Coping with cold weather

As weather turns colder and temperatures drop, we have to begin modifying our plans a bit.  Many people have asked us about how our MoHo handles cold weather, so I put this little overview together.

There are two primary areas of concern with cold weather:

  1.  Personal comfort for ourselves and our birdies.  We can bundle up but the birds really can’t tolerate cold temperatures.
  2. Mechanical comfort for our MoHo and its various systems.  Of particular concern is the prevention of freezing in the water systems.

I will talk about each of these comfort types, but first, I need to introduce a term called BTU.  British Thermal Unit. It is the amount of heat required to raise the temperature of one pound of water (about a pint) one degree Fahrenheit. So bringing a gallon of water (about 8 pounds) to a boil from room temperature (70 degrees) would require about 1200 BTUs.  Put another way, a 100-watt light bulb puts out about 300 BTUs.

Keeping our MoHo warm is simply  a matter of replacing BTUs lost to the cold outside air with warm air BTUs. BTUs out to nature balanced by BTUs in from a heat source.

So one way to help manage heat is to prevent BTUs from getting out. Just like putting on a wool hat slows heat loss from a bald head like mine, keeping the MoHo tightly closed keeps BTUs from escaping into the wild.

You have undoubtedly seen this concept for a typical house.

Image result for heat loss around door infraredOur Fleetwood is pretty well insulated for an RV.  Walls are Styrofoam core, and we have 5″ of insulation in the ceiling.  Our windows shut tight and leak very little air, and the slideout seals are surprisingly good at keeping air from leaking. Except one of the bedroom slides at the bottom, which may be by design.

To prepare for cold weather, first make sure your MoHo isn’t leaking BTUs anywhere.  A leak around a slideout seal that lets 5,000 BTUs escape just means you need to find 5,000 extra BTUs of heat to put back in.  Let’s face it. Even the best insulated RV is still very poorly insulated compared to a house, and each little leak of air just makes that worse.

Now that we’ve considered heat loss, let’s figure out how to put some heat back in.  Bring on the BTUs, baby!

First lets review the sources of heat in our MoHo. Our MoHo has 2 built in sources of heat, plus an optional 3rd system.  These systems are 2 separate propane furnaces, a rooftop air conditioner with heat pump function, and the ability to use electric space heaters.

Let’s talk about the heat pump first.  Our “bedroom” AC unit – which is really located mid-ship – is also a heat pump.  What’s a heat pump?  Glad you asked!

Rear heat pump
A heat pump simply moves warm air from one set of coils to another. You’re familiar with heat pumps because your air conditioner is a heat pump.

It moves the hot air inside your house past a set of coils where the heat is absorbed. This heat is then transferred to another set of coils outside your house where it is expelled. That’s the reason the air blowing from your outside “air conditioner” is so hot! That heat has just been pumped out of your hot house!

Voila.  A heat pump.

Well then, if that system were run in reverse, wouldn’t heat from outside air be moved INTO the house?  Yep.

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Sounds perfect right?  Use the AC unit already on the roof as a heater?  Well, it is pretty awesome. However, it requires the AC unit be designed to run forward (pump heat out of the MoHo) and backward (pump heat into the MoHo).  This adds cost and complexity so only one of our AC units has this capability.

The heat pump is capable of up to 15,000 BTUs of heat. Ours is a bit uprated, many heat pumps in RVs can produce only 10,000 BTUs.  As long as our heat loss is less than 15,000 BTUs, the heat pump can keep us warm.

The heat pump runs on electricity which is great since our campgrounds also offer electricity. As long as we are connected to shore power, we can run the heat pump forever. However, if we were boondocking, we would have to start the generator in order to run the heat pump.

Hmmm…that sounds like a potential disadvantage.  Are there others?

Yes.  One big disadvantage of a heat pump are that as the outside temperatures get lower, there is less heat in the air to pump into the MoHo.  Below a particular point, probably about 45 degrees, there just isn’t enough heat in the outside air to generate much warmth at all.

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So heat pumps are wonderful down to about 45-50 degrees. Any colder and they just don’t work.  Its a catch 22, because there is less heat in the outside air to pump into the MoHo AND at the same time we need more heat to offset heat leaking out of the MoHo.  Its a double-whammy.  More BTUs out than in.

One last disadvantage is that heat pump heat blows from the ceiling vents.  This means the floor never gets warm AND it means the mechanicals under the floor don’t get any heat at all. So the heat pump is good for keeping people/pets warm in cool -not cold – weather, but it doesn’t help the mechanicals at all.

This brings us to our second heating system. Propane. LPG.  Now we’re cookin’ with gas!

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Our MoHo has 2 propane furnaces, one in the middle of the coach and one in the bedroom.  Each one can produce up to 25,000 BTUs. Combined they can crank out 50,000 BTUs of heat.  Compared to our 15,000 BTU heat pump, these babies really warm things up!

There are other benefits to our propane heat.

