Installation Guide

11
Sizing Methods and Examples
routed to each appliance location. Manifold stations are located as close as possible to the
appliance(s) with the greatest load. Parallel layouts are most commonly used in ¼ to ½ PSI
systems.
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 pressure
is to have multiple man-
ifolds, 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 certied 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 dierent circumstances to demon-
strate how to select the proper size and conguration of HOME-FLEX® exible gas tubing.
These examples are presented to demonstrate the process of using sizing tables to determine
necessary pipe size and conguration. Every installation is dierent and this requires that the
installer go through the processes outlined below for the proper sizing and conguration 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. Dierent 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
Gas
Meter
25,000 BTUH
Range Oven
40,000 BTUH
Elevated
Pressure
60,000 BTUH30,000 BTUH
Furnace
Water
Heater
Dryer
Figure 3.3 A dual pressure system layout