There are several causes of noisy operation. If you adjusted the gas input screw that may have been the wrong adjustment, but hard to tell from the written word on posts. For burner roar, the air shutter has to be adjusted for the air fuel mixture. Also the blower wheel can be out of balance, rubbing, or just loose. Low input voltage can cause excessive noisy operation if the battery is bad or needs charging.

Another problem with old furnaces is that they may have rust, pinholes, or cracks in the heat exchanger, which would allow the combustion products, which include CO, to enter the coach. The only way to be sure if the heat exchanger, which seals the combustion chamber of the furnace from the air inside that is heated, much like a heater core in a car uses hot water from the engine, but will not leak the water inside, is to remove the heater and disassemble to inspect the heat exchanger. Of course renting a CO sniffer (instrument) or hiring a technician certified to check it and for CO will also tell you the same thing. But as you say, with an older heater it is just a matter of time.

A well maintained and inspected vented RV Furnace is totally safe and needs no inside ventilation, as long as the heat exchanger is intact, because it vents to the outside all the combustion products. I think that perhaps some folks are confusing a vented furnace in good shape with the characteristics of unvented heaters, both open flame, and catalytic.

Catalytic heaters need almost a fully opened vent to make sure that there is enough oxygen for combustion. As long as there is, it produces almost no CO, and nowhere near any dangerous levels. However, should it use all the oxygen, or you use it at very high altitudes, even a catalytic heater will begin to produce CO, because there is not enough oxygen for complete combustion.

Many folks confuse radiant open flame heaters like the Mr. Buddy heater from Mr. heater, with the catalytic heaters.. These are both open flame heaters just like the space heaters with ceramic bricks to maintain and project heat. Open flame heaters produce much higher levels of CO than any other heater, even when there is sufficient oxygen. You need almost a completely open window to safely use them because you are not just making sure of enough oxygen, but also exhausting CO! An open flame heater is just like trying to use the range or oven to heat. Very dangerous. Both open flame heaters, and the safer catalytic heaters are unvented heaters with one exception I’ll point you to later.

Because of the problems with oxygen depletion and CO, all newly manufactured heaters in most states require an ODS, or oxygen depletion sensor. Here is a good link that shows how an ODS works, and although a little confusing in the description, shows that at altitude, with less oxygen, no type of heater will work as efficiently, and if unvented, will produce a lot of CO.

It doesn’t say that the ODS senses CO, it senses the reduction of the flame, due to lowered oxygen levels not allowing combustion. They do note that as the levels of oxygen lower, the levels of CO2 also rise from the combustion, along with CO, long known to increase from incomplete combustion. It is a mechanical means to detect lowered oxygen levels, which result in increased CO2 levels. But it actually does not detect any gas, rather sensing a diminishing flame-due to oxygen depletion. But in explaining the actual operation, that site, and some others might be read that way.

However, many CO detectors use a colormetric change and a light passing through or obstructed, to indicate CO, which could also be stated it doesn’t measure CO, but the change in a physical state of the area as it reduces or allows the light to pass through. The key is that whether light sensing, flame sensing, or chemical/mechanical, the reaction used is the result of the increase, or decrease, of the properties of a given gas. So it actually does measure O2 depletion.

It is not true that Catalytics will not produce CO in oxygen depleted situations. The following quote is from my owners manual for my own Olympian 8100 catalytic heater:

” !WARNING! The Heater consumes air from the space in which it is used. Sufficient air must be provided to assure complete combustion of the fuel gas. Improper combustion can result in the production of poisonous Carbon Monoxide with resultant danger of asphyxiation and death. Carbon monoxide is an odorless, colorless gas. Symptoms of Carbon Monoxide poisoning often cannot be recognized before losing consciousness.”

The asphyxiation mentioned in the above quote is not from lack of oxygen in the air, but rather the action of the CO attaching to the red blood cells, blocking oxygen uptake anywhere in the body, be- -cause of none being carried by the cells. It results in a very visible change in the color of the blood when drawn for testing making it bright cherry red, as opposed to the much darker color observed in normal blood. Thus even before any further testing, that immediate visual cue is almost diagnostic for CO poisoning, and immediate steps are taken when a victim is seen in time at a hospital.

