Blown air heating vs Alde boiler

[Scouser1]

I'm just in the process of changing my van. The heating system does not suit our camping style- we are usually in a pub, on gas and battery, and out all year long. My wife is also disabled, and frets when it's not tropical where she is sitting.

The boiler system has two drawbacks;-

1. It takes ages to heat the van. It's at least an hour before it's liveably warm.

2. In this weather, it cycles about every 5 minutes- ignition, circulation pump and boiler fan. My battery lasts about a day, with a genny to top it up.

However, once it's heated up, it's just like your house.

The van we are getting has blown air. Can I expect the van to be as controllably warm as the one with the boiler? My missus is fretting it wo'nt be warm enough.

Thanks, Norman

 

[ProfJohnL]

Hello Scoucer,

Whichever system you go for there are strengths and weaknesses.

You will find that some people will swear by the wet systems and others by the blown hot air systems.

I have little experience of the wet systems, so I cannot make a valid comparison, but I can add a few tips regarding the blown hot air systems.

Modern blown hot air heaters usually have a choice of power sources. Traditionally they are gas powered, but in more recent years a set of mains electric heating elements have been added. So you have a choice but based on your posting it seems that mains is not always available to you.

The gas heaters are usually thermostatically controlled, using a mechanical modulating valve on the gas supply, so this means the size of the flame changes according to demand. This is quiet and required no power or re-ignition when additional heat is demanded.

There is a fan which has to operate when the blown air is required. This will put a drain on the 12V system, typically it will draw about 1.2A, or may be less if it is also a thermostatically controlled motor. The fans usually have two outlet ports and two lengths of ducting are run from them. However the gas heater can be used as a simple thermostatically controlled convector heater - using no electrical power at all.

One of the difficulties with blown air systems is getting a good heat flow to the extremities of a caravan. The ducting whilst necessary also imposes a significant resistance to the flow of air. Other features also can impede the flow, such as the length duct (seems obvious!) but also the number of bends in the duct, how some fittings such as 'T' pieces are inserted, and heat loss where ducting is fitted under the caravan floor.

Sometimes it is possible to re-route the ducting to achieve a smoother flow with fewer sharp bends to improve air-flow, fitting additional insulation to the under floor sections can also help. Refitting 'T' pieces so the bulk of the air flow goes through the head of the T rather than having to negotiate a rt angle bend. But to maximise the air-flow by adding a length of duct to create a complete hot air ring around the caravan can make a big difference.

With any blown hot air system, adjusting one outlet it will affect the flow of air to the others, so it is worth taking time to play with the system to tune it. I did some work for a manufacture where a 4 berth caravan was tested with an outside temperature of -5C. It was possible keep the inside temperature between 20 and 22C front to back and top to bottom. - Not all caravans would be this good!

I hope this helps.

 

[George2]

Also with blown air, you can run on both electricity and gas at the same time. In normal use this isn't necessary, but it can be handy to get a cold van warmed up much more quickly. On my van running them both at once brings the heater up to over 5Kw.

 

[Saladdodger]

Alde also can use both fuels simultaniously.

I usually heat up the van for a while before travelling and find that the caravan is still warm when the Alde is switched on again and we soon become warm and cosy.