Truma Combi Heating & Hot Water
Description:
The Truma Combi is a propane and/or electric furnace with indirect water heating. The design contains a propane burner and electric heating elements surrounded by a long, donut shaped water tank with a capacity of 2.64 gallons (10 liters). It takes approximately 23-30 minutes to heat the water, depending on initial water temperature and power level settings.
NOTE: When using the Shower Miser, switch to BYPASS for 20-25 seconds and then to SHOWER.
First Time User:
A propane switch on top shuts off the propane valve within the Truma for performing maintenance to the unit. If you picked up a new RV, it is possible this switch is OFF. (Things can fall out of the drawers above the Truma and will be magically be drawn to this switch and turn it off)
Another common issue with new vans is the water heater bypass valves may still be in winterization mode and you are not getting hot water.
Temperature Offset – When initially configuring the heater, the control module may require an temperature offset adjustment to calibrate the room temperature with the thermostat.
========================================================
Controls:
The control panel is a little cryptic and can be intimidating at first. To operate you press the button and turn it to select the icons.
Top row:
Flame = Heater
Thermometer in water = Water Heater
Bottle & Lightning = Propane and/or 120 volt AC
Fan = you guessed it, Fan Speed
Clock = Timer (see, this is getting easier!)
New Truma Combi models offer iNet app for remote control of the Truma and also offer a propane level sensor.
========================================================
Heater:
In heat mode, a thermostat sensor (usually located above the sliding door) will cycle the heater on & off maintaining the temperature set by the control panel.
CAUTION: If there is water in the container it will also be heated and could reach a maximum of 162 degrees F.
NOTE: The air heating function can still be used with the water tank empty.
========================================================
Water Heater:
When connected to shore power, the Combi can operate in electric mode with two power levels 850 watts (EL-1), or 1700 watts (EL-2). The Truma can run in combo mode with propane and 120 VAC heating elements operating together (MIX). If there is no shore power, the Combi will switch to propane mode and runs on 12 volts.
TIP#287: Truma Hot Shower Procedure –
1 – City water connected and turned ON or water pump ON
2 – Propane turned ON and set the Truma hot water heater to MIX BOOST
3 – Wait approximately 30 minutes for the water to heat up
4 – Check the temperature at the kitchen faucet
5 – Get into the shower and close the curtain
6 – Move the Shower Miser lever to DIVERT for 30 seconds
7 – Move the Shower Miser lever to SHOWER
8 – Turn on the shower and set to a comfortable temperature
9 – Wash and switch OFF the water at the shower head while applying soap
10 – Turn shower head back ON and rinse off
TIP#303: Extended Shower Time – One common question we hear is, How can I get a longer hot shower?
The Truma Combi volume is 2.64 gallons, which is a very short Navy shower. To get the maximum hot shower time, we need to blend very hot water with the cold for the longest shower. Setting the water heater to BOOST will heat the water to 144+ degrees F.
For an example, we will say the hot water is heated at temperatures between 105° F and 150° F, and the cold water is 60° F, and we are blending hot and cold water at the shower controls to achieve 105° F.
Setting the hot water temperature to ECO, you will get 105-degree hot water. This means you will be using ONLY the 2.64 gallons of water from the heater and not blending with any cold.
Setting to BOOST (approx. 150°F), you will be blending 50% hot and 50% cold to achieve a temperature of 105°F, so in essence using 2.64 gallons of hot and 2.64 gallons of cold to produce 105°F water.
The next chart shows the amount of time that you will have 105°F hot water at the showerhead when the water is heated at temperatures between 105°F and 150°F. As shown above, setting the Truma to Eco (105°F), you will be using ONLY the 2.64 gallons of hot water. Assuming a 1-gallon-per-minute showerhead, the shower time is about 2:38 minutes.
Setting to Boost (~150°F), you have doubled your shower time to 5:17 minutes by blending 2.64 gallons of hot and 2.64 gallons of cold to get 105°F at the shower head.
These results are approximations, and in the real world, when you run the hot water, cold water refills the tank, cooling the hot water that is in the tank. Essentially, you are only getting 70-80% of the hot water before the temperature drops. Since it takes about 30 minutes to heat a tank full, you won’t be gaining much heat in your 5-minute shower.
.
