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 > Norcold Fridge Question

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dougrainer

Carrolton, Texas

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Posted: 12/13/07 05:10pm Link  |  Print  |  Notify Moderator

Troubleshooter wrote:

While I won't try to go into the theory of why it happens, I personally know of a case where it has happened.
While moving from one abode to another, we put our freezer full of food in a unheated outside storage shed. Winter set in, and I didn't give it a second thought about the cold weather. About a week or so later the DW wanted me to get something out of the freezer, and when I opened it, you don't want to know what odors I was hit with. The temperature of the shed was about 10°F, whereas the internal temperature of the freezer was about 45°F.
Yes, it was plugged in, and there had been no power failure.
A lot of spoiled food disposed of, along with a freezer that we could never get the odor removed.
On our RV refer, when we are using it in sub-freezing weather, I always put a 40 watt bulb in the rear compartment, and partially block the air intake in order to insure that the refrigerant is circulated through the system.

Only One Old Fellow's Opinion


Was that freezer an RV absorbsion unit or a standard house freezer? Doug

Troubleshooter

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Posted: 12/13/07 05:42pm Link  |  Print  |  Notify Moderator

Quote:


Was that freezer an RV absorbsion unit or a standard house freezer? Doug


Standard Freon/Compressor version.


Bill
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Good Samaritan

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Posted: 12/13/07 08:36pm Link  |  Print  |  Notify Moderator

Freshair, to answer your question...no your Norcold does not have any such feature. The reason it will not work in cold ambients is because it is a gas absorption refrigerator. Gas absorption refrigerators are different from your home refrigerator that utilizes a compressor. Gas absorption refrigerators require some type of heat input to the cooling unit (this is accomplished with either an AC tubular type heater, a flame via an LP burner or via a DC tubular heater)which in turn causes a chemical reaction in the cooling unit. The cooling of a gas absorption refer is based on Daltons Law. To keep things basic and in laymans terms, in order to make cold...you must add heat. The chemical reaction in the cooling unit is very sensitive to heat and COLD. If the cooling unit gets too hot...it won't cool hence the reason it is very important to ensure proper venting during the summer months. At the same time, the cooling unit is very sensitive to cold. If the cooling unit gets too cold it distrupts the chemicl reaction in the cooling unit and thus will not cool.Dometic, on some of their units have a LAC switch which simply powers the interior light on all the time. Although it is not entirely clear to me but I believe the reason they did this was that by adding a 10watt heat source (light bulb) in the freshfood compartment they effectively warm the thermistor which in turn keeps the heat source to the cooling unit on more often. Typically a gas absorption refrigerator will work in cold weather as long as you don't let the heat source to the cooling unit shut off. If the heat source is off and the cooling unit is allowed to get cold it is extremly hard to warm the cooling unit enough to get the chemical reaction in the cooling unit to "get going" again. Anyway, Norcold refrigerators do not employ such tactics and I think Dometic gave up on it as it didn't work very well?? If you disconnect the thermistor and set your temperature setting to 9 setting the Norcold refrigerator will run on a 100% duty cycle (what they refer to as a BOM ...Backup Operating Mode). Less chance for the cooling unit to get too cold. Just remember to plug it back in when winter is over. Good luck and Merry Christmas to all!

dougrainer

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Posted: 12/14/07 09:03am Link  |  Print  |  Notify Moderator

1. Per Norcold--- Ambient below 20 to 25 degrees will see a big drop in absorbsion performance. Below real 0 degrees, you will see no performance. Norcold states also to NOT put any light or heat source in the back coil area (CYA for Norcold I believe).

2. Dometic states that to use the LAC below 32 degrees, but you will see a performance drop below 20 degrees even with the LAC on.

3. Both state to use LP gas as a fuel source below 32 degrees as the LP flame is more efficient in freezing temps. The LP flame will heat the back side area better than the insulated 110 elements.

4. Dometic states that they do recommend an additional 110 low watt lite source in the back area by the cooling coils.

5. Both state that the problem with absorbsion is sub freezing weather is the Ammonia mixture has some water and other chemicals that gel or crystallize in freezing temps.

6. In 30 years of RV service, I have never had this question come up.
You learn something new every day.

dougrainer

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Posted: 12/14/07 09:09am Link  |  Print  |  Notify Moderator

"If you disconnect the thermistor and set your temperature setting to 9 setting the Norcold refrigerator will run on a 100% duty cycle (what they refer to as a BOM ...Backup Operating Mode"

In performance check outs per Norcold, they have stated they DO NOT want the refer in "BOM" for more than 24 hours. 24 hours is long enough to do a cooling unit performance check. Disconnecting the thermister puts the Norcold in BOM without even using the temp control. The temp control has no effect once the thermister is disconnected. In BOM, the refer will NEVER shut off, which is NOT a good thing in freezing or very cold temps. Doug

Good Samaritan

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Posted: 12/14/07 06:45pm Link  |  Print  |  Notify Moderator

