Truma CP plus - eco setting

[roxburd]

Anyone figured out how the Truma CP plus eco setting works??
The manual says "A hot water temperature can only be maintained with combined room and water heating for a limited time at 40 °C"
I thought it was a manual, not a cryptic crossword! For f s!
Maybe it means the water will only be heated when the room is being heated? What's the limited time? After the limited time, then what? The water is still heated but not to 40°C?
On a scale of 0 to 10 for clarity, -10 to Truma.
I've tried setting the room thermostat to 5° and 30° (room temperature 20°) but neither caused the water heating symbol to flash. I believe it flashes when it's heating the water.
Anyone figured out her mysterious ways? It seems so temperamental, it must be female... ;-)

 

[DBK]

Our new van has a Truma system and I'm only just starting to understand it so I can't really help. However, our last van had a Webasto system which prioritised heating the inside of the van and would only switch to heating water once the hab side was up to temperature. I've been caught out by this and thought it was broken when there was no hot water. It had spent all the time trying to warm the living quarters.

This is likely to happen, in my experience, if you are using electric heating and have selected the low power (1kW?) option. On higher power settings it should be able to both heat air and water.

 

[BusyBuilder]

We just set our truma to eco for water, it's fine for a wash and brush up in the morning. The water symbol flashes till it reaches temp, 40degC I believe, then stops flashing.

 

[B+W vanman]

I wonder if it’s trying to prevent you storing water at 40 degrees C for the long term?
This can be dangerous, due to the risks of legionnaires disease

 

[roxburd]

We just set our truma to eco for water, it's fine for a wash and brush up in the morning. The water symbol flashes till it reaches temp, 40degC I believe, then stops flashing.

Yeah, we've been doing the same and its fine in the morning - when we also have the heating on. But I also put it on in the evening for the washing up (when the heating is not on) and it's 50/50 whether it heats the water or not. Totally unpredictable. No rhyme nor reason.
The flashing icon seems reliable, though- if the icon flashes the water's heated. But half the time it just don't flash.

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[Lenny HB]

Eco heats the water to 40° but the thermostat has a large hysteris and doesn't reheat the water until it drops to 27°

Basicly it's useless & not worth using.

 

[Ian_H]

As DBK says, if the blown air heating is on it takes a lot of heat from the water. In winter I have experienced the water not warming up much even when on 1800W electric, if the blown air heating is on high speed!

 

[Ian_H]

Eco heats the water to 40° but the thermostat has a large hysteris and doesn't reheat the water until it drops to 27°

Basicly it's useless & not worth using.

As well as any thermostat hysteresis our truma has a lot of thermal lag, in that the temperature may show 40 when the water heating turns off (no air heating on) but continues to rise for 10 minutes afterwards, so may show 47 then. The higher temperature seems more representative of what comes out of the tap. This also happens with the water heating on the other settings and can result in scalding hot water.

 

[Lenny HB]

This also happens with the water heating on the other settings and can result in scalding hot water.

I fitted a TMV on the shower supply.

 

[Windy66]

Eco heats the water to 40 degs. Warm enough to wash your hands and face. Tepid.

But the water heating may not kick in through the night if there is no flow.

Hot heats to 60 degs. Boost also heats to 60 degs and will turn off any heating in favour of heating water. Boost works for a limited period (I think 30 mins) then reverts to Hot setting.

We use Eco mostly but put it on Hot if we are washing up or having a shower. Takes 20 mins to go from 40 to 60 degs on Fuel setting. Not sure time for Mix setting. Much longer on EL.

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[Lenny HB]

Hot heats to 60 degs. Boost also heats to 60 degs and will turn off any heating in favour of heating water. Boost works for a limited period (I think 30 mins) then reverts to Hot setting.

Boost heats to 62° then turns off.

 

[Wanders from Glos]

We have found there is no need to put the hot water on if you have the heating on. The water gets heated anyway. Someone on here pointed this out a few years ago and we haven’t had cold water with the heating on since.

 

[Lenny HB]

We have found there is no need to put the hot water on if you have the heating on. The water gets heated anyway. Someone on here pointed this out a few years ago and we haven’t had cold water with the heating on since.

It does but it takes a long time to get hot and not hot enough if you both want a shower.

 

[Lenny HB]

A trick I do in winter to give hot water for a shower when you get up and a warm van.
I set the timer to turn on at say 7:00, water to Boost & heating to desired temperature.
At 7:00 the water will start heating then at about 7:40 the water heating will turn off and the heating will turn on. The van will warm up quickly as the boiler is hot and the heating will keep the water hot. Then you can get up at 8 to a nice warm van and have a shower.

Only one flaw in this, no way would I get up that early.

 

[Bramidan]

I’ve always just set the water to hot and just left it on constantly.
I’ve worked on the basis that the tank is small and there can’t be that much heat loss if the water is not being used, thus the water heater will only come on when the water temperature drops.
I’ve also found eco setting is not worth using, my wife needs hot water not tepid!

Should I be doing something different?

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[Lenny HB]

We only put the hot water on first thing in the morning, use a kettle for washing up lunchtime & evening.

Leaving the water on all the time means you will have to descale the boiler a lot more often.

 

[BusyBuilder]

Descale ? No need with Highlands water . Though we had to descale everything in our previous B544 as it was a southerners van.

 

[roxburd]

We only put the hot water on first thing in the morning, use a kettle for washing up lunchtime & evening.

Leaving the water on all the time means you will have to descale the boiler a lot more often.