As far as the furnace fan using up batteries in one night, the fan in and of itself sure can, with some of the larger ones. Mine uses 8.5 amps. (Atwood Excalibur 8535III) But even assuming a small fan, operating on batteries assumes no shore power, in which case there are several other additional loads on the batteries that need to be considered. Each control board for the furnace, Hot water heater, and reefer, use between .5 and 1.5 amps, as well, I will assume some lights on at night, which depending on type can really use up some amps. Add a radio or 12 volt TV, well, you can see how it can all add up pretty quickly to much more than one night’s worth of the furnace fan alone.

As well as the amp draw, batteries are subject to cold and will not deliver their full potential at colder temperatures, thus further reducing the time power can be supplied. The furnace is used in cold weather.

RV solar electric has already measured the amps of all the potential power draws in an RV, and include them on an easy to use worksheet. Go to the link and add up what you use, and instead of thinking solar, think batteries, and do the calculations. I just noticed a lot of good info and some misconceptions that really make quite a difference in the safety.

The question is simply is it a catalytic heater, and the answer will be no. I just got off the phone with them. The answer is that it is an open flame heater.

Catalytic heaters operate at much lower temperatures, and are almost 100% efficient, producing no appreciable amounts of CO as long as there is sufficient oxygen to support combustion. Thus ventilation of about 1 sq inch per 1000 BTUs of catalytic heater rating is required. There is no CO build up at all to vent out unless the Oxygen is depleted to the point of incomplete combustion, in which case it begins to produce CO.

Open flame heaters, whether called radiant, space heaters, etc. do produce CO even when operating perfectly, and with enough oxygen. Ventilation is needed for open flame unvented heaters to both sustain the oxygen supply, AND to exhaust the CO they do produce. Thus they require about double the square inches of ventilation per 1000 BTUs than catalytics.

Things common to both types of unvented heaters:

  • Both are now required to have oxygen depletion sensors.
  • Both produce a lot of water vapor and carbon dioxide, which also require the venting. Only the open flame heater produces CO while
  • operating normally.
  • Both increase CO production with oxygen depletion causing incomplete combustion. The catalytic from none to some. The open flame from some to a bunch.

If folks read the earlier links about the state of the art of CO detectors, they aren’t 100% as of now either. But there is no such thing as a 100% safe unvented heater of any type. Mechanical devices like ODS’ and safety propane shut off flame sensors can and do fail. But if you are going to use an unvented heater, it would be wise to have a CO detector, and a propane detector, for safety. It is also advised that you never sleep with an unvented heater in operation. If you do, be sure you understand it, and follow all the operation characteristics to the letter. Where to place a CO detector? This link from First alert, who does not certify their CO detectors for RV use, I know, I bought one that failed. But a good explanation of the weight and rising characteristics of CO. If you use an unvented heater read the manuals and thoroughly understand the warnings and operating instructions.

Under standing CO, and understanding any unvented heater type you buy, and the unique operating requirements of each unvented heater, is critical to your safety. Your stock RV forced air furnace is vented, and very safe with annual inspections and maintenance. Much safer than unvented heaters.

Here’s an excerpt from the CPSC or Consumer Product Safety com- -mission statistics on CO deaths for one year- 1998. I can find no current estimates, but with the explosion of RV sales and the increasing numbers of fulltimers selecting this lifestyle for both retirement, and mobility for younger contractors, I think it is imperative that we get the word out about the dangers of unvented heaters, especially in the smaller square footage of an RV, when compared to the build up of CO in an average sized house.

Quote: An average of 18 percent of deaths took place in temporary shelters, such as tents, recreational vehicles, campers, and trailers. In 1998, 26 percent of CO deaths, the highest percentage for the five-year period, took place in such temporary shelters. LP gas camping heaters were the products most frequently associated with these deaths, followed by charcoal grills. Note: They are referring to unvented heaters.

Much important info. Unfortunately, the victims can’t post that they “heard” it was safe, and made a mistake. And, unfortunately, online, in some cases (current company excluded of course), the “long reads” and links tend to be ignored in favor of three line answers. Most people consider an RV just a temporary shelter, and for those who are part timers they are. But winter brings out the auxiliary heating systems for both the part timers that use their RVs for ski trips and winter camping, and even the fulltimers in the South. (Yes, it freezes in a lot of our areas too) Getting the real skinny out to our fellow RVrs, even if it takes a few extra minutes of reading and/or research, if it can save one life, to me, is worth the slight effort.

To sum up. Listed in order of safety:

  1. Vented forced air furnaces.
  2. Unvented Catalytic Heaters at appropriate altitudes and with ventilation for air.
  3. Unvented open flame heaters at appropriate altitudes and with a lot of ventilation to exhaust the CO as well as take in air.