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Author Topic: Fast question on fridge...  (Read 2049 times)
Tully Lee
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« on: September 03, 2010, 06:49:07 PM »

My fridge runs on A/C  - D/C  or LP gas.

What is the fastest way of getting the fridge cold?  Using A/C or D/C?

Thanks,

Tully Lee
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steve wardwell
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« Reply #1 on: September 03, 2010, 06:56:25 PM »

I would guess AC (less amps)Huh
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« Reply #2 on: September 03, 2010, 07:10:54 PM »

DC won't cool the fridge as good as AC or LP if the fridge is cold and you switch to DC it will warm up running on DC, the fastest way is LP


good luck
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Will & Wife
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« Reply #3 on: September 03, 2010, 07:37:44 PM »

Tully Lee, my Dometic is AC/DC/LP and I can tell you that LP gas is the fastest and most efficient way to make things cold. Once you get it cooled down however, AC is the safest way to keep it cold. Meanwhile, DC is strictly for on the road if you don't have an inverter or generator, since it is not recommended to run gas while in motion. My manual even states that DC is only for short term use and not very efficient for cooling. Hope this helps. This is my real world experience also  Grin, Will
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gus
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« Reply #4 on: September 04, 2010, 03:33:53 PM »

My Norcold cools down best on AC, then while underway I use LP if the genset is off.

If the genset is on or I'm at a hookup I go back to AC.

DC is good only for emergencies in mild weather, it very hot weather it is almost useless.
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Lin
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« Reply #5 on: September 04, 2010, 05:19:12 PM »

Hey Gus,

Usually, my fridge cooled fastest on LP.  Recently it started doing better on AC.  I cleaned out the gas orifice, and LP is now back on top.  LP just puts out more heat.  More heat=more cooling.
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gus
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« Reply #6 on: September 06, 2010, 03:47:20 PM »

Lin,

You're probably right. I've never done a scientific study of this, it just seems this way to me. Maybe my burners need cleaning too but it does so well underway I'm not about to mess with it.

I'm also cheap, I don't use as much LP this way!! AC is just easier.

I also make sure the frige is kept full, air does not cool well.
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Lin
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« Reply #7 on: September 06, 2010, 06:13:46 PM »

Gus,

When you get to it, it is a quick fix.  I would even guess your manual suggests cleaning the orifice yearly.  I cleaned mine by unraveling a couple of inches of stranded wire and using one strand to ream it out.  I was even told that there are some spiders that like the scent of propane and will nest there.
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NJT5047
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« Reply #8 on: September 06, 2010, 06:56:21 PM »

LP, hands down,  cools the fridge the fastest.  As already stated, it's also the most expensive method... 
I travel on LP.  Never had a problem with flameout or any other issues.  I also realize this is like..."hold my beer and watch this..."
IF the LP mains are turned on, it doesn't matter whether the fridge is lit or not.  An accident might get nastier.   
I use LP almost exclusively in fact...it maintains cold adult beverages better in hot weather, and it frees up a few amps for the ACs...if you're on a pole.   Even though it's the most expensive fuel, it's still cheap to run a fridge on LP.  RV heaters are what soaks up LP.   A 30lb tank of LP will run most LP fridges for a long time. 
Cleaning the orifice is considered good fridge hygiene, but I've never really found anything to clean? 
JR

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JR Lynch , Charlotte, NC
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« Reply #9 on: September 07, 2010, 07:58:35 PM »

Mine will blow out during a hard rain or a very windy day but it keeps cold a long time so it hasn't been a problem so far. If things get serious I just crank up the genset and heat it up again. Sometimes I have to do this when it is really soaked.

I've tried baffles at the air intake but so far have had no luck. Next attempt will be baffles in a different direction.

The best temp stabilizer and aid to quick cool down is plenty of cold liquid in the empty spaces. Air space is the hardest to cool.
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Hcklbery
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« Reply #10 on: September 07, 2010, 08:49:38 PM »

Mine is the Dometic Sidewise W/ice & water dispenser in the door. (laa dee da) It's electronic controlled and defrosts itself. I have no real input on the cooling factors of propane over elec.

I just couldn't pass up the opportunity to brag up my fridge. Smiley

 Grin Grin Grin
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bevans6
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« Reply #11 on: September 08, 2010, 05:30:13 AM »

With my fridge, Dometic N841, I found that I have to take the chimney off and clean out the rust inside every year or so.  Combustion creates water vapour which corrodes the inside.  Definite life on that part.  You have to have the whole fridge right out of it's install to  take the chimney apart, usually.  Probably the major reason I will look at other options than propane when I have to change it out.  Or I will just make a new part out of stainless steel.

