Sunday, January 10, 2010

Heating RV's

Living in an RV ain't all romance and adventure, buckaroo. No sir, at times it can be downright challenging. For instance, how do we manage to stay warm on really cold nights?... and do so at the lowest possible cost? The recent cold weather (it's been in the 20's the past couple nights) made me think this subject might be mildly interesting for some readers. And I need to write something anyway... so here goes.

RV's are basically little boxes with very thin walls. When you've only got 8-1/2 feet (outside width) to work with, and because every RV buyer wants as much interior space as possible, thin walls are the resulting reality. But I don't care what kind of insulation is in those little skinny walls it's not enough to make any RV "easy to heat" in very cold temperatures.

Most RV's have a collection of various systems designed, to one extent or another, to make the unit usable in most weather conditions whether connected to full hook-ups (electricity, water, sewer), not connected at all, or when only partially connected. For example, the refrigerator runs on standard 120 volt power when hooked up to outside electricity, or on LP gas when not connected. Same with the water heater.

There are multiple systems that can be used for heating and which ones are selected depend on a number of factors. Here's a brief discussion of each:

Forced Air RV LP Furnace: These units use internal 12 volt power for the fan and controls and LP gas for the heat source so they're usable whether or not 120 volt power is available. Our LP furnace is rated at 40,000 BTUs. Unfortunately, these things are known to be very inefficient, and about half the heat produced by the burning LP gas is expelled outside as exhaust. So we're lucky if we get 20,000 BTUs out of this system. And they are loud, annoyingly noisy enough to drown out the TV or a conversation with your mate. Most of the time we leave ours off during the night, layer on the blankets, and only use it to warm things up in the morning. There are some newer systems that are hydronic -- that heat and circulate water throughout the coach floor for warmth. They're much quieter, more expensive, and are probably more efficient than the forced air unit we have.

Heat Pumps: Our RV came with two rooftop A/C-Heatpumps -- in cooling mode they're designed to move heat from the inside to the outside during warm weather (normal air conditioning), but can be switched to heatpump mode to move heat from outside air to the inside living space. Believe it or not, there's still enough heat in 40f degree outside air to make it work. They require 120 volt power which means you've got to be plugged into ground power or have the generator running. And because they require enough heat in the outside air they don't work well when temperatures drop below 35f or 40f degrees. Each one is rated at 13,500 BTUs, but inefficiency and reality probably bring the usable number down to 10,000 BTUs or so. They're quieter than the furnace but because they're on the roof and the air enters the RV through ceiling vents, the heat tends to stay near the ceiling and the floor feels relatively cold.

Electric Portable Space Heaters: These are the little plug-in heaters available almost everywhere. They come in all sorts of styles, sizes, and types. But they all have one thing in common... they all put out the same amount of heat. Assuming they're rated at 1500 watts (and they almost all are) they all produce 5,100 BTUs. And because they're 100% efficient (any inefficiency is expressed as heat -- exactly what the unit is designed to produce) you get all 5,100 BTUs. Here again, you need that 120 volt power from the grid or from the generator. We have one that serves as our primary heat source most of the time. Because we rely on this system so much, we carry a back-up unit just in case the one we're using croaks.

Portable Catalytic LP Heaters: These are units that claim to be safe for indoor use. Using LP gas as a fuel, they use a very efficient catalyst to burn the fuel in a flameless process to create radiant heat. Because they're so efficient there's no need for an outside exhaust. They don't require any power besides the LP gas, so they're popular with people who like to boondock and drycamp a lot. Available in different sizes between 4,000 and 12,000 BTUs, almost all the heat generated by the heater is usable. The downside of these things is that you've got hydrocarbon fuel "burning" inside the RV and even though they claim to be safe for indoor use, they still recommend keeping a window slightly ajar as a precaution against accidental carbon monoxide poisoning or a lack of oxygen. At this point in time, we don't have one of these units.

So during the past few cold days this is how we manage to stay warm: during the daytime when outside temps were in the 40's, I ran one heatpump which gives us the most bang (heat) for our buck (we're paying for electricity here). At night when the temps dipped into the 20's, we run the little electric heater augmented by the LP furnace.

If we were boondocking or drycamping with no hookups at all we'd have to rely on the RV's LP Furnace. Since most of our "no hookup" camping is done during warmer periods of the year, we've been able to make that work. But if we do more "no hookup" camping in colder weather we might look into a portable catalytic LP heater.

For the complete picture of these heating system decisions we should also factor in the price of LP gas, whether or not we have to pay for electricity and what the cost is, and then which of these two energy sources has the best price per BTU. Here in Rockport we've been paying $2.80 per gallon for LP gas and 13 cents per Kilowatt Hour for electricity. I won't bore you with the math but at these prices we get far more heat for our dollar with electricity than we do from LP gas. That's another reason to run the electric heater and the heatpumps instead of the furnace.

I hope this all made some sense and provides a little insight into our lifestyle.

Still under a pile of blankets and a comforter...

Thom