it with the shaft on the left side driving the main furnace blower and the shaft on the right side driving the combustion blower. Two blowers - one motor. The cylinder shaped mechanism to the right of combusion blower is the outside furnace vent. This is the design of late model forced draft furnace.


Overheating is ultimately controlled by the limit switch which will open and shut the furnace down when overheated but the best remedy is to avert the possibility of overheating with a simple routine inspection of the furnace. Besides, a hot running furnace will only place additional stress on the combustion chamber and burner and a cracked combustion chamber can leak lethal combustion gases into the coach rather than the outside where it belongs.

Furnace Inspection Checkpoints

#1. Check outside vents for soot

Soot is a byproduct of improper combustion which means you have a problem. Carbon monoxide is the other byproduct of improper combustion so a furnace exhibiting soot at the outside vent should be inspected and repaired BEFORE being operated again.

#2. Check return air vents (inside coach at the furnace)

Return air vents should be free of dust and lint and should NEVER be obstructed. Remove the return air vent and inspect the case of the furnace to be sure it is clean and free of obstructions. If there is any dust on the furnace, which cannot be easily removed with a vacuum, or air indicates, it has been there for a considerable length of time and a cleaning of the entire furnace is in order. Why? Because this dust will be everywhere including the inside of the furnace. Such dust can affect electrical switches, the furnace blower, and the furnace blower motor. Eventually a dirty motor and blower will slow down and the furnace will loose efficiency and if the blower slows down enough the furnace will not operate. (Another safety feature incorporated with the sail switch)

#3 Inspect heat ducts at the furnace

Heat ducts should be inspected at the furnace first to insure they are properly secured to the furnace AND that they are not leaking. Also, check the condition of the ducting. If it is stiff and brittle, it will be prone to cracking and subsequently leaking resulting in additional operating inefficiencies of your furnace. Such ducting should be replaced.

Conclusion:

Your rv furnace is the one area in which one should not skimp. Your comfort and safety far outweigh any reasons to shortcut here and safety in and of itself should mandate giving your furnace the attention it requires.




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