Truma combi 6 faults only gas fired unit

[Campfos]

I have a year old motorhome which I have had from new.

Now I am forever bleeding air out of the hot water taps.

I was away in the van last week not on any EHU and you would bleed the air out of the hot water system put the control on 60 have a shower no problems. Switch off the unit when you go to bed.

Wake up in morning turn on the hot taps no water loads of air.

 

Now when I picked the van up when new I stayed at the dealers for a few nights to make sure all was well.

The only problem was with the Truma when running it at 60 with the heating you would get air/steam out of the hot water system while in use. I was told this was due to there being no thermostat on water due to the heating being in use and it could overheat the water. And it was a common occurance was not happy with that answer but never got any further with that.

I did not have any of these problems in my old motorhome so cannot understand why it's like this in the new one.

When you turn off the unit at night no air in the hot water side and it's not run long enough to produce the steam / air that it's been doing from new. But as said above in the morning the system is full of air.

The units have heater elbow valve on them I was wondering if this could be defective or has anyone any other ideas experience with this problem.

 

[Colin Leake]

We've had just about every possible fault with one of these but never this one. Taint right and your dealers talking a lot of hot air. Try ringing Truma and insisting they send an engineer to sort it out. Happily ours seem to be running ok now. Only time we see a fault code is if we have it running on electric and unplug the supply without turning the syste off first in which case it sends a code telling us we've no mains power.

 

If anything we find that the water struggles to get hot enough when running heating and water electric only. Just a thought are you running on electric, gas or both?

[Keithl]

Hi Campbell,

 

Is this definitely only with the hot water or does it happen with cold as well? Or is it possible that you have just never noticed it with the cold taps?

 

If it does happen with both hot and cold then it could be an air leak on the pick up pipe from the tank to the pump or a cracked pump body allowing air to be sucked in.

 

Worth checking.

 

Keith.

[Robbo]

What water pump system do you have - submersible (located in the fresh water tank) or diaphragm ( such as shurflo).

 

The submersible pumps have a non-return valve between tank and Truma boiler. If this is faulty, water can drain back into the tank and let air into the system.

 

If you have a shurflo pump or similar first check the plastic filter housing at the pump inlet. These can sometimes crack and let in air. If air is getting into the system, the first sign is the pump keeps recycling frequently when no water is being drawn off.

 

It does help in diagnosing the problem if you tell us what make of van you have.

[Campfos]

Hi again,

 

The van is a sunlight T66.

It's fitted with a Reich submersible pump 19 l/m 1.1 bar.

The problem only with air only effects the hot water side of things.

That's why I think it's to do with the boiler if it was the pump non return valve it would effect both hot and cold.

The boiler has a elbow that has a vent line on it not sure the purpose of this.

 

Campbell

[Robbo]

The elbow with vent line is an aeration valve. When discharging water from the boiler either automatic via the dump valve or manually it allows air into the boiler to assist the drain down process.

 

I always thought it was some kind of pressure release valve but it is not.

[aandncaravan]

"when running it at 60 with the heating i would get air/steam out of the hot water system while in use"

 

I suggest you have the problem nailed when you write, "air/steam", but are focusing on the Air, rather than the Steam side?

 

If it is only happening when you use the Heating, and that has probably been on 'Max' with the recent cold temperatures, then maybe the Hot water is getting so hot it creates a lot of Steam which then 'drives out' the Water creating a vapour lock?

 

It is not uncommon with the Combi to 'Steam' the Hot Water when the Heating is set on max for long periods in very Cold weather, but not usually this bad. Maybe your thermostat has a slightly higher than average tolerance, say maybe not switching off until 75 degrees?

Using a slightly lower Heating temperature often 'calms down' the Hot Water.

 

 

Maybe it is an issue you might be able to reduce to a useable level by looking at how you turn it off?

 

Some people on some systems turn the 'Heating' temperature down 10 mins before turning it off completely as this distributes the Latent heat already at the heater unit.