Brian
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« Reply #12 on: September 08, 2010, 09:06:01 AM »

I don't believe you are experiencing the norm with that fridge Brian.

It may be that the fridge is older but I don't know if that would make or ought to make any difference.
 there should be no water vapor in the actual chimney I should think as the heat would keep it from collecting, but I am only thinking out loud here.

would you be knowing if this is typical ?
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steve wardwell
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« Reply #13 on: September 08, 2010, 03:11:08 PM »

I thought I heard somewhere propane was 20% water and that was why in an enclosed cabin/boat the windows would fog up using the stove.Huh?
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Sometimes the more I think about something the less I think about something.    As soon as I save a little money my bus finds out.                                      Why grab a plane when you can take the bus ?                         If I'm wrong 10% of the time how can the "Queen" be right 100%
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« Reply #14 on: September 08, 2010, 03:23:42 PM »

One of the significant byproducts of a propane flame is actually water vapour.  It indeed causes many condensation problems when you use propane heaters in enclosed spaces.  The other byproduct, besides heat, is CO2, which causes other problems in enclosed spaces.

Same thing with most any combustion, including gas engines.  The steam you see from your car exhaust on a cold day is exactly that - steam, from water vapour.  It's one reason why exhaust systems rust out so fast.

Brian
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luvrbus
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« Reply #15 on: September 08, 2010, 03:29:13 PM »

 I heard if propane does not have enough oxygen when flaming then it will make water,never heard it was 20 % water being a by product of natural gas and oil I doubt that


good luck
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« Reply #16 on: September 08, 2010, 04:10:56 PM »

(PER WIKIPEDIA)

Propane undergoes combustion reactions in a similar fashion to other alkanes. In the presence of excess oxygen, propane burns to form water and carbon dioxide.

C3H8 + 5 O2 → 3 CO2 + 4 H2O + heat
propane + oxygen → carbon dioxide + water
When not enough oxygen is present for complete combustion, incomplete combustion occurs when propane burns and forms water, carbon monoxide, carbon dioxide, and carbon.

2 C3H8 + 7 O2 → 2 CO2 + 2 CO + 2 C + 8 H2O + heat
Propane + Oxygen → Carbon Dioxide + Carbon Monoxide + Carbon + Water
Unlike natural gas, propane is heavier than air (1.5 times as dense). In its raw state, propane sinks and pools at the floor. Liquid propane will flash to a vapor at atmospheric pressure and appears white due to moisture condensing from the air.

When properly combusted, propane produces about 50 MJ/kg. The gross heat of combustion of one normal cubic meter of propane is around 91 megajoules[8]

Propane is nontoxic; however, when abused as an inhalant it poses a mild asphyxiation risk through oxygen deprivation. Commercial products contain hydrocarbons beyond propane, which may increase risk. Commonly stored under pressure at room temperature, propane and its mixtures expand and cool when released and may cause mild frostbite.

Propane combustion is much cleaner than gasoline combustion, though not as clean as natural gas combustion. The presence of CC bonds, plus the multiple bonds of propylene and butylene, create organic exhausts besides carbon dioxide and water vapor during typical combustion. These bonds also cause propane to burn with a visible flame.


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« Reply #17 on: September 08, 2010, 04:12:28 PM »

(PER WIKIPEDIA) 

http://en.wikipedia.org/wiki/Gas_absorption_refrigerator

An absorption refrigerator is a refrigerator that uses a heat source (e.g., solar, kerosene-fueled flame) to provide the energy needed to drive the cooling system. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where noise from the compressor is problematic, or where surplus heat is available (e.g., from turbine exhausts or industrial processes). For example, absorption refrigerators powered by heat from the combustion of liquefied petroleum gas are often used for food storage in recreational vehicles.

Both absorption and compressor refrigerators use a refrigerant with a very low boiling point (less than 0 F/−18 C). In both types, when this refrigerant evaporates (boils), it takes some heat away with it, providing the cooling effect. The main difference between the two types is the way the refrigerant is changed from a gas back into a liquid so that the cycle can repeat. An absorption refrigerator changes the gas back into a liquid using a different method that needs only heat, and has no moving parts. In comparison, a compressor refrigerator uses an electrically-powered compressor to increase the pressure on the gas, and then condenses the hot high pressure gas back to a liquid by heat exchange with a coolant (usually air). Once the high pressure gas has cooled, it passes through a pressure release valve which drops the refrigerant temperature to below freezing. The other difference between the two types is the refrigerant used. Compressor refrigerators typically use an HCFC, while absorption refrigerators typically use ammonia.
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