Truma Combi 4E Heater Problems

[milestogo]

Only used our Swift caravan twice since new, less than 6 months ago. First time out both the hot water and heater would not work at all and only showed error messages. This was replaced with a new heater. Next time out the water heater could not be relied upon to heat the water on its own and only worked intermittently; most of the time it was lukewarm.

Has anybody else suffered similar problems with their Truma Combi 4E heaters? :'(

[Derek Uzzell]

How are you heating the water?

 

If it's via gas, water-heating should be quite rapid - Truma quotes a water heating up time from approx. 15°C to approx. 60°C as around 20 minutes. When air-heating and water-heating are operated simultaneously, Truma quotes a water heating up time of 80 minutes.

 

If it's via 230V electricity, the water-heating speed will depend on whether you've chosen the 900W or 1800W setting. Heating will take quite a while on the 900W setting and, though it will (unsurprisingly) be quicker on the 1800W setting, it still won't be as quick as using gas. If you chose the 900W setting and ran air-heating simultaneously, heating the water to a reasonable temperature would seem to take forever.

 

The way Truma combination air/water heaters work needs to be understood by their users and (in my opinion) these appliances are a poor choice for caravans. Much better (for UK caravanning particularly) the traditional convector gas/230V 'fire' and separate gas/230V water-boiler.

 

As your Combi 4E (presumably) shows no signs of having technical problems (ie. there are no error messages), it may be that what you consider to be problems is exactly how an experienced Combi user might expect the appliance to function when it's working as Truma intended.

 

This link may help

 

http://www.coachman.co.uk/news/a-guide-to-the-truma-combi-system-exclusive-to-coachman-for-2012

 

If you believe your replacement heater isn't working properly, you'll need to take your caravan back to the dealership and ask them to check what it's doing. In principle, water-heating operation is straightforward - you just select the appropriate 'power-source' (gas, 230V) and the desired water temperature; then how long it takes to bring the water up to heat will depend on how cold the water is to begin with and how much oomph the power-source has.

 

 

 

[milestogo]

Many thanks for your detailed response.

Are you saying the Truma combination air/water heaters are a poor choice because they are difficult to understand, or, if not, what do you mean by this? When heating the water by electric only on the 1800W setting, the temperature would remain just lukewarm.

[Derek Uzzell]

The air-heating principle inherent in a Truma Combi air/water heater involves air being forced by a fan over a heat-exchanger 'core' that's heated by gas or, in the case of 'E' models by gas and/or 230V. Heat passes from the 'core' to the air passing over it and the warmed air is then distributed around the leisure-vehicle via air trunking.

 

Water heating is performed by the heat in the heat-exchanger 'core' transferring across an air gap to a water 'tank'. This indirect method is not a wonderfully efficient way of heating water - significantly less efficient than the 'kettle' method used for the traditional Truma B10/B14 "Ultrastore" boilers - nevertheless, it works (or SHOULD work) fairly well when air-heating is not being employed simultaneously.

 

When simultaneous air and water heating is chosen, as most of the heat in the 'core' is transferring to the air passing over the core, only a limited amount of heat can reach the water 'tank'. That's why the time needed to heat the water in the tank is so much longer when air & water heating is operating than when water-heating alone has been selected.

 

Truma combination air/water heaters have rarely been installed in caravans in the past, but there have been comments on motorhome forums over the years indicating that the technical limitations of this type of heater have not been appreciated by some motorhome owners. Essentially, it's not always been understood (despite the information being available in Truma's operating instructions) that it MUST take longer to heat the water when air-heating is operating than when it is not.

 

230V water-heating on Truma combination air/water heaters originally involved an electrical heating 'collar' that wrapped around the outside of the water-tank. This option was distinct from the heater's gas heating system and there was no means of air-heating via 230V - one had air and/or water heating via gas, or water-heating only via 230V. Truma then introduced the C6002-EH heater that had 230V heating elements attached to the heat-exchanger's 'core' and this design-principle was passed on to "E" versions of the current "Combi" range of appliances like your 4E.

