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  #1  
Old 11/09/09, 07:28 PM
 
Join Date: Nov 2002
Location: Alaska
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Propane refrigerator

Didn't want to hijack the "no elec" thread so I'll start another question. For those who have used them, what should one look for in a propane fridge? Where is the best place to get them? Brands? Where do you even look to find reviews? We are currently off-grid. The system is managing the fridge at the moment but it is a power hog and it would be nice not to have to watch our watts quite so closely. We've got a lot to consider, including a more efficient elec model and upgrades to our power system, but having info about the propane fridge would be a handy input to the equations. Reality is that DH would like to run a TV. Thanks in advance for any help!

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  #2  
Old 11/10/09, 06:11 AM
 
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Dometic and Norcold are probably the two most common brands.

Propane refrigerators cool down much more slowly than a compressor refrigerator. You don't want to put a lot of warm stuff in it at one time. They work better at keeping it cool than they do at cooling it down.

I haven't checked reviews, but I'm sure you can find a ton of stuff on a Google search.

You can get them from RV dealers and Lehman's (www.lehmans.com) carries them. You can probably find other on line dealers that have them as well.

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Old 11/10/09, 06:37 AM
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Servall (sp)

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  #4  
Old 11/10/09, 07:01 AM
 
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Back in the mid1980s when propane was cheap and PVs were expensive, we spent the money (nearly $2000) on a 12 cu ft Sunfrost 12 volt refrigerator to replace our old Servel propane fridge. We figured that the savings in propane over the life of the refrigerator would pay the cost of the refrigerator and the PVs needed to run it. The refrigerator and the PVs are still working properly, over 2 decades later, so we feel that we made the right choice, especially considering the cost of propane today.

Get more PVs and get an energy efficient electric refrigerator. Another benefit is no gas fumes in the house from the refrigerator.

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  #5  
Old 11/10/09, 07:13 AM
 
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Location: NC
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RV, travel trailer salvage yards are good places to find the dual fuel (110V/propane) refrigerators at a good price. Mine came from a travel trailer that had been wrecked.

Also, consider buying a used travel trailer to strip it of all the components that are useful in living off the grid. This time of year, people are more likely to get rid of them because they don't want to spend money to store them over the winter. The cost of the whole unit can be much less than buying the applicable components separately.

Dual fuel refrigerator
12v water pump
Propane furnace
Propane stove with oven
Lots of 12v lighting fixtures, wiring, receptacles, switches, etc.
Battery (may not be have that much good life left in it, however)
Converter, Inverter, Control/distribution panel, gauges

Naturally, these will vary by unit.

FWIW, I gutted and rebuilt the interior of a 5th wheel rig, using many salvaged parts.

In closing, once you strip the trailer of all thats good for re-use, the trailer can become a storage shed, workshop, or whatever secondary use you have for it. Or, you can sell the remainer to a scrap dealer, especially if it's and older one clad with aluminum.

Lee

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  #6  
Old 11/10/09, 08:31 AM
 
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Since you already have a power system in place, I think a better approach would be to get a more efficient fridge and/or upgrade the power system. The propane will be an added expense and unless you are already using it for heating, it'll be an extra task to worry about filling & moinitoring the tank. There are some articles on line about building a very efficient fridge from a chese freezer, you might look into that.

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  #7  
Old 11/10/09, 09:17 AM
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Quote:
Originally Posted by cfabe View Post
Since you already have a power system in place, I think a better approach would be to get a more efficient fridge and/or upgrade the power system. The propane will be an added expense and unless you are already using it for heating, it'll be an extra task to worry about filling & moinitoring the tank. There are some articles on line about building a very efficient fridge from a chese freezer, you might look into that.
That's true, We just got a new Fridge, there was a tag on it that said it would only cost $43 dollars for the whole year and it has an ice maker.
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  #8  
Old 11/10/09, 11:15 AM
 
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This house was already set up off-grid so we're still tweaking the system, learning the nuances and figuring out what needs to be replaced. It runs off a spring (pelton wheel) so we're also up against winter for some of the changes we can make. We'll probably end up reworking the spring head and some of the piping next year to try to get longer use out of the system (currently freezes up part of the year). I KNOW DH hadn't considered the cost of propane. He's got TV on the brain right now

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  #9  
Old 11/10/09, 02:39 PM
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Back when I was off grid, the propane fridge was the only way to go... I had/have free natural gas. The only negative is that it's a booger to keep things cold or frozen, especially if it's hot outside. I could have ice or ice cream, but not both.

My fridge, a Sibir, died about year 12, when one of the return tubes rusted through! Why, I don't know.... it's still in the barn, in case I someday figure out how to cut out the bad spot, splice it with new tubing, and recharge the puppy with ammonia.

What I want is an icy/ball... will have to make one one of these days...

