Truma Combi 6E electrical heating problem

[MasterW]

When using my heating system on EHU, the efficiency seems to have dropped right off. I have now monitored the AC current to the HU cable, with the following results. Note that all electrical appliances except the battery charger are isolated. I am using a Fluke multimeter with true rms capability.

 

Excepting that the battery charger current can vary dependant on the state of charge and water heating is not selected, these measurements were taken in quick succession:-

 

With electrical heating off, current measured was 0.75amp.

With one element selected current measured was 2.48amp. 2.48-0.75 = 1.73 amp, at 240V this suggests only 415W.

with two elements selected current measured was 4.16amp. 4.16-0.75 = 3.41 amp, at 240V this suggests only 818W.

 

This is very odd because the two consumption figures are quoted as 3.9A, (900w) and 7.8A, (1800w) for the two element electrical heating circuit.

its also odd that the second heater measurement was approx double the first, even though the measurements were 50% low.

 

Any ideas..?

 

Does this suggest that one of the elements (the first switched in) is open circuit, and the 1.73 additional amps are supplying some other heater circuitry? (Plus additional battery charger current due to the fact that the fan is also switched on). The odd thing is that with only one element selected, there is still some warm air generated. So I guess it must be in circuit. So do I have a poor connection somewhere else dropping 400W, if so this would be very dodgy and a possible fire hazard.

 

Apart fro doubting the measurements from the meter, I suspect that something else is going on but what I know not at the moment.

 

has anybody else made such measurements, I would love to hear...!!!

[Robinhood]

I'm pretty sure I've read somewhere that the elements (of which there are two) on the latest combis are both used at "half power" when the lower setting is selected (rather than using one element) in order to equalise out the usage of the elements. Patently, both elements would also then be used at full power when on the higher setting.

 

Should this be the case, then I would suggest one of the elements has failed.

 

[Derek Uzzell]

Truma technicians advised me that - for Combi(E) and the Trumatic C 6002EH heaters - the 230V heating elements always operate simultaneously when 900W or 1800W output is selected.

 

(I used to think the elements would operate independently (1 element = 900W or 2 elements = 1800W) as this seemed logical, but the Truma techs told me this was definitely not so.)

[Alanb]

A simple way to operate a heating element at half power, would be to incorporate a diode in series with the element. With two elements working on alternate half cycles of the supply, harmonic contamination of the local supply system would be avoided.

 

Alan

[MasterW]

Thanks for your responses. Both Robinhood and Derek seem to have hit the nail on the head, and would explain why I still get some modicum of heat from the system when 'low' is selected. Both elements would always be in circuit (unless one is open) and explains why I got the seemingly strange current readings. If both elements are operating at half power in low mode (maybe using diode or triac control) as Alan suggests, it would most certainly indicate that one of my elements is open circuit.

 

Anybody tried replacing the elements in one of these combi E heaters...???

[Derek Uzzell]

On the MotorHomeFun forum there is a 2018 ‘blow-by-blow’ account about replacing the 230V heating elements of a Truma Combi 4E - and your 6E will be much the same.

 

https://www.motorhomefun.co.uk/forum/threads/truma-combi-4-e-strip-down-replace-heating-elements.173899/

 

(It will be necessary to login to MHFun to make best use of the thread.)

 

There’s also this 2014 MHFun thread

 

https://www.motorhomefun.co.uk/forum/threads/fitting-a-new-element-in-truma-boiler.81902/

[MasterW]

Thanks Derek, I found that link yesterday, anybody got a week to spare...??

 

At £300+ for the elements, I wonder what the labour charge would be... looks like an off-season job, when I am feeling in a good mood and the wife has gone to her sisters for a week.

 

Sounds like a pigs breakfast; looking at other comments on the web, for something that seems prone to failure, you would have thought that replacing the elements would be simple. Hey-ho, another case of very poor design.

 

Don't get me started, particularly on AGM battery charging, alloy wheel corrosion, rear camera quality, failure of orthogonal 3-way plastic heater pipe connections, would I buy another Hymer...H'mmm.

[Basil]

Unfortunately the dreaded 'Truma' or should that be Trauma combis are fairly well universal now after Truma effectively bought out and discontinued the much more effective Carver system, so it's not just your Hymer thats affected.

 

I consider the Truma to be the biggest load of **** and the only thing on our current van that I really detest, poor quality, inefficient and regularly faulty with self destructing and overpriced electric heaters being the worst bit!!

 

Just my opinion of course but from experiences.

