Understanding Today’s RV Heating System Choices

March 2, 2008 by Lug_Nut · 6 Comments  
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Efficient heating systems in RV’s have not only made them more creature comfortable, but have extended the seasonal usage for many.  So much so, that so called “winter camping” has become increasingly popular.  So, just what is keeping these people warm? 

Most motor homes and trailers are equipped with a forced air propane fired furnace, like the Suburban.  The propane provides fuel for the heating while a 12 volt motor driven fan pushes the warm air through several vents within the living area of the vehicle.  Additionally, many have a separate switched fan motor capable of circulating warm air to the basement that houses the water tank and plumbing.  This can be armed to run whenever heat is required to prevent freezing temperatures from causing any damage.  This type of primary heating is currently the most common found in the average RV today and works well.

Hydronic heat is now the most sought after system in RV primary heating.  It has been supplied and sold as Hydro Hot, Aqua Hot  and Oasis, to name some common brands.

Hydr Hot 

In addition to being the furnace like device, it also looks after the heating of the fresh hot water thus eliminating the need for a separate tank assembly.  The water is heated in a fashion capable of supplying a continuous supply.

Now let’s look at how it works.  Housed in the basement, the hydronic unit is made up of an oil burner, electric heating elements, glycol tank and circuit, water reservoir, electrically driven circulation pumps and solid state controls.

The 12 volt DC powered burnerdelivers diesel oil to the nozzle at 145 PSI where it is burned to heat the system’s glycol.  This hot glycol can then be circulated as needed to heat exchangers that are in various locations throughout the coach.  Additionally, the hot glycol transfers heat to the fresh water hot circuit and is capable of maintaining the heat continuously should it be necessary.  The hydronic systems also have electric heating elements that operate on 120 volt AC for times when less heating is needed and shore power is available.  This is normally all you need while camping in warm weather and thus requires no diesel operation.  One great feature of this type of system is its ability to maintain a warm coach while driving in a cold climate.   This is accomplished by the engine’s coolant that is passed through the hydronic unit while the motor is running.   (Click on the above diagram to enlage)

Most coaches equipped with hydronic heat are outfitted with about 5 heat exchangers.  Each one is similar to a small radiator and has a 12 volt D.C. powered fan that is thermostatically controlled to run on demand.   When a zone within the coach calls for heat, the circulation pump for that heat exchanger starts pumping the hot glycol to it.  In addition to the heat exchangers within the living quarters of the coach, there is usually one located in the basement near the water bay.  This unit is controlled locally within the bay with a low temperature thermostat normally set at 40 degrees F. or so to prevent freezing in cold weather.  An optional pump circuit can be ordered that will circulate the hot liquid through the engine thus keeping it warm when desired.   

Servicing regularly of the hydronic burner is a must.  Regularly, is every year, without fail.  This consists of replacing the burner nozzle and fuel filter, inspecting and cleaning of the optical eye and generally cleaning the nozzle housing and burner assembly.  Failure to carry out this maintenance in a timely fashion will, in all likelihood, result in poor smokey operation, auto shutdown or both.  Please, don’t ask how I know that.  Also, if it shuts down, it will be on the coldest day or night.  I wonder how it knows that?  Again, I will leave it to your imagination as to how I know that.  

The hydronic heating system is probably the best system and method available and provides an extremely comfortable environment within the coach.  It is standard on many, if not all, high end coaches and is also available as an option on many.  This is, however, an expensive upgrade that generally runs between 8 and 12 thousand dollars.

The furnace and the hydronic heating systems are considered the primary source in a motor home, but many also have one or more secondary sources.  The most popular are heat pumps, like those made by Dometic.  These optional units are located and supplied by the air conditioners.  When operated in the heat mode, warm air flows out of the AC unit or vents instead of the normal cold.   The heat pump(s) can operate efficiently down to an outside temperature of about 40 degrees or so.  Generally, if the heat pumps are running, say overnight, when the temperature fluctuates from 50 F. down to 35 F. and then in the morning back up to 45 F., the heat pumps will automatically shutdown and the furnace or hydronic unit will start up.  In the morning as the temperature rises back to within the heat pumps efficiency range, the heat pumps will again take over shutting down the primary heater.

Heat pumps are a great option to have.  They can provide a comfortable warmth when sufficient AC power is available (generally 30 amp for one and a full 50 amp service for multiple units.).  This can reduce the consumption of propane or diesel and is a particularly thrifty way to heat your coach when the electric power is included in your lot fee.  

Heated floors are another secondary source and are becoming a more popular option on higher end coaches.  These are available on coaches that have the majority of the living space tiled.  They have electrical heating elements beneath the tiles and are divided into three circuits providing a three zone control choice.  These can make the floor feel very cozy and can also help raising the interior temperature slightly.  The cost for this can run anywhere from around 4 to 10 thousand dollars.


A slightly less popular secondary heating source is a fireplace.  These are available from some coach makers on specific models.  They can be operated in two modes, visual only (no heat) or visual with thermostat controlled electric heat.  The visual affect of these is quite real looking, as well as providing that fireplace glowing warmth feeling.   Again, this type of heat source, being electrical, can reduce the consumption of propane or diesel fuel while camping.

This pretty well covers the majority of what is available today in keeping your coach warm and cozy.  But, no matter which system you have or will get, you can be sure they are making improvements each year to make them just that much better.  Next week, on my regular Sunday morning blog, we will take a look at innovations in RV lighting and what is to come.  

  Just Some Warming Thoughts   -    Lug_Nut

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6 Responses to “Understanding Today’s RV Heating System Choices”

  1. bill herwig on March 3rd, 2008 10:05 am

    i,m lookin at the damon outlaw toy hauler. i have called the factory & talked to a rep, about ordering 1 w/o a furnace unit at all. an no floor vents cut. i inforded him that i,m going to put electric radiant under a hardwood floating floor. he said no 1 ever asked for that, i told him i,m just inquiring if he they do that. so he is going to ask about it. and get back to me, can,t wait for this call. even if they say no, i will take out the heat unit myself an doo it my way. an sell the heat unit. i put hydronic heat in my new home 8 years ago, an will never have another type of heat—its awesum. will keep you updated. safe rv,ing to all

  2. Hydronic Heat In Gas Powered Motor Homes? on March 16th, 2008 8:26 am

    [...] read my article of March 2nd covering the heating system choices available today; if not here is a link.  Rumor has it that one, or more, of the companies building the hydronic heating systems, like [...]

  3. Mollie Folmar on October 27th, 2009 11:44 am

    Does that mean the under-belly furnace will not come on uless the temperature goes below 40 degrees? How do you test it to see if it even works? Ours will not come on when you use the thermostat.

  4. Lug_Nut on October 27th, 2009 4:34 pm

    Mollie Folmar, No the furnace should run any time it calls for demand providing the unit is on. The 40 degrees is when the heat pumps revert to the furnace automatically if in use. Hope that is of some help. Thanks for your input.

  5. khalid on December 27th, 2011 11:17 pm

    i want to more info please

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