Section 2 — Installation
2-12 Part No. 750-263
supports and not supported by the boiler gas train or the bottom of
the drip leg. Do not pipe across the top of the boiler as the burner
swings up for service and must have proper clearance.
All gas piping and components to the boiler gas train connection
must comply with NFPA 54, local codes, and utility requirements as
a minimum. Only gas approved fittings, valves, or pipe should be
used. Standard industry practice for gas piping is normally Schedule
40 black iron pipe and fittings.
Before starting the unit(s) all piping must be cleaned of all debris to
prevent its entrance into the boiler gas train. Piping should be tested
as noted in NFPA 54 and the boiler must be isolated during any
tests.
After initial startup, the inlet screen to the gas valve should be
checked and cleaned of any debris buildup.
See Figure 2-12 for a typical piping configuration.
5. Gas Supply Pipe Sizing
For proper operation of a single unit or a multiple unit installation,
we recommend that the gas pipe sizing be sized to allow no more
than 0.3" w.c. pressure drop from the source (gas header or utility
meter] to the final unit location. The gas supplier (utility) should be
consulted to confirm that sufficient volume and normal pressure are
provided to the building at the discharge side of the gas meter or
supply pipe.
For installations of new boilers into an existing building, gas
pressure should be measured with a manometer to ensure sufficient
pressure is available. A survey of all connected gas-using devices
should be made. If appliances other than the boiler or boilers are
connected to the gas supply line, then a determination must be
made of how much flow volume (cfh) will be demanded at one time
and the pressure drop requirement when all appliances are firing.
The total length of gas piping and all fittings must be considered
when sizing the gas piping. Total equivalent length should be
calculated from the utility meter or source to the final unit
connection. As a minimum guideline, gas piping tables 2-2 through
2-6 should be used. The data in these tables is from the NFPA 54
source book, 2006 edition.
The boiler and its individual shutoff valve must be disconnected
from the gas supply piping system during any pressure testing of
that system at test pressures in excess of 1/2 psi (3.5 kPa).
The boiler must be isolated from the gas supply piping system by
closing its individual manual shutoff valve during any pressure
testing of the gas supply piping system at test pressures equal to
or less than 1/2 psi (3.5 kPa).
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