to derek uzzell

[Guest barrie]

good morning derek, ihave read your articles & postings with interest. in a recent question about diesel heaters you make mention of the combitronic. we are looking to replace our van & will probably end up with this system. i only have experience of cascade & propex items. any chance of your views / comments on the combitronic. thanks

[Guest david]

Hi barrie I know you directed your post to derek uzzell but thought you would be interested with our experience. We have been using a combitronic heater in our Autocruise Startraveller since last April. As a water/saloon heater it has performed brilliantly, if a little noisy on startup. This question of noise is relative though and what is too noisy for one person is ok to another. We have not found it too intrusive and it is not as irraitating as having a generator running nearby. The only way you will know is get them to demonstarte it from startup. In use it is, as I say, brilliant. Firstly, cutting down on gas usage was a big plus for us - even though you are using diesel it is easier to get diesel in Spain than calor gas. Ours does have mains electric too which can be used in preference to diesel or in tandem. At night it has an ECO mode which uses just the mains to maintain the internal temperature and water temp using a quiet 12volt fan. There are other smart facilities too such as a timer function to allow you to set the time for the heating/water to come on/switch off - useful if you are out for the day. An alarm and clock are built in. One useful feature at the moment is the frost setting. It has been -3 the lsat few nights and the frost setting has automatically kept the interior of the van above freezing using the ECO setting. Especially useful if, like us, you use the van through winter and don't want to have to drain everything down. Regards, david

[Guest Brian Ramsden]

Am I right that one disadvantage of these heaters is that you have to have the 12 volt fan running when the heater is on? If so, what sort of current does this take? This is a consideraton if you are planning to use aires/sostas/stelpatz type sites, or to wild camp. Brian

[Guest Derek Uzzell]

Barrie: I'm just a Combitronic voyeur, so David's comments based on his practical experience of the heater are much more valuable than my book-learning. (It might also be worth you checking out the Marquis Majestic "Starmist" Long-Term Test reports that MMM began in the August 2005 issue as this 'van has the Combitronic unit.) Brian: I dug out some Eberspacher leaflets I had picked up at the 2005 NEC show. These indicate that there were then 5 Combitronic variants - CT01 to CT05. CT01 and CT02 are modular, with a traditional "Hydronic" burner-unit mounted outside the vehicle's living area (the diagram depicts it located beneath the floor) and with the blown-air fan matrix and hot-water storage vessel inside the vehicle. CT03 to CT05 are self-contained, with burner-unit, fan matrix and hot-water tank all crammed into in a single externally mounted box. All Combitronics have diesel/mains water-heating. CT01 and CT03 have diesel/mains air-heating (3.5kW + 1.5kW respectively), whereas CT02 and CT04 dispense with the mains-powered air-heating capability. CT05 is a big brother to CT03 with 5.0kW + 1.8kW diesel/mains air-heating. (It sounds like David's Auto-Cruise has a CT03 or a CT05.) The Eberspacher leaflets give 12V electrical consumption as 23W to 85W for CT01 to CT04, and 28W to 106W for CT05, but I'm not sure whether these figures include the start-up phase. All diesel-fuelled heaters use the blown-air principle for vehicle interior heating and 12V consumption will depend on the demands of the fan motors at any particular time. A much smaller 12V consumption will relate to the fan that maintains the burner flame. I don't believe diesel-fuelled heaters when running are actually that much harder on 12V batteries than equivalent output blown-air gas heaters - it's the start-up current requirements of the diesel heater that demand a really well-charged battery. If one plans to be static and away from a 230V hook-up for long periods then (as you rightly say) how to maintain a healthy battery charge needs careful thought. Incidentally, Combitronics don't come cheap. For a CT03 + ducting kit, the Eberspacher leaflet quoted a list price of £2013 (VAT inclusive), but there would be significant installation costs above that figure for a non-DIY job.

[Guest barrie]

thanks to you all for your comments. david,your comments are really helpful.it's a pity we are not looking for a starblazer. thanks again. barrie

[Guest david lloyd]

Hi barrie Not the Starblazer barrie - it's a Startraveller. One of the latest ultra low profile models in the Autocruise line up - twin forward sofas and across the rear bathroom - any good to you at a very reasonable price? david

[Guest david lloyd]

Sorry barrie - I thought I had said in my original posting that we wanted to go back to a fixed bed model and are now awaiting delivery of a Knaus Sun Ti in April/May - so yes we are selling our present 2005 model van but have not advertised it. I hadn't intended to 'push' it toward you but if you are interest you can always email me on david.loyd@tiscali.co.uk Best regards, david

[Guest david lloyd]

Hi Brian and Derek I have just checked my combitronic and although I can't find anything on the unit that says CTO5 the plate does say it is a 5.0kw model. On the Startraveller everything - water storage tank, heater matrix and control box are all located under the offside settee. david

[Guest Derek Uzzell]

David: You never know with manufacturers - does 5kW = 3.5kW (diesel) + 1.5kw (230V) or 5kW (diesel) + 1.8kW (230V)? Everything-in-a-single-box "Compact" Combitronics can (according to the Eberspacher leaflet) be distinguished apart via the length of the box. CT03 and CT04 (3.5kW air-heating output on diesel) have a box length of 670mm, wheras CT05 (5kW air-heating output on diesel) has a box length of 720mm.

