Truma Combi diesel / electric water / space heater. Vents some water at end of water heating cycle.

[ProDave]

I have the above Truma combi diesel heater. A few questions:

First and most urgent question, is when it is heating just hot water, at the end or close to the end of finishing heating, it vents a small amount of water. Google tells me this is normal but I am not sure.

I have looked at the install and user manuals and not found any mention of this.

Now in a domestic setting, if your hot water heater vents water, then it is usually a fault with the expansion vessel. Some domestic tanks have a separate expansion vessel, others like Megaflow just maintain an air bubble at the top of the cylinder and there is a procedure to regenerate that air bubble.

So returning to my Truma, is this really considered "normal" or do I have a fault?

As a sanity check here is one random supplier selling the kit https://www.grasshopperleisure.co.u...-heater-with-inet-x-control-panel-44076-p.asp

There is no sign of an expansion vessel included with that kit so it must be built in.

Second question, why does it take a full half hour to heat 10 litres if water hot enough for washing up? I have had 2 previous trailer caravans with Truma gas water heaters and they have always heated it in less than half that time,

 

[colinm]

I'll pose a third question.
Do people fire up the Truma to do the washing up, or boil a kettle for washing up, and only fire up the Truma if wanting a shower?

 

[ProDave]

I fire it up for washing up, because 1 kettle full is not enough.

 

[Fisherman]

I have the above Truma combi diesel heater. A few questions:

First and most urgent question, is when it is heating just hot water, at the end or close to the end of finishing heating, it vents a small amount of water. Google tells me this is normal but I am not sure.

I have looked at the install and user manuals and not found any mention of this.

Now in a domestic setting, if your hot water heater vents water, then it is usually a fault with the expansion vessel. Some domestic tanks have a separate expansion vessel, others like Megaflow just maintain an air bubble at the top of the cylinder and there is a procedure to regenerate that air bubble.

So returning to my Truma, is this really considered "normal" or do I have a fault?

As a sanity check here is one random supplier selling the kit https://www.grasshopperleisure.co.u...-heater-with-inet-x-control-panel-44076-p.asp

There is no sign of an expansion vessel included with that kit so it must be built in.

Second question, why does it take a full half hour to heat 10 litres if water hot enough for washing up? I have had 2 previous trailer caravans with Truma gas water heaters and they have always heated it in less than half that time,

I have the 4kw diesel only Truma combi and it does take a fair bit of time to heat the water, but if you have the 6kw diesel electric I would have thought it would heat the water faster. I have noticed that I get a small amount of water maybe around 25ml when heating water, I don’t know if I get this when heating the van. But as you will know when heating the van you also heat the water to the eco temp of 40c.
Word of warning try to avoid simply turning it of during the heating process.
This seems to create a fault, and you have to do a reset by holding the switch until you get a yellow light, this can be a pain if getting to the boiler is difficult.

 

[Boris7]

When stationary I just leave the hot water on all the time wether I’m on EHU or not.

 

[TJBi]

I'll pose a third question.
Do people fire up the Truma to do the washing up, or boil a kettle for washing up, and only fire up the Truma if wanting a shower?

Boil a kettle for washing-up; it's normally been put on for hot drinks anyway. You can run off a lot of cold water to get hot through the pipes.

 

[horace]

Hi Dave the boiler unit does let a little water out on expansion , you can open the hot tap for a second or as you said fit a 2 litre expansion vessel in the hot pipe so its the same as your home megaflow

I have the above Truma combi diesel heater. A few questions:

First and most urgent question, is when it is heating just hot water, at the end or close to the end of finishing heating, it vents a small amount of water. Google tells me this is normal but I am not sure.

I have looked at the install and user manuals and not found any mention of this.

Now in a domestic setting, if your hot water heater vents water, then it is usually a fault with the expansion vessel. Some domestic tanks have a separate expansion vessel, others like Megaflow just maintain an air bubble at the top of the cylinder and there is a procedure to regenerate that air bubble.

So returning to my Truma, is this really considered "normal" or do I have a fault?

As a sanity check here is one random supplier selling the kit https://www.grasshopperleisure.co.u...-heater-with-inet-x-control-panel-44076-p.asp

There is no sign of an expansion vessel included with that kit so it must be built in.

Second question, why does it take a full half hour to heat 10 litres if water hot enough for washing up? I have had 2 previous trailer caravans with Truma gas water heaters and they have always heated it in less than half that time,

at home .

 

[horace]

We have been to truma with this fault and they changed the 4 bar safety valve to 4.5 safety valve that slowed it down only.

 

[guerdeval]

Mine heats much faster on gas than electric

 

[ProDave]

We are just back from another few nights in the MH. This time, the heater did NOT do this discharging of water thing at the end of the water heating cycle.

So the question to ask is what did I do between this trip, and the previous trip when it did discharge some water every time. And the answer is due to cold weather I had drained the water out of the heater, and only re filled it just before the trip.