On some systems if you just 'shut off' the Heating in it's entirety when it's hot, i.e. also stop that heat being taken away from the Heater by the pump/fan, the Heat at the Heating unit itself can reach very high temperatures for a short time before cooling down. In a Combi this might lead to short term Steaming?

 

For example on a Carver Fire/Fan based system if you run the 240v heater element at max for a while and then shut off the 240v element power AND the Fan, you will hear some very tortured clicking noises come from the poor Carver as the 240 element goes on putting out the Red Hot heat that is supposed to be drawn away by moving Air from the Fan. You will also generally detect that smell when things are very Hot.

If you turn off the Carver 240v power 5 minutes before shutting off the fan, so letting the Fan draw away the Heat already in the Unit, everything is much calmer inside the Heater. No Hot smell either. We think this way of operating also prolongs the 240v elements life.

 

Maybe, the way you shut down your system stops the water flow at an already hot Boiler casing which goes on 'super heating' the Heating water, which indirectly heats the Hot Water, hence the vapour Lock?

 

How about trying a slightly lower heating temperature, and maybe dropping that temperature to half way 5 minutes before you switch off every thing for the Night?

 

 

 

[Robbo]

On my Truma combi 6, circa 2008 (gas only version), you can ONLY have the water temperature at 60C if combined with space heating.

 

Without space heating the water temperature can be set to either 40C or 60C.

 

Perhaps the OP should try setting the water temperature to 40C (without space heating) to see if the same symptoms persist.

 

As aandncaravanservices suggested, perhaps the water temperature in the boiler is getting hotter than the 60C indicated by the control setting. A good way of checking would be to measure the temperature of the water at the tap when set to 60C. As far as I know there is a sensor or thermostat in the boiler to keep it to the specified temperature. Perhaps you should go back to Truma sevice department to ask that specific question.

[Campfos]

Hi

Update motorhome parked up at the house for the weekend going away tomorrow.

Checked all the taps both hot and cold no air in the system so don't think it can be the submerged pump.

Now I only have the basic controls only Water 60c with space heating , or water 40c or 60c no space heating or space heating on its own so can't turn it down when using space heating.

Will be living in it all next week so will let everyone know how things go.

 

Campbell

[Brian Kirby]

I strongly suggest you contact Truma technical at some point over the net day or so, and describe to them what is happening. It sound to me as though the high limit thermostat is faulty, and is allowing the water to get dangerously hot. If they are satisfied that all is normal, OK, but from your description I would think the water heating is operating outside its designed range and needs proper investigation.

 

I assume by steam you mean steam under some pressure, and not merely a mix of water vapour and hot air. For the water to be expanding to the extent that part of the heater contents is expelled, which would result in the air-locking you describe, I would think the water must at some point be reaching boiling point, or close. I'm sure this is not a design feature of these heaters and indicates a fault.

[aandncaravan]

The fact that it mostly works ok during the day with the biggest problem being first thing in the morning, does suggest it is an issue that can be helped with a progressive 'shutdown'? Hot water 'spatter' during the day is common if the heating has been on maximum for a while.

 

I don't mean select a lower Boiler temperature, but a lower habitation air temperature, as this will cause the Boiler Flame to shutdown.

Be surprised if there is not a separate 'room thermostat' style device that you can't put on a lower setting? However, if this isn't available then how about turning the Water to 40 and the Heating off for 10 minutes prior to a full shutdown at night?

Maybe even run the Tap for 10secs to drop the Boiler temperature?

 

Again when I suggest running a lower temperature, I meant on the 'room' thermostat, not the Boiler thermostat.

In our experience this issue is a bigger problem when everything on the heating side is on the Max setting for long periods.

 

 

I am not saying there is not another issue, I do suggest that maybe the thermostat has a bit too much tolerance, just that a 'controlled' shutdown might provide a work around while you progress it with the Dealer?

 

Regardless of whether this is the issue or not, it is good practice as it reduces stress on the Boiler and it's components. One of the reasons why most modern 'home' boilers continue to run the water pump for some minutes after the flames extinguish.

