Bosch 250 SXO NG - Manual (Page 10)

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Appliance details
2.8 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
connected.
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 with CGA
B149 INSTALLATION CODES and/or local installation
codes.
GAS LINE SIZING
The gas supply piping should be sized according to the
applicable plumbing code for a maximum draw of
175,000 BTUH. Measure the length of gas supply line
and use the tables in Fig. 12 or the gas line
manufactures sizing tables to determine the pipe
diameter necessary 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 2.9 for the
procedure to confirm gas pressure.
Fig. 11
B Install a manual gas shut off valve, on the gas supply
line.
B The use of a union when connecting gas pipe to the
gas inlet connection is important, this will facilitate
any necessary servicing and cleaning of the inlet gas
particle screen.
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
supplier.
The water heater must not be piped with gas supply
pressures in excess of 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.
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.
Gas piping
Inlet gas particle screen
Warning: The 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.
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.