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Natural Gas Air Conditioners Cons and Pros?

04/16/2012 9:52 PM

Does anyone have any experience with natural gas air conditioning? I know nothing about it, except that they have a much higher up front cost. There must be a bunch of reasons not to use them, since you hardly hear of them. Now that the price of natural gas is about two dollars per million Btu's (wholesale), is it time to reconsider them?

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#1

Re: Natural Gas Air Conditioners Cons and Pros?

04/16/2012 10:47 PM

My dad had a 5 ton lithium bromide absorption unit that his friends at the gas company talked him into in about 1970. Is that what you're considering? The unit performed okay and lasted about 15 or 20 years with minimal maintenance, but the operating cost savings didn't seem to develop.

1. It used a chilled water loop, so to keep the same 'evaporator' temperature as a direct expansion unit, the refrigerant temp has to be lower because of the extra heat transfer surface involved. This reduces the COP.

2. It still had sizable electrical requirements. As I recall, the condenser fan was larger than an equivalent vapor compression cycle, probably because more heat has to be removed. Then there was the chilled water pump motor and, I think, a refrigerant pump. The total electrical requirements were less than a vapor compression unit, but you have the gas cost to add.

3. Limited maintenance resources, if required. In Dad's case, the gas company was the only company that would work on it.

4. If I recall, wholesale gas price in 1970 was around $0.20 and by mid-70's was over $0.50 and rising. The electrical producers lock in their fuel costs for longer term, whereas gas prices are more short-term market-driven, i.e. volatile , and likely, in my opinion, to rise faster than electricity. Back in the 60's and 70's, the gas companies were trying to increase summer demand to better utilize their assets year-round. But now, with so many gas turbine generators installed, I think their demand is flatter.

Now if you could 'fire' it with a solar concentrator (or wood, pellets, etc.) and power the electrics with PV, you might have something, at least on clear days.

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#8
In reply to #1

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 11:32 PM

"Now if you could 'fire' it with a solar concentrator (or wood, pellets, etc.) and power the electrics with PV (or Peltier), you might have something"

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#2

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 12:13 AM

I found this site for Robur gas-fired residential units. The Robur units are ammonia-water, not water-lithium bromide as I remember my dad's.

Using my local utility's residential rates of $0.087/kwh and $0.735/therm, here's a quick comparison for the hourly energy cost for the chillers, less circulating blower (which should be the same for either), for about 5 ton capacity.

Absorption: 0.95 therm * $0.735 = $0.70/hr

0.75 kw * $0.087 = $0.06/hr

Total $0.76/hr

Compression: 5.0 kw * $0.087 = $0.44/hr

Total $0.44/hr

So for me it's a no-brainer - pay more up-front and higher monthly bill? No thanks, but your mileage may vary. They do have an option for free supplemental water heating, but I doubt it would tip the scale, for me at least. Does my utility's rate reflect $2.00 wholesale gas? Probably not, but even if it did I don't see a payout for my situation. Again, other locations might payout.

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#3

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 12:19 AM

There is also another type of natural gas powered a/c unit where an ICE is used to drive the compressor...York made these for many years...I've never been a fan of York units, and I think I've seen one of these gas powered units...The problem I think is that you needed a small engine mechanic paired with an a/c mechanic to work on them....and well the truth is you're lucky to find one or the other, but 2 in 1...a little too rare....who knows maybe one day they will come into their own, although I might say if not now, then when? I'm not really a believer in oddball units, the more common the technology, the cheaper the parts and the easier to find somebody to fix it...

http://blog.mlive.com/home_improvement/2007/10/gaspowered_air_conditioners.html

http://en.wikipedia.org/wiki/Triathlon_(heat_pump)

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#4
In reply to #3

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 10:49 AM

I wasn't aware that residential size units like this had been manufactured. Assuming ICE is 25% efficient, this would use about 3/4 the gas of the absorption unit and somewhat less electricity, so it would almost break even for me (purely on fuel cost, ignoring the maintenance, etc.) and could make sense for someone off-grid who is handy enough to keep it running.

Almost off topic: The church I grew up in, built in the mid-50's, was air-conditioned only in the sanctuary. The AC unit, 75 tons, used an open radial compressor driven by a six-cylinder Diamond Reo engine running on natural gas. When I became of age, I inherited the Saturday night job of starting the AC. It has since been replaced with electric units.

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#5
In reply to #4

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 11:12 AM

Wow, I've never even heard of one...Certainly rare in this neck of the woods...

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#12
In reply to #5

Re: Natural Gas Air Conditioners Cons and Pros?

