Alternative Heat Sources for an RV
Catalytic, Ceramic, and other buzzwords
David E. Damouth www.damouth.org
last update: 19 December 2011
A work in progress - comments, suggestions, and additions welcomed
All but the smallest Recreational Vehicles come equipped with a built-in ducted propane furnace. Yet a growing minority of RVers rarely use this furnace, opting for alternate forms of heat. This article will attempt to explain the reasons for these alternate heating systems, and assist the reader in deciding whether to acquire one of these options.
Advantages of the conventional ducted propane furnace: Although this article is not about the traditional propane furnace, reviewing the familiar characteristics provides a starting point for evaluating alternatives.
Familiarity and convenience: The great majority of Americans grew up with an automatic forced-air furnace in their home. The RV furnace seems very similar to a home furnace and is completely automatic - just set the thermostat and forget it.
Uniform Heat: In a well-designed RV, ducts carry the heated air from the furnace to several locations spread throughout the living space (and sometimes to basement areas as well, to keep water and sewage tanks from freezing in cold weather). Depending on individual preferences and lifestyle, the uniformity of heat distribution can be seen as either an advantage or a drawback.
Safety: The propane RV furnace has a long history of development, testing, and use. It is reasonably foolproof and (when properly maintained) is very safe.
Drawbacks of the conventional ducted propane furnace: There are several reasons (not all equally important) for not using the furnace:
12 v. power usage: All ducted furnaces depend on a 12v. fan to circulate hot air. The fan in my first RV drew 7 amps from the battery. Another RVer with a bigger rig and a higher output furnace reports that his unit draws 11 amps. On a cold night when the fan may run for many hours, this load, combined with other typical 12 v. power uses, may completely discharge a typical battery in a single night, if the RV is not connected to shore power.
Cost and Convenience: A typical RV furnace is probably, at best, about 70% efficient, meaning that 30% of the propane you buy does not contribute to heating your rig. (Some writers have suggested efficiencies as low as 50%). Also, the furnace heats the entire rig, and some people would prefer to heat only a small comfort zone where they currently are seated, using much less propane. Not only does excess propane use waste money, but in some situations it is inconvenient and time-consuming to replenish the propane supply, providing an incentive to make your propane last as long as possible. Also, in some RV Parks, electricity used for heat is "free" in that it is included in the price paid for the campsite, whereas propane is never free.
Noise: In a small RV, the noise of the furnace fan can seem quite loud and annoying.
Space: Some individuals in small RVs have completely removed their furnace, opening up a significant amount of space for other use.
Electric Heaters: There are many different types of portable electric heaters, some more suitable for RVs than others. Their power consumption generally is between 300 and 1500 watts. (The 1500 watt upper limit arises because this is about the most power that can be drawn from a standard 15 amp household circuit that is also shared with up to 300 watts of other typical household uses.)
Advantages of Electric Heaters:
Clean and efficient: All electric heaters are 100% efficient, and create no harmful byproducts.
Low Operating Cost (sometimes): In some RV Parks, electricity usage, even for heaters, entails no extra incremental cost. (On the other hand, when electricity is metered at your site, or when heater usage costs an extra $2.00 per day, electricity generally costs substantially more than propane for the same amount of heat). At the end of this article, I'll tell you how to figure out whether electricity or propane is cheaper in this situation.
Drawbacks of Electric Heaters:
High operating cost (sometimes): When electricity is metered at your site, or when heater usage costs an extra $2.00 per day, electricity generally costs substantially more than propane for the same amount of heat.
Safety Concerns: Good quality portable electric heaters generally have built-in protection against over-temperature and tip-over. But such protections may not be completely foolproof, and very old or very inexpensive heaters may lack these basic safety devices. Thus, safe use of portable heaters requires a certain amount of common sense, thought, and care.
Noise: The small "cube heaters", which are most practical for use in the limited space of an RV, depend on a small, high speed, noisy, fan to move enough air past the very hot heating element. Some are noisier than others.
The most common electric heater in an RV is the "cube heater", which is simply a very compact (typically a cube approximately 8" on each side) electric heater with a powerful fan. Many of these small heaters are labeled "ceramic" heaters, a word which some people confuse with the "catalytic" propane heaters discussed below. "Ceramic" refers to the material from which the actual heating element is manufactured. This is insignificant to the typical user. Some heaters are labeled "high efficiency". This is meaningless marketing hype: Every electric heater is 100% efficient. A heater should be chosen based on other features, not on whether it is "ceramic" or "high efficiency".
