Parker Hannifin Corporation
Parflex Division
Ravenna, Ohio
Bulletin No. 4660-PGP2T
18
Parflex
®
Flexible Gas Piping System
Design and Installation GuideSection 3.0 System Configuration & Sizing
Medium Pressure Natural Gas or Propane System
(Parallel)
Dual Pressure Natural Gas or Propane System
Medium Pressure System — Medium pressure
systems have natural gas and propane pres-
sure downstream of the meter or second stage
regulator at less than 2 psi. These systems,
commonly called 1/2 pound service, have the
regulator set at 13 to 14 inches WC. The maxi-
mum allowable pressure drop for these systems
is based on the difference between the regulator
output pressure setting and the appliance inlet
pressure requirement.
Dual Pressure System — The dual pressure system
incorporates two pressure regulators down-
stream of the meter. The primary pressure set
by the service regulator at the meter is normally
2 psi but can be higher or lower based on local
code and gas company policy. The secondary
pressure, set by the pounds-to-inches regula-
tor, is less than 1/2 psi (normally 8 inches WC)
which allows a 3 inch WC drop to each appliance.
In system designs where large appliance loads
exist, the secondary system should be as short
as possible and the pounds-to-inches regulator
and manifold should be in close proximity to the
appliance with the largest load.
Elevated Pressure System
— Elevated pressure
system layouts use CSST to deliver gas directly
to an appliance regulator located directly
upstream of the appliance. These systems
typically have long runs and high loads.
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