Webasto Thermo 90, Workshop Manual

1   Introduction

102

For the installation of the Thermo 90-TRS or 

Thermo 90 S-TRS in vehicles used for the transportation 
of dangerous goods, in addition to the StVZO, the 
requirements in TRS 002 and TRS 003 (Technical 
Guidelines for the Transportation of Dangerous Goods on 
Roads) must be met.

The heater may only be installed in motor vehicles or in 
independent heating systems with a minimum coolant 
capacity of 6 litres.

The heater must not be installed in the passenger or 
driver compartments of vehicles. Should the heater 
nevertheless be installed in such a compartment, the 
installation box must be sealed tight against the vehicle 
interior. There must be sufficient ventilation of the 
installation box from the exterior in order not to exceed a 
maximum temperature of 60° C in the installation box. 
Excessive temperatures may cause malfunctions.

WARNING

Due to the danger of poisoning and suffocation, the 
heater must not be operated in enclosed areas such 
as garages or workshops without an exhaust venting 
facility, not even if the start-up is activated by the 
timer or telestart device.

At filling stations and fuel depots the heater must be 
switched off as there is a potential danger of 
explosion.

CAUTION

Where flammable fumes or dust may build up 
(e.g. in the vicinity of fuel, coal, wood, cereal depots, 
or similar installations) the heater must be switched 
off to prevent explosions.

In the vicinity of the water heater a temperature of 85° C 
must not be exceeded under any circumstances 
(e.g. during body paint work).
A violation of this temperature limit may cause permanent 
damage to the electronics.

When checking the cooling water level, proceed in 
accordance with the vehicle manufacturer's instructions. 
The water in the heating circuit of the heater must contain 
a minimum of 10% of a quality brand anti-freeze.

Ignoring the installation instructions and its procedures 
will void the warranty granted by Webasto. The same 
applies for repairs performed by unskilled personnel and 
repairs without using original spare parts. This will void the 
water heater's "Official Marks of Conformity" and thus the 
vehicle's permit of operation. 

1.5

Legal Provisions for Installation

For testing the heater in accordance with § 19, 20, or 21 
of the StVZO the following regulations are to be observed 
in particular (§ 22 a StVZO):

Testing is performed upon presentation of the operating 
and installation instructions of the manufacturer. The 
year of the initial operation must be durably marked on 
the heater identification plate by the installing person.

Extracting combustion air from the vehicle interior is not 
permissible.

The exhaust line outlet is to be positioned at the top, at 
the side, or in case of exhaust venting, below the vehicle 
floor, to the nearest possible location of the vehicle's or 
cockpit side or rear end. Exhaust pipes must be routed 
so that exhaust fumes are unlikely to penetrate into the 
vehicle's interior. The function of any parts vital for 
vehicle operation must not be impaired. Condensation 
accumulation in the exhaust line must be directly 
drained. A condensation drain hole may be provided as 
required.

In installations the openings of the combustion air inlet 
and the exhaust outlet must not allow a ball of 16 mm in 
diameter to be inserted.

Electrical lines, switch gear, and control gear of the 
heater must be located in the vehicle so that their proper 
function cannot be impaired under normal operating 
conditions.

For the routing of fuel lines and the installation of 
additional fuel tanks, §§ 45 and 46 of the StVZO are to be 
adhered to. The most important regulations are:

•

Fuel lines are to be designed in such a way that 
they remain unaffected by torsional stresses in the 
vehicle, engine movement, and the like. They must be 
protected against mechanical damage. Fuel-carrying 
parts are to be protected against excessive heat and 
are to be arranged so that any dripping or evaporating 
fuel can neither accumulate nor be ignited by hot 
components or electrical equipment.

•

In busses, fuel lines and fuel tanks must not be located 
in the passenger area or in the driver's compartment. 
In these type of vehicles the fuel tanks must be located 
such that they do not pose a direct hazard to the exits 
in the event of a fire. Fuel supply must not be by 
means of gravity or pressurisation of the fuel tank.