Caravaning

Caravan Heating Mods

Another little mod, that is in progress, but I'll try and walk through what I've done

The 'van has Truma blown air heating, with 4 air vents, as opposed to some slightly more expensive caravans that have Alde based wet heating, much more like a conventional domesting central heating system, with a header tank and radiators.
Being a special edition, one of the upgrades we got was "butterfly" valves on these air vents, allowing shutting off / restricting the flow of certain vents, to encourage hot air out of the others.   This is needed to keep heat roughly balanced, as the air duct to the bedroom is significantly longer than the one to the lounge. This image shows roughly the route the 4 different ducts take.  The blue is to the bedroom and is the coolest.  The dashed portion is where the duct is underneath the van on the outside

 I have got to say that the normal flow out of the bedroom duct is quite minimal, even with a valve closed. Truma recommend having the heater positioned centrally in such a way that all ducts have roughly the same length, which is possibly why the air flow on the long throw to the bed in the bedroom is so low

So the first thing I've seen suggested is to make sure the outside section of ducting is insulated with a run of slightly larger ducting.  When I looked underneath, while tracking the duct, I noticed that it is already within a black ducting.

So, I've decided to be a little creative and increase the air flow without stopping all heat getting to the lounge/kitchen areas

The ducting is 60mm internal (though truma call it 65mm, which would be based on the external diameter), so with this in mind, I looked for some quiet 60mm computer case fans, which of course run on 12v.
These will sit in a "Y" splitter, and I'll also add a second vent on the other side of the bed.  There is a 12v feed which runs from under the bed to a 12v socket on the wall for tvs, so I can connect in to that circuit for a power feed, and I'll use a fan controller to allow me to turn them off / down at night time if they are a little noisy.

Parts List

Item	Quantity	Cost
65mm Ducting	2m	£6.99 /m
Truma Y Splitter	1	£6.41
Butterfly Valve	1	£4.16
Back Nut	1	£2.49
60mm Fan	2	£6.00
Fan Controller	1	£2.58
Small Case	1	£3.99
	Total	£45.61

Construction

 So I started by making sure the fans would fit inside the y splitter.  Although the fan was 60mm, the frame around them was a square and thus they wouldn't fit inside.  Out with the hacksaw!

 

The corners needed a bit of extra rounding, so I also ran them over a rasp to get a smother corner:

Before inserting them both in the y-splitter, and drilling a pair of holes so the wires could make it out:

 

Then it was a simple case of wiring the fans up and testing it.  The fans I got were 3 wire fans, where red was positive, black negative, and white would be used to signal to a pc what the current fan speed was.
So wiring to the fan controller was simple, with it being labeled as +ve -ve input and output

Then it was a simple case of cutting the existing ducting (a craft knife will cut it easily enough) and adding on the new duct, outlet and back nut, along with the original vent:

 

There is still work to do.  I'm awaiting delivery of the component box to house the controller in, and I've not yet patched in to the caravan 12v supply, or taken a 60mm hole saw to the other side of the bed to mount the new branch of the ducting.  Updates should follow soon!