Here is some details about two specific cube heaters which I have owned and used for about 14 years. They are fairly typical of the range of cube heaters available:Holmes Model HCH 4060T: This model is fairly typical of many low- to mid-priced heaters, and this brand seems to be widely available. The product seems to be well-built and durable.
Advantages: Has low and high power modes. High is 1500 watts. This may trip the circuit breaker on 15 amp circuits if the circuit is shared with more than 300 watts of lights or other electrical loads. The low setting will avoid this problem.
Drawbacks: The thermostat doesn't work very well - it's influenced strongly by the heat from the heating element, and is somewhat unpredictable. The thermostat has substantial hysteresis, so that there is a substantial ambient temperature swing as the heater cycles on and off. The fan is fairly noisy, and cycles between full-speed and off as the thermostat turns the heating element on and off. This can be quite distracting. This product does not have a tip-over switch, although its curved heat outlet panel prevents overly high temperatures in most tip-over situations.
The above model is no longer available. A current model that is somewhat similar is the Holmes HFH111T-U, about $20; 7.5" x 4.5" x 11.3". The Holmes HFH2986-U is somewhat larger (11 x 9.1 x 11.5 inches), with a larger, slower turning, fan which is advertised as "Whisper Quiet". 11" x 9.1" x 11.5"; about $33. This model has an annoying "one-touch" control which you have to push up to 12 times to cycle through the pre-set power and temperature settings. This is a major nuisance compared to the traditional rotary temperature knob and separate off-low-high switch found on most other heaters.
Pelonis Disk Furnace III, model HC-451. This heater is somewhat more expensive than the Holmes, but has several additional features which I like:
Advantages: The output is continuously variable. As the ambient temperature rises and approaches the thermostat setting, both the heating element power and the fan speed become gradually lower. Instead of cycling on and off, it settles down to a continuous output of just enough heat to maintain the temperature setting, with the fan turning quite slowly and quietly. This continuous quiet sound is much less obtrusive than the repetitive "click-roar-silence-click" sequence of most other heaters, and also results in a fairly uniform room temperature over time. Even at full power, it's quieter than the Holmes. It has both tip-over and over-temperature safety switches. The electronic thermostat seems to be more accurate and consistent, compared to the mechanical (bi-metal strip) thermostat in the Holmes.
Drawbacks: There's no low-power setting (but see below). It costs about $70. The ceramic heating element has rather small air passages, and can be clogged by dust (in spite of a built-in dust filter which has be be cleaned occasionally). We often sit our heater on a carpeted floor, a very dusty environment, and I occasionally have to disassemble the heater to brush dust out of a clogged heating element. After two years of use, several of the screws that hold the case together have stripped the threads in the plastic case (or the threaded areas have cracked). Some of the newer models have a steel rather than plastic case - perhaps an advantage.
This Model (HC-451)is still available (Current price about $70), 14 years after I bought mine, which says something about its quality and popularity. There are also several other very similar models, differing slightly in features. Model HF-N has added a low power mode (at about the same price) - it can be switched to a 600 watt maximum output. Model 461 is similar but has added a fifth ceramic disk, for a little more money. It is still 1500 watts. This provides more air flow with less fan power, perhaps making it a bit quieter. There are other very similar models, some of them marketed only throught a specific chain of stores. Some models now have a "fan-only" mode. Make sure the model you buy says "electronic thermostat" - this is an important feature.
Radiant Electric Heaters>: A radiant heater emits a beam of (mostly)infrared light which is absorbed by the body it is aimed at, thus heating the body without significantly heating the intervening air. There is no fan, so these heaters are absolutely silent.
The heater I have contains a coil of glowing wire at the focus of a shiny parabolic reflector which focuses the red and infrared radiation into a beam extending out from the front. It has a convenient stand that lets you tilt the beam up and down as well as side-to-side, so you can point it at your favorite tv-watching or reading chair. A substantial part of the heat is absorbed directly by your body rather than heating the whole room. It feels like sitting in front of an open fireplace or standing next to a red-hot potbelly wood stove. As a result, you can feel toasty warm in a rather cool room. I love it. It feels good and saves energy. It's only 800 watts, but it can warm me up quicker than heating the whole room with a 1500 watt heater. The stand has a little motor that can oscillate the beam from side to side, but I never use that feature.