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  #10  
Old 12/07/09, 05:42 PM
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Efficiency

Hi folks!

I've been doing some homework on the fuel consumption of the various forms of kitchen refrigerators, and, if I did my math right, found out some interesting things.

It's not too hard to compare the gas operated ones, as you can convert the gallons used in the LP models to the Dekatherm's Oklahoma Natural Gas (the supplier where we live) uses to calculate the cost of natural gas. The electrically-operated figures may or may not be correct - there is a LOT of differing opinions as to the average killowatt hours the typical machines use, but the following gives a good idea.

The modern LP-operated gas refrigerators are rated at 1.1 gallons of propane use per day. The older Servel's use 2.5 gallons per day.

At the current cost of propane here in NE Okla, that means:

* Cost of running the newer (1.1 gal/day of LP) units = $0.45/day, $13.30/mo, $159.60/yr
* Cost of running the Servel's (2.5 gal/day of LP) units = $1.13/day, $33.90/mo, $406.80/yr

Now - using the formulae found at http://www.energykinetics.com/saving...parisons.shtml, I converted the amount of LP gas used by both types of refrigerators to comparable amounts of natural gas, and came up with this:

*Cost of running the newer (1.1 gal/day of LP models on NG) units = $0.15/day, $4.50/mo, $54.00/yr
* Cost of running the Servel's (2.5 gal/day of LP models on NG) units = $0.375/day, $11.25/mo, $135.00/yr

However - this assumes that the amount of gas use is the same, and I'm not totally convinced that it is, as LP gas is much hotter than natural gas (more BTU output). Therefore, I have asked the people at Crystal Cold to tell me what the NG consumption of their refrigerators actually is. If it's different than why I've calculated above, I'll let you know.

As for electric refrigerators, the numbers are all over the board - each manufacturer and each website claiming to know what they're talking about gives a different rate of electricity usage for the various types/ages of refrigerators out there. That said, I believe the following is close to being accurate:

* Cost of running an electric refrigerator (avg efficiency) = $0.63/day, $19.12/mo, $229.44/yr
* Cost of running an electric refrigerator (high efficiency) = $0.23/day, $6.75/mo, $80.96/yr

SO - it would appear that the most fuel efficient refrigerator is a modern absorption-type using natural gas, and it costs the least to operate, followed by the high-efficiency electric model, followed by the lowly vintage Servel on natural gas, followed by the modern gas unit using LP, followed by by the older, less efficient electric unit, and, bringing in the rear, is the older Servel on propane.

Note: Pricing based on the cost of fuel here in Oklahoma. All units based on the same BTU output needed to provide the same amount of cooling.

Hope this helps someone!
http://vintageservelrefrigerators.8k.com

Todd W. White

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  #11  
Old 12/07/09, 08:38 PM
 
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Just don't hook a propane unit up to nat gas, nor a nat gas unit up to propane. They have different size orfices [SP} in them. Or any unit out of a rv as most are set up for propane. Good luck getting what you want. Sam

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Old 12/07/09, 08:49 PM
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Orifice's

That's right -

You have to make sure the unit you have is setup for the type of gas you are using. This is why it's so important that you get the service manual for it, which are usually available, even for the old Servel's.

When I rebuilt mine, I ordered a new orifice and turbulator for the specific cooling unit (2600 BTU's) and the type of gas I use (natural), as it was originally setup for LP gas.

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  #13  
Old 12/07/09, 09:26 PM
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I don't mean to nit-pick, Todd - but I think you mean that the natural gas is the cheapest, not necessarily the most efficient. The fact that it costs less may just reflect the fact that electricity is more $$ per kWhr / BTU of power.

Chris

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  #14  
Old 12/07/09, 11:01 PM
 
Join Date: Nov 2002
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Great research and information, Todd!

We've decided to go with something a little less conventional than any of the above options. The worst part about a refrigerator is that the door opens to the front, letting the cold air out every time you open that door. After a ton of research on as many of the options as we could find, we decided to use an energy efficient chest freezer with an external thermostat like this one:

http://www.midwestsupplies.com/produ...px?ProdID=4230

Chest type freezers are much more efficient than the most efficient uprights AND they cost less to purchase as well. The freezer we purchased has quite a few baskets and I'll probably use some milk crates in the bottom of the freezer to make it easier to get stuff out. We'll work up an easier way to retrieve stuff once we have the freezer here and play with it a bit. I suspect the biggest adjustment will be mental

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  #15  
Old 12/07/09, 11:24 PM
 
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Quote:
Originally Posted by Todd W. White View Post
The modern LP-operated gas refrigerators are rated at 1.1 gallons of propane use per day. The older Servel's use 2.5 gallons per day.
I think you mean pounds not gallons.

