Installation Guide
12
Sizing and Congurations
Dual Pressure Systems
Elevated pressure systems generally have a main line from the gas supply to one or more gas
pressure regulators and then a manifold with "home runs" to appliances. These runs may
branch o through use of a tee, if gas loads permit.
Elevated Pressure System
It is also possible to have
a complete elevated
pressure system where
the pressure regulators
are positioned at each
appliance. This method
is typically employed in
systems with high loads
or long runs.
Multiple Manifold System
Another variant used
with elevated pres-
sure is to have multiple
manifolds, each with a
regulator before the manifold. This approach allows for large BTU load demands while using
smaller diameter tubing.
Hybrid Systems (Rigid pipe and CSST)
The use of both CSST and rigid black pipe can be advantageous to minimize the pressure
drops typically encountered on systems with high loads or long runs. For example, a paral-
lel system could require a larger diameter main branch to provide the total appliance load.
HOME-FLEX® is certied for use with black steel pipe and copper tubing gas piping systems.
3.2 Sizing Methods and Examples
This section will outline sizing procedures under several dierent circumstances to demon-
strate how to select the proper size and conguration of HOME-FLEX® exible gas tubing.
These examples are presented to demonstrate the process of using sizing tables to determine
necessary pipe size and conguration. Every installation is dierent and this requires that the
installer go through the processes outlined below for the proper sizing and conguration of
the gas piping system given the circumstances and requirements at the installation location.
Sizing Tables
All piping systems introduce pressure loss, the amount of which depends on the piping size
and the gas ow (in cubic feet per hour). When "sizing" a system, the installer determines the
smallest size piping that will deliver the ow required given the allowable amount of pres-
sure drop. Sizing tables provide the maximum load for a run given the gas pressure, allowable
pressure drop, size of pipe and the length of the run. Dierent sizing tables are used for each
combination of system pressure and pressure drop.
Allowable pressure drop is the maximum pressure loss that can occur and maintain supply
pressure for proper equipment or appliance operation. Natural gas appliances are generally
designed to function with a minimum pressure of 4 inches w.c. LP appliances are generally
designed for a minimum pressure of 10 inches w.c. The sizing tables in this guide should be
used to provide no less than 5 inches w.c. to natural gas appliances and 10.5 inches w.c. to
LP appliances.
Allowable pressure drop can be calculated by subtracting the desired appliance inlet pres-
sure (recommended 5 inches w.c. for natural gas and 10.5 inches w.c. for propane) from
the gas source pressure (gas meter for natural gas or the secondary regulator for LP).
Gas
Meter
25,000 BTUH
Range Oven
40,000 BTUH
Elevated
Pressure
60,000 BTUH30,000 BTUH
Furnace
Water
Heater
Dryer
Figure 3.4 A dual pressure system layout