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Truma Combi 4E Heater Problems
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userBrian Kirby
Posted: 5 December 2013 11:22 PM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020002000100100100100
Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


No Chris, I decided the extra cost was not worth paying. However, what I was referring to was not a Combi E, but a standard combi with the optional addition of a 500W mains electric water heating jacket. It did nothing for space heating, heating only the water, and could be bought as an aftermarket item for fitting to existing systems. There was just an on switch, and it heated the water to about 60C, but held it close to that temperature. 12L of water at 60C was a nice little hot water bottle for the van, and made a surprising difference on cool mornings/evenings - mainly due to the not very impressive insulation of the heater mentioned by Derek.

The heaters with the E suffix have an electric heating element that works on the space heating, but at fairly low output. The distribution of the warm air in the Exsis is, however, excellent: there are warm air outlets all over the place, even by the windscreen, so temperatures inside are tolerably even from end to end.
userbolero boy
Posted: 6 December 2013 8:43 AM
Subject: RE: Truma Combi 4E Heater Problems
 


Epic contributor

Posts: 1616
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Location: Somerset 2017 Carthago C-Compactline i138


Thanks, i didnt know about this 500w water jacket. Our E version allows water heating on either 900 or 1800 Watts and i agree that in using water heating only can still produce a 'glow' from the unit which takes the chill off a little.
userDerek Uzzell
Posted: 6 December 2013 8:44 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020001000500100100100252525
Location: Herefordshire - 2015 Rapido 640F 2.3litre 150bhp


The advantages of the 'heating-collar' available as an option for Truma gas-only C-Series heaters were as Brian describes and, drawing only 450W of 230V current, the collar could be happily employed on campsites with very low-amperage mains power-supplies.

The disadvantages, though, were severalfold. As Brian says, the heating-collar option provided no air-heating, but it still required the motorhome manufacturer to install 230V cabling to the heater. It also wasn't cheap - around £150 extra (in 2007) for a C-Series appliance factory-fitted with the "EL" option and about £200 for an “EL” retro-fit kit.

As the number of campsites with low-amperage mains power-supplies dwindled, Truma were able to design a combination heater with a higher output 230V capability that could be used to heat air as well as water. The result was the C-6002EH that has a pair of 900W 230V heating elements integrated into its central heat exchanger. These elements operate in series (so Truma told me), drawing either 900W or 1800W, and can be employed to heat water, air or both, and can be 'mixed' with gas operation.

Current "Combi E" appliances have a similar 900W/1800W 230V arrangement to the C-6002EH's, a technical difference being that the latter had the capability to add the 1800W output to the heater's maximum 6000W gas-output maximum, whereas the output of a Combi operating in mixed 230V/gas mode is governed to 3800W (Combi 4E) or 5800W (Combi 6E) - probably a good idea as the thought of my own C-6002EH’s internal temperature if it were producing near-8kW of heat doesn't thrill me one bit!

In 2007 the difference in retail-price between a Combi and Combi E was around £200, meaning that, for an extra £50 over a C-Series unit with the heating-collar option, a leisure-vehicle owner could have 230V air-heating as well as 230V water heating.

What motorhome manufacturers charge nowadays for opting for a Combi E can vary radically. For example, Globecar fits a gas-only Combi 4 heater as standard and opting for a Combi 4E, a Combi 6, or a Combi 6E is quoted in (Continental Globecar price lists) as €469, €199 or €569 respectively. Carthago (in their “Malibu” PVC) fits a gas-only Combi 6 heater as standard, with the option of specifying a Combi 6E priced at a whopping €595.

There is one other difference (touched on by Brian) between C-Series heaters and Combis that will have a bearing on water-heating - the former have a 12-litre water tank and the latters’ tank is 10-litre. The Combi is claimed to be significantly more efficient at water heating than the C-series due to its revised design. However, although a Combi may be quicker at heating water to a given temperature, a 16% reduction in tank capacity will have an unavoidable effect if the tank is rapidly depleted of hot water when, say, two showers are taken in close succession.
user1footinthegrave
Posted: 6 December 2013 10:02 AM
Subject: RE: Truma Combi 4E Heater Problems
 


One thing that has surprised me, having now got my C6002EH in bits is the complete lack of any insulation, no wonder the water goes cold, the other thing that strikes me is the hugely complex electronics,sensors etc of this unit..............and the fact that the two PCBs are so poorly fixed to the unit. !
userbolero boy
Posted: 6 December 2013 10:38 AM
Subject: RE: Truma Combi 4E Heater Problems
 