 

bas

[MasterW]

Hi Basil, from your comments, do I assume correctly that you have been thro the replacement process, did you use a dealer, if so would you be happy (sic) to give me an idea of cost. I am not sure I want to delve into this bundle of tricks; at least with a dealer I might be able to extract some sort of warranty on the work carried out. it seems to be difficult to get any meaningful response under prevailing COVID conditions.

[Basil]

Hi, sorry for the delay in replying!

 

I actually carried out the work myself, I do have a 45 year background in heating and ventilation as well as gas and electricity. It is not a very difficult job and at least the replacements come in a kit with the necessary replacement gaskets. If you explore the exploded diagrams on the ordering sites and also working with the installation instruction booklet you will see it is not a complicated job to do but is somewhat time consuming, mainly due to having to remove the whole unit to work on it. To some extent it's delicate but well within the capability of a reasonable DIY individual particularly with some mechanical aptitude.

If you don't feel competent to carry out the work, it does necessitate disconnecting and reconnecting a gas supply, then my advice would be to take it to Truma's own repair workshop.

 

The spares cost alone is around £300 can't say about labour but it can be time consuming.

 

Basil

[MasterW]

Hi Basil, thanks for the info,

 

I also have >45 years background in Mech/Electrical engineering and the actual work would not be an issue.( No Corgi gas certificate tho)...

 

On Exmoor at the moment and I think both elements have now packed up, so the full kit would be necessary. Somebody told me that the dealer price for full replacement was between £500-£600 so if the kit is around £300, might just consider a Truma/dealer job, particularly if I get a warranty for the work. Will look around to check. At least if its a DIY job, care and attention would be paramount.

 

From what I have noticed, if you are using the 'mix' setting, the control system, does not know the elements have packed up and when it drops away from gas, there is no heating at all, so need to run on gas setting only..

 

Best regards

[Basil]

Hi as a point of interest you currently do not need gas certification if you are not carrying out the work as your business, i.e. if you are carrying out work on your own motorhome/caravan. As the only gas work involves disconnecting and reconnecting one gas supply pipe it is not demanding.

I would have said from your background you would have no problem at all changing the elements.

If you look on Leisure Spares

 

https://www.leisurespares.co.uk/spare-parts/popular-spares-and-miscellaneous/truma-popular-parts/3402000228-was-3402061100

 

this gives you an indication of what is supplied in the repair kit, as you can see all new fittings and gaskets are provided and there is a guarantee period on the parts.

 

Basil

[Derek Uzzell]

MasterW - 2020-09-22 7:04 PM

 

...Somebody told me that the dealer price for full replacement was between £500-£600 so if the kit is around £300, might just consider a Truma/dealer job, particularly if I get a warranty for the work. Will look around to check. At least if its a DIY job, care and attention would be paramount.

 

 

Several on-line adverts for the Combi E heating rod kit (Part Number: 34020-00228) include the caveat "Only to be fitted by competent persons” - a definition that is wide open to interpretation.

 

It’s plain that replacing the 230V heating elements of a Combi-E should be a practicable DIY task, but it would be wise to confirm with the vendor of the kit (and with Truma) exactly what the terms and conditions of any guarantee are. For example, Truma markets a 230V “Ultraheat” electric heating element for their S-Series gas convector fires, but one of the warranty exclusions is Instances where installations, repairs or any other procedures have been conducted by non-authorised parties”

 

This 2016 frum thread may be of interest

 

https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Truma-C6002EH-blown-heating-elements-/40630/

 

It discussed a Trumatic C6002EH appliance rather than a “Combi”, but it’s likely that the manner in which the 230V heating elements are ‘throttled’ is similar for both types. The thread also mentioned the possibility (at least in 2016) of Truma(UK) being prepared to trouble-shoot/repair appliances at their HQ at Foston, Derbyshire.

[MasterW]

Derek,

 

I will try contacting Truma UK and post any response...more later.

[MasterW]

I have now received three responses from Truma regarding the failure of electrical heating elements in Combi E heaters, the last of which released the following information.

 

'Elements on a Combi boiler have a lifespan of approx. 3000-5000 hours and it would not be considered unusual for them to need replacing after 5 years of medium use'.

 

If I consider the greater figure of 5000 hrs, that amounts to 208 days, so after 30 weeks of continual use, the owner can expect the heating elements to pack up.

 

If I take the lower figure of 3000 hrs, that amounts to only 125 days or 18 weeks before the elements pack up.