My heater is a no-name generic product that I found several years ago at Home Depot for about $20. I just did a Google search on portable radiant electric heaters and found one that looks quite similar: Radiant Heater. Google on the terms radiant portable electric heater and you'll find several others that are somewhat similar.
You will also see a different type of radiant heater which uses one or more long thin quartz heating elements, in a parabolic cylinder. I haven't tried to compare these to the heater above, but I suspect that they don't focus the heat as well (only focussed in one plane), and the quartz element can be fragile.
The Big, Expensive, Electric Heaters: We are often bombarded with newspaper and television advertising for big, heavy, impressive-looking electric heaters (BEEH), some with hand-finished hardwood decorator cabinets, and all claiming to be dramatically better in some way. EdenPure is one of the most advertised brands, but there are many others. Many of the owners of such products extol their advantages with almost religious zealotry. In spite of their size, the BEEH's range from 500 to 1500 watts, the same heat output as the small inexpensive heaters.
A year ago, I decided to look more closely at these BEEH products. I read and studied a bunch of their literature, and read many reviews and evaluations on the Internet. I acquired two different BEEH models from EdenPure (sent to me free by the company, who would like to sell more product into the RV market which they had previously ignored, and was presumably hoping for my favorable review in the article you are reading now). I watched Bob Vila's videos about the EdenPure BEEH. I kept these products around the house for almost a year, using them in various conditions in several different rooms.
Underlying much of the overblown advertising hype about BEEHs are two obvious truths: (a) A lot of older homes have obsolete, inefficient, leaky, poorly insulated, central forced-air heating systems. In such homes, the cost of running local electric heating may compare favorably to the running cost of the central system; and (b) In almost any home, you can reduce heating costs by keeping most of the house cooler and heating only the area currently being occupied. Most of the claims about saving money with BEEHs can be traced to one of these factors. While true, these facts are just as true for a $30 heater as for a $300 one. (Remember: the BEEH's and the cheap heaters are all exactly 100% efficient in converting electricity to heat). For most RVers (who rarely use their RV in very cold weather and use electric heaters only occasionally for a bit of warmth on a cool evening or morning), convenience, initial cost of the product, and compact storage are more important than the cost of electricity or propane.
One difference between a typical BEEH and a typical $30 cube heater is that the BEEH has a larger but lower rpm fan (sometimes, a centrifigul blower) which may be quieter and which emits a large amount of slowly moving warm air, whereas the cube heater emits a smaller volume of hotter, faster moving, air. The BEEH proponents claim that their slower, cooler, air has less tendency to collect at the ceiling compared to the cube heater (presumably giving greater comfort and less heat loss through the ceiling). Warmer air certainly does collect at the ceiling (which is one reason we install ceiling fans in high-ceiling rooms at home), but I very much doubt that this effect is measurably different for a BEEH vs. a cube heater. And it's largely irrelevant to an RVer anyway.
As to the specific performance and features of the EdenPure BEEHs I used, compared to the small heaters described earlier:
- Both BEEHs are quieter than a typical cube heater, but not by a lot. The 900 watt Gen 3 Personal Heater, in addition to the rushing air noise, had a quiet but annoying high pitched whine. The Gen 4 1500 watt unit has a new fan design that is a bit quieter. The Pelonis, when its full output isn't needed, settles to a lower fan speed and would be comparable in noise to the BEEH.
- The Gen 4 BEEH has an electronic thermostat for improved temperature accuracy and less hysteresis, but it cycles between two power levels (500 watt, 1500 watt) rather than having a continuously variable power like the Pelonis. The Gen 3 Personal BEEH has a mechanical thermostat and on-off cyclic behavior like most cube heaters. (a Gen 4 Personal heater is now available and has the electronic thermostat - which I believe switches between two power levels like the Big Gen 4).
