Blown air heating - ever got it working?

[grahamr_5041507]

May sound like a strange topic now summer has decided to appear, but after 3 years of vanning in 2 new ish vans I've never got the blown air heating (the one thats supposed to heat all rooms via ducting) working properly.

The mrs feels the cold and even set to 2k, auto blown or manual it never seems to belt out the warm air? It works fine without the blower and also even better when on gas.

I always aurgue its because it already warm in here! But to be fair it always seems to be cool air and nothing like a fan heater which it might be expected to perform like!!

 

[woodsieboy]

Hi Graham,

We are on our sixth van and have had varying success with the blown air,we find you need to run the fire on gas to warm it up and once the fire is hot then switch on the blown air, the least successful has been the vans with hot air vent in end washroom, and fire at front of van. One van had warm air pipes under the van on the outside, so lost most heat before it got to the back.We now use small fan heater to augment the blown air,and leave then fanmaster on 500 electric setting at night if needed with no blown air.

 

[ProfJohnL]

Hello Graham,

A properly installed and balanced blown hot air system can make a caravan very comfortable, but sadly some manufactured do not use the ideal layouts for reasons of cost or ease of installation during their build process. This will compromise the systems ability to provide an even heating balance.

You will never get quite the same effect as a separate fan heater, so whilst it is tempting to make the comparison, it is not really fair or valid. A fan heater delivers all its air in one direction, where as a blown air system shares its output along two ducts and has the resistance of the duct work to contend with.

To balance the system you will need to experiment with the direction and degree of opening of each outlet, bearing in mind that by opening one outlet more you will rob some of the flow from all the others.

The outlets furthest from the heater will have less air flow, simply because of the inherent resistance to flow of the ducting, also each time the duct bends 90 degrees, is like adding an extra meter to the length of the duct. In most caravans with end bathrooms, the hot air duct is installed under the caravan floor to reach the bathroom. Some manufacturers do provide additional insulation to this duct, but it will still loose heat and air flow because of its location.

Sometimes it is possible to re-install the duct work to maximize air flow by removing some of the bends, Ensuring that Tee pieces have the main flow across the top of the tee, and in some cases actually creating a complete ring of duct around the caravan, so that the outlets can receive air from two directions.

 

[Marcus_5113048]

Graham

I agree that the air never seems particularly warm when on electric. However make sure that the heater is on for at least ten minutes before starting the fan. Although the air still feels on the cool side, the van should start to warm up after another ten minutes or so.

 

[Robert_374242026]

I am amazed that some of you have somehow not got your heating working.Since 1980 we have not had a unit which has not got sufficient tempeture that we have to resort to other means. Our present Coachman 460/2 is so hot in the bathroom when my wife goes in there of a morning that she ends up turning on the extractor and in the evening when we sitting i am everlasting adjusting the tempeture to suit her .It does not matter whether its on gas or electric or combination of both. As i said heating has never been a problem and we also use the ducts for cool air in warmer climates.Please do not add about adjusting as i have got the proverble "T" shirt.

 

[gary]

Apart from what JohnL has said and not forgetting the Truma Ultra-heats temperature sensor being incorrectly sited.

What I think many people don't realise is when first switched on the fire has to warm the whole fabric of the van, once the structure is thoroughly warm though, it then acts as a store and quickly gives off heat to warm the air if it's cooled from opening a door etc.

However if enough heat is not used to start with, the structure never reaches this point so is constantly drawing heat in it's attempt to do so, result is always a cold feel to the van. Solution is to run the fire at maximum, gas and electric, for at least an hour and much longer in very cold weather, I think then you will find the blown air feels hot coming from the outlets.

I have found once this 'equilibrium' point is reached the lowest heat setting (1kw) maintains our 19ft van unless a door is left open for a prolonged time when a quick boost (2kw) will be required.

 

[gary]

I might add caravan ventilation standards were changed in the very late 90's and vans built to the new standards should not be a problem. However vans built from the late 80's had far to much floor level ventilation.

If this is the case then increasing heat output of the fire only serves to speed up the flow of air passing through with little increase in temperature.

Our latest van built in 96 had four large holes (5"x2.5") in the floor other that is than the door vent, fixed gas drop holes and other sundry low level wall vents.

Understanding the new regulations, these larger holes were shall we say 'adjusted to suit' and the van as said now warms up correctly and stays warm!

 

[Denise4]

We have Truma blown air heating. I always use the fan when it is on. Is it safe to have the heater on without the fan. We too find the back of the van always seems cold, when warm air is pumping out the front. It is much more effective on gas - why is this? Denise

 

[Jeff-Pontypridd]

We gave up on the blown air heating years ago. Like Graham describes, it never seems to put any actual heat in the 'van. We use the heater without the fan - works well.

 

[ColinA]

We put the heater on without the blower to start with. Once the heater is warm we put the fan on and use the 500 watt or 1000 watt setting depending on th weather. the whole van including the washroom is kept perfectly warm enough in this way. You have to balance the flow through each of the ducts to get the best set up. Only in the coldest weather do we use the 2000 watt setting or occasionaly gas for the inital warm up.

Colin

 

[ProfJohnL]

Hello Denise,

The reason that the system seems more powerful on gas than electric is simply that it is more powerful.

On electric you have about 2kW of heat where as on gas it puts out 3.6kW - nearly twice as much.

 

[Icemaker]

a lot of vans built from 2000 to mid 2004 did not have the truma ultra seperate sensor fitted and as such the heating was very poorly controlled.