 

With the warmer weather set for the next few weeks I suspect the problem will reduce anyway. It normally does.

 

 

[Campfos]

Hi update,

 

When away in the van this week so far

Contacted Truma by email no answer so far.

Now trying running the water at 40c heats the water up to temp fine as far as I can tell.

Then using the space heater settings on its own to heat the van it cuts out on the thermostat ok the fan stops.

System then turned off check both hot and cold water taps no air just water last thing at night.

Up in morning try taps hot side full runs for a good min while it expels the air.

This still does not work right so no idea why it my last van I went on site turned the system on to both water and space heating and it just worked.

One of the differences I have found is the fan in my previous van was a little noisier and seemed to have a greater air flow but the unit was fitted in the Wardrop not in the garage as in this one is so that could explain that one.

Campbell

 

[Campfos]

Hi update

 

Last night just run the space heating setting at mid range so it was cutting in and out.

Now was able to have a shower lots of hot water no problem there.

Turned the space heating thermostat right down and system shut down no fan running before going to bed.

Now woke up this morning and the hot water tap still had air in it not as much as in previous mornings.

Here is a question you only have one space heating setting on the system which seems to be the only setting you need to work both heating and give you lots of hot water.

This has got me thinking that if the space heating fan is not giving enough air over / through the heat exchanger this could cause it to overheat. So how does one check the fan is giving the right air flow.

 

Campbell

 

 

[colin]

Stupid question, but have you checked the drain valve to make sure it's closed?

[Campfos]

Drain valve closed and checked for being tight.

 

Campbell

[Campfos]

Drain valve closed and checked for being tight.

 

Campbell

[aandncaravan]

That there was less 'air' when running at a lower 'Room' temperature does suggest we are on the right track with the cause.

 

In your new Motorhome there is a single Heat source, so if you run the Space Heating at a High temperature, the Water will also be heated to the same level, regardless of the Hot Water thermostat.

 

I guess you have previously had independent Hot Water and Space heating systems so not used to the effect the Space Heater setting has on the Hot Water?

 

You write in the last post,

"Turned the space heating thermostat right down and system shut down no fan running before going to bed".

Did you wait about 5 minutes, as we suggested above, between switching the Space Heating temperature to low before then shutting off the fan or powering off the system? The delay between turning down the Space Heating and doing a full system 'shutdown' should be long enough to get rid of the excess Heat which would otherwise go into the Water, potentially 'superheating' it, because it is one 'Combined' heater unit.

 

Maybe, like Robbo suggested above, try turning the control so that only 40 degrees Hot water is selected, with Space Heating off, 5 minutes before you then do a full shutdown?

 

It will promote longer trouble free life of any Heater unit, but especially a Combi unit, if you do a 'Soft' shutdown that lowers the heater unit temperature gently.

 

 

.

 

 

 

 

 

 

 

 

 

[Campfos]

aandncaravan - 2016-05-05 10:42 PM

 

That there was less 'air' when running at a lower 'Room' temperature does suggest we are on the right track with the cause.

 

In your new Motorhome there is a single Heat source, so if you run the Space Heating at a High temperature, the Water will also be heated to the same level, regardless of the Hot Water thermostat.

 

I guess you have previously had independent Hot Water and Space heating systems so not used to the effect the Space Heater setting has on the Hot Water?

 

You write in the last post,

"Turned the space heating thermostat right down and system shut down no fan running before going to bed".

Did you wait about 5 minutes, as we suggested above, between switching the Space Heating temperature to low before then shutting off the fan or powering off the system? The delay between turning down the Space Heating and doing a full system 'shutdown' should be long enough to get rid of the excess Heat which would otherwise go into the Water, potentially 'superheating' it, because it is one 'Combined' heater unit.

 

Maybe, like Robbo suggested above, try turning the control so that only 40 degrees Hot water is selected, with Space Heating off, 5 minutes before you then do a full shutdown?

 

It will promote longer trouble free life of any Heater unit, but especially a Combi unit, if you do a 'Soft' shutdown that lowers the heater unit temperature gently.

