Domestic Hot Water Recirculation - Bosch 940 ESO Instruction Manual

Installation instructions
Connecting the pressure relief valve (PRV)
A listed pressure relief valve 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. 29. 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. 29 Plumbing Connections (with shutoff valves)
and Pressure Relief Valve
22
7.4

Domestic hot water recirculation

Although recirculation directly through the tankless
water heater is allowed, temperature stability is
improved by recirculating through a mini-tank as shown
in Fig. 30. By using the design in Fig. 30, there is no
recirculation of hot water through the tankless water
heater and therefore, does not affect the heat
exchanger warranty. Direct recirculation through the
tankless water heater is permissible, however, the heat
exchanger warranty is reduced; contact Bosch
Thermotechnology for further installation requirements.
The following drawing is provided to outline one
possible recirculation design using the water heater in
conjunction with an Ariston mini tank water heater. 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.
5
1
Ariston Minitank
Fig. 30 Recirculation application
1 Full port isolation valve
2 Circulator (pump on timer)
3 Check valve
4 PRV
5 Expansion tank
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
Thermotechnology if further information is needed.
940
ESO
2
4
3
6720608158-77.1AL
6 720 644 956