 

I don't know how "difficult" people found the earlier heaters to understand, but there's little doubt that the ability to 'mix' gas and 230V heating on C6002-EH and Combi "E" appliances mystifies some users when it comes to operating these heaters. Truma has now introduced a digital control-panel for these heaters that's supposed to be more user-friendly, but we'll see!!

 

It's plain that a Truma combination air/water heater offers advantages for the leisure-vehicle manufacturer when it comes to simplifying installation requirements, but I'm unconvinced that having a heater in a caravan that MUST use a fan to distribute warmed air around the interior is a desirable alternative to the convector gas/230V convector 'fire' (with "Ultraheat" blown-air option) that was used traditionally and paired with a separate boiler dedicated to water heating. I recall discussing this with a Truma representative who said that the company made products based on the stated requirements of the motorhome/caravan industry, and those requirements might not be 'best' for the motorhome/caravan owner. We both agreed that the Thinking Motorhome/Caravan Owner's heating system would comprise a convector air-heater and separate water boiler.

 

Regarding your "When heating the water by electric only on the 1800W setting, the temperature would remain just lukewarm" statement, if you can't get the water beyond lukewarm using 230V, you are either not allowing sufficient time or there's someting wrong with your heater.

 

Assuming your caravan were connected to 230V and you'd selected water-heating only via the 230V 1800W setting, I'd expect the water temperature to reach 60°C within 30 minutes. My C6002-EH can do this using 230V/1800W and my heater has a 12-litres water capacity not your Combi's 10 litres.

 

If your heater is able to heat the water to some degree from cold (even to only lukewarm), this suggests that the heating elements do operate. If "lukewarm" is the best your heater can do (after, say, 30 minutes of 230V water-heating only), this suggests that the thermostat controlling the operation of the heating elements is cutting off early. It's quite possible that an early-closing thermostat would not produce a diagnostic error.

 

If it's evident that your heater cannot heat water via 230V to a reasonable temperature reasonably quickly on the water-heating only 1800W setting, then it will be a problem peculiar to your heater and not to Combi "E" appliances as a breed.

 

What's your caravan dealership say about this - presumably you've contacted them?

 

 

[milestogo]

Thanks again for another detailed response.

 

The electric heating (240v 1800w)has been left on overnight and it is found to be only lukewarm!

 

I was interested to hear that your Truma rep thought they were not the best systems for c'vans.

I too spoke to a Truma rep who said that these heaters were originally only intended for motorhomes and not c'vans. I was informed that for the past 3/4 months a new circuit board has now been fitted to overcome cut out temperature issues.

 

Why have the latest versions of Swift caravans had their Truma combi heaters uprated from 4kw to 6kw in less than a year after introducing it as a new heater, when it was supposed to comply with the latest Millbrook cold chamber testing?

 

Yes, I am in correspondence with the dealer, but I am not a happy man!!!!

[Derek Uzzell]

milestogo - 2013-10-10 7:27 PM

 

...Why have the latest versions of Swift caravans had their Truma combi heaters uprated from 4kw to 6kw in less than a year after introducing it as a new heater, when it was supposed to comply with the latest Millbrook cold chamber testing...

 

The difference in retail-price between a Combi 4E and 6E is not huge and would undoubtedly be reduced when a commercial company like Swift is bulk buying from Truma.

 

A 4E's maximum output is limited to 4kW on gas alone or 3.8kW on gas+230V, whereas the maximum output of a 6E is 6kW on gas alone or 5.8kW on gas+230V. One might expect a 4E to be capable of providing and maintaining adequate heat within a caravan (that's pretty 'box-like' inside) whatever its overall size, but the extra output of a 6E will permit a shorter heating-up-from-cold phase.

 

I would have expected a 4E to be easily capable of providing sufficient heating in a caravan to meet the Millbrook testing regimen you mention. Where a 6E's extra oomph should be advantageous is with large motorhomes (that, as a species tend to be less 'boxy' inside), where hotter air can be delivered more quickly throughout the vehicle.

 

I can't really answer your question, but plenty of motorhome manufacturers standardise on the Combi 6 for quite compact vehicles where it's plain a Combi 4 should suffice. Better overkill than underkill when it comes to a heating system's capability and I expect Swift can 'lose' the extra cost of a 6E over a 4E somewhere within their pricing structure, or just increase the leisure-vehicle's price and advertise the change in heater-model as a significant improvement.

