18 | Installation instructions
Never block or seal the outlet of the PTR
valve or it's drain for any reason.
The warranty will be void if the relief valve or
other safety devices are tampered with or if
the installation is not in accordance with this
Connect the outlet of the relief valve to a suitable open drain so
that the discharge water cannot contact any electrical parts,
persons or animals and to eliminate any other possible risks.
A drain line from a relief valve must comply with the
requirements of AS/NZS 3500.4.
To reduce the risk of excessive pressures
and temperatures in this water heater, install
temperature and pressure protective
equipment required by local codes and no
less than a combination temperature and
pressure relief valve certified by a nationally
recognized testing laboratory that maintains
periodic inspection of production of listed
equipment or materials, as meeting the
requirements of AS/NZS 3500.4, AS/NZS
3000 and all local codes and regulatory
Always use a valve of the same rated pressure and temperature
as the PTR Valve supplied with the unit.
4.4.5 Thermal expansion tank (not supplied with the
Thermal expansion is a natural process where heated water
increases its volume. When this water is stored in a tank, this
volume increase will in fact mean a pressure increase. This
pressure increase can result in a dangerous situation. If the
safety settings on the relief valve are reached, then the relief
valve will operate during the heating cycle. Thermal expansion,
if normally reaching the relief valve nominal values, can cause
premature valve failure and contribute to increased
Bosch recommends therefore the installation of an expansion
tank in order to relieve this over-pressure, avoiding repeated
relief valve operation.
Please contact a licensed professional, water supplier or
plumbing inspector for more information about this subject.
6 720 801 244 (2013/08)
4.4.6 Temperature mixing device (not supplied with the
This water heater can heat water to
temperatures which can cause scalding.
Bosch recommends the installation of a temperature limiting
device between the water heater and the hot water outlets in a
bathroom or similar usage point, in order to reduce the risk of
Additionally, a certified plumber may have the legal obligation
to ensure the water heater installation meets the hot water
delivery requirements listed in AS/NZS 3500.4.
4.4.7 Pressure limiting valve (not supplied with the
In installations where the mains water supply temperature
exceeds that specified for this product (listed in chapter 3), an
approved pressure limiting valve is required and must be fitted.
If the water heater is supplied with low pressure water, below
the minimum working pressure specified for this product
(listed in chapter 3), then a pressure pump should be installed
in order to minimize the forming of air traps in the hydraulic
4.4.8 Expansion control valve (not supplied with the
Local regulations, a saturation index greater than +0.4 or in
corrosive water areas where there are sufficient quantities of
silica dissolved in the water may require the installation of an
expansion control valve (ECV) in the cold water line, being the
last valve installed prior to the water heater.
Do not incorrectly connect electrical
connections. 230-240V AC must be applied
to L1 and L2 wires as shown in Fig. 11.
Failure to do so will VOID the warranty, and
can result in 120V applied to water heater,
which may damage the compressor or other
Check the markings on the rating plate of the water heater to be
certain the available power supply corresponds to the water
Compress 3000 DW FO