 

Thank you for this advice

Now in my previous motorhome it had a combi system which did not have these problems.

If the water in the combi tank gets as hot as this in use the fan cannot be blowing enough air across it to take the heat away as there never seems to be a large air flow through the vents.

So would this system work better with the electronic control instead of the classic control that I have.

 

Campbell

 

.

 

 

 

 

 

 

 

 

[Derek Uzzell]

Campfos - 2016-05-06 7:28 AM

 

...Now in my previous motorhome it had a combi system which did not have these problems.

If the water in the combi tank gets as hot as this in use the fan cannot be blowing enough air across it to take the heat away as there never seems to be a large air flow through the vents.

So would this system work better with the electronic control instead of the classic control that I have.

 

Campbell

 

”Combi” heaters are significantly different to the preceding Truma C-Series ranges of combination air/water heaters.

 

If your motorhome’s water system has been completely filled so that it contains no air and air gets into to it subsequently, the air must be getting in somehow.

 

When air enters and the water system includes a submersible water-pump the prime suspect must be (as Robbo said) the non-return valve between the pump and heater. Otherwise a water-leak ‘downstream’ of the non-return valve (perhaps through the FrostControl safety/drain valve) could allow air to be sucked in through the vent-valve in the ‘elbow’ fitting on the Combi’s hot-water outlet.

 

Whatever the cause of the problem, it should not be necessary to develop work-arounds that involve playing about with control-panel settings to try to overcome the air-entry problem. And if a Combi won’t operate properly when the control-panel is the simple “CP Classic” type, the chances are minimal that a “CP Plus” digital panel replacement will provide a miraculous fix.

 

If you don’t get a reply to your emall I suggest you telephone the Truma(UK) technicians for advice.

 

Tel: 01283 586020

 

Email: technical@trumauk.com

 

Opening times:

 

Monday - Thursday: 8 am to 5 pm

Friday: 8 am to 1.30 pm

 

Weekends and Bank Holidays: Closed

 

 

[Campfos]

Derek Uzzell - 2016-05-06 9:10 AM

 

Campfos - 2016-05-06 7:28 AM

 

...Now in my previous motorhome it had a combi system which did not have these problems.

If the water in the combi tank gets as hot as this in use the fan cannot be blowing enough air across it to take the heat away as there never seems to be a large air flow through the vents.

So would this system work better with the electronic control instead of the classic control that I have.

 

Campbell

 

”Combi” heaters are significantly different to the preceding Truma C-Series ranges of combination air/water heaters.

 

If your motorhome’s water system has been completely filled so that it contains no air and air gets into to it subsequently, the air must be getting in somehow.

 

When air enters and the water system includes a submersible water-pump the prime suspect must be (as Robbo said) the non-return valve between the pump and heater. Otherwise a water-leak ‘downstream’ of the non-return valve (perhaps through the FrostControl safety/drain valve) could allow air to be sucked in through the vent-valve in the ‘elbow’ fitting on the Combi’s hot-water outlet.

 

Whatever the cause of the problem, it should not be necessary to develop work-arounds that involve playing about with control-panel settings to try to overcome the air-entry problem. And if a Combi won’t operate properly when the control-panel is the simple “CP Classic” type, the chances are minimal that a “CP Plus” digital panel replacement will provide a miraculous fix.

 

If you don’t get a reply to your emall I suggest you telephone the Truma(UK) technicians for advice.

 

Tel: 01283 586020

 

Email: technical@trumauk.com

 

Opening times:

 

Monday - Thursday: 8 am to 5 pm

Friday: 8 am to 1.30 pm

 

Weekends and Bank Holidays: Closed

 

 

Hi Derek

 

Thank you for the information I will try calling on Monday.

I do agree with you that you should not have to do work around as the system should work.

At present I am living in the van during the week as I help out on the Waverley Paddle Steamer which is in Drydock in Greennock to save me travelling everyday from home.

I vented the system this morning travelled home tonight no heating on and no air in the system so hopefully the Truma service can help.

 

Campbell.

]