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Old 12-07-2009, 09:25 PM   #1
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Default Gas Refrigeration

Hello All!

I'm new here, and though I don't claim to know everything about the subject, I'm very interested in gas-powered (also called absorption) refrigeration, and would like to offer to share what I've learned on the subject.

I have a 1955 Servel Gas-powered Refrigerator in my home - I bought it locally off of Craigslist, restored it, and now am using it. I am very pleased with it, and it's quite efficient. In the process of doing so, I've learned a lot about these units, and am willing to share what I've learned, answer questions, and help others find ways to get away from electric refrigeration.

So - ask away! I'll try to help!

Todd in NE Oklahoma
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Old 12-08-2009, 12:23 AM   #2
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You're going to be sorry you asked... I have a boatload of questions. Gas is considerably more efficient and more affordable than electric but you can't find a new gas refrigerator to save your life... I looked... and looked... and they don't exist... they are no where to be found. What really happened to them and why don't we have a choice between gas or electric like we do for our clothes dryers and hot water heaters?
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Old 12-08-2009, 05:45 AM   #3
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When renovating "this old house" I looked for a gas refrigerator too, and discovered that they are very hard to come by, as Equilibrium did.

Equilibrium, I was looking for the link to Lehman's Hardware appliances page for you, to include in VintageServal's "Intro" thread, and discovered that they have a few refrigerators. Might be worth a trip to Ohio with a rented U-Haul to pick one up? http://www.lehmans.com/store/Applian..._all=&sort_by=

Last edited by Hedgerowe; 12-08-2009 at 05:55 AM. Reason: Added link.
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Old 12-08-2009, 09:04 AM   #4
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Todd, what kind of gas is that? Propane or piped-in natural gas?

I'm interested in them, but I don't know if I could live without my deep freezer, and I can't imagine finding both items in gas (if there even are gas freezers!)
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Old 12-08-2009, 09:07 AM   #5
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...Then I looked at Hedgerowe's link and discovered that there are indeed gas freezers. And the refrigerators are LP, except for one that's kerosene (!)
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Old 12-08-2009, 11:57 AM   #6
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Yes, there are several companies making gas-powered refrigerators and freezers. The better ones are made by the Amish here in the USA.

Examples;

Built by the Amish:

http://www.crystalcold.com

EZ-Freeze Cabin Refrigerators


Dometic (import), labeled Servel (not the same as the vintage ones made in the USA) -

Propane Gas Refrigerators and Freezers - Models

There are some others, but these are the most prominent. You can google around for the best prices.

They're all setup for LP gas, but can be ordered setup for natural gas, too.

Anyone interested in what it costs to run them?
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Old 12-08-2009, 12:18 PM   #7
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Sure! What does it cost to run them?
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Old 12-08-2009, 12:48 PM   #8
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We need to compare the BTU use of each type of unit, because the LP gas people and the natural gas people don't measure their products using the same units. So, I have made the following calculations using the BTU's used by the different units, and the BTU's that are available from the different types of energy.

Just keep in mind that 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, but, after several revisions, I "think" these numbers are correct:


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, the electric one is 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.

One more thing -

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...

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

- Todd
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Old 12-08-2009, 12:57 PM   #9
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Wow. Most impressive calculations, VintageServel! Is it safe to assume that the carbon footprint related to the manufacturing of gas (either type) or electric refrigerators or freezers is roughly the same? Or are there significant differences in the way that the systems are made/distributed that would make a notable impact one way or the other?
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Old 12-08-2009, 12:59 PM   #10
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I dunno - but I do know it doesn't make a lot of sense to burn gas to make electricity, like they do around here, when you could just burn it yourself.
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