Possible cause of Norcold problems

[moisheh]

Our Bounder has the infamous Norcold 1200 fridge. The PO never had any recalls performed. I took the unit to Tucson and had the latest recall done. I asked the service mgr. if he could look at the burner area when he removed the foil insulation. I wanted to know the burner condition. His reply was that they are always rusty. I started to think that maybe the insulation was the problem. many years ago we had a Vogue MH with a 440 engine. I did a bunch of exhaust mods to try and get some of the heat out of the doghouse area as we kept burning p lug wires and the exhaust manifolds were red hot. I installed Hedman headers and wrapped them with header wrap. This is an insulating material that is used in drag racing. In one summer the headers burnt right through! The reason was that when you turned off the engine and the headers cooled down moisture formed between the wrap and the header tubes. Instant rust! Could the insulation around the boiler be doing the same thing? I have read that one of the problems with the Norcold was that the cooling unit was undersized and the boiler gets too hot. Could the insulation make it worse? I don't remember seeing any insulation around my older Dometic units but it may have been there. Anyone here with a Dometic that can check?

[jesilvas]

Dometic boiler flues all have insulation, just sheet metal instead of foil on the outside. They don't rust near as bad.

[RV Wizard]

What causes the rust through on Ammonia, water absorption refrigeration is the ammonia. That is why sodium chromate is added to the system to help reduce the corrosive effect of the ammonia. This is true for any brand of refrigerator.

[NeilV]

So are they just going too light or being inconsistant on the chromate? I made mine in small batches adding the chromate to the water before mixing in the anhydrous amonia to make up the refridgerant.

[moisheh]

Rv Wizard: Thanks. I do understand that the mixture is corrosive. BUT if the boiler or tubing is rusty on the outside and yet still serviceable that would mean that some of the rust is from the outside, If you keep a piece of thin steel damp it will rust. Flaking on the outside of the boiler or tubes would indicate rusting from the outside. I of course am not an RV tech but in my youth I was an automobile rustproofing specialist . I still do not understand why the fridge tubing and boiler are not made of stainless?

[RV Wizard]

Originally Posted by moisheh

Rv Wizard: Thanks. I do understand that the mixture is corrosive. BUT if the boiler or tubing is rusty on the outside and yet still serviceable that would mean that some of the rust is from the outside, If you keep a piece of thin steel damp it will rust. Flaking on the outside of the boiler or tubes would indicate rusting from the outside. I of course am not an RV tech but in my youth I was an automobile rustproofing specialist . I still do not understand why the fridge tubing and boiler are not made of stainless?

Like anything made today; it comes down to cost. Each manufacturer is competing for what the consumer wants. It is as much the consumers fault because we are too focused on price instead of quality. Keeping the cooling unit running (as it was originally intended) will eliminate the tubing from staying damp and rusting much if at all since they are painted but for the boiler.

[H. Miller]

As an example of the inferior "quality" of the Norcold cooling unit, one person (of reasonable strength) can lift it....It takes two people for the Amish unit.

[NeilV]

Also Norcold had to meet the weight requirements of the coach building industry who puts large coaches on chassis only marginally capable of supporting them. As it sits some coaches only have enough chassis capacity to carry an additional 1,000 lbs so if you add a refridgerator that weighs 100 lbs more than the original you could be loosing 10% of your capacity to carry bottled water, food clothing, emergency supplies, cookware, dishes etc.

On a side note these units are also used in the gallies of pleasure boats and small commercial boats all over the world yet we do not hear regular mainstream news reports of refridgerator fires there either.

[docj]

Originally Posted by NeilV

On a side note these units are also used in the gallies of pleasure boats and small commercial boats all over the world yet we do not hear regular mainstream news reports of refridgerator fires there either.

Interesting point; maybe the fact that RVs are subjected to "pounding" as they drive down the highway contributes to the problem. Boats can get smacked by the waves, but these fridges would be on relatively large boats that probably aren't subjected to the same level of vibration and shock as are the things in an RV. Just a thought?

[NeilV]

Originally Posted by docj

Interesting point; maybe the fact that RVs are subjected to "pounding" as they drive down the highway contributes to the problem. Boats can get smacked by the waves, but these fridges would be on relatively large boats that probably aren't subjected to the same level of vibration and shock as are the things in an RV. Just a thought?

The vibration from an out of balance tire, expansions joints or road hazards would not be there but salt corrosion would. A lot of the boats they put these in aren't that big either starting in the mid 20 foot range but it is a different set of dynamics. Either is much different to one installed in a stationary land based structure not exposed to the elements. In a stationary structure you usually don't see refridgerators installed directly vented through the wall only a few inches away from the weather with a constant wet potentially salty mist blowing by at 60 or 70 mph when its raining.

It does make one wonder what part the coach builders choice of location on the coach and variations in how the venting is installed has if anything to do with it.

[94-Newmar]

Originally Posted by moisheh

I still do not understand why the fridge tubing and boiler are not made of stainless?

Agreed. Likewise, all the problems could be solved using a pressure switch installed in the system. The installed pressure on these units is around 200psi while not running. So For instance, If the system exceeds 500psi (or whatever the rated burst pressure is for the system) or drops below 150psi something is wrong and the heat source should be shut down immediately. If it exceeds XXXpsi there is obviously a burner/heater runaway situation, and if below XXXpsi obviously there has been a leak. Either I'm missing something or as Mike states above, it could be completely due to competition costs.

[dforce1]

To answer your thoughts 94-Newmar. A new product. There is a set up for the RV refrigerator coming out now, as an add on option to make all RV refrigerators safe from damage or causing fires from over heating due to any an all kinds of reasons. Check this link out for details:

https://sites.google.com/site/arprvsafer/home

[94-Newmar]

dforce1, again, this is nothing more than a glorified temperature sensor. Remember, a stress crack forming due to poor welding, vibration or even rust will cause the refrigerant to be released in a flammable vapor even if the temperature of the entire unit is within normal operating range. At that point all it takes is an ignition source - which may or may not be the burner (whether using AC heaters or LPG) within the refrig itself. I honestly believe that, of the fires that can be directly traced to an absorption refrig fire, they may not have necessarily been in an "overheat" situation. For example, what if the unit wasn't even turned on? A pressure sensing device would not prevent a fire caused by some other sort of ignition from the release of the refrigerant, however it would help prevent the unit's own boiler from igniting it.

[NeilV]

Here is the fact sheet on anhydrous amonia which is generally considered non-flammable unless heated and pressurized and in the presence of strong ignition. A refridgerator that is not running and turned off in storage should not then present a fire hazard.

AMMONIA, ANHYDROUS | CAMEO Chemicals | NOAA