 

There have been modifications made to the Combi since its mid-2007 inception, including circuit-board alterations, so another pcb change doesn't surprise me.

 

While what you've described (lukewarm water after 230V water-heating operating overnight) certainly isn't right, you might find it useful to carry out more focused testing.

 

On 230V (water heating only) I would expect a Combi to be able to raise the water temperature from cold to 40°C using the 900W setting within an hour and to 60°C within 1.5 hours. On the 1800W setting the heating times should be within 3/4 hour or 1 hour respectively. You may well have confirmed that your heater is not doing this but, if not, I'm going to suggest that you check.

 

It's possible with your overnight test that the heater does heat the water to the chosen temperature, shuts off and then does not recommence heating when the water cools. These appliances have little insulation around the water tank and water heated to 60°C will be lukewarm 12 hours later if not reheated in the interim. It's academic really, as your heater will need to be checked over by someone with a suitable diagnostic capability (or be replaced again), but it might be useful if you've gone through the motions and can say with certainty what your heater does and doesn't do.

[bolero boy]

Have carried out any gas-only water heating tests to verify whether the issue lies on the 230v side only or applies to all forms of power source.

[Derek Uzzell]

bolero boy - 2013-11-05 6:35 PM

 

Have carried out any gas-only water heating tests to verify whether the issue lies on the 230v side only or applies to all forms of power source.

 

I think milestogo covered that earlier when he said "When heating the water by electric only on the 1800W setting, the temperature would remain just lukewarm."

 

Although he never specifically said that his Combi heater functioned properly when operating on gas, nor that it heated air OK when operating on mains-electricity only, it's reasonable to assume that it was just water-heating on mains-electricity alone that was problematical.

 

As I said earlier regarding more extensive testing of the water-heating process "It's academic really, as your heater will need to be checked over by someone with a suitable diagnostic capability (or be replaced again), but it might be useful if you've gone through the motions and can say with certainty what your heater does and doesn't do."

 

As almost a month has passed since milestogo's last posting, hopefully the problem has been resolved by now.

[bolero boy]

Fair comment Derek. Looks like he posts as infrequently as he uses his van, shame!

[Derek Uzzell]

Perhaps there's nothing to say...

[Rayjsj]

I have been following this thread,as the performance of the Combi 4E in my Autotrail has been less than outstanding, so much so, that I have to carry a 'backup heat source'. It has left us 'Freezing cold' first thing in the morning and with NO hot water for a shower , more times than i care to remember. Red error light on the Control, no heat and no hot water (this is on Electric hook up, 1800w, no gas on).

It's just had it's first Habitation service and I asked them to check out the Combi, and told them of the problems.... they could find NO fault, and suggested that I was closing too many of the Output grilles and the heater was 'tripping out' overheating ? we were not, even though going into the toilet was like walking into a furnace (until of course the heater stopped altogether !!) The Combi has been a pain since we picked up the van, a fuse blew on the control PCB after 1 weeks use (which is when we 'invested' in an Oil filled radiator) had to wait a week to get spare fuses,AND had to get a 'Registered Mobile Truma Engineer ' to fit it, otherwise I'd have 'invalidated the warranty' according to the Truma person I spoke to. Altogether I feel like the original OP, a bit fed-up. And wish for my Eberspacher system back (in an Autocruise) which gave me nothing but WARM pleasure and never let us down. Ray

 

 

IS there anyway to check if any PCB upgrades are available for my/our heaters ? 'Recalls' etc.,

[Guest 1footinthegrave]

Oh for the simplicity of a convector heater, I've just changed my van, it's got a C6002eh combi, just in the process of taking it apart due to it's erratic behaviour, I think it's the air circulation fan, it's listed on the Truma site as being " may be unavailable" oddly the previous owner said it was working fine, yes right. >:-( And you should see where this unit has been sited, buried behind and under the "L" shape kitchen, I reckon it was the first thing to be put in the van, a bloody nightmare to get at it.