The current national average for propane is $2.28 per gallon or $0.785 per pound. The average yearly cost to run a modern servel is then $222.73. ($2.28/4.11 X 1.1 X 365)

You must also consider that these refrigerators are only 8 cubic feet.

Quote:
* Cost of running an electric refrigerator (avg efficiency) = $0.63/day, $19.12/mo, $229.44/yr
* Cost of running an electric refrigerator (high efficiency) = $0.23/day, $6.75/mo, $80.96/yr
These are for large refrigerators 18+ cu. feet and you are thus comparing apples to oranges.

Let's look at a brand new GE Spacemaker® Compact Refrigerator Model #: GMR06AAPBB which, at 5.7 cubic feet, is a better comparison. It will use 360 KWh per year; the US average rate is $0.1205 per KWh; which means the total yearly cost is $43.38 to operate.

So then, using a modern servel is 5 times more expensive than using a comparable electric fridge.

whistler
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  #16  
Old 12/07/09, 11:45 PM
 
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Quote:
Originally Posted by Todd W. White View Post
Now - using the formulae found at http://www.energykinetics.com/saving...parisons.shtml, I converted the amount of LP gas used by both types of refrigerators to comparable amounts of natural gas, and came up with this:

*Cost of running the newer (1.1 gal/day of LP models on NG) units = $0.15/day, $4.50/mo, $54.00/yr
* Cost of running the Servel's (2.5 gal/day of LP models on NG) units = $0.375/day, $11.25/mo, $135.00/yr

However - this assumes that the amount of gas use is the same, and I'm not totally convinced that it is, as LP gas is much hotter than natural gas (more BTU output).
If we want to compare natural gas we have to take an extra step - compare BTU to BTU. A pound of propane has approximately 22,154 BTUs. Currently, 22,154 BTUs of natural gas costs $0.313. (The current national average for natural gas is $0.0000141477 per BTU) Thus it would cost $125.84 to run the newer Servel on natural gas per year. ($0.313 X 1.1 X 365)

Again electricity comes out the winner; this time by a factor of almost 3.

Whistler
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  #17  
Old 12/08/09, 10:56 AM
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Corrections

Well, let me see if I can make a little more sense....I went back and revisited this issue, using the BTU's required to operate, as suggested above, and I "think" the following is correct. I was a victim of the "New Math" program in the US public school system of the 1960's, where the emphasis was on teaching me "why" I was doing the math, rather than how to get the correct answer, so here goes -

Crystal Cold rates their smallest (12 cubic foot) and largest (18 cubic foot) refrigerators use use .35 gallons per day. The BTU usage of the small one per day is 1750/hr, and the large one is 1825/hr.

So - we have the amount of BTU's these things consume per hour.

Now - there are 95,500 BTU's in a gallon propane.

So -

The 12cf unit uses 1750 BTU's/hour. 95,500/1750 = 54.57 hours from one gallon of LPG, which = 2.27 days (54.57/24).

The 18cf unit uses 1825 BTU's/hour. 95,500/1825 = 52.33 hours from one gallon of LPG, which = 2.18 days. In other words, they're essentially the same.

That means it takes 13.21 gallons of LPG to operate the 12cf unit for 30 days (30/2.27), and 13.76 gallons of LPG to operate the 18cf unit for 30 days (30/2.18).

At the current rate of $1.89/gallon of LPG here in Oklahoma, that breaks down as follows:

The 12cf unit will cost $0.83 per day (13.21 x 1.89, divided by 30) to operate, and the larger, 18 cf unit will cost $0.87 per day (13.76 x 1.89, divided by 30) to run.


Now - let's translate that into use of natural gas.

Natural gas has 1,000,001 BTU's in a DekaTherm, which is the unit Oklahoma Natural Gas, where I live, prices their gas.

The 12 cf unit requires 1750 BTU/hour to operate, and the 18cf unit uses 1825 BTU/hour.

1,000,001/1750 = 571.43, so that means we get 571.43 hours of use out of our 12cf unit out of each DekaTherm, which = 23.8 days (571.43/24). The cost here of 1 DekaTherm of natural gas is $6.75.

1,000,001/1825 = 547.95, so that means we get 547.95 hours of use out of our 18cf unit out of each DekaTherm, which = 22.8 days (547.95/24). The cost here of 1 DekaTherm of natural gas is $6.75.

So -

The 12 cf unit will cost $0.28 per day to operate on natural gas ($6.75/23.8), and the larger 18 cf unit will cost $0.30 per day to run (1,000,001/1825 = 547.95, and 547.95/24 = 22.83 days, and $6.75/22.83).

In other words, if I got this right this time -

To produce the same amount of BTU's -

* The 12 cf unit costs $0.83 per day to operate on LP gas.
* The 18 cf unit costs $0.87 per day to operate on LP gas.