Epic contributor

Posts: 1616
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Location: Somerset 2017 Carthago C-Compactline i138


No doubt MILESTOGO (the OP) has had great fun with this rivetting technically biased thread, i know i have learnt a lot
Always good to watch the thread staying power of the "vanners" as opposed to the hardy "Campingcaristes".
user1footinthegrave
Posted: 6 December 2013 10:40 AM
Subject: RE: Truma Combi 4E Heater Problems
 


One thing I've learnt is we were all better served with a kettle, and a gas convector heater.
userBrian Kirby
Posted: 6 December 2013 11:05 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020002000100100100100
Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


Derek Uzzell - 2013-12-06 8:44 AM..............The disadvantages, though, were severalfold. As Brian says, the heating-collar option provided no air-heating, but it still required the motorhome manufacturer to install 230V cabling to the heater. It also wasn't cheap - around £150 extra (in 2007) for a C-Series appliance factory-fitted with the "EL" option and about £200 for an “EL” retro-fit kit. ........................

Apologies for the continuing OT, but just to complete it. The actual cost of the EL option, on the Burstner, in 2005, was €145.02.

Hymer's 2013 list price for the Comb1 4E option, as against the standard Combi 4, was an extra €535.

My conclusion was, for the relatively few occasions on which we were likely to use it, relative to the extra cost of using gas for heating when we wished to do so, it was not worth the extra - so I spent €450 on a Fantastic Fan, instead!
userDerek Uzzell
Posted: 6 December 2013 11:11 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020001000500100100100252525
Location: Herefordshire - 2015 Rapido 640F 2.3litre 150bhp


bolero boy - 2013-12-06 10:38 AM

No doubt MILESTOGO (the OP) has had great fun with this rivetting technically biased thread, i know i have learnt a lot ...


Milestogo's most recent forum logon was on 17 November, so he may have yet to enjoy this thread's fun-factor.

If the discussion has done nothing else, it will perhaps have dissuaded people from making the mistake of buying a caravan with a Truma Combi heater.
userDerek Uzzell
Posted: 6 December 2013 11:17 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020001000500100100100252525
Location: Herefordshire - 2015 Rapido 640F 2.3litre 150bhp


Brian Kirby - 2013-12-06 11:05 AM

...so I spent €450 on a Fantastic Fan, instead!


Is that a roof-vent or this?

https://www.facebook.com/FantasticMsFanny
user1footinthegrave
Posted: 6 December 2013 11:20 AM
Subject: RE: Truma Combi 4E Heater Problems
 


Derek Uzzell - 2013-12-06 11:11 AM

bolero boy - 2013-12-06 10:38 AM

No doubt MILESTOGO (the OP) has had great fun with this rivetting technically biased thread, i know i have learnt a lot ...


Milestogo's most recent forum logon was on 17 November, so he may have yet to enjoy this thread's fun-factor.

If the discussion has done nothing else, it will perhaps have dissuaded people from making the mistake of buying a caravan with a Truma Combi heater.


In my more lucid moments I wonder why I gave up package holidays.............the only hassle was airport check ins.

Just heard back from Truma, apparently my main PCB is fine, Mmmmmmm, now what

Sorry, wrong thread

Edited by 1footinthegrave 2013-12-06 11:21 AM
userBrian Kirby
Posted: 6 December 2013 11:55 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020002000100100100100
Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


Derek Uzzell - 2013-12-06 11:17 AM

Brian Kirby - 2013-12-06 11:05 AM

...so I spent €450 on a Fantastic Fan, instead!


Is that a roof-vent or this?

https://www.facebook.com/FantasticMsFanny

Nay, nay; naughty Derek! 'Tis one of these: http://tinyurl.com/4hoch2 and very well it doth work! In fact a bit too well at times!
usermilestogo
Posted: 19 December 2013 5:06 PM
Subject: RE: Truma Combi 4E Heater Problems
 
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Posts: 6



Thanks for your help so far Derek.
Just to keep you updated. A Truma engineer came to check the Truma water heating. I had previously switched the system on the day before his visit and set it for water heating only, 240v 8amps at 40 degrees (summer setting). I checked one hour after switching on and sure enough the water was nice and hot measuring 49 degrees. Upon checking the temp 4 hours later it was only luke warm. (I had done previous tests with similar results).