[Guest david lloyd]

Hi derek Sorry I may have confused things by saying that evreything was in the underbed locker - in fact the heater (burner) itself is located beneath the vehicle floor directly under the bedlocker and then the water tank (inc immersion heater), heater matrix and control box are all in the locker. I have had another look and cannot see any other heat reference other than the 5kw - the control box itself is a small blue rectangular box measuring about 120mm across so nothing like the 670mm or 720mm of the 'all in one' you mention. david

[Guest Derek Uzzell]

David: In fact I did wonder which variant of Combitronic you had. You said that you obtained your Startraveller last April, so, if my Feb 2005 leaflet is correct, then your 'van should have the 'modular' CT01 model with 3.5kW (diesel) + 1.5kw (230V) air-heating. (I note that Eberspacher's website has a fair amount of information on Combitronic but is a mite coy about exactly what models are available.) When you've had some use out of your forthcoming Knaus, it would be interesting to learn how you rate its gas heating system against your current diesel-fuelled one.

[Guest Brian Ramsden]

Although using the fan on a gas fired system may use the same amount of electricity as the fan on a diesel fueled system, the advantage of the gas system is that you can use it without the fan, as a simple convector heater. To my mind this is a huge advantage, as surely everyone might find themselves overnighting without electricity at some time? Brian

[Guest david lloyd]

Derek & Brian Yes - I've had various gas heaters before and Brian is right about the facility to use them as a covector particularly at night. The Knaus is fitted with a Truma C6002EH so it will be interesting to see the difference although this is affected by other things such as insulation qualities within the vehicle. One of the advantages of the Combitronic though is the added flexibility of using diesel instead of gas and that was the main attraction when we bought this vehicle. david

[Guest Derek Uzzell]

Ignoring catalytic heaters, the only gas-fuelled leisure-vehicle heating appliance that uses no 12V power when operating is the convector type with piezo or 'torch battery' igniter (eg. Truma S2200 or S3002). Although these remain the norm in caravans, they are increasingly rarely installed in motorhomes a) because of their limited output (3.4kW max) and b) because they tend to complicate the design of the motorhome's interior layout. Truma do market a more powerful 5.5kW convector heater (the S5002), but, as this is essentially a double-depth S3002, it's a bulky beast. Designed with large caravans in mind, to the best of my knowledge professional motorhome manufacturers have never chosen to use the S5002. All other types of gas heater will use 12V power to a greater or lesser degree. The most economical in terms of battery drain relative to heat output is Alde's Compact 3000, with a maximum of 6kW output and around a 1A consumption (to power the pump that circulates the heating fluid). Compact 3000 heats the leisure vehicle via a 'wet' system using convector radiators in a similar manner to domestic central heating. It's downsides are (exactly like domestic systems) a slow warm-up and very careful thought being needed to produce a logical and efficient installation. When I said earlier "I don't believe diesel-fuelled heaters when running are actually that much harder on 12V batteries than equivalent output BLOWN-AIR gas heaters", I wasn't including convector gas appliances with a blown-air option. Inherent in the blown-air heater concept (whether the appliance is diesel- or gas-fuelled) is the need for 12V power to drive the fans that circulate the warmed air. Combination air/water heaters (like Truma's C-Series "Combi" range) will not only draw 12V current when heating air but also when heating water (to power the burner fan). In fact, if we're being picky, a Combi uses 12V even when it's 'resting' (0.001A), as does the frost/safety drain valve that's normally part of the package. David mentions the C6002EH. When in water-heating-only mode this appliance draws 0.4A (for the burner fan), but, when heating air, you can add from 0.2A to 5.9A depending on the speed of the air-circulation fan. Note that I'm not in any way denigrating the traditional gas 'fire'. In fact I believe I once referred to it on the forum as "the thinking motorcaravanner's heater of choice" for its simplicity and ability to be used in pure convector mode with no 12V current drain and no fan noise. When we were looking for a new motorhome, if there had been a model that met our particular requirements and had this type of heater I would have been a very happy man. Unfortunately there wasn't and my back-up choice - something with a diesel-fuelled air-heater + gas water-boiler - also proved to be a non-starter. Only the Hobby T-600 FC came near to matching our selection criteria and it was either buy one and accept the heater would be a Truma Combi or give up motorcaravanning for the foreseeable future. All I hope now is that the Hobby's C6002EH proves to be a whole lot more reliable than its predecessor.

[Guest Mel B]

Ah, we love our convector heater, we can use it without the fan or with the blown air as well. You can't beat standing next to the convector heater with your top pulled forward so that the warm air coming from the convector top can go up inside and warm you up nice and toasty ... pure bliss!!! It's also a good way to warm your clothes on a winter's morning by putting them on a hanger just above it for a few minutes.

[Guest Derek Uzzell]

You had better hang on to your present 'van then, as I notice that all Rapidos now have a Truma Combi heater (presumably beneath the mattrass in the case of the 709). Warm top or warm feet? A tricky choice!