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LP Gas System Tips & Hints
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The LP Gas Systems
The gas used in RV's is stored in a liquid form. It is the
vapor from propane that burns. It is heavier than air.
(Which is why leak detectors are located near the floor).
Propane is colorless, during manufacturing it is
"odorized" for easy detection. Approximately 91,500 BTU
are contained in one gallon of LP.
Storage Vessels
There are two methods of storing LP on RV's: Department of
Transportation (DOT) cylinders are typically mounted on
the front of trailers. In fifth wheel units and in truck
campers, it is found in exterior compartments. The most
common size used on RV's are the 20 and 30 pound tanks.
These tanks must be re-certified every twelve years. The
latest generation DOT tanks are fitted with quick closing
coupling (QCC) valves, which have three safety features.
If you open the service valve without having a fitting and
hose properly attached, there will be no gas flow. It also
has a fuse that will shut off the flow of gas if the valve
gets hot in case of a fire (while in use). If the pigtail
should break, the flow will automatically be restricted.
DOT tank outlet valves have left-handed-thread connection
known as the POL connector. The other type of tank is
American Society of Mechanical Engineers (ASME), are in a
horizontal configuration that is used almost exclusively
on motorhomes. They have a separate port for filling, and
are designed to be bolted to the RV's frame. They must be
filled in place. They do not require re-certification but
when the label rusts off, the tank must be replaced.
Regulators
The appliances in an RV are designed to operate at a lower
pressure level. The regulator is designed to reduce the
high tank pressure (150 psi full) to a steady 11 inches
water column, about 0.4 psi. Two stage regulators are
actually two regulators in one. The first stage reduces
the pressure to about 10-15 psi, the second stage is
needed to further reduce it to the 11 inches of water
column. Regulators are not repairable. Open the valve
slowly, quickly opening the valve can be hard on the
regulator diaphragm. The regulator vent is covered with a
fine mesh screen. It should be checked and cleaned
regularly. Even a small blockage could cause enough of a
pressure drop to allow the pilot to blow out.
Automatic Regulators
These are typically, used on travel trailers, fifth wheel
and pick-up campers when the pressure is too high then
pig-tails are used. Both tanks are left on at the same
time, the regulator uses the "service" tank as indicated
by a mark on a knob or lever. When the service tank is
empty, the regulator automatically switches to the other
tank and an indicator pops up indicating it is empty.
Stop Fill Valves - the ASME (motorhome) tank use stop-fill
valves, which automatically stop the filling process when
the tanks are 80% full. Stop-fill valves operate like a
float mechanism on a household toilet. The float is pushed
up by the rising liquid in the tank. The float then exerts
enough pressure on the valve to stop the flow of gas.
POL Fittings
These are special fittings that are used to hook
pigtails to the tank. The POL have left -hand threads, and
are a high pressure fitting. When re-filling the tanks
inspect the POL making sure there are NO NICKS OR
SCRATCHES, which could make a poor seal which could result
in a leak. Current code calls for brass on brass seal.
Check for leaks with soapy water. Never use soap with
harsh chemicals. These can corrode the lines and fittings.
Propane tanks can be filled at an LP gas service facility.
It is not a self-service operation. Safety Certified
Professionals should fill LP tanks.
Leak Detectors
Propane is heavier than air and will seek the lowest
level. Therefore units with electronic leak detectors have
the sensors near the floor. When gas is detected they
sound an alarm. On some RVs a tank mounted solenoid
shutoff valve immediately shuts off gas flow when the
alarm is activated.
The supply of LP in your tank will be used according to
the size (BTUs) that your appliances have and how often
they are used. |
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