Truma heater

[Guest Malcolm]

Simple question. Can I use my Truma C 3402 heater without water in the system? The manual says yes but I would appreciate confirmation.

[Guest Derek Uzzell]

Simple answer - YES. Early versions of the Truma combination air/water heater (designated C3400 and C6000) had a water jacket with vitreous-enamelled inner surfaces and these appliances must NEVER be run empty of water. The C3402, C6002 (and the latest C4002) models have a completely revised construction with a stainless-steel water jacket. As the manual says, it is perfectly acceptable for these to be run 'dry'.

[Guest bill h]

As a back up to Derek's comment. Page 9 of the Truma operating manual (Trumatic C 6002 EH reads) Quote; "Heating is always possible in all operating modes (gas, electric and mixed operation) without restrictions, with or without water" end of quote. This entry is not to overide Derek in any way, its entered as a reminder to myself that the space heater can be used 'dry' From the cut-away picture it would appear that blown air circulates through the heat exchanger which is separated from any water vessel. ie; there is no 'imersion heater element' such as in a domestic boiler. bill h

[Guest Derek Uzzell]

Truma C-Series (Combi) Heater - A Brief Overview It's probable that Truma's C-Series appliances are now the most commonly fitted heaters in new motorhomes, combining warm air and hot water facilities in a single unit. First marketed in the early 90s, original "Combis" had the designators 3400 or 6000 indicating their maximum heat output (3.4kW or 6kW) in blown-air mode and this convention continues today. These heaters had water jackets with vitreous enamelled inner surfaces that can crack over time, with consequential rusting leading to water leakage. If this happens repair is impossible. A redesigned second generation Combi range bearing a 2 suffix (ie. C3402 or C6002) appeared around 1996 with a stainless steel water jacket and more modular construction. C3400/C6000 Combis must never be run empty of water, whereas '2-suffix' heaters can be run dry. Visually there is little to distinguish a 1996 C-Series from the latest versions and the general operating principles are identical. A fan-assisted gas-burner (sealed from the leisure-vehicle's interior) takes in air and exhausts burnt gases via a roof- or sidewall-mounted flue with concentric ducts. This burner is housed within a central heat-exchanger that transfers heat to a surrounding air chamber that, in turn, passes it to the water jacket. Blown air distribution is handled by a totally separate fan-unit that drives air down through the heater's hot innards into flexible air-trunking emerging from outlets at the heater's base. As Combis are designed to recirculate the warmed air, wherever the appliance is installed there should be a sizeable ventilation opening into the vehicle's interior to allow the heater to 'breathe'. This requirement is essential for efficient operation, but (like so many of Truma's installation recommendations) is regularly ignored by motorhome manufacturers. The C-Series control panel permits selection of water-only or blown-air heating. Water-only mode involves a 2kW gas-burner setting and there is a choice of 40°C or 60°C water temperatures. The gas-burner setting (and fan speed) used for air-heating depends on the model of heater, the interior temperature of the leisure vehicle and the 'room temperature' chosen via the control panel. Basically, you turn the temperature dial to the chosen position, switch the Combi on and the heater takes control. If the water jacket is full when air is being heated, then you get water-heating as a by-product. The latest control panels no longer carry the 'room' thermostat (to simplify installation for motorhome converters this is now separate) and have an extra blown air gas-saving switch position that ignores water heating. C3402EL and C6002EL models include a 230V water heating facility that employs a 450W electrical heating collar that wraps around the outside of the water jacket. This is surprisingly effective and, because less than 2A is needed, can be used with virtually any campsite hook-up. The heating collar can be retrofitted via a Truma kit (approx. £200), but it's very unlikely that this task can be performed with the Combi in situ. Recent developments include the C4002 model - a 4kW replacement for the C3402 - and the C6002EH. C6002EH seeks to answer longstanding requests from campers for a Combi 230V blown air heating capability. Its central heat exchanger has two integrated 900W elements that can be selected individually or together and can be used independently from or in conjunction with gas operation. The standard control panel is still employed, with a completely separate panel dealing with 'power selection' from 230V/1800W, 230V/900W, gas-only, 230V/900W + gas, or 230V/1800W + gas. When running in 'mixed mode' (the last two cases) for air heating the appliance will prioritise on 230V and only use gas when it's necessary to raise (or maintain) the leisure-vehicle's inside temperature beyond the ability of the electric heating. Similarly, if you happen to select mixed mode just for water-heating, gas won't be used - this is to prevent internal overheating of the appliance. By the way, you can't upgrade a C3402 or C6002 to provide 230V air heating - only the C6002EH offers this capability. Despite C6002EH's undoubted sophistication, given the choice I'd opt for C6002EL's relative simplicity and use a cheap 230V fan-heater for air heating. At least with C6002EL, if the appliance develops a fault in gas operation there's every chance the 230V side will continue to work OK (and vice versa), but with C6002EH, with its blended gas and 230V functions, it's pot-luck what the knock-on effects of a fault will be. The main benefit of C6002EH seems to be that 230V air-heating mode will employ the leisure-vehicle's blown-air ducting. This should provide optimum warmth distribution and the ability to direct warm air to those parts that an ordinary fan-heater cannot reach (eg. to between-floor water tanks and pipework). However, being a pessimist, I remain wary of the thing's innate complexity, especially as there's a C6002EH lurking under my Hobby T600 FC's bed!