Trailer Owner’s Manual

10 Operating the Systems

10.1 Roof Vents

Roof vents provide several very important functions:

  • • While cooking with the stove, a side window and a roof vent must both be opened at the same time to allow fresh air into the trailer. Using the stove without fresh air will result in death.

  • • An open roof vent plus an open side window can greatly improve comfort while camping in warm conditions.

  • • During a storm, a roof vent can be cracked slightly open without letting in rain because the vent’s top has a wide edge, whereas a side window can let in rain even if it is only slightly open.

  • • People exhale water vapor as they breathe, and this vapor can build up in the trailer, causing condensation to appear in the form of water drops on the insides of windows and metal surfaces, freezing if conditions are cold enough. A slightly open roof vent and side window can be sufficient to let out this water vapor and prevent condensation on the inside of the trailer.

Simple roof vents have just a knob to crank the vent lid open and closed, plus a screen to keep out insects. For those trailers with a very high roof, a plastic PVC pipe with notches cut into the end may be used to turn the knob from below.

Roof vents are also available with a power fan, using battery power to move large amounts of air, either inward or outward. An open side window plus a low fan power setting blowing air out of the trailer is usually sufficient. The fan might not run until the vent lid is opened a sufficient amount.

Some roof vents have a powered system to open and close the vent lid, perhaps with a sensor to automatically close the lid when rain is detected.

Some roof vents have a latch to help keep the vent closed while traveling. Be sure to secure any roof vents before towing the trailer.

10.2 Sink and Water Pump

The sink receives water either from the fresh water tank via the water pump, or the city water connection which does not use the water pump. For information about supplying water to the trailer, see Section 6.1 (Loading Water).

Water going into the sink drains through an outlet on the exterior of the trailer. Water from this outlet should be gathered in a container instead of being allowed to spread on the ground. This container must allow air to escape for water to flow down the drain, but may also be a sealed container which is collapsed when empty and expands as necessary when water flows into it.

The water pump has an on/off switch which provides power to the pump. Keep this switch off while the trailer is being towed, so that the pump does not run water in the event that a faucet is shaken open or a pipe is loose. When the pump is turned on, it runs until the water lines are pressurized, then the pump stops. The pump continues to monitor the water pressure, and it runs again to fill the lines as necessary.

If the hot water heater is empty when the pump is turned on, the pump might run for a while as it fills the tank. If the hot water tank or the water lines had air in them, this air will spurt out the faucets when they are first opened. If this occurs, allow the pump to run until both the hot and cold water lines flow freely.

For information about upgrades to avoid the loud hammering actions of the typical on-demand water pump, see Section 16.2 (Plumbing).

10.3 Stove
Manual Ignition
Electric Ignition
Indoor / Outdoor Stove
10.4 Furnace and Air Conditioner
Thermostat Controls
10.5 Outside Shower
10.6 Cassette Toilet
10.7 LP Tanks

Figure 15: LP Gas System


Figure 16: LP Gas Tank Valve



The lp (“Liquid Petroleum”) tanks supply gas (“propane”) to various appliances for heating and cooling uses. LP tanks are an efficient way to package and transport a large amount of energy.

LP fuel is kept under pressure in a liquid form inside the tank, and it is released in a gas form when it comes from the tank into the system. If two tanks are included, a changeover valve selects which tank is currently being used. A pressure regulator controls how much gas is available to the appliances. Some appliances may have an additional pressure regulator built into them.

Safety Improvements

Modern lp tanks have several safety improvements. These tanks are recognizable by the three lobed valve handle on top of the tank, and the green knob used to connect the hose to the tank.


The tank valve has an “Overfill Protection Device” (opd) built in, which limits how much fuel can be stored in the tank.

Green Knob:

The green pigtail hose knob tightens in the expected direction using only moderate hand force, and includes a system which cuts off the propane supply in the event of a fire.

Flow Limit Valve:

In the event that a gas line breaks or a stove burner is left on while opening the lp tank valve, a flow limit valve in the tank closes to allow only a small flow of gas to escape.

Pressure-Release Valve:

Another valve releases excess pressure built up when a tank gets overly hot, such as when sitting in direct sunlight on a hot day.

Choosing which LP Tank — The Changeover Valve

In a system with one lp tank, the tank’s output is directly connected by a hose to the pressure regulator, which is then fed into the trailer’s lp gas lines which go to each appliance.