- The big Gen4 1500 watt heater is about 18" x 13" x 16" and weighs 27 pounds. It has wheels, but not a convenient lifting handle. Unless you want to use it as a table, it is far too large for a typical RV. The new Gen 4 Personal is Width: 13.5" x Height: 15.5" x Depth: 10" and weighs 19.5 lb. It also lacks a convenient carrying handle.
- I find the controls on both units to be functionally ok, but less convenient to use than those of the Holmes or Pelonis units described earlier.
- A remote control came with the Gen 4 1500 watt heater, and could be purchased as an option for the Gen 3 Personal Heater. This could be a major convenience for a person with limited mobility, but is otherwise not a significant advantage.
Summary: I find both EdenPure heaters to be solidly built, probably reliable and long-lived. The noise levels are acceptable but not exceptional. The controls are a bit less convenient than the other two cube heaters. But the overriding factors are that both are far too large for convenient use and storage in a typical RV, and both cost far more than can be justified in comparison to other heaters.
Heat Pumps: Think of a heat pump as an air conditioner installed backwards, so that it cools the outdoors and heats indoors. In fact most heat pumps are air conditioners with additional valves and controls so that they can operate in both modes - either cooling or heating the inside of your RV. Some newer high-end RV's have heat pumps either as standard or as an extra-cost option.
Advantages of Heat Pumps: In heat pump mode, a heat pump delivers two to four times as much heat per unit of electricity, compared to the simple electric heaters discussed above, and hence costs two to four times less to operate. If the unit is ducted, it will deliver the heat evenly over the entire RV.
Disadvantages of Heat Pumps: The initial cost is much higher - substantially higher than the traditional air conditioner. (But useful life may be 10 years or more, so when amortized over the life of the unit the extra cost is modest and may be recovered in electricity or propane savings (depending on the cost of these fuels in your area)). A heat pump is quite noisy, although a basement-mounted ducted version may be quieter than the typical ceiling-mounted non-ducted air conditioner/heat pump. On the other hand, the basement-mounted heat pump in our current motorhome is mounted almost directly under the bed, making it seem very noisy when we're trying to sleep.
Also, heat pumps only work when it's not very cold. As the outside temperature approaches freezing, the heat output and efficiency of the heat pump diminishes, and it will frequently turn off and go into a defrost cycle for a while. Below 30 to 35 degrees, they won't work at all.
Kerosene Heaters: Kerosene generally burns much less cleanly than propane, so that these heaters have a higher probability of emitting dangerous gases, and pose a serious risk in enclosed spaces. They smell bad, too!
Non-catalytic Propane Heaters: Inexpensive portable propane heaters are available. They work well, but are not approved for use in enclosed living spaces. Because they have an open flame, and because they may emit carbon monoxide, they are generally not considered safe for use in an RV. Some RVers use them successfully or use their propane kitchen stove or oven as a space heater (with suitable ventilation to admit fresh air and get rid of carbon dioxide, water vapor, unburned hydrocarbons, and carbon monoxide (CO). These uses are not recommended, may be illegal, and may violate the provisions of your RV or Homeowners insurance policy.
There are a great many varieties of such heaters. One Internet store lists over 100 different models. (See Heater-Store). In this category, the Mr. Heater "Buddy" series of heaters needs special mention since this family of heaters has, in the past, been prominently advertised as safe for indoor use. Current literature has modified this claim and added cautions. The owner's manual for the Portable Buddy heater states
"This heater is safe for indoor use in small recreational enclosures having means for providing combustion air and ventilation, such as enclosed porches, cabins, fshing huts, trailers, tent trailers, tents, truck caps and vans. It may be used for emergency indoor heating when connected to a disposable 1-lb. propane cylinder and for indoor use in commercial enclosures, having means for providing combustion air and ventilation, such as construction trailers or temporary work enclosures.
They base this claim partly on the fact that these models contain a tip-over shutoff and an Oxygen Depletion Sensor, which shuts the heater off if the oxygen level in the room drops below around 18%. The idea is that open flame propane combustion becomes less efficient and likely to emit more CO at lower oxygen levels. This has the effect of limiting the use of the product to altitudes of less than about 7000 feet above sea level. (Propane or natural gas heaters intended for permanent installation in fixed locations avoid this altitude problem by providing a mechanical manual adjustment of the propane/air ratio.)