When the engineer arrived I noticed that the water was up to temperature and behaving itself! He disconnected the mains connector lead (JST) to the Truma to put a test link in for testing the current. When he pulled the connectors apart (which was hidden from sight under air ducting) he discovered that the JST connectors were discoloured (indicating that it had been making a bad contact or overheating for some reason). He did several tests and the heater performed OK on each of them (over a 2 hour period).

He refused to connect the connectors up again for fear of a fire (he did not have a replacement)!!


Do you think it is the connectors that are at fault or was this coincidental?

Are the JST connectors taking too much current for the load?

Are other member experiencing a similar problem. i.e. When set on hot water only, the water initially comes up to temp (say 40 degrees), but after being left on for several hours (left on ever night) the water is just luke warm?

It has not as yet been rectified as I have been in dispute with the suppliers!
userDerek Uzzell
Posted: 19 December 2013 6:48 PM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020001000500100100100252525
Location: Herefordshire - 2015 Rapido 640F 2.3litre 150bhp


I'm not familiar with how a 230V mains power-supply cable connects to a a Combi - and Truma's Installation instructions are deliberately uninformative.

However, if there has been a sufficiently poor 230V connection at the heater that the connectors are now showing visible signs of damage, that can't have helped. Conversely, the heater does come up to heat correctly initially and you've said that the Truma engineer's 2 hours of testing revealed nothing unusual.

Combi-Es have been produced since mid-2007 and it's reasonable to assume that, if the 230V connectors Truma use were inadequate to handle the 8A load needed for the heating elements, it would be a well-known problem by now. It's possible, of course, that the connectors fitted to your particular Combi are sub-standard, or that a bad batch of connectors found its way on to the Combi production-line.

As the Truma engineer has noticed that the 230V connectors are discoloured and diagnosed that this will have been due to a bad contact or overheating, I assume the next step will be for the connectors to be replaced. If that fixes the problem you'll know that the connectors were the culprits: if it doesn't, then at least you'll have new undamaged connectors. But, until the connectors are replaced, there's no real way of knowing what, if any, part they might have played in relation to the water-heating problem.

If your heater continues to behave erratically, I think the only way forward would be to remove it, send it to Truma(UK) and ask them to test/monitor 230V water-heating over an extended period.
usermilestogo
Posted: 21 December 2013 10:41 PM
Subject: RE: Truma Combi 4E Heater Problems
 
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Posts: 6



Thanks Derek. I am actually going to conduct some tests myself!

Within what temperature limits is the Truma set to to maintain the 40 degrees. i.e. How many degrees either side of 40 should it be?

This is when it is set to 240v 8 amps summer setting, water heating only!
userDerek Uzzell
Posted: 22 December 2013 9:44 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020001000500100100100252525
Location: Herefordshire - 2015 Rapido 640F 2.3litre 150bhp


milestogo - 2013-12-21 10:41 PM

Thanks Derek. I am actually going to conduct some tests myself!

Within what temperature limits is the Truma set to to maintain the 40 degrees. i.e. How many degrees either side of 40 should it be?

This is when it is set to 240v 8 amps summer setting, water heating only!


When in water-heating-only mode ('Summer Operation') gas or 230 V electrical power can be chosen and the desired water temperature can be set to 40°C or 60°C.

Whether the 900W (3.9A) or the 1800W (7.8A) setting is selected on the Power Selector Switch, whatever water temperature has been chosen (40°C or 60°C), that's the temperature that the water will be heated to. Obviously, when 900W has been selected, heating the water to the selected temperature will take a good deal longer than when 1800W has been chosen.

I'm no expert when it comes to the technicalities of a Combi-E, so I don't know exactly what thermostatic arrangement there is to control water heating. I'm guessing that there are two thermostats (one for the 40°C maximum and another for 60°C) attached to the outer surface of the Combi's water tank. Each thermostat would allow water-heating (via 230V or gas) to continue until the appropriate temperature were reached and then shut off the gas or 230V power. When the water temperature had fallen to a certain point, the thermostat would cause water-heating to recommence. Even if the technicalities are different to what I've just described, the principle still stands.

I don't know how accurate the 40°C or 60°C settings are. You say that you chose the 40°C setting and, an hour later, the measured water temperature was 49°C, so there may be some leeway.

