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Old 09-06-2017, 06:08 PM   #1
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heater problems at high altitude

I am new to the camping world. I just bought a used 2013 rockwood ultralite 2304s, and so far love it. I was camping last weekend and the heater worked on and off but I was at 10,000 ft. never had problems with it before or after at 7000 . any one else have this issue?
thanks
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Old 09-06-2017, 08:17 PM   #2
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You need to describe in more detail what you mean by "worked off and on." That could mean that fan blew air the whole time, but maybe wasn't hot. It could mean that it would stop blowing, even though it didn't seem to get warm enough inside your trailer to trip the thermostat. Were there noises? Were there smells? And so on.

In general, altitude shouldn't affect your furnace. There is less oxygen at 10K than 7K, obviously. However, this doesn't mean that there won't be combustion of propane. What it means is that the combustion is inefficient and incomplete. Complete combustion produces CO2 and water. Incomplete combustion produces CO2, water, and CO. This is why you have to be careful with propane heaters indoors. With RV furnaces, the exhaust is expelled outside ... so it doesn't matter as much that you're producing CO. A quick google will tell you more about combustion reactions and the production of CO.

OK, that's a long way of saying that you should get the same heating performance from your furnace at 10K as 7K.

My experience is with a popup, but those use a similar Atwood/Suburban furnace. I never had a problem camping and using a furnace at 10-11K feet.

But, again, describe your problem. There are about 328 different ways for things to break. So, simply stating that you have an issue makes it difficult for people to help. The more detail and specificity you can provide, the better your chances of finding a solution.

Good luck.
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Old 09-06-2017, 09:02 PM   #3
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Quote:
Originally Posted by wyoming camper View Post
I am new to the camping world. I just bought a used 2013 rockwood ultralite 2304s, and so far love it. I was camping last weekend and the heater worked on and off but I was at 10,000 ft. never had problems with it before or after at 7000 . any one else have this issue?
thanks
In a nut shell...Yes ! High altitude does affect the performance of propane and gas appliances. Notice when you cook at high altitude...unless you're using a packers stove built for high altitude, it takes longer to cook anything. There is old research out there that figured you lose 3 to 4% of your btu's for every 1000 feet above see level. Do some research and you'll find how altitude affects propane and the appliances they are connected to.
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Old 09-06-2017, 09:31 PM   #4
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Took us forever it seemed to boil water at 9,000 feet.
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Old 09-06-2017, 10:12 PM   #5
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I live in Colorado and take my fiver toy hauler everywhere across the state....camping at high altitude. Yes, altitude affects cooking efficiency and the air is thinner, but it should not affect the actual operation of your appliances. I have no problems with my propane furnace, hot water or cooking appliances from 5000 to over 10,000 feet above sea level. You most likely have a functional problem with your furnace or its air/fuel mixture components.
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Old 09-07-2017, 10:05 AM   #6
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thanks every one for the help!
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Old 09-07-2017, 10:52 AM   #7
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You probably need a new orifice for high altitude. Lots of threads on this issue. Here's one related to the fridge:

http://www.forestriverforums.com/for...de-115051.html
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Old 09-07-2017, 02:34 PM   #8
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We had a 2005 TT we took to Yellowstone in 2012 - At prox 7000' we had problems with everything propane - that is heater, fridge, cook stove and HW heater. Took to local service station and he cleaned the appliances (& assume orifices) and not sure he made any adjustments but all worked again but I don't think after that we were above 5000'. He did tell us he sees this a lot especially with older units that hadn't had the appliances cleaned and even some that were.
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Old 09-07-2017, 05:21 PM   #9
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Over the years I have had problems with a furnace and a refrigerator at high altitude. Operation was intermittent. The issue Is placement of the igniter relative to the propane jet. Thinner air at high altitude lets the propane disperse into the air faster and it may be too weak at the spark to begin combustion. Any wind can aggrivate the problem. So the space between the jet and igniter has to be spot on. A less than ideal spacing will still work fine at lower altitudes.
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Old 09-07-2017, 07:54 PM   #10
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Read the thread about refrigerator issues at higher elevations and they had a lot great ideas. We're at 8250 feet and the LP gas part of the refrigerator is very fussy. Water heater and gas heater seem to work fine but we have a compact ceramic heater if the main heater doesn't want to work.
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Old 09-07-2017, 11:22 PM   #11
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Never had a problem with any propane device at higher altitudes.

Your camper heating system needs a good cleaning. You will probably find rusty flakes where the propane flame is emitted that needs a mild brushing and elimination.
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Old 09-08-2017, 09:43 AM   #12
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Propane pressure regulators are altitude compensating. You will get less lp at higher altitude because there is oxygen in the air and therefore you will use less lp to maintain correct combustion and therefore get less heat output from an lp applience. In other words if atnospheric pressure goes down, lp pressure will go down. Hopes this helps.
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Old 09-09-2017, 10:51 AM   #13
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So, I did some research and found lots and lots of sources that spoke about the derating of propane appliances with altitude. However, none of these articles detailed the why ... merely the consequence. For example, an article might state the rule as 2% per 1000 ft and then proceed to discuss the various ways to change orifices and equipment for better performance. But, I can't find the derivation or science that explains the phenomenon.

Propane has about 91,000 BTUs per gallon. That's a fixed property that won't change. Burn a gallon of propane at sea level and you'll get 91,000 BTUs. Burn a gallon of propane at 12,000' and you'll get 91,000 BTUs. So, why then, would using a propane stove at each of these locations produce different results when the fuel itself is unchanged?

