As for the heating/hot water system… It seems such a long time ago that I researched this I can hardly remember. The bottom line is, I went for the kit supplied by Eberspacher. I spent time looking on Marine forums at posts regarding diesel heaters, the two main ones being Eberspacher and Webasto. They’re commonly installed on all types of small water craft and I found this was the best way to find info on them. These are the market leaders and their systems are fitted to many vehicle types, including commercial vehicles, watercraft, coaches/buses, motorhome's, automobiles and military vehicles. There really isn't much to choose between the two.

The kit supplied by Eberspacher I chose is called the Modular system and here is a layout of that system…

I’ve just installed this kit into my Unimog and it’s no different from this diagram.

I purchased this from http://www.automotive-electrical.co.uk. The guys here were really helpful and knew their stuff. They fit them into motorhome's at their own workshop so have plenty of experience. As you can see in this diagram the system is not connected to the coolant system of the vehicle. There’s no reason why you can’t connect it but I found a lot of people had problems later on with that set up. Have a chat with the guys at Automotive electrical, they recommend keeping it separate from the engine coolant system. I would only connect mine to the coolant system if I had a large calorifier so needed to heat a large volume of water, or I was going to be spending time in a cold climate where engine pre-heat would be beneficial.

As for the size of your calorifier; I had a lot of advice to go large. Why? I couldn’t see why. A friend of mine owns a boat yard and he said go for about 70ltrs! His reasoning was that if you are running the engine, make the most of that free energy and store it in the calorifier. Sound advice but the more water stored in the calorifier the more energy is needed to maintain the high temperature. If you're parked up for days at a time, as I will be, it would consume a lot of energy to maintain the temperature in a large calorifier. Remember that the temperature of the water inside is very hot, hence the need for a mixer tap before the domestic hot water system. The hotter the water, the more energy needed.

The calorifier in the Eberspacher kit is relatively small, about 10ltrs if I remember correctly. By the time this has gone through the mixer tap, you should be getting between 15 to 20ltrs at the domestic hot tap. In my last motorhome conversion I had a standard caravan hot water system running off the gas. This held less than 10ltrs of hot water held in a boiler that went straight to the hot taps. We found this was plenty, even when water was in ample supply and we could have a luxury shower. So from this, a supply of about 15ltrs before it’s reheated will be adequate for us. Another point to make, a company like Eberspacher (market leaders) are supplying a 10ltrs calorifier for the motorhome market. Motorhome users spend there time on campsites with unlimited water supply and use it like it comes out of a tap!! If it can heat all their water, it can heat our stingy little bit!

Have a look at the pictures of the installation...