Yep, I think that's what we'll do too!! We only need a small amount of warm water for the washing up in the evening - hardly worth firing up the boiler for. Especially on a hot day when you don't want the whole van heated by the heat that inevitably leaks from the system.

 

[Pausim]

I wonder if it’s trying to prevent you storing water at 40 degrees C for the long term?
This can be dangerous, due to the risks of legionnaires disease

Unlikely. Legionella bacteria multiply where temperatures are between 20°C and 45°C. The bacteria are dormant below 20°C and do not survive above 60°C. You would be safer using the boost setting of 62°C to kill them.

 

[B+W vanman]

Unlikely. Legionella bacteria multiply where temperatures are between 20°C and 45°C. The bacteria are dormant below 20°C and do not survive above 60°C. You would be safer using the boost setting of 62°C to kill them.

I understand that!
I was trying to interpret the manual quoted in the OP’s original post

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[Millcourt]

The clue is in the name “Combi-Boiler” i.e. one heat exchanger heats both water and the blown air. Although you can heat the air with no water in the system, if water is present it will always be heated when the heat exchanger is switched on.

Heating the blown air is a bit like a fan heater. You control the room temperature at which the blower turns on/off by a room thermostat at the temperature set on CP Plus Panel (5-30 ºC). A fan heater might typically have 2 power settings. The Truma has 5. These are EL1 (0ne electric element of 850 watts); EL2 (Both electric elements giving 1700 watts); Gas (equivalent to 6000 watts in the Combi 6 and 4000 watts in the Combi 4); Mix 1 (Gas plus 1 electrical element); Mix 2 (Gas plus both electrical elements). So, in the Combi 6E model, Mix 2 will give a total of 7700 watts of heating power. You can also control the fan speed which blows the air through the ducting/vents. The options are: Vent (air circulation only, which I have never found a use for as it just circulates air within the van with obviously no cooling effect in hot weather); Eco (low speed); High (high speed): and Boost (higher airflow, but only when the difference between the room temperature and the thermostat setting is greater than 10 ºC).

Heated water temperature can be set to 3 levels: Eco (40º C); Hot (60º C); and Boost (a rapid heating mode for up to 40 minutes, raising the temperature to 62º C, before reverting). However, as has already been mentioned above by Lenny HB, the thermostat has a large hysteris and will not switch on/off precisely at these temperatures.

Others have already mentioned the risk of Legionella. To play safe, we always use the Hot setting for water heating.

Obviously, on those occasions when we have EHU included in the pitch price, we mostly try to use electric-only heating. However, this not very effective in cold weather (max 1700 watts). Mostly we are off-grid, so rely on our twin Gaslow installation. However, do not under-estimate the gas consumption in cold weather. On gas, the Combi 6 burns about 480 g of LPG per hour when running continuously. In practice, it cycles on and off, so except in freezing weather you should not expect to be continuously burning at this rate.

 

[DBK]

The clue is in the name “Combi-Boiler” i.e. one heat exchanger heats both water and the blown air. Although you can heat the air with no water in the system, if water is present it will always be heated when the heat exchanger is switched on.

I think that's an over-simplification as you can set the water to OFF. It will still take the chill off the water but presumably heat is ducted away from the boiler so the water won't get very hot unless you select one of the 3 temperatures.

 

[Millcourt]

I think that's an over-simplification as you can set the water to OFF. It will still take the chill off the water but presumably heat is ducted away from the boiler so the water won't get very hot unless you select one of the 3 temperatures.

DBK I think you may be correct. My experience has been that when I have used heating only I found the water also became hot. However, I have been digging a bit more and found the following explanation:

• In heating only mode, the Truma Combi 6E blows hot air through a heat exchanger that wraps around the water tank.
• Some of that heat naturally transfers into the water, so after a while the water will be warm, often around 25–40 °C depending on room temperature, fan speed, and run time.
• It won’t reach the 40 °C or 60 °C targets that the water heating mode provides, and the boiler won’t try to maintain any specific water temperature.

So, it seems I have been getting pleasantly warm water for washing hands etc, but not reliably hot enough for a shower. As we always fully heat the water for showering (to minimise the risk of breathing in small droplets infected with legionella), I must have been misleading myself.

 

[Wanders from Glos]

It does but it takes a long time to get hot and not hot enough if you both want a shower.

Yes it takes a while and also depends how hot you have the heating.

 

[Wanders from Glos]

I think that's an over-simplification as you can set the water to OFF. It will still take the chill off the water but presumably heat is ducted away from the boiler so the water won't get very hot unless you select one of the 3 temperatures.

Over a few hours it can get hot enough for a good hot shower. But it takes a fair while. However if you have the heating on from say 4pm in the winter and need to wash up at 8pm, you will have good hot water. Or at least we do.

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[Wanders from Glos]

DBK I think you may be correct. My experience has been that when I have used heating only I found the water also became hot. However, I have been digging a bit more and found the following explanation:

• In heating only mode, the Truma Combi 6E blows hot air through a heat exchanger that wraps around the water tank.
• Some of that heat naturally transfers into the water, so after a while the water will be warm, often around 25–40 °C depending on room temperature, fan speed, and run time.
• It won’t reach the 40 °C or 60 °C targets that the water heating mode provides, and the boiler won’t try to maintain any specific water temperature.

So, it seems I have been getting pleasantly warm water for washing hands etc, but not reliably hot enough for a shower. As we always fully heat the water for showering (to minimise the risk of breathing in small droplets infected with legionella), I must have been misleading myself.

I have to say we have found it is hotter than when on you heat water on ECO, but it does take a few hours.