 

We had an Eberspacher on a previous vehicle, everyones experience is different I found that a pain as well with expensive parts and servicing costs,that was sited under the van exposed as it was to all the weather, and of course like the combi boilers the need for battery power to run the bloody things, do any of us really need multiple air distribution in a space the size of the average M/home - Caravan especially given the hassle and expense of all of these units. :-S

 

As for the OP you have my sympathies,as does the poster above, you really shouldn't be having this grief on a new vehicle.

[Derek Uzzell]

1footinthegrave - 2013-11-27 5:23 AM

 

Oh for the simplicity of a convector heater, I've just changed my van, it's got a C6002eh combi, just in the process of taking it apart due to it's erratic behaviour...

 

If you are accustomed to a Truma convector appliance for air-heating, the functionality of a C-6002EH may well seem peculiar.

 

It's probable that someone unfamiliar with a C-6002EH should still be able to distinguish between the appliance failing to operate correctly, or merely operating in what seems to be an odd manner. But there's no doubt (based on previous forum comments relating to Truma C-Series and "Combi" heaters) that their 'normal' operation still causes confusion.

 

It may be the case that the "erratic behaviour" that's causing you to dismantle the heater, and that you think may involve the air-circulation fan, makes it obvious that there's a fault. Conversely, as your motorhome's previous owner said the heater was working fine, there's the possibility you might be treating a C-6002EH's to-be-expected behaviour as abnormal.

 

I've 8 years experience of a C-6002EH, so (if you think it might help) if you describe what yours is doing that's "erratic" I might be able to comment usefully. It would be a pity if, having spent time and money on your heater, you found that its present behaviour was unchanged.

 

[Guest 1footinthegrave]

Thanks for the offer of help Derek, on switching on heating mode sometimes the air circulating fan turns slowly, all the solenoids click and the boiler fires up, warm air results. On other occasions fan does not turn at all and boiler goes to lock out, on yet other occasions fan turns increases speed as heat demand is called for, starts to rattle like hell, eventually starts to slow down, then stalls altogether, and boiler once again goes to lock out.

 

Only had the van a few days, call me paranoid, but there may be a clue in the seller saying it was fine, as many of the screws holding the various furniture panelling surrounding it are missing or loose, and the power board cover has been left hanging off, and another cover screw on the PCB board cover is missing, unless of course a very poor service has been attempted at some point :-( The positioning of the whole unit has to be seen to be believed, but that's another story, oh well, any help you can offer appreciated.

 

I should add of course that this is exactly the same unit as fitted to our IH that operated without issue all the time we owned it ( 4 years ), so I am familiar with the various clicks and sounds it made and operating modes selections. ;-)

[Derek Uzzell]

OK - you're accustomed to a C-6002EH's little ways.

 

Your diagnosis that the fan-unit is the prime suspect for the lock-outs makes perfect sense.

 

There was a Truma safety recall in 2006 that affected a large number of C-Series appliances (including my own C-6002EH). This involved replacing the top of the heater and its fan-unit. If remedial work had been required for your motorhome's heater, it's plain from your description that the appliance would have needed to have been removed to carry out the task. It might explain why screws are missing/loose and the pcb cover is hanging off. Just a guess though...

 

Best of luck.

 

[Guest 1footinthegrave]

The safety recall is very interesting indeed, I wonder what safety issue was involved, and of course was this one ever attended to, I'll try to find the serial number and see if Truma have any record, thanks Derek.

 

Oh and a P.S apparently this motor is now in short supply or obsolete I'm told, mmmmmmmm have put in an order, I'm waiting with bated breath to see if it's fulfilled, if not my "bargain" Rapido may turn out to be not the bargain I thought. :-(

[Derek Uzzell]

These are earlier forum threads relating to the Truma recall. They explainthe reasons for the recall and the first link includes serial numbers for the heaters that needed attention. For the C-6002EH model these were

 

C xxxxx-x-15 329 001 to C xxxxx-x-17 159 000

 

http://www.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Truma-Safety-Recall/4470/

 

http://www.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Truma-Re-Call-update/4532/

 

http://www.outandaboutlive.co.uk/forums/General-Chat/Chatterbox/TRUMA-RECALL/7405/#M47743

 

As the revisions were internal, I don't think it's possible to identify visually whether a heater involved in the recall was attended to.