 

Remembering that this is not a kettle element, used for only 3 minutes each time, If we consider that warm air heating would only be necessary for 6 months of the year, (in the UK that is a forlorn hope) so that in any one year the usage would be 50%, in the worst case of 3000 hrs only, any owner of a Truma Combi E boiler can expect total failure of the elements in the heating system, anytime after 36 weeks of use. at 25% use, the figure might stretch to 72 weeks or perhaps a year and a half.

 

Good aye......

 

 

 

[Derek Uzzell]

Yes, but a Combi-E’s electric heating elements will only be operating when a 230V power-supply is available and won’t be operating when a motorhome is being driven or when the leisure-vehicle is not in use.

 

Extended continual use of a Combi-E’s 230V heating is like extended continual sex for a man - it just won’t happen... ;-)

[MasterW]

Of course the electrical elements will only be operating when connected to 240V mains supply ...Dooh...

 

Some of us do not wild camp and always look for MHU when stopping, either for just 1 night or 3 months. I was simply trying to illustrate the very short life span of these elements (compared with the life of the motorhome) and do not consider the elements mortality to be anything near good design. We are not discussing continual use here, simply the total hours of operation.

 

Regarding your latter point...I couldn't possibly comment....

 

If all the mains operated devices in our homes packed up in this short time, we would all be complaining, so why should we accept it in a motorhome; very possibly the second most expensive item any of us will buy in our lifetimes.

[spospe]

I have a Baxi gas central heating system. The boiler came with an included 7 year parts and labour guarantee when it was installed three years ago. I have not had to call on the guarantee.

 

The cost of the boiler was little different to the cost of a Truma system The boiler is switched on 24/7 to supply both heating and hot water.

 

The Truma system does not seem very reliable by comparison to the Baxi.

 

 

[MasterW]

Hi spospe,

 

Does the Baxi unit have separate 240 mains heating elements..? Touch wood, the gas side of the Truma boiler has performed well and to date, I have no issue with heating from gas.

 

it is the additional electric heating elements that seem to be so unreliable. The benefit of course of having the additional electrical elements, is that having paid pitch fees that include a 16amp source (such as Caravan Club sites) it is advantageous to have the means of heating with electrical energy not just gas. it allows you to keep the gas handy for when it is absolutely necessary.

[spospe]

MasterW

 

No, the Baxi Duo Tech boiler is gas heating only.

 

What strikes me is that a domestic product costing less than the Truma, can be made so reliable. A gas boiler must be harder to make and control than an electric one (which really is just some wire on an insulating former). We, the motorhoming community seem willing to accept (with a slight feeling of disappointment) that much of the stuff we have in our vehicles is prone to expensive failure.

 

Off to York tomorrow for a two week tour of Yorkshire, so I hope that MY system works OK :-S

 

 

[Derek Uzzell]

There’s no doubt that there are plenty of reports on leisure-vehicle forums about failure of the 230V heating elements of Truma Combi-E appliances, but - as far as I’m aware - there are no statistics for how many Combi-E appliances have been fitted to motorhomes/caravans and how many of those heaters have had element failure and when in the appliances’ lifespan the failure occurred.

 

I recall talking to Peter Lievers in the early 2000s (when Peter was Truma(UK)’s technical and training manager) and asking him what he thought the likelihood was of Truma adding a 230V blown-air capability to Trumatic-C heaters. He was dismissive, saying that - given the restricted space inside the appliance - only ‘background’ heating would be possible and who would want that? Then along came the Trumatic C-6002EH...

 

I had a Trumatic C-6002EH in my 2005 Hobby motorhome and that was reliable for 9 years. But I’ve never cared for the way the 230V elements are shoehorned in to the heater and, when ordering my 2015 Rapido, I chose to have a gas-only Combi rather than the Combi-E that was part of the UK Package.

 

Alde Compact heaters have 230V heating elements capable of providing up to 3kW of output, but these are sbmerged in fluid (as in a kettle) rather than in air as in a Combi. Although there are reports on-line of Alde heating system problems, those problems don’t seem to involve element failure.

[Steve928]

Derek Uzzell - 2020-10-04 9:55 AM

 

Alde Compact heaters have 230V heating elements capable of providing up to 3kW of output, but these are sbmerged in fluid (as in a kettle) rather than in air as in a Combi. Although there are reports on-line of Alde heating system problems, those problems don’t seem to involve element failure.

 

Hmmm, it doesn't exactly inspire confidence. Along with occasional on-site EHU use I used the 230V function of the Alde in our Bailey over 5 winters, set at 5 degrees C as frost protection. I was planning to do same with the Combi 6E in the current van but am less inclined to do so now, having digested this thread. I think I'll pick up a 47Kg propane bottle and fit an extra long pigtail and use gas instead.