However the ODS does not solve the problem that open propane flames are likely to emit some CO even under ideal conditions. One user of the Mr. Heater Buddy has told me that he owns a good CO detector and that he has to use a lot of air supply and ventilation in his RV to keep the CO level below 10 ppm. He also says that he has never seen any measurable CO reading with a Coleman catalytic propane heater in the same RV.
A published CSPC test, apparently of the small Coleman catalytic heater (see Reference 3, below), shows much higher levels, typically above 100 ppm if the ventillation is less than 1 ACH (air exchanges per hour). I don't know any way to measure ACH, nor can I quantitatively relate ACH to the size or configuration of open window areas.
The above document also points out another potential issue: Any propane heater will also emit some unburned propane, and this can reach fairly high levels if ventillation is inadequate, particularly if oxygen level is somewhat depleted. While unburned hydrocarbons in the air are not nearly as toxic as carbon monoxide, it is still a significant concern.
This raises the issue of just how much CO is "safe". I've searched the Internet and found that there is no single authoritative statement as to the safe level. I can't find any authoritative source for safe CO levels in the home. In the United States, there are at least three organizations who have published workplace recommendations or standards for CO:
- OSHA (Occupational Safety and Health Administration) has set the following enforceable standards: permissible exposure limit (PEL) for carbon monoxide is 50 parts per million (ppm) (55 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration [29 CFR Table Z-1].
- NIOSH (The National Institute for Occupational Safety and Health) has established a recommended exposure limit (REL) for carbon monoxide of 35 ppm (40 mg/m(3)) as an 8-hour TWA and 200 ppm (229 mg/m(3)) as a ceiling [NIOSH 1992]. The NIOSH limit is based on the risk of cardiovascular effects.
- ACGIH (The American Conference of Governmental Industrial Hygienists) has assigned carbon monoxide a threshold limit value (TLV) of 25 ppm (29 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 15]. The ACGIH limit is based on the risk of elevated carboxyhemoglobin levels [ACGIH 1991, p. 229].
The above three paragraphs are from an EPA (Environmental Protection Agency) document. This document also has quite a few other useful references. I recommend reading it.
Some organizations cite medical problems arising from exposure to as little as 10 ppm, and have set much more conservative recommendations, typically giving 10 ppm as the level at which one should start worrying.
It's worth noting that a typical CO detector in an RV may not sound an alarm until CO level has been at or above the 50-100 ppm range for an extended period (hours).
My recommendation is that non-catalytic propane heaters, including the Mr. Heater "Buddy" heaters should not be used in an RV.
Catalytic Propane Heaters: Catalytic heaters differ from other propane heaters in that the propane is combined with oxygen to create heat on the surface of a hot platinum catalyst, so that there is no flame. The absence of an open flame, and the relatively low temperature (the catalyst in the Olympian glows a faint, dull, red - visible only in the dark) increases the safety, relative to open flames. The catalytic process also results in a nearly perfect conversion of propane and oxygen into harmless carbon dioxide and water vapor, with no significant carbon monoxide produced.
Advantages of Catalytic Heaters:
Portability: Because of the "clean" burning of the propane, a catalytic heater need not be vented to the outside. It can be installed on or in any wall. When used with an attached 1 lb. tank, or connected to the RV's existing propane piping with a flexible propane hose and quick-connect fittings, it is almost as portable as an electric cube heater.
Note that NFPA 58: Liquified Petroleum Gas Code prohibits the indoor use of propane containers holding more than 2 pounds of propane, except in emergencies. There is work underway to eventually approve a special new design of non-metallic propane tank for certain indoor applications.
Directionality: A substantial amount of heat is radiated straight out from the front of the heater, warming the body it is pointed at. Sitting in front of the heater is almost like sitting in front of an open fireplace - the cozy feeling of the radiant heat allows keeping the rest of the room cooler.
Quiet: In very quiet surroundings, a very faint hiss may be heard. In most conditions, this is inaudible.
No Electricity: Most catalytic heaters use little or no electricity - a major advantage when boondocking in cold weather.
Efficient: The catalytic heater is 100% efficient in converting propane to heat. This is a somewhat misleading statement, since a window must be opened slightly while the heater is in use, to remove water vapor and CO2, and to supply oxygen. Even with the heat loss from the open window, the catalytic heater will use considerably less propane than a conventional propane furnace.
