Space Heating - Overview

Space heating is taken care of by two separate heaters, one fuelled by diesel, and one by LPG. Both types of burner have their good and bad points but having both allows us to use the heat source most suitable in the circumstances. Availability of fuel, quietness of operation, and the ability to work unaffected at altitude are just some of the factors that make access to both types of burner appealing. Also, if one system fails we will not be totally without warmth. The systems are connected - via an asymmetrical ‘Y’ piece - to ducting that carries warm air to outlets situated at chosen points around the truck. The burners can be used independently, or together. Use of the asymetric connector, supplemented by the addition of a standard Truma slide controlled butterfly valve, meant we combated any potential issue of one heater forcing air back into the outlet of the other when only one burner is in operation.

The ducting system terminates in the shower room as we’ve found that washroom space, when heated, is really useful for drying very wet clothing. Additionally, there is a small diameter (35mm) branch duct system that taps into both heater outlets and pipes hot air under the slightly raised rear floor section. This provides background underfloor heating at the very rear of the cabin and circulates mild air to the water tank and take off pipes to prevent any frost damage / freezing issues.

Diesel Heater

The diesel heater itself is a Webasto Air Top 2000 ST. I chose this having talked to the Webasto staff at a motorhome show. I was persuaded by their knowledge and ability to supply all the fitting kits and extras that anyone would ever want from stock. I also got it a ‘show special’ price and saved a couple of hundred pounds on the normal retail price. The heater itself was supplied by a Webasto main dealer – PB Auto Electrics, who were also very knowledgeable and helpful. Though PB Auto Electrics supplied everything to my specification, including a deeper than usual floor mounting plate (our floor is 63mm thick) a free stand-pipe, and detailed fitting instructions, I was still a little reluctant to get stuck in as there is a lot going on with these things. You have to find a suitable place for the heater mounting, tap into the diesel tank to establish a fuel supply, site a fuel pump within its ‘lift’ tolerance capability, ensure the fresh air entry is sited appropriately, and fit an exhaust / silencer system; again in a suitable position taking into account road debris and the possibility of combustion gasses finding their way back into the habitation area. Add to this mix the need to then wire and plumb everything neatly and out of harm’s way and it really is a test of logistics. Fair to say I spent a very long time measuring, thinking, and re-measuring before I finally plucked up the courage to drill a 5 inch diameter hole through our very expensive floor.

In truth there was nothing that testing about the actual fit, all the hard work was in working out where everything would physically and logistically go in the first place. Only one thing went wrong. I adapted the supplied stand pipe with a brass fitting I happened to have laying around to allow it to fit in a very convenient threaded fitting that was already present in the top of the truck’s fuel tank. This seemed like a really elegant solution and saved me drilling through the tank with all the attendant worries about swarf. The trouble was that the stand pipe, once inserted in this most convenient hole, then fouled the fuel level float and wouldn’t allow it to move through its full arc. I discovered this having put £50 worth of fuel in and being horrified it didn’t even lift the needle out of the red! A couple of patient hours working gynaecologically through the tank's filler tube inducing a gentle curve into the stand pipe and float arm resolved this though.

The LPG powered heater is a Truma Trumatic E2400. I’ve been generally impressed by Truma’s combi-boilers in the past and was advised from a trusted industry source that Truma’s air heater was vastly superior in build quality and operation to any of its direct rivals. A major bonus was sourcing it at a really good price from MV Conversions. The only thing that went slightly awry was being unable to source a 24V version at any price. I was messed around by a couple of high profile Truma dealers and direct contact with Truma UK themselves revealed only one 24V version available for supply in the entire country, hardly confidence inspiring if I ever needed to source a new circuit board at short notice. I settled for the 12V version but saved just about exactly the right amount of money with the bargain MV Conversion price to fund a 24-12V Battery to Battery charger - which was a far better solution to keeping the 12V battery charged than the (cheaper) one I’d originally planned. Using a 12V heater was a slight change of direction, but all-in-all it seemed stupid not to go this route, so the 12V version it was.

Fitting the heater was reasonably straightforward as it will fit in almost any orientation and on any plane. Only the combined air inlet and exhaust ducting run to the wall mounted cowl is slightly fussy in terms of its tolerances for length and incline. All the allowed options are contained in the instructions. The wall cowl itself was perhaps the trickiest part to fit as it’s cast in a downward incline, presumably to prevent water ingress, and this made it slightly awkward to calculate the offset required when drilling through (thicker) walls. I had to drill the inner wall 10mm higher than the outer, and then tunnel through the insulation, to get the right relief. The instructions don’t warn of this and seem to assume the cowl will only ever be fitted to walls of a couple of millimetres thickness: an expensive mistake waiting to happen. Poor show with the installation instructions there, Truma.

One unforeseen irritation was that the Truma's hot-air outlet is designed for 80mm diameter ducting, whilst the rest of our system runs the ubiquitous 65mm. In spite of there being available just about every conceivable ducting adapter, nowhere could I find a simple 80-65mm reducer. I ended up fabricating one from some spare Propex fittings from old projects and have mounted this right on the heater outlet. I had a slight concern that reducing the outlet size would mean that the heater would be choked in prolonged use, but this proved unfounded and all seems well.

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