In a system with two lp tanks, a changeover valve is included. Each tank is connected to this valve, the valve is then connected to the pressure regulator, and then the regulator is connected to the gas lines which go to each appliance. See Figure 15 (LP Gas System).

The changeover valve feeds to the pressure regulator the output of only one of the two tanks. Which tank is used is determined by a selector lever on the valve, pointing to either one side or the other. A small indicator with a green or red color shows whether gas pressure is present in the selected tank. So long as this tank has gas, its gas will be fed to the regulator, and gas from the other tank will not be used. Once the selected tank runs out of gas, the changeover valve’s indicator will change to red, and the valve will route gas from the opposite tank instead. Appliances will still be fed gas as long as any is available in the second tank. When this occurs, move the selector lever to point to the new tank, and the indicator will change back to green if the new tank has gas pressure. Once both tanks are empty, the indicator will show red regardless of which tank is selected.

When a tank is empty and the changeover valve is pointing to the opposite tank, the empty tank can be closed and removed from the system and taken for refilling. After it is refilled, it can be reconnected to the system and it will be selected automatically by the changeover valve once the opposite tank is empty.

Opening the LP Gas Tanks

Open the lp gas tank valves slowly. Each tank has a built-in check valve which is designed to trip if it senses a sudden rush of gas leaving the tank. If this occurs, close the valve, wait a while, and slowly re-open it.

The valve to use is the large one with a knob on the top of the tank. Do not use the small pressure-release valve on the side of the valve body. See Figure 16 (LP Gas Tank Valve).

Open each valve all the way until it stops. Use only gentle hand pressure; do not force the valve.

Purging the LP Gas Line

If this is the first time using the lp gas system since the tanks were installed out of storage, the lp gas lines may have air inside of them, causing it to be hard to light the refrigerator, water heater, furnace, or stove. You may quickly purge the air from the lines by trying to light the stove until it finally starts up, or you may wait for a few minutes after opening the lp tank valves before trying to start the lp appliances.

Even after the air has been purged as far as the stove top, there may still be additional air in the rest of the gas lines leading to other lp gas appliances, so you can expect that they may still be harder to start the first time they are used.

To purge the lp gas line with the stove:

  • 1. Slowly open the valves on the lp tanks. Opening the valves quickly may cause the internal anti-leak stop valve to trigger. See Figure 15 (LP Gas System).

  • 2. Open a side window and a roof vent. These must be opened any time the stove is in use to prevent dangerous oxygen depletion.

  • 3. Open the stove.

  • 4. Have a lighter ready.

  • 5. Turn on the stove to its light position. Listen for the sound of air or gas coming from the stove.

  • 6. While the air is coming out of the stove, light the lighter and hold it near the stove.

  • 7. The stove will not light until the air is purged and replaced by lp gas from the tanks. This can take several seconds.

  • 8. Continue applying flame or spark to the stove until it finally lights.

  • 9. Turn off the stove and the lighter.

  • 10. At this point, most of the air has been purged from the lp gas line, and other appliances such as water heater or refrigerator will now be easier to light.

LP Gas Starvation

If an lp appliance is for some reason left on (such as a stove-top valve having been left open) when the lp tank is opened, the tank’s flow-limit valve should activate, allowing only a small flow of gas to be available. This means that an lp gas appliance might work, but not very well, and several using appliances at once could cause a starvation of the gas supply, resulting in low or no operation of the lp appliances.

If it seems that the lp gas appliances are not working:

  • 1. Turn off all lp gas appliances.

  • 2. Keep the lp tank supply valves open.

  • 3. Wait 15 seconds to several minutes for the flow-limit valve to open again.

  • 4. Try turning on the lp gas appliances again.

  • 5. If the lp gas appliances still do not work, try this procedure again with a longer wait time.

  • 6. If the lp gas appliances still do not work, turn them off and search for leaks in the lp gas system. See Section 10.7.

Purging New or Exposed LP Tanks

A new lp tank must be purged of regular air before being filled with lp fuel. Some tanks are purged at manufacture, but if much time has passed they should be purged again before being filled. See the tank’s labels for details.

Any lp tank which is emptied and exposed to the atmosphere while its valve is still open must be purged before being refilled.

Refilling the LP Tanks

A propane tank may be exchanged or refilled when it is empty. To remove and reinstall the tank:

  • 1. Close the hand valve of the empty tank.

