Installation Instructions

ALLOWABLE PRESSURE DROP:

The Pro-Flex® gas piping system is required to be “tested, listed and installed in accordance with the

NSI standard for fuel gas piping systems using corrugated stainless steel tubing, ANSI LC-1-2005. This

standard, among other things, requires the manufacturer to provide installation instructions including the

necessary pipe sizing tables and methods.

ith respect to gas piping sizing, the intent of all model codes is to ensure there is sufficient gas volume

and gas pressure supplied to the appliance for proper operation. Language from the International Fuel

Gas Code clearly illustrates this point.

“Allowable pressure drop The design pressure loss on any piping system under maximum probable

flow conditions, from point of delivery to the inlet connection of the equipment, shall be such that the

supply pressure at the equipment is greater than the minimum pressure required for proper equipment

operation.”

Natural gas appliances are typically designed to operate with a minimum inlet pressure of 4.0 inches

water column. Propane appliances are typically designed to operate with a minimum inlet pressure of

10.0 inches water column.

The natural gas capacity tables published by Tru-Flex Metal Hose Corp. (Pro-Flex® CSST), should be

used to provide for no less than 5” water column pressure to the appliance inlet. The propane capacity

tables should be used to provide no less than 10.5” water column pressure to the appliance inlet.

This can be done by subtracting the desired appliance inlet pressure (5” WC for NG, 10.5” WC for LPG)

from the gas source pressure (gas meter for NG, secondary regulator for LPG) to get allowable pressure

drop. Use the Pro-Flex® capacity table labeled with the appropriate allowable pressure drop and gas

type. This will result in an additional pressure drop capacity over the commonly used 1/2” WC drop asso-

ciated with the Longest Run Method.

Reference Data for Proper System Sizing:

PRESSURE CONVERSION FACTORS FUEL GAS INFORMATION

1/4 psi = 6.921 in w.c. = (approx. 7” WC) Natural Gas Propane

1/2 psi = 13.842 in w.c. = (approx. 14” WC) BTU per Cubic Foot = 1000 2516

1 psi = 27.684 in w.c. = (approx. 28” WC) Specified Gravity = 0.60 1.52

psi = 55.368 in w.c. = (approx. 56” WC)

5 psi = 138.42 in w.c. = (approx. 140” WC)

Note: to determine the CFH of Natural Gas,

divide by BTU load by 1000. To determine the

CFH of Propane, divide the BTU by 2516