The furnaces blow at floor level which helps keep the floor warm.  And since hot air rises, the heat mixes inside the MoHo better in general than if it comes from the ceiling. The one exception is that the front of the bus has no heat vents so the driver area gets pretty chilly even when the propane is on.

Second, it heats FAST.  The heat pump takes a while to get going and then it blows warm (never hot) air.  The furnaces blow HOT air. They ain’t fooling around.

Third, some of the heat from the propane furnaces is ducted down below into the mechanical spaces specifically to prevent the freezing up of plumbing and holding tanks.

Living room propane heat vents
The colder the weather, the more we use the furnaces and the more they heat the pipes and tanks. Even if our heat pump worked below freezing, we would have to use the propane to keep our mechanicals from freezing.

So the propane heat is faster, more powerful, works at any outside temperature, heats the floor, and heats the mechanical spaces. It keeps the creatures and the mechanicals comfortable.  Why not just use it all the time?

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Simple.  Cost and convenience. Electricity for the heat pump is free (included in our campground fees) and never runs out.  Propane is about $5/gallon and we have to find a propane filling station.  Many – but not all- RV campgrounds will fill propane tanks.  Usually at a higher price than a fuel station.  Convenience isn’t free.

Our propane tank is 38.7 gallons. However, as you will learn, a propane tank cannot legally be filled to capacity.  It can only be filled to 80% of capacity.  You can see this on our gauge.

Notice that Full is just beyond the 3/4 mark?

This is because propane, specifically LPG, will expand with heat and so buffer space must be left in the tank to prevent explosions. Preventing explosions is generally considered “a good idea.”

So our 38.7 gallon tank will really only hold about 30 gallons of propane. Still, that’s quite a bit of propane.

If you plan to be in cold weather much, or if you are boondocking a lot in cooler weather, you really should choose a MoHo that has a large propane tank.  It will save you a lot of trips to fill up on propane and minimize the chances you will run out on a cold weekend night when you can’t get more.

We filled our tank in Gallup New Mexico in May.  We filled it again in Burlington on Oct 1. During that time (5 months)  we had used 7 gallons.  Mostly for cooking (our stovetop is propane) but some for heating.  At that rate, 30 gallons would last us 2 years.

However, that was during summer.

How much propane will we use in cold weather?

Finding the answer to that involves a little math.  Our furnaces each generate 25,000 BTU per hour. Together generate 50,000 BTU per hour if they run nonstop.

One gallon of LPG (propane) has roughly 90,000 BTU. So, if we ran our furnaces nonstop, we’d burn 5/9s gallon of propane per hour. Or, about 60% of a gallon of propane per hour.

That means 30 gallons of propane should last about 50 hours.

50 hours.  Two days. We could run both furnaces for two days and then we would be burning the furniture for warmth.

Fortunately, it would have to be REALLY cold to require our furnaces to both run non-stop. Way colder than we hopefully ever experience.

More typical would be running about 25% of the time in freezing weather.  Maybe 10% of the time if the temps are in the upper 40s.

So if the outside temps stayed around 30 degrees 24 hours a day and we didn’t absorb any heat from the sun, we would exhaust our propane every 7-8 days.

That’s $1 50 in propane costs per week.

You can see why we like electric heat!  It never has to get refilled, and is free!

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Heat from the sun, by the way, should not be underestimated. You know how hot your car gets sitting in the sun?  Well, MoHos can be a little like that.  Its a big pain in the summer, but welcome in the winter months.

The last source of heat is electric. Now, you might think the heat pump is electric heat, and it definitely requires electricity to work.  But the heat pump isn’t using that electricity to create heat, its only using electricity to move heat around (outside to inside).

Electric heaters create heat directly.  Electric heaters use a LOT of electricity for a comparatively small amount of heat, but they are important to talk about.

Some RVs come with a fake electric fireplace that simulates a real wood-burning fire.  They can range from extremely cheesy looking to somewhat authentic. Most of the time, they are a decoration feature that just takes the place of storage. Our MoHo had one as an option but instead we use that space to store a case of wine.

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These fireplaces are also electric space heaters.  Most are around 1500 watts which is around 12.5-13 amps. Keep in mind that is the absolute limit of most 15amp circuits so hope your RV builder put in a 20amp line to that area instead of just plugging into a 15amp outlet.

Why can’t a 15amp outlet handle a 12.5 amp load, you ask?  Simple. Residential wiring is only rated to sustain 80% of its maximum value.

15 x 0.8 = 12.

So a 15amp plug shouldn’t have more than 12 amps steadily pulling power for any length of time. 12.5 amps is just slightly higher than that and your wiring itself could get unacceptably warm.

This will also come out of your total household amp draw.  Hopefully you have 50amps to work with, but you might be stuck with only 30amps.

