Heating and hot water.

My Unimog campervan has a 5kW diesel powered "wet" central heating system made by Eberspächer. (Hydronic D5WS-24)

This system is very similar to a domestic oil fired central heating/hot water system. A small furnace (burning diesel fuel) heats water that is circulated through a "hot water cylinder" (a calorifier) and two fan heaters (fan matrix).

The furnace and circulation pump are mounted in a stainless steel box (400 x 300 x 150mm RS 186-4934) suspended below the rear left storage area of the vehicle.

The furnace takes its air from the outside and exhausts fumes through a small silencer to the rear of the vehicle. The furnace heats water (plus 30% anti-freeze) that is carried by two 22mm rubber pipes up through the floor into the waterbox.

The furnace uses a "glow pin" for ignition, this may need to be replaced after six months of use. I have modified access to the furnace to make this job easier. Remember to carry a spare "glow pin".

The furnace and pump ready to be mounted in the box. 
Furnace box mounted under floor.
Furnace box (lid open) from below.

Within the waterbox the hot water from the furnace is circulated through a nine litre calorifier (light green cylinder) and two fan heaters (see below).

This type of heating system is often connected to the engine cooling system, but because the body of my campervan is above the top of the radiator (and to simplify the plumbing) mine has a separate pressurized header tank (black).

The water in the calorifier is heated to about 85°C and before use is mixed with cold water via thermostatic mixing valve just visible lower left.

The pipe that carries hot water from the calorifier to the mixer valve needs to be able to stand 85° water. Standard red plastic "hot" water pipe can not!

Heating is provided by two matrix heaters fed with hot water from the furnace. Each matrix heater provides about 2kW of heat.

With the insulation used in my campervan these heaters should be able to maintain at least 35°C temperature difference between inside and out.

I have changed the pipe routing and mounting to make bleeding the air from the system easier.

The Eberspächer system is controlled by a programmable timer and thermostat mounted in the main control panel above the table.

This control panel also allows the fan speed to be selected as well as hot water only (no heating).


In October 2003, on my return from Iceland, I added under-floor heating to my Unimog campervan.

To do this I embedded about 12 metres of 10 mm copper pipe into a 9.5 mm deep routed groove in part of the 18 mm plywood floor.

The entire floor was then covered with a 2mm aluminium plate to spread the heat out evenly..

To ensure that water only circulated through the under-floor pipe when it was required I fitted a 24 volt solenoid water flow valve.

Home pageLast updated 2003-10-28.