Disadvantages of Catalytic Heaters:
High Cost: A catalytic propane heater costs considerably more than a good quality electric heater. The catalytic element may eventually become contaminated and (for the Olympian brand heaters) must be replaced at the factory - a substantial expense. [Note added 9 April 2010: Our Olympian is now 14 years old; Recently, I dug it out of storage for loan to a friend whose home furnace had failed. It still worked just fine after being stored in its protective vinyl cover for about nine years.]
Installation required: Unless you understand plumbing and are "handy", you will have to hire someone to connect the heater to your existing propane supply. I did it myself - see below. Some smaller models use disposable 1-lb tanks. This avoids the installation problem, but makes them much more expensive to operate. Another option is to use a long extension hose to a 20 lb tank which must (by law) be kept outside the living area.
Large Size (for some models): Compared to an electric cube heater, my Olympian catalytic propane heater is substantially larger and more awkward to store. The Coleman product, on the other hand, is quite compact. The propane hose is stiffer than an electric cord, and can't be plugged in to as many locations in the RV. The small Coleman heater can only be used with one-pound tanks, a cost and convenience issue.
Altitude limitations: The models with oxygen depletion sensors can not be used above 5000 to 7000 feet (depending on brand). The Olympian models without ODS can be used up to 12,000 feet, according to Olympian.
Safety Concerns: Any portable heater requires care and common sense. A portable propane heater requires additional care. There is no tip-over shutoff (at least on our model - some brands do include this), although the legs on the portable model make it quite stable. Although the temperature of the heating element is much lower than that of an open flame (and much lower than many electric heaters), it still could start a fire if in contact with flammable material. The flexible hose and connections on a portable heater need periodic inspection for leaks. The propane should be shut off at the source when the heater is not in use. Forgetting to open a window when the heater is in use is a risk. These heaters are often mounted permanently on or in a wall. This eliminates some (but not all) of the above safety concerns.
I have experience with only one brand - Olympian - and what follows below is directly applicable only to this brand. I have heard second-hand unfavorable comments about a Coleman catalytic propane heater, but have not seen one. Vented catalytic heaters are available, but these are lower efficiency, much more restricted in their installation options (requiring a permanent vent through a sidewall of the RV), and may require electricity for a fan.
I would note that the size and configuration of the catalytic medium is very different between the Coleman and Olympian heaters. The geometry of the Olympian looks to me as though is is inherenently more efficient than the Coleman. Also, the catalyst might be a different material with different conversion efficiency. Olympian says the catalyst is platinum (perhaps partially explaining the high cost of the product). Coleman does not identify their catalyst.
Olympian makes several models of heater suitable for RV use. For comparison, a 1500 watt electric heater puts out 5200 BTU/hr. Counting some loss for the required ventilation, the 6000 BTU/hr propane heater is roughly comparable to a 1500 watt electric heater.
(min. - max.) BTU/Hr
|Wave-3||1600-3000||manual - no thermostat, no electricity needed. Wall or portable mounting options. Piezoelectric spark ignition|
|3100 ODS||3000||has oxygen sensor; can not be used above approximately 5000 feet above sea level. Wall or portable mounting. No electricity needed.|
|6100 ET||6000||has automatic thermostat; Wall mount only. requires 12v. electricity - 5 amps while igniting, <0.2 amp thereafter.|
The "Wave" models may violate RV building codes in some areas, (California and Canada?) making the "ODS" version the only option available in those areas.
If used in an unventilated space, any propane heater will consume oxygen until there is inadequate oxygen for human breathing. The oxygen sensor in the ET or ODS models senses a low oxygen level and turns off the heater if the level gets too low for safety.
Although an oxygen sensor makes the heater safer, it restricts the heater to use at altitudes below about 5000 to 7000 feet, depending on brand. For many RVers, this is a really major disadvantage, since some of the nicest camping locations are at higher altitudes, and the heater's primary use may be for the cool nights found year-round at high elevation.