Anyone with any basic chemistry background knows that a combustion reaction, in its most basic form, is a reaction of a hydrocarbon with oxygen to produce carbon dioxide and water. This is the easiest way to argue against the idiots in the world that insist that oxygen is combustible. It's not. Try to write a combustion equation for oxygen. You can't, because oxygen isn't combustible.

And, we don't have to make it any more complicated than that, considering that propane is a very simple, straight-chain hydrocarbon: C3H8.

The perfect equation for complete combustion is: C3H8 + 5 O2 > 3 CO2 + 4 H2O

As altitude changes (or ventilation is terrible in a closed space), oxygen becomes limited ... there isn't 5x amount of O2 as propane. There isn't enough oxygen to react with the supplied propane. We start getting incomplete combustion, which can actually be written in several forms.
Here are two such equations, but there are others:

2 C3H8 + 7 O2 > 2 CO2 + 2 CO + 2 C + 8 H2O

2 C3H8 + 7 O2 > 6 CO + 8 H2O

First of all, what we see is a dirtier reaction. We're forming soot (C). Second, we see a dangerous reaction. We're forming carbon monoxide. For RV furnaces, the reactants and products are all expelled via the exhaust outside the RV; the fan blows the heat inside the RV. But, portable propane units obviously do not have this separation or an exhaust port/vent. This is why when using a portable propane heater in a tent, for example, you tend to get a lot more condensation -- combustion produces a ton of water vapor. It's also why you have to be careful, since you can potentially be creating carbon monoxide, an extremely lethal gas.

But, we still haven't explained why appliances would put out less heat. Regardless of complete or incomplete reaction, we're burning the same amount of propane which will produce exactly the same amount of energy and heat.

The regulator on the tank should be producing the same 11" WC for propane, regardless of altitude. It works off pressure differential (gauge pressure, not atmospheric pressure). Thus, the flow of propane should remain constant, given properly functioning valves, tubes, and such. So, again, we shouldn't see a decrease in energy, since the same amount of fuel is being supplied.

This leaves me with the only logical conclusion is that oxygen becomes so limited that you end up with a reaction that looks like:

a C3H8 + b O2 > c C3H8 + d CO2 + e CO + f C + g H2O

I'll let others work out the stoichiometric coefficients a-g. Note that propane now shows up on both sides of the equation. What this means is that we're not actually burning all of the propane being supplied ... we're dumping propane out the exhaust without burning it. Now, it's not just incomplete combustion, it's partial combustion. (And, yes, I know that I've conflated a reaction equation with a sort of mass balance ... but I created this "model" to illustrate the point.)

Now you can start changing orifices and other components to get a better fuel mixture. Or, you can blend the propane with other gases to dilute it down for the same effect -- achieving a better ratio. This won't restore the heat output, as you're still limited to burning a finite and fixed amount of propane; you're supplying less propane now, which will, of course, produce less energy/heat from the appliance.

It will, however, prevent you from wasting fuel and from potentially quenching the flame. At some point, you'll supply so much propane, that it will overwhelm the oxygen and stop the reaction (flame). Sort of like lighting some newspaper and a few pieces of kindling ... then immediately throwing 9 pieces of wood on top. Sure, wood burns, but if you dump all that fuel on a small flame, the whole thing goes out.

Anyway, that's my conclusion.
  1. At sea level, all propane is burned and heat/energy output is maximized. At altitude, only some propane is burned and heat/energy output is therefore less... OR ...
  2. At sea level, normal amounts of propane are supplied, all is burned, and heat/energy output is maximized. At altitude, a reduced amount of propane is supplied, all of it is burned, but energy/heat is limited due to the limitation of propane supplied... OR ...
  3. The excess propane supplied at altitude becomes so great and the oxygen available becomes so restricted, that the combustion reaction is quenched and the appliance fails to function at all. Catastrophic failure.

Happy to hear other points of view, because I don't believe I fully understand everything that's going on that limits efficiency and output of propane appliances at altitude.

Good luck.
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Old 09-09-2017, 12:13 PM   #14
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Let me try this from another direction. A cubic ft of air at sea level atmospheric pressure (14.7 pounds per sq inch absolut psia) there are a given number of oxygen atoms. As we go up in altitude atmospheric pressure deceases therefore the air is not compresses as much resulting in fewer molecules of air therefore fewer atoms of oxygen and nitrogen. Forget about the nitrogen only the O2 is used in combustion. With fewer O2 molecule availble for combustion you will be able to burn fewer molecules of fuel gas (lp). The O2 is the oxidizer that promotes combustion. If less O2 is available, then less fuel can be burned resulting in less heat being produced. As I stated earlier, an lp regulator is altitude compensating by its nature; the lp perssure will be reduced as the regulator goes up in altitude (lower atmospheric pressure). This will reduced lp perssure and there will less lp (molecules) available for combustion resulting in less heat.
I hope this explaination clears up why there is less heat at higher altitudes.
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Old 09-09-2017, 12:28 PM   #15
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One thing I forgot to address. Unless you're dealing with a special case of pressure regulator (such as automotive feedback controlled systems), one side of the regulator is in contact with the gas and the others side is exposed to the atmosphere, that is why it is altitude compensating. As was said it is a pressure differential device. Gas pressure on one side and a combination of spring and atmospheric pressure on the other side of the diaphram. Pressure is determined by basic spring pressure and assisted, and varied by the atmospheric pressure.
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