Hello Mike,
You seem to have some miss-conceptions concerning blown air gas/electric heating in caravans. You are correct when you say that the heat source needs to be hot to negate the heat loss along long lengths of ducting, and as most caravans are now fitted with a 3.6kW gas heater, the gas is going to be quicker in raising the temperature in a caravan than just the 2kW electric element.
But what is often overlooked is that gas control incorporates a thermostat and unless the gas control is set max, the heat output from the gas system will reduce as the temperature in the caravan rises. - so over a half an hour of so the average heat input into a caravan may be less than 2kWh - in which case the electric element would eventually raise the necessary room temperature.
You actually say the gas is "hotter". This is not necessarily true. If you were to measure the surface temperature of the electric elements when they are running and up to temperature you will find they are hotter than the surface temperature of the gas fires heat exchanger. What you should have said is the gas heater provides more heat than the electric elements. This is true because the surface area of the gas system is greater than the surface area of the electric elements.
You also say you believe the gas is more "calorifically efficient" than the electric elements. This depends on how you consider the comparison.
If you are comparing the amount of heat you get in the caravan against the amount of energy you use, then the electric element wins, because it is 100% efficient at converting electrical power to heat, and as there is no chimney required, none of the heat is lost - it all enters the caravan. As for the gas system, it is only about 75% efficient, mainly due to the heat needed to drive the flue gasses which is lost through the flue. The older 1800 series heaters are much better at about 92 to 98% as the flue is virtually balanced under the floor and so it uses less heat to drive flue products These ran in condensing mode but were limited in the maximum heat they could handle in the under floor configuration.
The efficiency calculation is different if you are making the comparison between the burning of the fuel at the power station and gas heater, Now the situation changes. The best conversion of fuel to electricity in a power station and with transmission losses is about 40% - so the gas fires 75% is better on this comparison.
The situation is even worse if you are using a small portable generator, as these do not generally exceed 8 to 10% efficiency of fuel to electric power.
Damian has already challenged you about the safety aspect of using a gas fire overnight, I would add to that comment though, if you are happy enough to use a gas heater during the day, then what changes to make it more dangerous at night? - in the case of a room sealed heater - nothing.
It is of course a personal choice whether to use the heater at night or not - but please be assured that there is no technical reason not too.
With regard to the fire fronts dislocating during towing, I know from both Carver and Truma that have done considerable design and testing to out find out if the front case do dislodge under normal and some extreme conditions. The products are pretty resistant to it, but the other side of the coin is the panel must be removable for inspection and testing without too much difficulty.
Historically where the problem did occur it was either the clips had been bent or broken, or the caravans cut-out for the heaters installation box was too wide by between 5 to 15mm and The heaters installation box had to be splayed a little to allow it to be screwed to the furniture but this meant the clips were too far apart to engage the front cover properly. This is caravan manufactures problem not necessarily the heater manufactures problem.
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