Because these heaters use oxygen and emit water vapor and carbon dioxide (not carbon monoxide!), any space in which the heater is used must be ventilated (a window opened slightly), both to add new oxygen and to get rid of the excess moisture. Olympian recommends one square inch of free air opening per 1000 BTU/hr of heat output for "rooms of average airtightness". (This means that for the Wave 6 heater, an RV window 2 feet wide would would be cracked open 1/4 inch.) I have found that our travel trailer is leaky enough to provide sufficient oxygen for two people to breathe while the heater is in use without opening windows. A friend with a large high-end fifth wheel trailer has also found this to be true. We ventilate anyway, largely to keep the moisture level reasonable. But it's comforting to know that if we forgot to open a window before going to bed, it wouldn't kill us.
This comment should be understood in the context of our own tolerance for reduced oxygen levels. We have camped at altitudes of 10,000 feet and hiked as high as 14,000 feet without problem. Individuals with impaired heart/lung function, or those who suffer from altitude sickness at much lower elevations, will want to be much more careful about ventilation.
For our 35' travel trailer, we chose the 5800 BTU/hr manual model (similar to the current Wave-6 model) and fitted it with legs and a 10' flexible hose for portable use. We also purchased a fitted vinyl cover, to preserve the life of the platinum catalyst by keeping out dust and dirt while the heater is not in use. As of December, 2011, the Wave-6 is available on the Internet for about $250, plus around $13 for the legs, about $19 for the cover, and about $35 to $80 for flexible hose and copper fittings to tap into the existing propane piping. RV Solar Electric offers both a fixed and portable installation kit, each containing everything needed for a typical installation.
My installation was rather simple. My furnace is under the sofa in the living area, in the middle of our trailer. I unscrewed the propane line from the furnace, screwed a "T" fitting into the furnace, screwed the propane line back into one leg of the "T", and attached a shutoff valve and the flexible line to the other leg of the "T". When not in use, the catalytic heater, still attached to the hose, slides under the sofa, in a vacant space adjacent to the furnace. The 10' of hose is sufficient to allow placing the heater most of the way down the hallway, pointing into the rear bedroom, or in the kitchen pointing at the dinette seating, or pointing at any of the seating positions in the living area. (This is an easy do-it-yourself project, but only if you understand basic plumbing procedures and materials and understand how to test for propane leaks).
Our 35' travel trailer (without slide-outs) is fairly average as to air infiltration and insulation quality - some are significantly worse, and some are significantly better. Under typical conditions, our 5800 BTU/hr heater's high setting will maintain the entire trailer at 25 to 30 degrees above the outside temperature. The specific region toward which the heater is pointing will be about five degrees warmer, and a person at which the heater is pointed will feel even warmer because they are absorbing the radiantly beamed heat. With this heater, we have boondocked comfortably in night-time temperatures down to about 27 degrees. We generally travel so as to stay in areas where the night-time temperature is rarely below 50, and under these conditions, the lowest setting can be too warm. For many people, the smaller 2800 BTU/hr heater would be a better choice. In very large or poorly insulated rigs, or for colder climates, the big 7600 BTU/hr model may be desirable.
Comparing Costs of Electrical and Propane Heat
One gallon of LPG (Liquified Petroleum Gas - the more accurate name, since what we usually call propane is actually a mixture of propane, butane, and smaller quantities of assorted other similar gases) contains about 91,500 BTU of energy, depending on the exact mix of the various gases. Since propane heaters have an efficiency ranging from perhaps 50% to 90% (I'll use 80% in this calculation), the useful energy content is approximately 73,200 BTU, which is 21.44 kilowatt-hours. (1 KWH = 3414 BTU).
Thus, if electricity costs $.10 per KWH, LPG would have to cost $2.14 per gallon in order for the cost per unit of energy to be the same for the two sources.
Simply multiply the cost of a KWH of electricity by 21.4 to determine the cost of propane per equivalent amount of heat energy. (This is a compromise number. For a traditional propane furnace, use 17.42 (assumes 65% efficiency); for a catalytic heater, use 24.12 (assumes 90% efficiency).
Some campgrounds have electricity included in the cost of the campsite, but charge an extra $2.00/day for use of an electric heater. To determine whether to use electricity or propane in this situation, you have to know in advance how much heat you will need each night. For example, if you ran a 1500-watt electric heater continuously for 10 hours, you would use 15 KWH at a cost of the $2.00 surcharge, or $.133/KWH. If propane costs less than $3.22/gallon, it will be more economical to use a catalytic propane heater (or $2.32 for a conventional furnace).
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