[MasterW]

To add salt to the wounds of Truma Combi E's and very much my purchasing dealer, back in July 2016, I brought to the attention of the dealer the fact that I was getting a strange burning smell, whenever I had the heating on.

 

I repeated my complaint at least 20 times to them over a period of 2 years, I have the emails. Some times it was only faint and sometimes it was quite strong, particularly in the washroom which had a warm air outlet very close to the boiler. I was told that it was the newness burning off (bear in mind my van was nearly 18 months old by then), I was told that there was a problem with the flu and they had modified it and fixed it, I was told that they all do that anyway...!!! Yes that stock old phrase.

 

I actually complained direct to Hymer and the dealer was told to investigate. Fat lot it did, and now, to my annoyance, I am told by Truma that the elements are out of warranty anyway.

 

Much to my own fault, I discontinued my search for the cause of the burning smell because it sort of discontinued smelling, to a point, but only 6 weeks ago I smelt it again.

 

I now consider it a real possibility, either because of poor design, or maybe poor installation of the elements, that the beginning of the end was back in 2016 when I first brought the smell to the dealers attention.

 

So folks if you think you can smell a strange whiff of burning from your Combi E heater, however faint, don't be fobbed off, chase it down until you isolate it and prove it to your dealer. it could well be worth the effort in the end.

[Derek Uzzell]

Truma provides comprehensive installation instructions for Combi heaters, but it’s commonplace for motorhome converters to ignore these to a greater or lesser degree. It’s also not that unusual for motorhome buyers to be provided with Combi operating instructions documentation but not with the installation instructions leaflet.

 

The attached drawing below relates to a Combi’s warm-air ducting and the lower two paragraphs and Fig. 21 refer to ‘short’ air ducts. My Rapido’s Combi 4 was installed with three long warm-air ducts that snake under the floor going to who knows where. The fourth duct was very short - about 20cm - and went straight out from an upper outlet on the air-duct ‘muff’ (arrowed in red on the drawing) to an air outlet on the side of the bed base.

 

Truma recommends that all the warm-air ducts of a Combi (or Trumatic C) appliance should be roughly the same length so that warmed air is distributed evenly around the leisure vehicle and, in principle at least - this allows the heater to operate without butterfly vanes in the outlets being used to adjust the volume of air being distributed.

 

Teo things would result from Rapido’s failure on my motorhome to comply with Truma’s installation instructions and both are fairly obvious. Firstly, with 3 long ducts and one ultra-short duct, the Combi would blast air out of the short duct in preference to blowing air out of the long ducts. Secondly, as the short duct led point-blank into the Combi’s interior, when the heater was operating but air was not flowing through the duct (eg. when the heater had switched itself down or water-only heating had been selected) convection would still cause hot air to emerge from the outlet and that hot air often has a burning smell.

 

This is not a new phenomenon (GOOGLE-search on “truma heater burning smell) and it was mentioned here in 2012

 

https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Smell-from-truma-Boiler-Combi-6/26864/

 

There was sufficient room around my Rapido’s Combi heater to modify its warm-air ductings to extend the length of the short duct and it’s smell-free when just heating water. My Combi does not have the 230V feature, so I don’t know if electric heating is more smell-prone than gas heating.

[MasterW]

My heater ducting appears to be reasonably balanced and the outlets all have butterfly vanes. The washroom outlet which always is the smelliest, is not the shortest but maybe has fewer bends/flow restrictions.

 

I read with interest your reference to the 2012 forum discussions and my immediate comment would be "why has Truma not sorted this smelly problem over the last 8 years? The smell is most certainly pungent and being a electronics and electrical engineer over 40 years, I also think I recognise the smell of overheating electrical components, in this case I think it is the overheating of the electrical heating elements or more particularly, the mounting arrangements of these elements. Unless I am mistaken, when the elements are switched off by the control system, the circulating fan also cuts, leaving the element surroundings to overheat for a period of time because the cooling effect of the circulating air is no longer available. If Truma try to maintain the air flow after the current is cut, I suggest it is not long enough. I think a series of these overheating periods causes the burning smell and the problem is compounded because the system controls both electrical and gas energy sources and uses them as the demand changes. This makes it more difficult to assess the source of the smell.

 

Having spent many years in the aircraft industry, I recognise the attention to detail in the layout and mounting of services under the skin of my Hymer bodywork and I would be surprised if the problem lies with the actual installation. having said that I have had the same water pipe connection break twice because of the strain placed by poor pipe routing..!!

 

I will continue to press Truma for further comment.

 

PS. couldn't find your attachment.