Blown air heating

[JeremyClarksson]

I know this was covered fairly recently but do not remember a conclusive answer.

Has anyone got blown air heating to work well in a large van, we have settled for using the fire on its own as this seems to keep the whole van much warmer than using blown air.

I have tried to get it to work better by closing vents etc but without much joy. I wonder if actually moving the air around causes it to feel colder than it actually is.

We also do a fair few non hook up winter rallies which rules out using the fan anyway so not a massive problem but would like to know if it can be done.

 

[Jeff-Pontypridd]

I gave up trying! I stick to the heater now.

 

[WilliamTups]

In our Bailey 550/6 we use the gas fire to initially heat up the caravan and then when it is up to temp, we then use the blown air system to keep an ambient temp.

On the blown air system we set power to the 500 setting (keeps the power usage on the caravan down), temp setting set at max, but the air flow setting is slow, we have that the higher the air flow the cooler the blown air system feels.

Overnight we may take the power setting up to max if its cold plus at this point in the evening there is normally not much electrical systems being used.

How also found it can be helpful to close the vent in the toilet.

 

[JeremyClarksson]

Thanks William

Tried this, it works very well.

I would say that the van feels warmer on 500 with a low fan setting than on 2000 with no fan.

 

[George2]

As William says, let it warm up first without the fan, then the fan should work fine, however, on my van the air at the front and the washroom, is very warm, but by the time it gets to the back it's not too good. The washroom is like a sauna !!!!. If it's cold though, like now, you really need to keep the heating on all the time, it take quite a while to warm up from cold.

If you really need to get heated up quickly, then you can use electric and gas at the same time, this double the heat output from the heater.

 

[ProfJohnL]

Hi Garry,

There is a science to getting a caravan with blown hot air to warm up and feel comfortable. A few years ago now I was contracted to investigate blown air heating caravans.

Without blown air, all the heat emerges from the front of the gas heater. Your school science will remind you that warm air rises over cool, and the result is that you get stratification of temperature between the top of the roof and the floor. In some experiments I did it is possible to get 27C at roof level and 0C at floor level with and outside ambient of -5C. This gives the sensation of a hot head and cold feet, which if you are sitting is quite uncomfortable.

The introduction of blow air can radically improve the situation. In the best blown air installation I came across, you could get 20C at floor level and only 23C at head height throughout the whole caravan inc. a rear bathroom.

In fairness, we had to re-engineer some of the duct work achieve this, but this was restricted to creating a s hot air ring main, re aligning the tee pieces to balance the flows better.

And that is the key to it. Is balancing the ducts and the butterfly openings to move the hot air around the caravan to where it is wanted.

 

[WatsonJohnG]

The heater in the Oklahoma is very good at warming the van but a lot of heat was wasted

The drawers and cabinet above the heater were getting very hot and so I fitted bigger grills above the fire and also one on the cabinet side below where the heater thermostat was fitted

I also have a small computer fan that can be switched on to assist heat extraction when on 2Kw

I say was fitted because I moved the thermostat to be within reach of the seating area when seated.

This has given a bonus in that the thermostat is not responding to the hot cupboard side and switching the heater off

I have also fitted an extra outlet in the bottom of the cupboard so that the hottest air can be directed across the doorway

There is a lever on the ducting at the back of the fire to divert hot air to the front or back of the van

As has been said it its very cold heat up first on the gas 3Kw and on 2Kw electric only switch on the blower after the elements have heated up .

Hope that helps

 

[peteh1]

hi gary we use our blown air heatig very successfully on electricity it heats our coachman 520/4 very well start on high setting then adjust when we are not on electric hook up we use it on gas but i hav,nt tried blown air on gas as i would think it would flaten the battery quickley regards peter

 

[Jeff-Pontypridd]

Having just spent a week in the caravan, I was able to do a little experimenting. Using just the heater, the top of the van (with 2 kids in top bunks) got super hot, even at 500watts. Us parents in the front of the van remained relatively cool, however.

The blown air did not work (as previously reported) on its first attempt - the front end kept blowing cool air. Then tried letting the fire heat up on 2kw before switching the blown air on - amazing! Worked really well thereafter, even when switched to 500 watts for the night. Heat spread was much more uniform, and top bunk dwellers were as comfortable as us pond life.

S'pose the trick is to experiment until it works.

 

[gary]

As the electric heating is thermostatically controlled by what the dial is set to, it will switch on and off automatically to maintain that temperature.

It therefore follows it does not matter what heat setting the elements are set at as long as it's powerful enough to reach the set temperature. It's only just struck me the lower heat setting are really to allow for it's use if the available hookup is only 6 or 10 amps, in which case it would accordingly trip the hookup if set too to a higher settings.

If set then to 2kw it will reach temperature quickest and switch off, while off it may seem cooler air is coming from the vents, however as this air is one in the same as the rest of the air in the van, in truth it must be the same temperature.

At some point the heater should switch back on, Truma fires should respond to a drop of less than 2degs, if this is not the case then the sensor,(and this is common fault), is probably positioned in the wrong place.

Once throughly warm and you drop the setting to 500w then it maybe able to cope and from time to time switch off and on, however if it's struggling on this low setting it will stay on and the constantly heated air from the vents always be that much warmer. That is until the overall temperature drops and a higher setting required to boost it back up.

Possible conclusion then, if on 16A hookup leave it on 2kw, 10A and 1kw, perhaps 6A and 500w if only chilly outside or use the gas fire.

I could say the definitive answer is retro fit a Carver 5500 because I'm always toast in my van...but I won't! LOL