Section 2 — Installation
Part No. 750-263 2-17
5. Gas Supply Pipe Sizing
For proper operation of a single unit or a multiple unit installation,
we recommend that the gas piping 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. Higher supply pressure systems may allow
for a greater pressure drop. In ALL cases, minimum supply pressures
must be met for proper operation of the boiler(s). 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, see gas piping Tables 2-4 and
2-5. The data in these tables is from the NFPA 54 source book,
2006 edition.
To verify the input of each device that is connected to the gas piping,
obtain the btu/hr input and divide this input by the calorific value of
the gas that will be utilized. For instance, a unit with 750,000 btu/
hr input divided by a gas calorific value of 1060 will result in a cfh
flow of 707. The single boiler is approximately 20 feet from the gas
supply header source. And with a measured gas supply pressure of
10" w.c. we find from Tab l e 2-4 that a supply pipe size of 1-1/4"
should be used as a minimum.
!
Caution
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).
To Next Page
Loading...
Need help?
General