Doug,

When Norcold says not to operate any more than 24 hours in the BOM, they are refering to "suspect" cooling units. If you have a cooling unit that isn't cooling (possible blockage or what have you)you don't want to keep putting heat into it (these cooling units tend to run hotter than a "working" cooling unit and if you continue to apply heat to them you take a chance of rupturing them). The temperature selector determines the duty cycle of the BOM when the thermistor is unplugged. If the temperature setting is set to 9 with the thermistor unplugged the duty cycle will be 100%. If it is set to 5 then the duty cycle will be closer to 50% (in other words the heat source to the cooling unit will be ON for 30 minutes and then OFF for 30 minutes)All I was trying to point out is,as you said, there is water in the amonia solution and this water can and will freeze. This becomes possible when the heat source to the cooling unit is allowed to be powered off.Applying heat to the cooling unit 100% of the time in very cold temperatures will lesson the likelyhood of the amonia solution to freeze.Bottom line is gas absorption refrigerators don't like cold or hot ambients and these temperatures can and do have adverse effects on their ability to cool.Again, it is perfectly alright to run in the BOM for more than 24 hours providing you have a "working" cooling unit. In fact you could always run in the BOM if you wanted to and as I stated earlier, the BOM duty cycle is determined by the temperature setting selected.

dougrainer

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Posted: 12/17/07 07:52am Link  |  Print  |  Notify Moderator

Good Samaritan wrote:

Doug,

When Norcold says not to operate any more than 24 hours in the BOM, they are refering to "suspect" cooling units. If you have a cooling unit that isn't cooling (possible blockage or what have you)you don't want to keep putting heat into it (these cooling units tend to run hotter than a "working" cooling unit and if you continue to apply heat to them you take a chance of rupturing them). The temperature selector determines the duty cycle of the BOM when the thermistor is unplugged. If the temperature setting is set to 9 with the thermistor unplugged the duty cycle will be 100%. If it is set to 5 then the duty cycle will be closer to 50% (in other words the heat source to the cooling unit will be ON for 30 minutes and then OFF for 30 minutes)All I was trying to point out is,as you said, there is water in the amonia solution and this water can and will freeze. This becomes possible when the heat source to the cooling unit is allowed to be powered off.Applying heat to the cooling unit 100% of the time in very cold temperatures will lesson the likelyhood of the amonia solution to freeze.Bottom line is gas absorption refrigerators don't like cold or hot ambients and these temperatures can and do have adverse effects on their ability to cool.Again, it is perfectly alright to run in the BOM for more than 24 hours providing you have a "working" cooling unit. In fact you could always run in the BOM if you wanted to and as I stated earlier, the BOM duty cycle is determined by the temperature setting selected.


I just talked to Norcold Tech Service to verify MY understanding of the Bypass (BOM) mode. Norcold stated that once the Thermister is disconnected, then NOTHING you do with the Temp set will keep it from going 100%. Once the Control board does NOT seem the Thermister Ohm readings, it goes to 100%. Can you tell us where you received your Info for your understanding of the BOM? Was it from Norcold? Doug

Good Samaritan

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Posted: 12/18/07 06:09pm Link  |  Print  |  Notify Moderator

You may want to call that Norcold service technician back and point it out that the BOM is described in their service manual?! Look at either their of the service manuals for their current 12/8/6 models.

John / Angela

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Posted: 12/18/07 06:35pm Link  |  Print  |  Notify Moderator

So here is a real world performance report on a 1200 series 12 cudic foot 4 door norcold on our 2003 Revolution that we have full timed in for four years.

We have been in sustained minus 25 celcius temps. During the day it would rise to minus 12 or so and at night as low as minus 25. Although it ran fine for the most part, at one point we got a "NOCO" fault. We reset it and it was fine for awhile. Then we got another (next night) and it needed to be reset by grounding certain test point to ground. Seems after a certain length of time that the thermostat doesn't call (in cold weather) the board will spit out a "NOCO" fault. An RV tech friend of ours took a look, blocked off two of the three air inlets at the back with tape and it ran fine for the rest of the cold snap. The ice maker valve never froze the whole time. ALthough we ran it on electric the whole time we have learned since then to run it on propane in this situation.

We have been lucky enough to relocate to warmer temps when the weather gets cold since that time.

* This post was edited 12/19/07 03:29pm by an administrator/moderator *


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dougrainer

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Posted: 12/19/07 07:49am Link  |  Print  |  Notify Moderator

Good Samaritan wrote:

You may want to call that Norcold service technician back and point it out that the BOM is described in their service manual?! Look at either their of the service manuals for their current 12/8/6 models.


YOU are right and kind of wrong[emoticon] The service manual DOES state that when you go into BOM, it is a "Ajustable" cooling cycle. BUT, it does NOT explain what and how this is done. Norcold tech service explained that the adjustable is determined by the 1-9 temp setting like you described. According to Norcold, each number is the time it stays on. IE- set on 4, then it will run 40 minutes, set on 7 it will run 70 minutes and so on. I did not ask the shut off wait time before it comes back on. Do you know that time? But, do you think this will even work in temps below 20 degrees, since when the unit is NOT on, will the outside temp cause a problem with the coolant mixture? Doug

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