* The 12 cf unit costs $0.28 per day to operate on natural gas.
* The 18 cf unit costs $0.30 per day to operate on natural gas.


With regard to the older Servel's, let use my 1955 Model 856G as an example.

My Servel is around 12 cubic feet inside, and has a cooling unit rated at 2600 BTU's, so let's plug in that number into our equation, and the results are:

My Servel uses 2600 BTU's/hour. 95,500/2600 = 36.73 hours of operation from one gallon of LPG, which = 1.53 days of use per gallon. 30 days divided by 1.53 = 19.6, so it uses 19.6 gallons of propane per month.

That means it takes $37.04 to operate my Servel for 30 days on LPG (19.6 gallons x $1.89 per gallon).

This translates to an actual operating cost of $1.23 per day ($37.04 divided by 30).

With respect to natural gas -

My Servel requires 2600 BTU/hour to operate. There are 1,000,001 BTU's in a DekaTherm of natural gas.

1,000,001/2600 = 384.62, so that means I get 384.62 hours of use out of my Servel out of each DekaTherm, which = 16.03 days (384.62/24). At the current cost here of 1 DekaTherm of natural gas of $6.75, that means my Servel costs $0.42 per day to operate on natural gas ($6.75/16.03)

That should be comparing apples, er, BTU's to BTU's.


Now, let's look at a similarly sized electric model.

General Electric's GTR12HBXRWW is a 12 cubic foot electric refrigerator. It requires 412 kwh per year to operate, which equals 1.13 kwh per day to run.

General Electric's GTS18IBRBB is an 18 cubic foot electric refrigerator. It requires 478 kwh per year to operate, which equals 1.30 kwh per day to function.

The current price per killowatt hour where I live is, averaged for the year, is $0.034 er kwh.

Bottom Line:

* The 12 cf unit costs $0.83 per day to operate on LP gas, and $0.28 per day on natural gas.
* The 18 cf unit costs $0.87 per day to operate on LP gas, and $0.30 per day to operate on natural gas.
* The older Servel, like mine, costs $2.89 per day to operate on LP gas, and $0.42 per day on natural gas.
* GE's 12 cf electric unit costs $0.04 per day to operate (1.13 x $0.034), and
* GE's 18 cf electric unit costs $0.044 per day (1.30 x $0.034) to run.


So, yes, Whistler is right about the electric being less costly to operate, though I wonder what the price to operate them, amortized over time, would be, with respect to longevity and the cost of parts and service...I suppose we'll never know that.

Of course, this is supposing a person has access to the electrical grid - if you don't, you can plug the cost of whichever type of gas is available to you to determine the cost of operating a gas refrigerator, as the cost of running a generator to run an electric one would be, in my estimation, way too much.

If I made any errors in all this, I am certainly open to correction.

- Todd

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Last edited by Todd W. White; 12/08/09 at 11:50 AM. Reason: ...fixed a typo.
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  #18  
Old 12/08/09, 11:44 AM
 
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Quote:
Originally Posted by Todd W. White View Post
Of course, this is supposing a person has access to the electrical grid - if you don't, you can plug the cost of whichever type of gas is available to you to determine the cost of operating a gas refrigerator, as the cost of running a generator to run an electric one would be, in my estimation, way too much.

If I made any errors in all this, I am certainly open to correction.

- Todd
Most off-grid people have some form of elec, usually solar, wind or water (less common) so their cost comes primarily from setting up and maintaining the system. A gas or diesel generator is usually not the main source, might be backup. Very hard to set a cost because you don't always know how long the parts will last when you set it up. Our system was already in place. We're tweaking to try to get more out of it. Going to look at LED lights today to replace HUGE fluorescent units which suck a pile of energy when you have such big ones.
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Old 12/08/09, 11:53 AM
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Servel (the real one - not the folks at Dometic) made an electric version of their gas-fired absorption refrigerator. As best I can tell, the only difference was it had an electric heating element providing the heat, rather than the gas flame.

Since these systems have to have continual heat to operate, even though it fluxuates depending on the amount of cold needed, the element in an electrically-operated system would have to be "on" all the time, and the element would have to be turned hotter and cooler, as needed.

With the advances in technology, I'm wondering if it would be possible to put a high-tech element in there to do the job the flame does, and make it more close in efficiency (and, therefore, operating costs) as the compressor-type electric fridge...

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Old 12/08/09, 08:49 PM
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Caveat...

I've put in calls and email's to the Gas Co. and the folks who make/sell the different modern gas refrigerators.

What I am trying to determine is:

A. What the gas consumption of the refrigerators is when setup for natural gas (not asking the Gas Co. this).

B. Does an appliance setup for propane use the same amount of gas when switched over to NG.

The answers I get may change my report...

They DID! See below -

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Last edited by Todd W. White; 12/09/09 at 04:53 PM. Reason: Updated information
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