 

If you do as you intend - find the serial number and quote it to Truma(UK) - they may be able to confirm if it was modified. I say "may be able to" because I'm not confident that Truma recorded the serial number of every heater that was worked on. I vaguely remember, when I contacted Truma(UK) after my heater had been modified and I asked for a 6-months warranty extension, that they had no record of the task having been carried out. So it wouldn't surprise me if some heaters within the scope of the recall have not been modified, nor if some heaters that were modified aren't recorded in Truma's 'It's been done' records.

 

(I would have thought it should still be possible to obtain a fan-motor for a C-6002EH. I believe it's the same motor as used for the C-4002 and C-6002 models, and these were fitted to thousands of motorhomes until 2006 when the "Combi" range was introduced. Not sure if your having to order a motor implies that they so rarely fail that it's not worth Truma(UK) keeping any in stock, or that they fail so often that supply can't keep up with demand.)

[Guest 1footinthegrave]

I'll keep you posted...........from their website...............

 

 

Name 34000-77300 C6002 Air Circulation Motor [Truma Spare Parts]

SKU MIR34000-77300

Manufacturer Truma

Manufacturer Code 34000-77300

Availability At Last Update Subject To Availability - Possibly Unavailable

 

:-S

 

Like you said, thousands in use, that cannot be correct.....can it ? I'll soon know.

[bolero boy]

Derek Uzzell - 2013-10-08 10:07 AM

 

Water heating is performed by the heat in the heat-exchanger 'core' transferring across an air gap to a water 'tank'. This indirect method is not a wonderfully efficient way of heating water - significantly less efficient than the 'kettle' method used for the traditional Truma B10/B14 "Ultrastore" boilers - nevertheless, it works (or SHOULD work) fairly well when air-heating is not being employed simultaneously.

 

When simultaneous air and water heating is chosen, as most of the heat in the 'core' is transferring to the air passing over the core, only a limited amount of heat can reach the water 'tank'. That's why the time needed to heat the water in the tank is so much longer when air & water heating is operating than when water-heating alone has been selected.

 

derek, when 'heat only' is selected (and there is water in the boiler) the water must get heated as a by product, albeit slowly as in your description above.

What controls the heat of the water differently when 'heat and hot water' is selected as opposed to 'heat only'?

Thanks.

[Guest 1footinthegrave]

bolero boy - 2013-12-03 9:32 AM

 

Derek Uzzell - 2013-10-08 10:07 AM

 

Water heating is performed by the heat in the heat-exchanger 'core' transferring across an air gap to a water 'tank'. This indirect method is not a wonderfully efficient way of heating water - significantly less efficient than the 'kettle' method used for the traditional Truma B10/B14 "Ultrastore" boilers - nevertheless, it works (or SHOULD work) fairly well when air-heating is not being employed simultaneously.

 

When simultaneous air and water heating is chosen, as most of the heat in the 'core' is transferring to the air passing over the core, only a limited amount of heat can reach the water 'tank'. That's why the time needed to heat the water in the tank is so much longer when air & water heating is operating than when water-heating alone has been selected.

 

derek, when 'heat only' is selected (and there is water in the boiler) the water must get heated as a by product, albeit slowly as in your description above.

What controls the heat of the water differently when 'heat and hot water' is selected as opposed to 'heat only'?

Thanks.

 

Sorry to be answering instead of Derek, but the nature of these heaters means the water will always be heated, if there is water in the system there does not need to be of course, and you have two heat settings in any event, when heat and hot water is selected on the lower setting that seems to be the compromise in order to achieve a lower water temp, the resulting air temperature on heat will be lower as well and take longer for the van to get up to room temp

[bolero boy]

Mike, no worries, thank you.

My question was borne from the fact that i had asked Truma at the NEC about water not getting upto tem when heat/water was selected. Replies there and here have confirmed that this is not the best way to achieve nirvanah of warmth and lovely hot water.

Truma also said that selecting heat only would, eventually, heat the water up to a very high temp as a by product of the heating, so i will try this.

