Truma combi blown air heating

[JRD2026]

Evening everyone,
After a recent very cold trip to Wales, I decided that I better do some investigation into the blown air heating system in our 2005 Swift caravan.
While we were away, we need the heating on, but found the blown air to be blowing round cold air.
We used the electric space saver heating set to 2000 and the thermostat set to 9, heat came out from the fire nice and warm, but not the blown air.
With the caravan at home I took a look into what maybe happening.
The heat output from the elements heated up to 70 degrees, and the fan worked in manual and auto when switched on.
Next I took the fan housing off, the fan rotates, but found that it is in a housing.
So can't find anything wrong electronically or mechanical, so is the just a poor design? As cannot see how the hot air gets into the fan assembly effectively.
Any advice appreciated

 

[Mr Plodd]

Look underneath your caravan and see how many metres there are of totally uninsulated hot air ducting. You will probably then have a better understanding of the reason!

 

[IanB1485]

When you say 'cold air' did you actually measure its temperature at the outlets? . putting your hand if front of them can give misleading results, as you cant' detect 'hot' air at anything less than about 30 deg C due to water on the skin which evaporates actually cooling the skin. Secondly did you measure the current load on the mains with it set to 2kW ( should be about 8A) if only 4A then its only taking 1 kW and if 2A then 500W. Thirdly the fan is a forward curved centrifugal impeller as it spins it pushes air outward into its housing and through the supply tubes , drawing air in from its centre (third picture) and hence the rear of the top of the heater element /heat exchanger area.Fourthly did you check the impeller is firmly attached to the shaft and spins correctly and the faster you run the fan, the cooler the air will be . and Finally as Mr Plodd says if the supply tubes run unde the van at any point a lot of heat will be lost ( this usually happens at the rear of larger vans .You may also have a balancer lever which selects whether the rear of the van gets a larger or lesser portion of the air.From picture 2 you posted the fan housing may be fitted incorrectly the fan 'aperture' should line up with hole in the rear of the main unit.

 

[Gafferbill]

....the Truma blown air ducting found internally is of coiled wire and paper/cardboard construction.
It is not waterproof and readily desipates heat along its length.
Where this tubing is run externally under the caravan it is waterproofed by running it through larger diameter metal ducting.
The subsequent air gap between the two ducts provides excellent insulation.
Nothing stopping anyone adding further insulation of course!

 

[Mr Plodd]

....the Truma blown air ducting found internally is of coiled wire and paper/cardboard construction.
It is not waterproof and readily desipates heat along its length.
Where this tubing is run externally under the caravan it is waterproofed by running it through larger diameter metal ducting.
The subsequent air gap between the two ducts provides excellent insulation.
Nothing stopping anyone adding further insulation of course!

Sorry but I have to differ!

I had a Bailey Olympus a few years back, there was just short of 2m of heater ducting from the heater running under the entrance way and back up into the caravan. It most certainly did NOT have any form of outer external ducting, it was exactly the same trunking as was inside the can. I insulated it with some closed cell foam tube insulation and it made a phenomenal difference.

 

[Gafferbill]

.....you've told me that before.
My experience is with Truma blown air heating in Swift caravans .....draw your own conclusions!

 

[Mel]

I have a Swift Caravan where the heating duct is partially external. At the Woosie Fest we can have a group evaluation. 😀
Mel

 

[Andy Norfolk]

We had it in a motorhome and it was useless. It's a little better on gas than electric. I'd use something else to supplement it.

 

[Dustydog]

I can say without any hesitation the entire system on the Wyoming is internal!

But the warm air via the ducting is just that,luke warm. However turn on the gas as well as the electricity and you could dry your hair😎