Our 2003 coachman vip 520/4 and my dads vip 460/2 plus my sisters avondale dart all 2003 models had very eratic control of the heating on electric, when i reported this to glossop caravans they new of the problem and said i needed a seperate sensor fitting under warranty.

the sensor was a small black round item fitted at about head hight and it transformed the system, we no longer had a van that was too hot then long periods of cold untill the heating switched on again, no longer did we need to be constantly adjusting the thermostat we just left it on 7 and it was fine.

Both my dads and my sisters van allso had this modification and all 3 vans had the same positive result.

Since this time i have had 3 more new vans and all have come with the sensor fitted as standard and all have been fine, even the twin axles at 27 foot which you would think where too big for 2 kw where fine.

Check your van, if you have not got this sensor fitted then it is allmost certainly the cause of the problem.

 

[Surfer]

We had a lot of trouble with our blown air heating even when it went back to the manufacturer. On return from tghe manufacturer about two weeks later the blown air heating packed in altogether and the fan and gas heater stopped working.

A techie guy from the same dealer but not our local one came down to the caravan removed the gas fire and replaced and also changed the fan.

In doing so he showed me that on the back of the Truma fan there is an adjustment to channel either more or less hot air down either ducting. Any way he set it up for us and after two years of complaining the caravan now heats evenly with the heater switching on and off with the thermostat!

This adjustment is on the rear of the fan and is a small lever that is easily adjuable. I think in a lot of cases they don't bother to set it up.

 

[Nigel_5077906]

In this thread there's mention of "properly balanced and designed system".

I noticed on my Burstner, underneath the seats, the ventilation pipes were punctured in several random places.

At the service interval I reported them as a fault. The dealer said that these were a design feature for the even distibution of air under the seats.

There's no end to what some people would call cgood design!

 

[RobRoy]

A word of warning re fan heaters.

I was sitting in the van reading a magazine and had the fan heater going when I heard a change in the note and glanced at the heater just as the front turned red hot and, before I could get to the switch, to white hot. The heater was replaced by the accessory shop where I had bought it but the replacement did exactly the same. This time the accessory shop's workshop stripped the heater down and found a fault in the wiring.

I related all this to a caravanning friend who was in the habit of putting his heater on a timer when he and his wife went out for the evening so that the van was warm on their return.

He doesn't do that now!

Rob S.

 

[Glenn_5132962]

The carver blown air system in my 1998 swift 5 berth works brilliantly. Even in the depths of winter it keeps the van warm enough on electric only. In fact the bathroom gets too hot really but this makes a great drying area for coats etc.

 

[Pelyma1]

We got fed up with it in our Abbey, combined with the fact my son burnt himself, so we switched to a van with Alde heating, far far better IMO

 

[ajmacintosh]

I have just purchased a new Caravan and tried the blown air heating last weekend for the first time. The caravan is a Bailey 470/4 with a truma ultrastore heater. I decided to try it on electric only and was very impressed with the result. initially the air was cool but after approx 10 mins it was lovely and warm, even in the bathroom at the back of the van.

I aint tried it on gas yet but will do when we are away this weekend. But overall, very happy.

 

[Avril_374306697]

We have managed after trial and error to get ours working evenly in our Swift Charisma 2004 the success is leaving the heater to warm sufficiently before turning on the fan the secret is to run it low, if on high it just blows cold.

 

[ProfJohnL]

Hello Nigel,

On of the difficulties that customers with early blown air systems encountered was toasty warm feet, but cool backs when they sat down. Also condensation on windows was annoying.

To overcome this, many manufacturers built a small slot at the back of seat/bed deck against the outside wall. They also added a false back board spaced away from the wall. This allowed any hot air in the bedding locker to rise behind the seat back, and not only kept the seat back warmer, it also partly demisted the window.

As an additional benefit it also ventilated the bedding locker both at night to keep condensation in the mattress down, and during the day the content of the bedding locker.

As an improvement, Truma sold special fittings to positively duct warm air to the demisting slots, but these were quite expensive, and took moor fitting. Manufactures found that by locating the normal hot air ducts inside the bedding locker, against the outer wall, it was possible to pierce the duct to provide a jet of warm air at the slot which was better for demisting.

So far from it being an excuse - it really was a design feature.

 

[kenneth_374315528]

I have a 1997 Abbey GTS VOgue. I was always under the impression you can't switch the heater on without the fan going. This is a safety feature to stop the heater overheating. Certainly you can put the switch onto the 'on' position but the heater doesn't come on until the fan is switched on. Ken

 

[gary]

Kenneth, you are probably referring to the Carver mk1 Fanmaster as that was the only electric heater of the time!. With this system the elements are enclosed within the unit and rely totally on air being blown across the elements by the fan.

The later mk2 Fanmaster, 98/99 and Truma's version since, have their elements in 'free air' so can run without the fan, this being silent is a useful feature during the night.

 

[kenneth_374315528]

You're right Gary. It is a Carver Fanmaster. Ken

 

[paul_374300602]

We have a fanmaster in our1998 lunar.

Inside the wardrobe and out of obvious site is a switch that isolates the heating side of the blown air system. with this 'off' the fan will blow but no heat.

Another possible is.. There is a cutout switch in the fan housing (in ours this is under a lift out panel in the bottom of the wardrobe) If the system overheats because say the outlet vents have all been closed or the outlets are obstructed this will trip out the heating elements but the fan will keep running, Both these explanations would maybe explain why it stll works ok on gas but gives off no heat set to electric fan.

paul.