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Water Connections - Bosch Pro Tankless GWH-450-ES Series Manual

Temperature modulated with electronic ignition - normal duty suitable for recirculating potable water only
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Water connections

B When facing the water heater, the ¾" return is on the
bottom right and the supply is on the bottom left.
Install the heater centrally in the building if possible
and make piping runs as short as possible.
Fig. 23
B The use of a union when connecting both water
pipes to the return and supply connections are
recommended, this will facilitate any necessary
B Although water piping throughout the building may
be other than copper, we recommend that copper or
suitably rated stainless steel flex line piping be used
for the water connections for 1.5' on either side of
the water heater (follow local codes if more
B Never sweat any rigid piping directly to or beneath
the water connections, damage can occur to the
internal parts of the heater from heating of the pipe.
B Plastics or other PEX type plumbing line materials
are not suitable for connecting directly to the water
B Keep water inlet and outlet pipes to no less than ¾"
(19.05mm) diameter to allow the full flow capacity.
B If the cold and hot connections to the heater are
reversed, the water heater will not function. Be
certain there are no loose particles or dirt in the
piping. Blow out or flush the lines before connecting
to the water heater.
B Full port valves should be installed on both the cold
water supply and hot water outlet lines to facilitate
servicing the water heater (see Fig. 24).
B For installation on a private well system with the use
of a pressure tank, the lowest pressure range setting
recommended is 30-50 psi (2.07 and 3.45bar).
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 water heater. No
6 720 607 915
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 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. 24. 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. 24 Plumbing Connections and Pressure Relief
3.10 Electrical connections
disconnect the power supply to the
heater before any service or testing is
Warning: This water heater must be
electrically grounded in accordance
with the most recent edition of the
National Electrical Code. NFPA 70. In
Canada, all electrical wiring to the
heater should be in accordance with
local codes and the Canadian Electrical
Code, CSA C22.1 Part 1. Do not rely
on the gas or water piping to ground the
metal parts of the water heater.
The GWH-450-ES requires an electrical power supply
from a 120VAC 60Hz circuit and must be properly
A means for switching off the 120VAC power supply
must be provided.
The heater is wired as shown in the wiring diagram
(chapter 4.7, Fig. 29).
Installation instructions



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