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Gas Piping & 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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Installation instructions
Supporting the exhaust vent system
Fig. 19 Horizontal side wall venting installation
(combustion air piping not being shown)
Note: Pitch vent away from heater
Gas piping & connections
Before connecting the gas supply, check the rating
plate on the right side of the heater to be sure that the
heater is rated for the same gas to which it will be
In the United States: The installation must conform with
local codes or, in the absence of local codes, the
National Fuel Gas Code ANSI Z223.1/NFPA 54.
In Canada: The Installation should conform to CGA
B149 INSTALLATION CODES and/or local installation
Warning: DO NOT connect to an
unregulated or high pressure propane
line or to a high pressure commercial
natural gas line.
Warning: The water heater must be
isolated from the gas supply piping
system during any pressure testing of
that system at test pressures equal to or
more than 0.5 psig. If overpressure has
occurred, such as through improper
testing of the gas lines or malfunction of
the supply system, the gas valve must
be checked for safe operation.
B Install a manual gas shut off valve, on the gas supply
B Install a union when connecting gas supply.
B The minimum diameter required for any appliance
connector used is ¾".
B National Fuel Gas Code requires that a sediment
trap (drip leg) be installed on gas appliances not so
equipped. The drip leg must be accessible and not
subject to freezing conditions. Install in accordance
with the recommendations of the serving gas
When connections are made, check for gas leaks at all
joints. Apply some gas leak detection solution to all gas
fittings. Bubbles are a sign of a leak. A combustible gas
detector may also be used to detect for leaks.
Danger: If you have a leak, shut off the
gas. Tighten appropriate fittings to stop
leak. Turn the gas on and check again
with a gas leak detection solution.
Never test for gas leaks using a match
or flame.
The gas supply piping should be sized according to the
applicable code for a maximum draw of 120,000 BTUH.
Measure the length of gas supply line and use the tables
in Fig. 21 or the gas line manufacturer's sizing tables to
accommodate the BTU demand of the unit. If there are
more gas drawing appliances on the line, size the gas
line according to the total maximum amount of BTU
draw for all appliances.
Note: Under sizing the gas line may result in diminished
output and improper operation. See chapter 3.8 for the
procedure to confirm gas pressure.
Gas piping
Fig. 20
Inlet gas particle screen
6 720 607 915



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