  • Electric fireplace = 13
  • Electric water heater = 12
  • Electric heat pump = 12 (surge to 30)
  • Interior lights = 3
  • TV – 3 amps
  • MacBook charger = 2 amps
  • iPad charger = 2 amps
  • Hair dryer/ coffee maker = 12 amps and OH NO I JUST BLEW THE BREAKER

Still, assuming that electric fireplace isn’t any kind of a safety hazard, you have a 1500 watt heater.  Since we’ve been talking BTUs, that’s about 5000 BTUs.  This shows the value of a heat pump, by the way.  A 15,000 BTU heat pump uses about the same amount of electricity as one of these fireplaces, but the heat pump generates 3 times more heat!

Only you can decide if you want one of these fireplaces in your MoHo.

If you don’t, you can use a small electric space heater which you store away when not in use.  We have one similar to this and we use it about 5 months out of the year.

Between the small space heater and the heat pump, we can generally avoid using propane unless temps get below 45 degrees.  One we hit 45 degrees, we’re loosing too many BTUs, the heat pump stops working, AND we need to worry about freezing the mechanicals.

There is an alternative heating system to what I mentioned.  Hydronic heating.  

These systems work by heating water in a boiler and then circulating that hot water around the coach.  Aqua Hot and Oasis are the two most well-known hydronic heating systems.

Hydronic heat systems are available on high-end coaches as an option. Usually a fairly expensive option.

As I mentioned, hydronic heat systems use a water heater to heat water that runs under the floors and behind heat registers to generate their heat.  Generally they will use a combination of propane or diesel fuel and electricity to heat the water.  In cool temps, electricity may be enough. In really cold temps, electricity plus propane or diesel fuel might be required.

Because the systems are constantly creating hot water, they can also provide limitless hot water for showering, washing clothes, doing dishes, etc. They can also circulate warm water into the engine to keep it warm and ready to start on cold days.

We have an electric engine block heater that does the same thing. (10 amps).

Also, the diesel systems benefit from using regular engine fuel meaning no more stops to fill propane.  And, no tunnel restrictions.  Many tunnels will not allow compressed propane through the tunnel and our propane tank definitely counts.  Aqua-Hot systems with diesel backup do not have that issue.  As I’ve also covered before, diesel is very safe as it does not give off explosive fumes and is not pressurized.

I would definitely consider hydronic heat in a coach.  Keep in mind Aqua-Hot requires an annual servicing of its diesel fuel filter and burner by a certified technician that will cost a minimum of $200.  Oasis filters can be easily changed by the owner and the burner only needs service every 3 years. My RV mentor and dad Rex has had both systems and says th Oasis is superior, in no small part because it generates more heat on electricity than the Aqua-Hot system did.

Only you can decide if it is worth the extra money.  Keep in mind too that if anything happens to the boiler, you may not have a secondary heating system to kick in.

The last item of cold-weather concern, and its a big one, is the external water hose connection.  It will be the first thing to freeze, since its exposed to the elements and gets no heat from anywhere.  If this freezes,  you will likely need a new water hose (no big deal) and the campground will charge you to fix the frozen faucet (big deal).

So how do you solve THAT problem?  Propane or electric?

The answer is neither.  If it is going to get below freezing over night, we fill our fresh water tank and unhook the fresh water hose completely.  Our fresh water tank holds 100 gallons, more than enough for multiple days if need be.

We actually tested this in New Mexico and we can go for 5 days before we run out of water IF we aren’t doing laundry.

This, by the way, is a good reason to keep your fresh water tank and plumbing system sanitized. We do that at least every six months.  More often if we suspect bad water or the weather has been really hot.  Sanitizing water systems is a topic for another post though.

Speaking of water, there is one more factor to consider when the weather turns cold.  Condensation.

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Since RVs are not particularly well insulated and since they are small spaces, moisture from living in them raises the humidity of the interior very rapidly.  Taking a shower for example dramatically increases the humidity inside the MoHo.

If it is cold, that moisture will condense on the cold areas of your MoHo. Some areas you can see, like windows and interior walls.  Other areas you cannot see like behind cabinets and inside walls. Over time, this moisture can lead to the growth of mold, rotting of wood, softening of glue, rusting of parts, etc.

So even though I said one of the best ways to keep warm is to prevent BTUs (heat) from escaping in the first place?  Well, you will have to vent your MoHo regularly to keep moisture from building up.  Run the fan when you take a shower.  Yes, it will suck all that heat right out of your MoHo but the moist air will go along for the ride.

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Trust me on this.  You are better off loosing some of your heat for a few minutes than you are learning your wood trim is warping and mold is growing on your walls.

Everything I said is true of a house as well. It just happens sooner and takes more effort to manage in a MoHo.  But, you’ll get the hang of it quickly and while I wouldn’t recommend wintering in Maine in an RV, you should be fine in some chilly weather.  As you head south.

Nights getting below about 25 degrees is no place for a MoHo.

There are some people who have spent truly cold winters in an RV, and they will talk about things like skirting the RV, electric pipe heater wraps, multiple electric space heaters, etc.

If that kind of winter weather is in your plans, I would suggest you reconsider your plans. And if you can’t you should look for those who have done it and see how they coped.

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Good luck and stay warm!!

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