RV refrigerator leveling: why an absorption fridge needs to be level

Two kinds of RV refrigerator, and only one cares about level

RV refrigerators come in two kinds, and the difference decides everything that follows.

• Absorption. This is the one with no moving parts. It makes cold by applying heat to a sealed circuit of ammonia, water and hydrogen, and it runs on a propane flame, a 120 volt AC element, or a 12 volt DC element. Because the fluid has to circulate by gravity, the unit has to sit close to level when the coach is parked. This is the type that people mean when they say an RV fridge needs levelling.
• Compressor. A small 12 volt compressor refrigerator, like a domestic fridge scaled down, with a refrigerant and a motor. It does not care about level, any more than the fridge in your kitchen does. It also cannot run on propane.

You can tell them apart without opening anything. The two way and three way models, the ones that list a gas mode alongside electric, are absorption. A refrigerator with no gas option is almost always a compressor. Model plates and the selection of power sources on the control panel confirm it.

What "level" means in practice

Level here does not mean perfectly level. The makers publish a tolerance, and it is wider than most owners expect. Norcold publishes 3 degrees off level side to side and 6 degrees off level front to back, measured as you look at the front of the refrigerator.

In real distance on a coach, those angles are large. For each 8 feet of length or width, 3 degrees is about 5 inches. A coach 32 feet long and 8 feet wide would have to be roughly 20 inches off level at one end, or 5 inches low along one side, before it reached 3 degrees of tilt. Most parking spots never come close.

The practical version is simpler than the number. If the coach is level enough that you cannot feel the slope underfoot, it is level enough for the refrigerator.

Why an absorption refrigerator stalls when it is tilted

The clearest published description of the mechanism is this:

"If the absorber coils are more than 3 degrees out of level, the fluid will accumulate in the downhill turns. This will stop the gravity circulation of the fluid and block the upward recirculation of the hydrogen. The fluid level in the boiler also will be affected, as tilting in the direction of the boiler initially will flood the boiler, and tilting away from the boiler will starve it. A starved boiler will overheat".

Put plainly: there is no pump pushing the fluid around. It moves because it is heavier in some places than others and finds its way downhill through the turns of the coil. Tilt the coils far enough and the fluid pools in the low turns instead of returning, the circulation stalls, and the boiler, which is still being heated by the flame or the element, runs dry and overheats.

Overheating does lasting harm. The fluid carries sodium chromate as a corrosion inhibitor, and grossly overheated solution can throw that out as small hard particles that lodge in the narrow passages. That fouling does not clear itself. The damage is cumulative and permanent, which means each bad episode leaves the unit closer to failure.

The two published figures, and one maker that publishes none

• Norcold publishes the degree figures: 3 degrees side to side and 6 degrees front to back, and adds that operating beyond them can damage the cooling system and create a risk of personal injury or property damage, so the vehicle should be level before the refrigerator is operated.
• Dometic publishes the requirement but not the angles. Its consumer wording is that the refrigerator must be kept level when the RV is parked for several hours or more, and that loss of cooling could occur if the refrigerator operates in a noticeable out of level position for several hours. Dometic's consumer manual gives no degree figures at all.

Do not carry the 3 and 6 numbers across to a different brand. They are Norcold's figures. Dometic asks for level and leaves the tolerance unstated, so on a Dometic unit the safe reading is that a noticeable slope, held for hours, is the thing to avoid. Where a maker does not publish a number, no number should be assumed.

Driving does not matter. Parking badly does.

This is the part that saves owners the most worry. The Norcold manual's own wording is that while the refrigerator should be level when the vehicle is stopped, performance during travel is not usually affected. The requirement is tied to standing still.

The reason follows from the mechanism. The fluid circulates by gravity, so it only pools and blocks a set of turns when the coach holds one fixed angle long enough for it to settle. A coach in motion is constantly changing which way is downhill, so the fluid keeps moving and does not settle into the low turns. The road's motion keeps the coolant moving. What harms the unit is not the drive but the arrival: backing into a badly sloped site and leaving the absorption fridge running at that angle for hours or days.

How long is too long is not published as a fixed time. One widely quoted figure from the maintenance literature is that in average temperatures it now takes a few hours of critically off level operation to cause damage. Short stops, a lunch break, an overnight at a near level site, are not the concern. A severely tilted site held for a day or two is.

What off-level damage looks like, and why it is not a warranty claim

• The fridge stops cooling, often the fresh food compartment first. The freezer may keep working longer than the lower compartment when the unit is only marginally out of level, because the available cooling shows up in the freezer first. On Norcold models a fault code for a cooling unit that has stopped cooling lists the vehicle being level among the things to check.
• It may recover if you catch it early. The first responder method is to switch the refrigerator off, level the coach so the fluid can return to the boiler and absorber vessel, let the cooling unit come down to ambient temperature, which takes a couple of hours, and then switch it back on. If it was only starved and not yet fouled, it may run again.
• It may not recover, and the loss is permanent. Once the solution has been fouled by overheating, the restriction is still there and the problem returns. That is a cooling unit replacement, not a repair.
• It is not a warranty claim. Neither maker's warranty covers damage from misuse or from not following the operating instructions. Norcold's warranty excludes parts and assemblies subjected to misuse, improper or abnormal service, and abuse, and Dometic states that damage due to improper use is not covered and that the warranty does not apply where the operating instructions are not followed. Keeping the unit level is an operating instruction, so an off level failure sits on the wrong side of that line.

