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Flexible gas connector installation: how to select & install a flexible connector for gas fueled appliances or heating equipment.
This article summarizes manufacturer's advice for the selection & installation of flexible gas connector tubing to assure adequate gas flow to support the input BTUH rating of the connected appliance, and to avoid some common sources of gas leaks such as stretching, vibration, or mechanical damage to the tubing.
Flexible Gas Appliance Connector Installation Procedures & Warnings
The manufacturer typically warns of the following safety hazards when using flexible gas connector tubing, mostly in the form of "Do Not" admonitions:
Install a gas supply line shut-off valve between the end of the gas supply line and the point at which the flexible gas connector will be mounted to the gas supply.
Our photo (left) shows an un-coated stainless steel corrugated flexible gas connector line connected directly to the iron pipe natural gas supply line. This is a poor installation as there is no shutoff valve installed. When you see an error like this you should be alert for other amater workmanship measures that may be improper or unsafe.
Select the proper flexible gas connector size (in diameter) necessary to support the input BTUH rating of the appliance, and in accordance with the length of tubing. A table of lengths and tubing diameters and BTUS is provided below. There you will see that the BTU flow rate capacity of tubing is reduced for smaller tubing diameters, longer tubing lengths, and somewhat by the number of tubing bends.
Do not install flexible gas connector tubing much longer than is needed to safely install and remove the appliance. Excessive tubing lengths may mean extra bends and kinks, reduced tubing flow rate capacity, and extra risk of vibration damage in some locations.
Do not install flexible gas connectors in multiple or ganged sets - use a single flexible connector line between the appliance and the gas supply connection point.
Do not use flexible gas connectors longer than permitted by local building codes. Typical maximum gas connector line length is six feet, or three feet in Massachusetts and possibly some other jurisdictions. Check with your local building department.
Do not re-use flexible gas connectors, fittings and valves; they are designed for use only on original installations. The concern is that removal and re-use of a connector tubing and additional handling may damgae it, making it unsafe for re-use.
Do not use flexible gas connectors with appliances that are mounted on rollers, casters, or wheels that permit the appliance to move readily about. Flexible gas connector tubing is intended for limited movement after installatin. Repeated bending, flexing, extreme vibration, stretching, can cause metal fatigue, cracks, holes and dangerous gas leaks.
Photo at left: coated corrugated flexible stainless steel gas connector tubing. We know from the color that this will be 1/2" I.D. tubing - see the table below.
OPINION: We note, however that flexible tubing will be flexed or bent to and fro when moving the connected appliance, such as a gas-fired clothes dryer. Watch out against extreme movement, kinks, bends, or punctures that may occur due to vibration such as that induced by a clothes dryer vibrating such that the connector rubs against another surface.
Do not connect a flexible gas connector line directly to an LP gas tank. To avoid dangerous over-pressures, fire, or explosion he appliance must be connected through a gas pressure regulator, never directly to a gas tank or other gas source (that will be at higher pressure).
Do not use flexible gas line connectors on appliances in moving vehicles such as campers or RVs. Use of these connectors is permitted, however, in stationary, permanent "mobile homes" such as those mounted on a foundation and not intended for regular movement or relocation.
Do not use flexible gas connectors if the part has been in a fire;
Table of Flexible Gas Connector Lengths & Diameters vs. BTUs
Tubing Inside Diameter
Tubing Color Code
Tubing Lengths in Inches vs. Capacity in BTUH
(1000 Input BTUs per Hour of the Appliance)
1. * = not permitted in some jurisdictions such as Massachusetts
2. Straight tubing length capacity in BTUs per Hour is based on the assumption of natural gas at 0.64 specific gravity with a heating value of 1,600 BTUs per cubic foot of gas. 1KBTUH = 1SCFH (standard cubic feet per hour). Multiply the BTUs shown in the table by 0.632 to convert to standard capacity of 50 pa (0.02 in water column) pressure drop. Some reduction in gas flow rates will be imparted by the number of bends in the tubing - keep tubing bends as gentle and as few as possible.
3. Watch out: this table is adapted from tubing manufacturers' instruction sheets. Be sure to check the tubing specifications and applications and installation instructions provided by the specific maufacturer of the tubing that you are purchasing.
4. Adapted from product literature from BrassCraft Gas Products, 39600 Orchard Hill Pl, Novi, MI 48375, United States
+1 248-305-6000, Website: http://www.brasscraft.com/
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Questions & answers or comments about inspecting, testing, diagnosing, and repairing gas piping, gas regulators, and gas storage tank defects used with LP or natural gas burning appliances
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
U.S. Energy Information Administration - eia.doe.gov/
U.S. Environmental Protection Agency - epa.gov/solar/energy-and-you/affect/natural-gas.html
At Natural Gas.Org www.naturalgas.org/environment/naturalgas.asp#emission you’ll find a table of combustion products
At geocities.com/rainforest/6847/report1.html is an interesting and detailed though not “neutral” report on the components and contaminants in the combustion of natural gas. You’ll see a long long list of emissions products, but look again – most of the contaminant levels listed are in the picograms.
apvgn.pt/documentacao/iangv_rep_part1.pdf lists the components in natural gas exhaust from vehicles
The Need Project, Manassas, VA: need.org/needpdf/infobook_activities/SecInfo/NGasS.pdf
Kroschwitz, Jacqueline I., and Mary Howe-Grant (eds.). "Gas, Natural." In Encyclopedia of Chemical Technology. 4th ed., vol. 12. New York: John Wiley and Sons, Inc., 1993.
Tussing, Arlon R., & Bob Tippee. The Natural Gas Industry: Evolution, Structure, and Economics. 2nd ed. Tulsa, OK: PennWell Publishing, 1995.
Thanks to reader E Leal for suggesting the addition of details about how to convert gas burning appliances from propane to natural gas or from natural gas to propane. 8/4/09
Thanks to reader JR for discussing LP and natural gas operating pressures and leak detection safety, October 2010.
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