Eberspächer Hydronic D4 Installation Manual - page 9
Positioning the heater
8
1
Water pipework
9
General guidelines
In order to obtain the best performance from the
system, restrictions in the water flow should be kept
to a minimum. The use of right angle bends and large
variations in height should be avoided where possible.
Ideally, the Hydronic should be mounted as low as
possible in regard to the other water components in the
system. This will minimise the possibility of air collecting
in the Hydronic heater and assist with initial air purging.
The above is especially important when an expansion
header tank based system is used.
The use of flexible water pipework such as rubber or
polybutylene is recommended, as this is easier to install
in the boat and allows for vibration and movement.
The preferred pipework circuit configuration is a two
pipe, flow and return system as shown in Figure 5. This
will ensure equal water flow (regulating valves may
be required for selected components) to all the water
components resulting in even heat distribution regardless
of the distance and order that the matrix or radiator is
from the heater.
Single pipe systems (Figure 4), that connect radiators
or matrices in a loop, one after another, should be used
with caution as they give priority to the first components
on the system. As a result the water temperature
reduces as it passes and is extracted through each
subsequent radiator or matrix. This will therefore make
attaining an even temperature throughout the boat
difficult to achieve, with the furthest cabin from the
heater receiving the least heat, as well as increasing the
restriction on the water flow returning to the heater.
However, if the water system contains only a small
amount of pipework and one or two components (as
shown in Figure 4), then a single pipe circuit can
be adopted as long as the internal diameter of the
components used do not restrict the water flow of the
heater (18 - 20mm). In addition bypass valves should be
fitted to reduce possible restrictions in the water flow as
well assisting to a degree in balancing the system. Full
heating systems with several matrices or radiators on
systems using larger amounts of pipework should not be
piped using this type of system.
Hydronic D4 / D5 heaters are to be piped using 18mm
rubber hose or 22mm polypipe to a length of 20 metres
total (supply and return pipe added together), use 15mm
pipe to connect to components (maximum 10 metres).
Types of water systems
There are generally two types of water systems that
can be used. The most common type is the expansion
header tank system as shown in Figure 4/5. This type of
system uses an expansion tank situated at the highest
part of the system. This ensures the system always has
a head of water and allows for the expansion of the water
as it rises in temperature.
Pressurised or sealed systems use a pressure vessel
and gauge as shown in Figure 6, and can be filled and
topped up by a filling loop.
For ease of installation and simplicity an expansion
header tank system is preferable as long as a suitable
high position for the tank can be found. A pressurised/
sealed system does not have this problem although it is
initially more complex to install. This type of system is
less affected by the height variations of the system water
components.
3
Expansion Header
Tank (Twin Outlet)
Hydronic
Towel Rail / Radiator
Calorifier
* By-pass regulation valves
Figure 4
Single Pipe System
*
*