Negative 18
degrees for a low is a bad time for a furnace to go out in any domicile.
Depending on heat from a breakable system of fans, control boards, ignition
systems, switches and relays is a recipe for an eventual critical situation. In
an RV, the situation is slightly different because the walls are 1.5” thick
Styrofoam and only retain vital heat for so long. Since I just experienced this
situation, I realized it was a story worth telling. Thankfully, through all of
my planning and forethought, I had backup plans in place that allowed me to
experience this calmly and without damage.
The Suburban
SF-30 furnace that came with my RV failed on a frigid February morning. It
actually silently failed overnight, but I didn’t notice until the evening that
day. The only way I noticed was that the cabin was a couple degrees colder than
normal when I came home and the furnace didn’t appear to be firing. The only way
the cabin wasn’t stone-cold was that I have electric heaters with thermostats
that come on at a finely tuned temperature. With the electric heaters as a
backup, everything was saved.
The furnace
failure was quiet, but marked by obvious signs – signs which I caught onto
quickly and responded to. The signs were a cooler than normal internal
temperature and no sign of furnace firing when it should be. Once I realized
what was going on, I entered into my first phase of emergency backup plans. The
only way my first layer of backup plan was different than what I was doing
anyway was to install a small, personal heater in the water compartment under
the bed, so the internal water pipes didn’t freeze. The rest of the cabin was
warmed by electric heaters on a supplemental basis anyway, so this one step was
quite simple.
Since I
realized the failure around 6pm on a February night, it had already been dark
for an hour and was already quite cold – negative 11 or so when I checked. In
my preparedness, I pulled on my arctic-insulated Carhartt bibs, a fleece coat,
an expedition-weight down coat, a wool hat, and wool glomitts. This insulation
was necessary because the furnace is accessible only from outside. I grabbed my
volt meter to test relays and power to the motor, and a few other tools, and
started testing the device. Before I put on my deep-cold winter gear, I looked
at the manual and came up with theories for what was wrong first – the
schematics give enough information to get an idea of how the device works and what
could be wrong.
Truth be
told, it took me a while to narrow down what went wrong, but that first night
spent outside until 10pm in negative 18 degree temperatures allowed me to begin
forming hypotheses to test the next day – mostly, it gave me an opportunity to
familiarize myself with the device and to sleep on my experience.
The next
morning, I went out and started testing my hypotheses with a written plan of
things to test. I even came up with theories for what tests would determine
what part(s) were the cause of the failure. Once I found tests that were
falling into my range of theory of what was wrong, I was able to start
gathering parts that needed replacement. My theories were pretty rough
estimates at best, largely because I was unfamiliar with this device and how it
worked – I had never seen the internals of the furnace before, or any RV
furnace for that matter.
My tests
revealed that the “time delay relay” was likely out due to a failed voltage
test with the thermostat on and calling for heat. Then, the motor
simultaneously was not showing continuity where and when I hypothesized that it
would have continuity. Whether the motor was actually bad is something I didn’t
actually care to test further – the motor was likely original and almost definitely
on its last legs anyway. The furnace in my coach is 15 years old this year and
I have put year-around-dwelling pressures on it. As a 12 VDC motor, it was
likely to go bad any time.
Upon finding
the likely candidates for failure, the next phase was to figure out how to
extract the guts of the furnace to work on it and to locate parts. My location
doesn’t have a parts dealer, so I had to go to the nearest city, over 40 miles
away. The commuting time for such travel added roughly three to four hours to
an already long day, which included a lengthy diagnosis and learning period
already.
All the
while, I learned that each propane-dependent device did not have its own
shutoff valve. That meant that if I wanted to service the furnace, my water
heater and stove become non-operational. In a full-time living situation,
that’s not practical or safe. So, another project got added into the mix: The
project of adding a shutoff valve to the furnace’s propane line. That also
meant learning how to do this correctly and safely.
The cold
snap that both triggered and increased the severity of this failure led me to
have to learn systems quickly and to pick up new skills fast. I had to learn
how to make flare fittings in copper gas line, how to properly install gas
fittings, and how my furnace worked in order to get the right parts. Being able
to pick up these skills fast was critical, but was underlain by a long history
of working with vehicle electrical and mechanical systems that made these
skills fast and easy to pick up.
Safety in
this case was critical. Working with gas lines and valves becomes dangerous and
I can only hope that I did it all as well as I think I did. Failure to set new
gas fittings properly could lead to explosive consequences, which I believe I
avoided by doing my work right. I suppose time will tell.
In the end,
the lesson is that it is always good to have backup plans on top of backup
plans and to respond quickly and effectively to these kinds of critical
failures. When I rebuilt the furnace, I made sure to clean every part,
lubricate anything that moves, and to preemptively replace something if it is
destined for failure. The blower motor and the time delay relay had to be
replaced, which required a nearly total disassembly and reconditioning of the
furnace. The time delay relay was even discontinued, but I was saved by the
presence of an aftermarket model that will likely outlast the original by a
number of years. In the end, I spent hours outside in sub-zero temperatures,
but was never uncomfortable or concerned for my safety through extensive
preparation for such an event. I had hoped that I would never have to see such
a circumstance, but now that I have, I realize that my preparations were
fantastically appropriate and that it could have been worse and I would have
been unscathed. That’s a pretty incredible statement considering the complexity of
the job and the weather extremes that I was faced with.