So this leads weight to my theory that the expansion is taken care of normally by some form if air bubble in a similar way to the domestic megaflow tanks. And draining and refilling the heater re created the expansion bubble. It would be nice if there was something in one of the manuals to confirm or deny if this is the case.

And another "it would be nice to know" things we discovered. One one occasion we tried it doing space heating and water heating at the same time. After it had been on well over an hour we tried running water for washing up, but it was only luke warm. So this suggests it gives priority to heating and if you want it to heat water quickly you have to turn the space heating off. Again it would be nice for the manual to say that.

 

[Fisherman]

We are just back from another few nights in the MH. This time, the heater did NOT do this discharging of water thing at the end of the water heating cycle.

So the question to ask is what did I do between this trip, and the previous trip when it did discharge some water every time. And the answer is due to cold weather I had drained the water out of the heater, and only re filled it just before the trip.

So this leads weight to my theory that the expansion is taken care of normally by some form if air bubble in a similar way to the domestic megaflow tanks. And draining and refilling the heater re created the expansion bubble. It would be nice if there was something in one of the manuals to confirm or deny if this is the case.

And another "it would be nice to know" things we discovered. One one occasion we tried it doing space heating and water heating at the same time. After it had been on well over an hour we tried running water for washing up, but it was only luke warm. So this suggests it gives priority to heating and if you want it to heat water quickly you have to turn the space heating off. Again it would be nice for the manual to say that.

you do have the boost option on heating water, this prioritises heating water, and heats it too 65c.
but if trying to heat a van in winter with a 4kw boiler you would be better only carrying out one function at a time.
on heating mode your water is heated to 40c which is the temperature on eco setting.

 

[ProDave]

you do have the boost option on heating water, this prioritises heating water, and heats it too 65c.
but if trying to heat a van in winter with a 4kw boiler you would be better only carrying out one function at a time.
on heating mode your water is heated to 40c which is the temperature on eco setting.

Where did you find that information? You must have a much more comprehensive manual than I have. I never could figure the difference between "hot" and "boost" "Eco" is nowhere near hot enough for washing up.

I wish it was like the old gas water heater in our previous caravan that just had an on / off switch and a temperature dial.

 

[Fisherman]

Where did you find that information? You must have a much more comprehensive manual than I have. I never could figure the difference between "hot" and "boost" "Eco" is nowhere near hot enough for washing up.

I wish it was like the old gas water heater in our previous caravan that just had an on / off switch and a temperature dial.

To be honest I don’t know, but I have been using the combi for six years.
My last one was the 6kw gas electric, my new one is the 4kw diesel.
Try looking on YouTube I think I learned a lot there.
The Truma combi is a great bit of kit.

 

[Fazerloz]

We are just back from another few nights in the MH. This time, the heater did NOT do this discharging of water thing at the end of the water heating cycle.

So the question to ask is what did I do between this trip, and the previous trip when it did discharge some water every time. And the answer is due to cold weather I had drained the water out of the heater, and only re filled it just before the trip.

So this leads weight to my theory that the expansion is taken care of normally by some form if air bubble in a similar way to the domestic megaflow tanks. And draining and refilling the heater re created the expansion bubble. It would be nice if there was something in one of the manuals to confirm or deny if this is the case.

And another "it would be nice to know" things we discovered. One one occasion we tried it doing space heating and water heating at the same time. After it had been on well over an hour we tried running water for washing up, but it was only luke warm. So this suggests it gives priority to heating and if you want it to heat water quickly you have to turn the space heating off. Again it would be nice for the manual to say that.

There is an expansion/vac valve on the boiler. The difference is when you drain the boiler then refill with cold water the pump fills the boiler and closes the valve. When heated the water expands against a already closed valve. When finally left to cool the water contracts opening the valve to stop a vac forming in the boiler which could collapse the boiler. Vacs can do serious damage to tanks and boilers.. Commercial coffee machines work exactly the same way.

 

[Geek]

Google tells me this is normal but I am not sure.

Google only ever repeats what it has read in the Internet.
Google used to give a very short snippet and a link to the source, where you could read the source and assess its credibility and trustworthiness.
Nowadays Google just shows you an AI cobbled-together summary with no reference to who it stole the info from. You have no way to tell how reliable the data is.
As time goes in, more and more websites are just made out of AI summaries, so are less and less accurate.

 

[Geek]

Where did you find that information? You must have a much more comprehensive manual than I have.

He probably worked it out for himself. I did.
Truma manuals are very dumbed down to avoid scaring users.
Did you realise that if you set the heating to be on, for instance, from 10 until 2, yes it will be on for that period, but what will happen at 2?
That depends on what it was doing at 9.59. It will revert to that state, not turn off.
This is really useful in very cold weather. You could set the heating to 10 or 12 degrees, with the timer set to be at a more comfortable temperature in the day. Then when it turns off at night, it isn't completely off.
We generally use the HW Boost function when we expect to use hot water; we don't the other hot water settings much at all.