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Refrigerator Maintenance

May 14, 2010, 03:03:47 pm

I was performing the annual on the Norcold (1997 vintage) and I'm concerned with the amount of rust developing in what looks like the ammonia system.  Can anyone help by looking at the pictures if the condition is unsafe?

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Re: Refrigerator Maintenance

Reply #1 – May 14, 2010, 03:25:12 pm

There are only two main failures with gas RV refrigerators (Dometic, Norcold and selected other).

#1 The RV refrigerator is run unleveled causing the cooling unit boiler to overhead, block and crack.

#2 The RV refrigerator cooling unit's steel tubing rusts and the ammonia/hydrogen gas leaks out.

The single biggest killer of gas refrigerator cooling units is corrosion. The common misconception is that it's the rust on the exposed pipe at the bottom of the cooling unit (down by the burner) that causes the leaks. In fact, this is rarely the case. The rust often seen on the exposed pipes is largely superficial even though it may look terrible. In gas refrigerator cooling units, the worst corrosion always occurs on the evaporator piping (the pipes that get cold) because they are physically located inside the refrigerator cabinet (right behind the back wall of the interior) and is covered by insulation. While the refrigerator is running, moist air finds its way to the cold evaporator pipes and condenses on the surface. Since the evaporator pipes are encased, the condensed water cannot readily drain away and therefore is held next to the steel pipe. After several years rust develops.

 The rusting is accelerated when the refrigerator is turned off for the season, allowing the evaporator to warm up. The rusting eventually progresses to a point where severe pitting occurs in the surface of the steel. These pits eventually extend all the way through the pipe wall into the inner space of the pipes. The result is a leak.

 You will usually, but not always, smell the leak when it occurs. If the leak does occur on the outside piping, you probably won't smell it. Sometimes, even if the leak is on the inside, you may not smell it if mostly hydrogen is leaking out. Most of the time, however, you will know that your refrigerator is leaking because of the pungent ammonia smell coming from inside your cabinet.

 After your refrigerator starts leaking, it will eventually (usually very soon) stop cooling. The worst thing you could do at this point is to delay getting your refrigerator repaired because corrosive ammonia is eating away at the cooling unit steel (ammonia doesn't corrode the steel while it's inside the cooling unit because of the rust inhibitor inside). The longer you delay getting your refrigerator's cooling unit rebuilt, the lower the odds are of a successful and reliable repair. Also the ammonia gas will eat up the inside of the cabinet and the parts. The light and thermostat will need to be replaced if left too long and the inside plastic will turn yellow. You can see why removing all rust from the cooling unit by sand blasting and rust proofing the cooling unit are essential steps in a proper cooling unit repair. Just as with your car, if you don't remove the rust, it'll just come back and, after another season or two of use, the cooling unit will fail again.

Boiler blocks or cracks - If the refrigerator is run while not leveled for an extended period, the cooling unit water will not flow into the boiler. The boiler as a result gets excessively hot and can bake the rust inhibitor. This will in-turn block the small 1/4" tube in the boiler and all flow will stop. If the refrigerator is kept running under these circumstances the boiler tube will get so hot that it will crack open.  If this happens a yellow powder around the burner area may be visible indicating that the cooling units rust inhibitor is leaking.

Leaks - When a unit rusts and leaks as a result, the ammonia gas is lost first. You can sometimes smell the ammonia gas. However when the door is opened or if the leak is small there can be little or no smell. Under these circumstances there could be a boiling sound at the back of the refrigerator. This means the hydrogen gas has also leaked out and the water is now boiling. Ammonia smells or large gurgling sounds from the refrigerator are indicators that the refrigerator cooling unit is leaking.

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Re: Refrigerator Maintenance

Reply #2 – May 14, 2010, 04:46:12 pm

This is a test of an email reply to a "notification" on Tech Topics subject:
Refrigerator Maintenance.

(This is now a modification to my post performed on the Forum site [in parenthesis].  The email got posted w/o a hitch)

Looking good!

Now to test the starting of a new topic in Tech Talk.

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Re: Refrigerator Maintenance

Reply #3 – May 14, 2010, 04:52:45 pm

Peter, Now you are showing off. 

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Re: Refrigerator Maintenance

Reply #4 – May 15, 2010, 10:23:50 am

Hello Peter B, We just replaced our  RM4804 (ammonia leak) with a N841. I purchased it from PPL, total cost with freight to our home address was $1252.28. I had to remove door and hinge to remove old frig. and also to get  new frig. in. The N841 is approx 2 " shorter so i cut  a piece of old black finish to fill in.
Rick Zika 1995 U240 2004 JEEP

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Re: Refrigerator Maintenance

Reply #5 – May 16, 2010, 03:05:58 pm

Rick, that price was for a new fridge unit?  How far fom PPL (Houston?) are you?  Besides getting the old and new units in/out of the coach, how difficult a job is it?

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Re: Refrigerator Maintenance

Reply #6 – May 16, 2010, 06:35:48 pm

Peter,

Removing the Dometic RM4804 from a MID ENTRY U240 (and replacing with same size unit) can be done by removing the inside grab bar-- then everything goes out/in.

No idea as to whether this is as easy on the front entry bus style, particularly with larger refrigerator.

Brett

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Re: Refrigerator Maintenance

Reply #7 – May 17, 2010, 09:29:58 am

Peter B,  list price $1093.59 no tax, (N841) plus shipping $158.69. Ordered from PPL Houston TX. But the new frig. was shipped from Indianapolis In. to Edgar Springs, Mo. 65462
As Brett said in his post, you have to take off the grab bar, I also had to take the entry door and hinge off. We turn frig. on side, no problem getting through door way. ( 2 person job)  Remove old step platform for RM4804, put in place 3/4" plywood for new N841. The N841 will sit lower
than the RM4804 in relation to vent grill. Also I talked to Brett Sat. and he asked if i had installed a 1"1/2  ;)hose or pipe, (through floor) if a leak occurred to get rid of the gas, because this frig. sits lower than vent grill. Not really a hard job,but another learning experience on how this motor home was put together.

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Re: Refrigerator Maintenance

Reply #8 – May 18, 2010, 06:19:08 am

Thanks Rick, this is very helpfull.  I know I have problems with the Norcold in the not too distant future as on average the unit is turned on and off about 8 times a year (not a full timer).  My father-in-law (RIP) used to tell me "just turn it on and never turn it off and the fridge should last a good 20 years or more."  And now I know why due to the input from folks that know, care & have done it in the past.

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