  • 2. On a system with two tanks and a changeover valve, point the changeover valve handle to the full tank.

  • 3. If both tanks are empty, or soon will be, turn off all gas appliances and close the hand valve on both tanks before removing either one.

  • 4. Unscrew the green knob to disconnect the tank from the gas line.

  • 5. Unscrew the bracket holding the tank to the trailer.

  • 6. Remove the tank and have it exchanged or refilled by a technician.

  • 7. To connect the lp tanks, see Section 6.3 (Connecting the LP Tanks).

Testing for Leaks

A technician can test for leaks using special tools. You may test for leaks yourself using either an electronic leak detector, or a commercial lp gas leak detection fluid which is sprayed onto the lines and fittings. Do not use soap and water, as it can corrode the brass fittings and eventually lead to new leaks.

Re-Certification of LP Tanks

Propane tanks must be inspected and re-certified for safety on occasion. Read the tank’s label for details.

10.8 Electrical Systems

Figure 17: Electrical System — Overview


Figure 17 shows a block diagram overview of the electrical system.

Electric power from the campground comes into the trailer through the trailer’s large power cord, and is sent into the electrical panel which has a series of circuit breakers. This power is the same as your household wall outlets, and the circuit breakers protect the wiring from overload the same way your household circuit breakers do. See Section 10.8 for information about the circuit breakers.

Your trailer will have a main circuit breaker for the entire system, along with separate circuit breakers for things such as the converter, air conditioning, and the trailer’s internal wall outlets.

The converter is also inside this electrical panel, and it takes this power and converts it to a low voltage 12 V dc format for use in several major trailer components, such as the lights and furnace. These components are protected by a fuse panel, which is also located inside the electrical panel. The fuse panel will have a pair of main fuses for the entire panel, plus a row of additional fuses, one per circuit. A label on the electrical panel will show the functions of each fuse and circuit breaker.

Power Limits

Your campsite might have several type of power outlets for your trailer to plug into. For a diagram of the outlets, see Figure 12 (Campground Power Outlet Types). Each style has limits to how much electrical power it can handle:

15 A:

Similar to a regular household outlet. Limited to one small air conditioner or one other high power item, but not more than one high power item at a time. This limit applies to both 15 A outlets as a combined total.

30 A:

Specific to camping rvs only, this is a 120 V ac outlet intended for higher current use. Allows the use of an air conditioner, and might allow one more high power item at the same time.

50 A:

Two 120 V ac circuits which may be combined into a 240 V ac circuit. Used in large rvs to allow the simultaneous use of a second air conditioner. Limited to two air conditioners, and might allow one more high power item. Air conditioners may have to be turned off if using other large appliances.

High power items include an air conditioner plus electric items such as a room heater, water heater, coffee maker, iron, etc. It is best to only use one of these at a time. If too much power is used at once, a circuit breaker will trip, shutting down much of the 120 V ac electrical system.

Overloads and Circuit Breakers

When too much power is drawn from the electrical system at once, causing an overload, a circuit breaker should trip to prevent an electrical fire. The electrical circuit will be disabled and everything connected to it will lose power. To re-enable the circuit:

  • 1. Turn off or unplug all high power appliances.

  • 2. Look for a tripped circuit breaker, both in the trailer’s electrical box and also at the campsite electrical box where the trailer is plugged in. One some trailers, an additional circuit breaker may be located behind the electrical converter. A tripped circuit breaker looks like it is mostly but not quite all the way on.

  • 3. Switch the circuit breaker all the way to off.

  • 4. Switch the circuit breaker back all the way on.

  • 5. Turn on or plug in fewer of your appliances at the same time. Turn off one before turning on the next.


The trailer’s wall outlets are similar to household wall outlets. Normal appliances may be plugged into these outlets, but they will only work if the trailer is plugged into the campsite’s power outlet or a generator.

Some outlets are protected by a “ground fault interrupt” (gfi). This is a device with two buttons on the face of the outlet, labeled test and reset. This outlet is wired so that it turns off if it thinks that you might be receiving an electric shock. Keep the area around the outlet dry, and do not poke anything into the outlet or touch it with wet hands. To re-enable the outlet, press the reset button. If it still doesn’t work, have an electrician look for a wiring problem.