12/02/2013 8:43 PM

I had a natural gas fired central air conditioner ( chilled water ). In the early 60's. Really trouble free. House was about 1850 SF. No insulation in the walls. 3 ton unit. In the hottest day in July or August I kept the house 72 degrees without any problem. Only had a small water pump & exhaust fan. No other moving parts. The chilled water left the outside unit about 40-45 degrees. That is why it is called chill water..The main thing is no expensive repair bill. No expensive fluids to relace..Used plain water & a pound of baking soda in the chiller tank once a month..No compressors. I highly recommend them...

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#13
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Re: Natural Gas Air Conditioners Cons and Pros?

12/02/2013 9:42 PM

Thanks for your reply. I think that it is one of those things that could greatly improve efficiency, but has just not caught on yet. Gas dryers in a similar state.

I am biased since I am a volunteer in the Natural Gas Revolution: https://docs.google.com/document/d/19Yf0MWpo91vrlu-mmJtjB1ERukjJo5W41oi4RZVQBug/edit

IMHO CNG and LNG use should be maximized. It is about one fifth the cost, per unit of energy, as is oil. It is taking off in ships, locomotives, and trucks. More impressively it is replacing coal , for electrical generation, in the USA and more slowly elsewhere. Coal is the largest pollution problem in the world.

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#14
In reply to #13

Re: Natural Gas Air Conditioners Cons and Pros?

12/02/2013 11:37 PM

You used a very good example with the gas dryer. I have a gas dryer that is at least 30 years of age. Still working. Put a new belt on it, that's all.

In Texas right now, there are energy agencies that are trying to increase our electric bill by demanding extra standby generating power. If the gas companies would push the gas air conditioners like they did in the 60' & 70's. They financed my unit. That would cut the need for electricity quite a bit. Gas companies are pushing natural gas emergency generators now. I have one. Came in quite handy when IKE paid us a visit. 12-13 days without electricity. I cannot say enough good things about natural gas air conditioners...Extremely reliable..Costs more, but so does the high efficiency electric models....

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#6

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 10:40 PM

We used propane powered ones on sail boats and trawlers when at sea for a few days never had any problems except for running out of fuel.

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#7
In reply to #6

Re: Natural Gas Air Conditioners Cons and Pros?

04/17/2012 11:29 PM

Surely those were continuous ammonia/water units.

I've always wanted to run one of those on a solar collector.

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#9

Re: Natural Gas Air Conditioners Cons and Pros?

04/18/2012 12:00 AM

Conditioning is one of the applications of refrigeration. Vapor absorption system is one of the types of refrigeration system . Most of conventional refrigeration systems are Vapor compression system which needs electrical energy to operate the compressor. In V.A system compressor is replaced by generator and absorber and any type of heat source can be used. Li-Br - water vapor and Ammonia - Water vapor are available refrigerant & absorbent combinations. Smaller capacity units were used for vaccine refrigeration and remote area application where electrical networks were not available. Commercial Higher capacities from 300 T.R to 1000TR are available in the market. Wherever cheap heat source is available VA system is preferred than V.C system.

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#10

Re: Natural Gas Air Conditioners Cons and Pros?

04/18/2012 5:15 AM

Interesting blog here, many thanks to all concerned.

Although we rarely have temperatures over 40°C for very long here in Germany, a few weeks in summer between June and September, we have a small portable unit that we used to cool the bedrooms.

But since we fully insulated the house, we simply have not needed it, not even once.....

I know that in areas with longer lasting higher temperatures, AC will still be needed, BUT, if the house is fully and properly insulated, the cost of running the AC can be seriously reduced and maybe switched on later in the year for the first time, and also switch off earlier.

People come into our house when it is really hot outside and ask how long have we had air conditioning!!! I say, many years, but it is never switched on anymore.....

So an AC unit that costs relatively less to run and has little maintenance requirement, would seem to be the order of the day.

So don't forget house insulation and planting trees to shade the house from the Sun in the hot days of summer......work out the hours required and the position of the sun at those times....

I had never heard of Natural gas AC up till today, so something new for me and very very interesting. Thanks to all concerned.

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#11

Re: Natural Gas Air Conditioners Cons and Pros?

04/18/2012 7:38 AM

http://www.gasairconditioning.org/FAQ.htm

I had a notion about Japan using a lot of natural gas air conditioning. It's 30% according to this site.

brgds

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#15

Re: Natural Gas Air Conditioners Cons and Pros?

05/28/2016 4:20 AM

When I bought my first house, back in 1970 (if I recall correctly), I was persuaded that I could save money in the long run if I put in a gas air conditioner, which was a commercial option for homeowners at that time. I don't now recall the brand nor do I know what technology it used. I only know it chilled water that was circulated through a heat exchange coil located in air flow in our home. It worked very nicely for the several years we owned that house. I never figured out what the payback time would have been. I do think at least then it was cheaper to operate than an electric AC.