They also said that my original query was exacerbated by the programming in the PCB and that there is a free upgrade (to all, i believe) to a newer PCB which puts more emphasis on heating the water when 'both' is selected.

I will be checking with my dealer.....if i dont change the van first.

[Guest 1footinthegrave]

Just a point of interest really, but on one van we had an Eberspacher diesel fired heater for room heat, and a separate gas / electric powered water boiler. The downside for us is he Eber, never gave out the kind of heat a combi did, and as it was installed underslung under the van it was a right royal pain to have serviced, and servicing was fairly frequent, and that too eventually packed up with a resulting large bill..................come back my cheapo package hols is a thought I sometimes have. :D

[Derek Uzzell]

Recent-ish Truma C-Series heaters and “Combis” have two heating ‘modes’ – Summer Mode or Winter Mode.

 

In Summer Mode the appliance just heats the water in the heater to 40°C or 60°C according to choice. Heat transfers from the heater’s heat-exchanger across a narrow air-gap to the water ‘tank’, but, as air-heating is not being carried out, the heater’s blown-air fan does not run and air is not blown through the heater’s interior. When the 40°C or 60°C water-temperature has been attained, the heater’s gas-burner (and/or 230V elements if the unit has them and electric heating has been selected) shuts off.

 

Winter Mode has two options – (1) - Heating WITH hot water requirement or (2) Heating WITHOUT hot water requirement.

 

(1) - Heating WITH hot water requirement

 

Air-heating and water-heating are both carried out. When the ‘room temperature’ set via the heater’s control-panel is reached, the heater’s blown-air fan shuts off. But the heater’s gas-burner (and/or 230V elements) will continue to operate and water-heating will continue until the 40°C or 60°C water-temperature chosen is reached. During air-heating, air is being blown through the heater’s interior and over the heat-exchanger. As much of the exchanger’s heat will pass to the air, water-heating will be much slower than in Summer Mode.

 

(2) Heating WITHOUT hot water requirement.

 

Only air-heating is actively carried out by the heater. When the ‘room temperature’ set via the heater’s control-panel is reached, the heater’s blown-air fan shuts off, as does the gas-burner/230V elements. Water (if present) will be heated passively as a by-product of the air-heating process, but even more slowly than in (1). This option would be selected when the heater is empty of water, but it also provides potential gas savings if there’s no need at the time for hot water.

 

In both (1) and (2) the water can reach a high temperature (Truma suggests 80°C) if air-heating is prolonged.

 

(The above is explained in greater detail in Truma’s downloadable operating instructions.)

 

In cold weather, when our motorhome is not on 230V hook-up, I tend to treat my C-6002EH heater as if it were a water boiler and a separate air-heater. As we both shower in the motorhome each morning (and I always have to go second!) I’m very keen to have hot water at shower-time. So I hop out of bed early, select Summer Mode 60°C and nip smartly back into bed for three-quarters of an hour or so. Then, when my wife gets up for her two-cups-of-tea fix, I again hop out of bed, this time select Winter Mode (1) 60°C and dive back into bed until she’s temporarily satisfied her tea addiction.

 

These appliances are poorly insulated and, as hot water leaves the heater, cold water enters it. Bitter experience has taught me that, by the time I get into the bathroom, I might get an unpleasant cold-water surprise part way through my shower. So I’m pretty careful to ensure that there’s adequate hot water in the tank and, if I have the least suspicion there isn’t, I put the heater back into Summer Mode 60°C for a while before venturing into the shower.

[bolero boy]

Thanks Derek, your morning ritual not unlike others, including us.

My query came about as, in the summer, we use summer mode at 60 deg and the resultant hot water is enough for me to nip in and out quickly and for SWMBO to luxuriate for as long as the water lasts, which is fine.

As the weather gets a little cooler, i have been using winter mode with water being heated to 60 deg. I check that the yellow light has gone out meaning the water heating phase is complete and then commence the shower ritual. On some occasions (not all, i admit) you can tell straight away (by the need to change the shower temp lever) that the water is not heated as high as usual and this, of course means the water runs out a bit sooner.