TIP#294: Tank Decalcification – Truma recommends decalcifying and cleaning the water container at least twice a year with full time use. (I would think once a year at the beginning of the travel season is probably enough.)
They recommend using Citric Acid diluted in 3+ gallons (1 cup per gallon). The one shown is 12 ounces from Walmart.
1 – Mix the citric acid in 3 gallons using a 5 gallon bucket.
2 – With the RV water supply off, open the Truma drain valve and the sink hot water faucet.
3 – When the tank is empty, close the Truma valve and sink faucet.
4 – Pump the citric acid into the Truma (see options)
5 – Let the Citric acid sit in the Truma for about an hour.
6 – Drain the Truma: open the Truma drain valve and the sink hot water faucet.
7 – Close the Truma valve and sink faucet
8 – Connect to city water and refill the tank by opening the sink hot water faucet.
9 – Once the tank has refilled, drain the fresh water again.
10 – Refill and the process is complete.
(Now would be the perfect time to sterilize the tank)
TIP#295: Bucket and Pump – There are several options to add fresh water, sanitizing chemicals, winterizing antifreeze, or decalcifying chemicals to the plumbing system:
Submersible pump.
Drill powered pump
The RV water pump and the winterizing suction tube.
TIP#063: Tank Sterilization – In order to avoid growth of micro-organisms, regularly heat the water in the boiler to 158 °F as follows:
1 – Select energy mode “LP gas” on the control panel.
2 – Select the hot water level “boost”.
3 – When the water has reached 158°F, the display will not flash anymore
4 – Leave the heat switched on for another 30 minutes without using any hot water from the system.
Winterizing: When winterizing the water system, antifreeze chemicals can damage the Truma, so the bypass valves to and from the Truma must be closed and the crossover valve placed in bypass mode. The water tank can be drained using the pressure relief valve. (We really need page van winterization process!)
Warning: When winterizing the water system with anti-freeze, bypass valves must be closed to prevent anti-freeze from going into the water heater tank.
TIP#246: Truma Flapper Vent – There have been a few incidents of the Truma HOT WATER heater exhausts highly heated air into the van and in some cases, melting the heater vent register. This is caused by a “stack effect” or “chimney effect” type of thermal syphon due to the incorrect installation of the heater ductwork by the installer. A work-around solution from Truma is to install a flapper vent register that remains closed when the heater is off.
========================================================
Safety:
Pressure Relief Valve – A safety pressure relief valve is rated for 65.25 psi and also functions as a drain valve for emptying the water from the Truma hot water tank.
Temperatures in the Cabinet – The interior exhaust duct can reach temperatures of 190+ degrees F inside the kitchen cabinet. Warm air may also be expelled from the heater vents when running the hot water heater. (It is possible to melt the interior plastic vents when in Boost mode and heater OFF).
Outside Exhaust Temperatures – The outside vent is a combination propane exhaust and combustion air inlet. While some may suggest a child can put their hand on the vent with no harm, the vent can reach temperatures of 180+ degrees F. Moisture from burning propane may exhaust as steam or condense on the vent and drip down the side of the van.
========================================================
Trouble Shooting:
Error # 112 – Not getting Propane. Check that exterior tank switch is ON, control cabinet switch is ON, Switch on top of the Turma unit is ON, Check propane tank levels.
Error Reset – To clear an error from the control panel, turn the knob to select the error triangle symbol and press the knob. If this doesn’t clear the error you may need to remove the cover on the Truma unit and press & hold the reset button until the led indicator light changes color.
FUSE – A 12 volt fuse is located under the connection cover. The fuse is: 10 AT time-lag 5 x 20 mm IEC 60127-2 standard.
WARNING: Damage can occur to the water container with water pressure above 40.6 psi.
WARNING: Coachmen has installed a pressure reducer on the cold water line going into the Truma. Our pressure reducer is in the wrong place since it does not reduce the entire cold water plumbing pressure. When using the shower shut-off at the head or the outside shower sprayer and shutting it off at the spray nozzle, the cold high pressure can back-feed to the Truma and could cause damage. Truma installation diagram shows the pressure reducer on the line after the water pump so ALL water lines are reduced.
========================================================
Wrap-Up:
Other Heat Options – Small ceramic space heater, Electric blankets, Cuddly Dog. 😉
========================================================
12 – Electrical Controls Cabinet
13 – Heating
14 – Cooling