Now I live in another home. One we bought 20 years ago. At that time I asked for a gas AC unit and was told that none were available any more. Later on I learned that the salesman lied to me about a number of things--possibly including that!

Now the overall HVAC system I bought then is dying and I need to replace it. It has two independent systems, one of which is a two-zone system. My present thought is to put in solar thermal panels on the roof to heat water and store it in some large tanks at about 180 to 200 degrees Fahrenheit (82C to 93C), and then use that to run though heat exchange coils in the airflow for any of the three zones that needs heating. I would like to have either a gas or a hot water driven AC unit that could produce chilled water to run through those same heat exchange coils for whichever zone(s) needed cooling. If the sun ever failed to produce enough hot water for this, I could have a gas water heater included in the system to heat the water in those storage tanks to that high level as needed. (We live in Southern California, in the USA, so we get a lot of sunlight. I already have 14kW peak generating capacity in solar PV panels on our roof, but I think there is enough other roof space to put in the needed solar thermal panels.)

I've not yet done any calculations to verify what, if any, savings I could expect from such a system. I do know it will likely cost more, but our experience with using such a system for heating in our previous home was quite delightful. Whenever we needed heat it arrived in the form of very gently warmed air, instead of as a blast of hot dry air that typically comes from a gas furnace.

I'm glad to have found this discussion, and hope I can learn here how best to move forward on my HVAC system redesign.

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#18
In reply to #15

Re: Natural Gas Air Conditioners Cons and Pros?

01/20/2017 12:41 PM

Hi John,

I'm looking to install natural gas air conditioners in 16 electricity starved townhouses in Los Angeles, but can't find any units or installers. Did you get an answer to your questions?

Please let me know. jgvrentals@gmail.com 310-770-8081

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#22
In reply to #15

Re: Natural Gas Air Conditioners Cons and Pros?

01/12/2019 12:05 AM

John

Look into sun tracker pericolic mirrors that concentrate sun to a center tube. Than look into eutectic salt. this becomes a liquid at a very low temp and transfers heat at a very high %. Use the heat collected to run your absorbs ion A/C. It also creates potable hot water. I used to own a Soler business in the 70 we used 12"X12"X1/2" tray's filled with eutectic salt to store the energy and release it as needed. I am sorry I am not a good writer but I have been preaching all of Theas devices for 30+ years. I would like to make voice contact with you to discuss what I have learned.

Thank You

Dave

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#16

Re: Natural Gas Air Conditioners Cons and Pros?

06/30/2016 9:31 PM

I installed my first 5T NG air conditioner in 1972 and have only had to replace it once some time in the 90's due to a chemical leak. The new one was more efficient and still going strong. Every spring I drain and clean the water tank and fill to the proper level with clean water.. The system uses chilled water to cool the house so I have 2 100' insolated water hoses going to the chiller on my furnace.

I live in S.CA and it gets in the 100+ at times. I have a 2 story 2300 sq.ft. Electrical runs $56 and gas $78 on the level pay. Compare that to 5T of electric and having to run charged lines.

It may cost more to buy but cheaper to run and install.

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#17
In reply to #16

Re: Natural Gas Air Conditioners Cons and Pros?

08/09/2016 8:38 AM

I use to install and service these units here in Philadelphia until they became extinct. Not sure if yours is or was an Arkla Servel or a Robur. I would guess since you are in S Carolina, your winters are very mild and you don't need anti freeze in your tank like we do here in the Northeast. When we cleaned our tanks, we did a 50/50 mix and added anti foam and anti alga to the tank which helped keep the mix clean. I miss working on those beasts. A lot of moving parts.

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#21
In reply to #17

Re: Natural Gas Air Conditioners Cons and Pros?

07/10/2017 8:57 AM

I have known 2 friends whose family purchased Bryant NG units in the late 60's. Though remembering the constant hissing and clicking of those, surely upset neighbors. Both eventually were replaced with electric models.

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#19
In reply to #16

Re: Natural Gas Air Conditioners Cons and Pros?

01/20/2017 12:45 PM

Hi Dar,

I want to install 16 natural gas A/C units in Los Angeles, but can't find an installer. Can you help me?

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#20
In reply to #16

Re: Natural Gas Air Conditioners Cons and Pros?

01/21/2017 3:04 AM

Unclear to me where you live. Is S.CA South Carolina, and one person thought, or Southern California (which happens to be where I live)? I live in Garden Grove, CA 92844, and I'm the only John Goodman there in the AnyWho.com directories. Please call me if you can so we can discuss what you bought in the 90s. Maybe I can still get it now.

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