Connecting the pressure relief valve (PRV)
A listed pressure relief valve supplied with the heater
must be installed at the time of installation. No valve is
to be placed between the PRV and the heater. No
reducing coupling or other restriction may be installed
in the discharge line. The discharge line must be a
minimum of 4" above a drain and installed such that it
allows complete drainage of both the PRV and the line.
The discharge line must be placed where it will not
cause any damage.
The location of the PRV must be readily accessible for
servicing or replacement, and be mounted as close to
the water heater as possible. See Fig. 16. To install the
PRV, a suitable fitting connected to an extension on a
"T" fitting can be sweated to the hot water line.
Support all piping.
Fig. 16 Plumbing Connections (with shutoff valves)
and Pressure Relief Valve
temperature can exceed 140°F (60ºC), a
3-way valve or mixing valve must be
installed before the appliance to prevent
water exceeding 140°F (60°C) from
entering the appliance.
6 720 608 158
The GWH 715 ES Protankless water heater is
approved for domestic hot water recirculation. The
following drawing is provided to outline one possible
recirculation design using the water heater in
conjunction with an Ariston mini tank water heater.
Recirculation directly through the tankless water heater
is also allowed. This schematic is for illustration only and
must not be used for actual installation without
appropriate engineering and technical advice from a
properly licensed professional in the locality where the
installation is made.
Fig. 17 Recirculation application
Full port isolation valve
Circulator (pump on timer)
The use of a small electric mini-tank water heater (4-6
gallon size) should be used for this application and
designed so the pump will circulate the water through
the mini-tank and the building's hot water return loop
only. Timed or thermostatically controlled operation of
the pump is commonly done. Contact Bosch Water
Heating if further information is needed.
3.10 Combustion air requirements
Warning: In areas where outside
temperatures commonly fall below
36°F, a twin pipe venting system is
required. Failure to do so may result in
cold outside air being drawn in through
the venting system due to a negative
pressure in the house and across the
heat exchanger coil causing it to freeze
and burst. This failure is not covered
under the manufacturer's warranty.