I don't own a Combi appliance, but my C-6002EH doesn't "maintain" the water temperature as such.

Let's say I choose the 40°C setting. The water will be heated until the heating process stops, at which point the water will be pretty warm. I've never bothered to check whether it is then at 40°C, though I do know that, if I had chosen the 60°C setting instead, water heating would have gone on longer and, when it stopped, the water would be a good deal hotter.

Once my C-6002EH heater ceases water-heating, unless a significant quantity of hot water is used soon (eg. a long shower is taken) it will be a fair while before the heater recommences the heating process. My heater does not heat the water to, say, 40°C, then shut down, then recommence heating at, say, 38°C - a much larger water-temperature drop is required to cause the heater to recommence heating.

I don't carry out water-heating unless I plan to use the resultant hot water in the nearish future, so I don't know how long it would take from a 40°C 'shut off' to water-heating restarting. If I used none of the heated water, I wouldn't surprise me too much if I found that it took an hour for the water's temperature to reduce to a point low enough to cause the heater to recommence heating. I wouldn't expect the water's temperature to need to drop to a level when it's merely "lukewarm" before water-heating restarts, though I suppose that depends on how hot "lukewarm" is considered to be.

From what you say, it sounds like your heater's thermostatic control may be iffy. I would have thought that, once your heater had brought the water temperature to 40°C, even if you did not draw any of the water off, re-heating should occur within a 4 hour period. However, assuming that the same water-temperature control-system is used when water-heating via gas, it's a mite odd that the problem only occurs during 230V operation. Leaving 230V water-heating on overnight and checking the water's temperature in the morning is not a valid test. I'd expect a normally-behaving heater to have gone though several heating cycles during, say, a 10-hour overnight period, so - when you've checked the water-temperature in the morning and found it well reduced - the heater might be about to recommence its next heating cycle.

You'll see from Brian Kirby's 5 December 2013 10:52 AM posting that, even when heating water via gas, his experience (like mine) is that a significant drop in water-temperature is needed between 'shut off' and the heating restarting, by which time the water may be less than hot.

I continue to wonder whether your Combi is actually faulty. You may think what it's doing is not what it should do, and you may dislike what it's doing intensely. But it's possible that your heater's behaviour is what all Combi-Es do.


Edited by Derek Uzzell 2013-12-22 9:47 AM
usermilestogo
Posted: 26 January 2014 5:04 PM
Subject: RE: Truma Combi 4E Heater Problems
 
Just joined

Posts: 6



I think I have worked out why the Combi does not heat the water constantly over a long period of time!

I have conducted tests over a long period of time and discovered that the heater (set on summer i.e. NO heating) will heat the water up to temperature in say 45 minutes. The temperature will then drop to half its pre set temp over a 2 hour period giving luke warm water. The thermostat will then switch the heater on again and bring it up to temp. This cycle will continue all the time the heater is left on.

I believe that this could be due to the fact that the heater is positioned horizontally. The water in a spherical jacket will not allow the water to circulate easily as it would do in a round or rectangular tank (i.e. allow the hot water to rise and the cold to fall giving an even temp throughout the tank)

This might account for the fact that when water is drawn off it soon becomes cold (or luke warm) because the small amount of hot water trapped at the top half of the water heater is being sensed by the thermostat and fools the system into thinking all the water in the tank is hot, and therefore switches itself off!!

I am told that Combi was first used in a vertical position, am I correct? This would resolve the problem outlined above!



userBrian Kirby
Posted: 27 January 2014 10:49 AM
Subject: RE: Truma Combi 4E Heater Problems
 


5000500020002000100100100100
Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


What you describe is, in my experience, how combis of both types work. The hot water thermostat has a very wide range between its "on", and "off", set points.

This probably reflects an expectation that folk will only heat water when they want it hot, and will the turn off the water heating cycle once they have used it, in order to conserve gas. Since keeping 13 or so litres of water continually hot when not required would pointlessly consume both electricity from the battery as well as gas, this approach seems logical.

FWIW, I also gain the impression (untested) that the thermostat re-sets when water heating is turned off, so that it will re-commence its heating cycle when switched back on, even if the "on" set point applicable had it been left running has not been reached.

You could always ask Truma technical for details of the two set-points, and whether they can be varied in any way. They may be able to re-set the software if you wish to operate the heater differently.
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