Fires are a separate fault, not a leveling problem

It is worth being exact here, because the two issues get mixed together. Off level operation is a way to damage the cooling unit and overheat the boiler. It is not established that it starts fires.

The fires that regulators have acted on come from a different cause. The NHTSA recall notices state the defect plainly: a fatigue crack can develop in the boiler tube of the affected refrigerators, which can permit the release of pressurised coolant solution, and if that solution is exposed to an ignition source under certain specific circumstances it can result in a vehicle fire. The remedy is a recall kit fitted to the refrigerator: a secondary burner housing, a thermal fuse and a melt fuse on the Dometic units, and a faster responding high temperature sensing thermocouple kit on the Norcold units. The recalls cover large populations. The fire investigation literature that reviews these campaigns puts the Dometic recall at about 926,877 affected units and two Norcold recalls at about 28,144 and 8,419 units.

The fire investigators trace the fires to the boiler tube crack and to the burner area around it. Their write ups do not list leveling as a cause. So the two things stand apart: keep the coach level to protect the cooling unit from an early, expensive death, and rely on the recall remedy to address the cracked boiler tube fire risk. Leveling does not prevent a fire.

What to do if you see yellow staining or smell ammonia. Either one points to a leaking cooling unit, and a leaking unit should not be run in any mode. Leakage or staining at the back, yellow residue at the back or the sides, and the smell of ammonia are the warning indicators the recalls name. Switch the refrigerator off, shut the gas off at the tank, leave the living area if the smell is strong, and have the unit inspected before you trust it again. Never open the cooling unit yourself. It is under high pressure.

How to check your coach is level enough, with no special tools

You do not need a levelling system to answer this. Any of the following will do.

• A phone level app. Most phones have one built in or available free. Rest the phone flat on the floor at a few spots and read the angle. It is accurate enough to tell 1 or 2 degrees from 6.
• A spirit level on the floor. Any short bubble level laid flat on the floor, across the coach and along it, shows the slope in both directions. Remember which way is which: side to side is the tighter limit at 3 degrees, front to back allows 6.
• A bull's eye bubble level. In the guidance published for owners, when half of the bubble falls inside the black ring that is approximately 1.5 degrees of tilt, which is well inside tolerance.
• The comfort test. The same guidance concludes that if the coach is level enough for your comfort, it is level enough for the refrigerator. Walking it and not feeling a slope is a valid answer.
• The fridge door as a rough check. Open the door part way and let go. A door that swings itself open or shut on its own is telling you the coach is on a slope. A door that stays where you leave it is telling you the slope is slight. Treat this as a rough indicator only, not a measurement.
• On a slope. Ramp or block the low wheels, chock the coach so it cannot roll, and check again with the phone or the level. If you can get the coach close to level, the absorption fridge is fine. If you cannot, move the coach or switch the fridge off.

When to switch the fridge off

• Parked, and you cannot get level. The requirement is about the parked condition. A short stop is fine; a badly sloped site held for hours is not. If you cannot level the coach and you are staying put, switch the absorption fridge off.
• Yellow staining or the smell of ammonia. Off immediately, in every mode, and do not restart it until it has been inspected.
• Refuelling. Gas operation is not permitted at a petrol station, and the same prohibition applies on ferries and on motorail trains.
• After a bad episode. If the fridge quit while the coach sat severely out of level, switch it off, level the coach, let the unit cool back to ambient temperature, then restart.
• Not a switch-off case. Driving is fine. The road's motion keeps the coolant moving, and the makers treat travel as normal use.

Sources

• Norcold refrigerator owner's manual, models N400 and N510, for the published 3 degrees side to side and 6 degrees front to back figures, the warning that operating beyond them can damage the cooling system, the instruction to level the vehicle before operating, the statement that performance during travel is not usually affected, the cooling unit fault code that lists the vehicle being level, and the warranty exclusions for misuse and abnormal service.
• Family RVing (FMCA), RV Refrigerator Maintenance, for the quoted description of the mechanism, the sodium chromate precipitation and cumulative permanent damage, the conversion of 3 degrees into inches of tilt, the bull's eye level reading of about 1.5 degrees, the comfort test, and the recovery method of switching off, levelling, and letting the unit return to ambient.
• Dometic absorption refrigerator operating manual, 8 series, for the requirement to keep the refrigerator level when parked for several hours or more, the loss of cooling from a noticeable out of level position held for several hours, the absence of any degree figures, the instruction to leave the living area if ammonia is smelled, the high pressure warning against opening the cooling unit, the gas prohibition at petrol stations and on ferries and motorail, and the warranty exclusion for damage due to improper use.
• NHTSA recall notice, Keystone RV Company, Dometic refrigerators (RCONL 08V325), for the statement that a fatigue crack can develop in the boiler tube, that this can release pressurised coolant solution, and that if exposed to an ignition source it can result in a vehicle fire, along with the recall rework of a secondary burner housing, a thermal fuse and a melt fuse, and the warning indicators of leakage or staining, yellow residue, the smell of ammonia, and poor cooling.
• NHTSA recall notice, Norcold models 1200, 1201, 1210 and 1211 (campaign 10E-049), for the Norcold fire risk recall and the high temperature sensing thermocouple recall kit used as the remedy.
• AEGI Forensics, Investigating Absorption Refrigerator Fires, Part 1, for the review of the three NHTSA recalls, the boiler tube fatigue crack as the fire cause, and the affected unit counts for the Dometic and Norcold campaigns, which together show that the fire investigation literature attributes these fires to the boiler tube crack and not to leveling.