How to Use the Truma UltraRapid Hot Water System in Your Mars Caravan

The Truma UltraRapid hot water system fitted to selected Mars caravans is a compact gas / 240 V electric storage hot water service. It heats and stores a small volume of water so you can enjoy hot showers and washing water on the road, whether you’re plugged into mains power or running on gas while off-grid.

1. What Is the Truma UltraRapid Hot Water System?

The Truma UltraRapid is a storage hot water unit (typically around 14 L capacity) that can heat water using:

• LPG gas (for off-grid and general use), and
• 240 V electric element (when connected to mains power).

In simple terms:

• The tank is filled from your caravan’s fresh water supply.
• The unit heats the water and keeps it hot until you use it.
• You can run it on gas only, 240 V only, or (in many installs) both to heat faster.
• Hot water is delivered to your taps and shower through the caravan’s plumbing.

Because it is a storage system, there is a limited volume of hot water. Once the stored hot water is used, the unit needs time to reheat a new tankful.

2. Before You Use the System

Each time before using hot water, quickly check:

• Water supply: Your fresh water tank has water and/or you are connected to mains water.
• Water pump: The pump is turned on if you’re using tank water (rather than mains pressure).
• Gas supply (for gas mode): At least one LPG bottle is turned on and has gas available.
• 240 V power (for electric mode): You are plugged into a powered site or suitable mains outlet.
• 12 V power: The caravan’s 12 V system is on (for ignition and control, even in gas mode).
• External vent clear: The Truma hot water access door and vent are not blocked by chairs, walls, covers, plants, snow or other obstacles.

Important: Never attempt to open the Truma appliance casing, adjust gas components or carry out internal repairs yourself. All gas work must be done by a licensed gas fitter or authorised service technician.

3. Filling the Hot Water Tank

Before turning the Truma UltraRapid on for the first time (or after draining the system), always ensure the hot water tank is full:

1. Make sure the drain plug (if fitted) is closed and any drain valves are set to the “operating” position.
2. Turn on your water supply:
   • Open the water tank outlet and turn on the pump, or
   • Connect to mains water and open the mains tap.
3. Open a hot tap (e.g. kitchen or bathroom) and let the water run until the flow is steady with no spurting air. This confirms the hot water tank is full and the air has been bled out.
4. Once the flow is steady, you can close the tap – your hot water system is now full and ready to heat.

Never operate the Truma UltraRapid with an empty water tank – it can damage the unit.

4. Running the Truma UltraRapid on Gas

Using gas mode lets you have hot water whether or not you’re connected to mains power. Follow the steps below (exact switch layout may vary depending on how Mars has installed your unit):

1. Turn on gas and 12 V
   Open at least one gas bottle and make sure the caravan’s 12 V system is switched on.
2. Locate the Truma gas control switch
   Inside the van (often near the main control panel or ensuite) you will find a Truma hot water control switch or combined switch panel. Set the gas mode to ON.
3. Allow time for ignition
   The unit will automatically attempt to ignite the burner. You may hear a soft “click” and faint burner noise. Some panels have an indicator light that shows ignition and fault states – refer to your van’s manual for exact meanings.
4. Heat-up time
   From cold, expect around 20–30 minutes for a full tank of water to reach operating temperature (exact time depends on model, temperature, and installation).
5. Check for hot water
   After the heating time has passed, open a hot tap and confirm the water is hot.

If the burner fails to ignite and a fault light shows, switch the gas mode OFF, wait a few moments, then try again. If repeated attempts fail, see the troubleshooting section in your manual and contact support.

5. Running the Truma UltraRapid on 240 V Electric

When you are plugged into mains power, you can use the electric element to heat water. This is ideal for caravan parks and powered sites.

1. Connect to mains power
   Plug the caravan into a suitable 240 V outlet using an approved lead and make sure the caravan’s main 240 V RCD and breakers are ON.
2. Turn on the Truma electric switch
   Inside the caravan (or occasionally near the heater) you’ll have a separate switch for the 240 V element. Turn this ON to heat using electric power.
3. Allow heat-up time
   As with gas, the water will take some time to reach temperature – allow around 20–30 minutes from cold.
4. Check hot water
   Test a hot tap to confirm the water is hot.

In many Mars installations you can use gas and electric together to reduce heat-up time. If both switches are ON, the unit will use both energy sources (within the design of that specific model).

6. Using Hot Water at the Tap or Shower

Once the UltraRapid is up to temperature, using hot water is straightforward:

1. Turn on the hot tap or mix to warm
   Open the hot tap or adjust your mixer to your desired temperature.
2. Use hot water in short bursts where possible
   Because this is a storage tank, you have a limited volume of hot water. Quick showers and efficient use of hot water will help it last longer.
3. Allow time for recovery
   After heavy use (e.g. multiple showers in a row), the tank will need time to heat back up. Leave the gas and/or electric switched on and allow a full recovery period before expecting another long shower.

If the water becomes lukewarm or cold during use, you may have simply used the stored hot water. Give the system time to reheat before trying again.

7. Turning the System Off

When you don’t need hot water (for example, while travelling or storing the van):

1. Turn the gas mode OFF at the Truma control switch.
2. Turn the 240 V hot water switch OFF if you are on mains power.
3. Turn off gas bottles and 240 V as part of your normal pack-up routine.

If your van will be stored in freezing conditions or for a long period, follow the draining / winterisation instructions in your Truma and Mars manuals to avoid damage from freezing.

8. Basic Do’s and Don’ts

Do:

• Ensure the hot water tank is full before switching the unit on.
• Keep the external vent and access door clear at all times.
• Use both gas and electric (if available) when you want faster heat-up at powered sites.
• Have the system serviced by a licensed technician in line with Truma/Mars recommendations.

Don’t:

• Operate the Truma UltraRapid with no water in the tank.
• Block or cover the external vent or access door.
• Attempt DIY gas repairs or open the unit casing yourself.
• Ignore warning lights or strange noises – seek support instead.

9. When to Contact Support

Stop using the system and contact Mars support or an authorised Truma service agent if you notice:

• Repeated ignition failures or persistent fault lights.
• Water leaks from the heater or around the access door.
• Unusual noises, smells of gas, or visible damage to the unit.
• Very slow heating or no hot water despite gas/240 V being available.

When you lodge a support request, please include:

• Your Mars caravan model and VIN.
• Whether you were using gas, electric or both at the time.
• Any indicator lights or patterns you noticed on the Truma control.
• Photos of the external Truma access door and internal switches.

Summary

The Truma UltraRapid hot water system in your Mars caravan is a reliable gas / electric storage unit that provides hot water for showers and everyday use. Make sure the tank is full, choose gas, electric or both, allow time for the water to heat and then enjoy your hot water in sensible bursts.

Keep vents clear, follow basic safety practices and leave any internal or gas-related work to qualified technicians so you can enjoy many years of safe, comfortable hot water on your Mars adventures.