To see if the gfi outlet works properly, press the test button and verify that the outlet makes a click sound and no longer powers anything. Press the reset button to return the outlet to normal operation, and verify that the outlet now powers an appliance. Repeat the test and reset buttons once more to be sure that the outlet clicks off when test is pressed, and returns to operation when reset is pressed.

Round 12 V dc “cigarette lighter” style power outlets might also be available. These outlets are active whenever the trailer’s battery is charged up, and they power automotive-style devices such as cell phone chargers.

Battery Voltage

The 12 V dc battery is recharged by the tow vehicle if wired properly and if the tow vehicle engine is running. The battery is also recharged by the trailer’s converter when the trailer is connected to the campground power post or a generator. The battery might also be recharged by a solar or wind system.

If none of these is available, the battery will be gradually drained as you use the 12 V dc appliances such as lights, furnace, or water pump. To avoid damaging the battery, it is important not to drain the battery too far. The battery should be recharged as soon as possible. A battery which is left uncharged for a long period of time gradually becomes damaged through an internal chemical process, and the longer it sits uncharged the less well it will work in the future.

To estimate the battery’s remaining charge, turn off all 12 V dc appliances such as lights and furnace, wait a minute, then check the voltage using a battery voltage meter plugged into a 12 V dc outlet. See Table 2.

Table 2: Battery Voltage And Capacity

Voltage % Full Comments
12.7 100 On a hot 100 °F day.
12.6 100 On a mild 60 °F day.
12.5 100 On a cold 10 °F day.
12.0 50 Stop using the battery. Recharge now!
11.5 0 Dead battery.
Battery Charging

Several methods may be used to charge the trailer’s battery:

Tow vehicle via hitch cable:

While the trailer is connected to a properly wired tow vehicle, the tow vehicle can slowly charge the trailer’s battery though the hitch electrical cable. A low battery can take all day to recharge this way.

Tow vehicle via battery jumper cables:

Faster than the hitch cable, but will still take a while to charge the battery.

Campground power, trailer has a simple one-stage converter:

Much faster charging, but it can still take hours. On a hot day, avoid battery overcharging by turning off the converter at its circuit breaker and re-activate as necessary to recharge on occasion.

Campground power, trailer has a three-stage converter:

Boost mode gives much faster charging, and storage mode avoids over-charging. Plug it in and don’t worry about it.

Campground power, trailer has a four-stage converter:

Similar to the three-stage, but the converter activates boost mode every now and then to keep the battery stirred up. Can cause boil-over on hot days, so you may wish to disable the converter once the battery is full, then re-enable it every now and then to recharge as needed.

Generator, trailer has a single-stage converter:

Use the 120 V ac generator output to plug in the trailer. Slowly recharges the battery.

Generator, trailer has a three- or four-stage converter:

Use the 120 V ac generator output to plug in the trailer. Recharges much faster than a single-stage charger.

Solar panel or wind turbine:

Use an intelligent charge controller. Slowly charges the battery and keeps it at full charge.

In storage, trailer has a single-stage converter:

Plug in the trailer for one day per month to keep the battery charged up. Unplug the trailer the rest of the time to avoid over-charging.

In storage, trailer has a three-stage converter:

Leave the trailer plugged in all the time.

In storage, trailer has a four-stage converter:

Leave the trailer plugged in all the time. Unplug the trailer during very hot weather to avoid boil-over from the fourth stage’s boost mode, unless it has temperature compensation.

In storage, battery removed from the trailer:

Leave the battery plugged into an intelligent three-stage charger full time, or a simple battery charger for one day per month.

Electrical Circuit Diagram

See Figure 18 for a detailed diagram of the trailer’s internal wiring.

Figure 18: Internal Wiring Diagram — Example


Tow Vehicle — Trailer Connections

See Figure 19 for a diagram of the tow vehicle to trailer connections, including tail lights, marker lights, reverse lights, brakes, and power.

Figure 19: Trailer Cable — Wiring Example


Cable Plug Pins

See Figure 20 for a diagram of the pin assignments of the trailer cable’s plug.

Figure 20: Trailer Cable Plug — Pin Assignments


  • 1. Ground

  • 2. Electric brake

  • 3. Tail lights, marker lights, licence plate lights

  • 4. Battery charge

  • 5. Left stop / Turn

  • 6. Right stop / Turn

  • 7. Aux / Reverse