It was this specific that i memtioned to Truma at the NEC and was told that the new PCB ensures the water heating remains on, possibly when the heating burner is off.

I had my suspicions that when in winter mode, water heating would only continue if the air heater was firing.

Thanks for your helpful response.

[Derek Uzzell]

bolero boy - 2013-12-03 3:46 PM

 

...It was this specific that i memtioned to Truma at the NEC and was told that the new PCB ensures the water heating remains on, possibly when the heating burner is off...

 

Such a scenario is impossible, as the gas-burner that heats the water also heats the air. The only difference is that - when water-heating-only is taking place - the gas-burner's output will be restricted to 2kW, whereas, when air-heating is operating, the burner's output can be much higher.

 

These are the relevant Truma operating instructions for a "Combi" appliance of the type fitted to your Bolero.

 

"WINTER OPERATION

 

- HEATING WITH WATER TEMPERATURE MONITORING

 

Select gas, electrical or mixed operation using the power switch. Illumination of the yellow LED (g) on the power selector switch indicates that the unit is operating with 230 V.

 

Move rotary switch on control panel to operating position (n).

 

Set the rotary switch (h) to the desired thermostat setting (1 – 5). The green LED (k) for operation is lit and simultaneously indicates the position of the selected room temperature. The yellow LED (p) indicates the water‘s heat-up phase.

 

The device automatically selects the required power setting in accordance with the temperature difference between the temperature selected on the control panel and the current room temperature. When the room temperature selected on the control panel is reached, the heater switches back to the smallest setting and heats the water to 60°C. Once the water temperature is reached, the heater switches off and the yellow LED (p) goes out.

 

– HEATING WITHOUT WATER TEMPERATURE MONITORING

 

Select gas, electrical or mixed operation using the power switch. Illumination of the yellow LED (g) on the power selector switch indicates that the unit is operating with 230 V.

 

Move rotary switch on control panel to operating position (m).

 

Turn the rotary switch (h) to the desired thermostat setting (1 – 5). The green LED (k) for operation is lit and simultaneously indicates the position of the selected room temperature. The yellow LED (p – water‘s heat-up phase) will be lit only when the water temperature is below 5°C!

 

The device automatically selects the required power setting in accordance with the temperature difference between the temperature selected on the control panel and the current room temperature. Once the room temperature selected on the control panel has been reached, the heater switches off. The warm air fan continues to run at slow speed until the outgoing air temperature (on the unit) has fallen to 40°C or less.

 

If the boiler is filled, the water will automatically be heated at the same time. The water temperature is then dependent on the heating output being given off, and the duration of heating required to reach the desired room temperature."

 

It will be apparent from the above that selecting "Heating with water temperature monitoring" (which is what you've being doing) causes the gas-burner to continue to operate until the water temperature attains 60°C despite air-heating having shut down.

 

My Truma C-6002EH's functionality differs from a Combi's, but the operating principles are much the same. My experience tallies with yours, that there's no 100% certainty that the heated water will always be as hot as one might expect and, like you, I use the position of the shower's mixer-lever as a warning signal that I might be in for a coolish shower!

 

When in "Heating with water temperature monitoring" mode, a Combi's air-heating operation will turn on and off according to the 'room temperature' read by a remote thermostat in the vehicle's living area, and its water-heating operation will be turned off by a thermostat on the heater when the water reaches 60°C. Although it's not specifically stated in the operating instructions, it's also the case that, if sufficient water is drawn from the heater after the 60°C temperature has been reached, water-heating will recommence. My experience is that there's a quite wide temperature 'gap' between the 60°C shut-off temperature and the lower restart-heating temperature.

 

I can't see how a PCB change would improve water heating on a Combi unless the delay between 60°C shut-off and water-heating recommencement is programmable, though I can imagine that a thermostat revision to shorten the delay period might help. In either case I can't see you benefitting, though, as your heater appears to take it into its head occasionally to stop water-heating before 60°C is reached.

 

Combis are dual-purpose and complex and sometimes seem to have a mind of their own. The best owners of leisure-vehicles with this heater can do is understand the appliance's operating principles, operate the heater within those principles and hope for the best.