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Results From 20 Years of Research on Interior Gas Distribution Technologies

Robert TorbinManager of Business Development

Foster-Miller, Inc.Waltham, Massachusetts 02451 U.S.A.

www.foster-miller.com

ABSTRACT

Over the last 20 years, the gas industry has experienced many changes in the way natural gas isdistributed within residential and commercial buildings. One of the most radical departures fromtraditional practice is the elevated pressure, corrugated stainless steel tubing (CSST) system. Researchresults have shown that elevated pressure CSST systems are less expensive to install; provide theconsumer with enhanced features not available with conventional low pressure steel piping systems;and provide future expansion options. In the single-family market, these features have successfullyincreased the gas load per installation. The retrofit of CSST with installed low-pressure, steel pipesystems also encourages more gas usage.

GTI sponsored research has supported many innovations in this technical area including:

• Gas Load Center: A prefabricated piping assembly and enclosure that focuses consumerattention on the addition of more appliances.

• Gas Convenience Outlet: A quick-connect coupling with an integrated manual valve andsafety interlock used with movable appliances.

• Larger diameter (up to 50 mm): Expanded the use of CSST in the commercial and residentialmarkets.

The benefits of using CSST systems are clearly demonstrated based on numerous field studiesperformed in a wide range of new and existing buildings and applications.

INTRODUCTION

Over the last 20 years, the gas industry has experienced many changes in the way natural gas isdistributed within residential buildings. One of the most radical departures from traditional methodsis the elevated pressure, corrugated stainless steel tubing (CSST) system. Since 1983, the GasResearch Institute (now known as the Gas Technology Institute or GTI) has supported numerousresearch projects aimed at addressing the technical, economic and institutional issues affecting theintroduction of innovative interior gas distribution products. GTI sponsored research results haveshown that 2 psi (13.8 kPa) flexible gas piping systems can be less expensive to install; will providethe consumer with enhanced features that are not available with conventional low pressure steel pipingsystems; and will provide future expansion options typically not associated with gas piping systems.

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FLEXIBLE GAS PIPING SYSTEM

CSST is commercially available in a variety of sizes ranging from 0.375 in. to 2 in. (9.5 mm to50.8 mm) internal diameter. The tubing is packaged in long coils on spools (that facilitate thedispensing of the tubing) and the coils are available in lengths varying from 100 ft to 500 ft (30m to150m), depending on tubing diameter. Reusable mechanical fittings are provided to connect thetubing with other components within the overall gas distribution network. The tubing can be easilycut and field assembled with the mating fittings using standard hand tools. All fittings are requiredto incorporate standard NPT threads for connection to conventional plumbing components andappliances.

Unlike conventional plumbing products, CSST is sold as a system and is certified in accordancewith a nationally recognized standard known as ANSI LC-1. The system, as shown in Figure 1,includes the tubing, fitting and certain other necessary components used within the overall gas pipingsystem such as:

Figure 1. CSST System Components (Photo courtesy of Titeflex Corporation)

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• Multiport manifolds.• Appliance termination outlets.• Special metallic striker plates.• Pressure regulator (for elevated pressure systems).

The CSST manufacturer is also responsible for preparing and distributing a system design andinstallation manual, as well as providing training for all installers. The installation instructions mustbe revised and reprinted as needed, and the trained installers kept abreast of all pertinent changes tothe hardware, installation practices and sizing methods.

CSST can be used in either conventional low pressure or elevated pressure [up to 5 psi (34.5 kPa)]systems. The choice of design pressure and allowable pressure drop will depend on several factors,including the application, availability of elevated pressure in the street, local plumbing coderestrictions, required gas load, delivery distance, and the locations of the appliances within thebuilding. Regardless of the system pressure, the gas distribution network can be installed in one ofthree arrangements: either in series, in parallel, or a combination of the two. A series layout, like thedesign of a conventional steel pipe system, is best described as one main feed line with branch lines(or “drops” located along the main) supplying individual appliances. Thus, the gas load will varyalong the main as each appliance line branches off. In the parallel arrangement, a main line is installedfrom the meter to a multiport distribution manifold. The manifold can be located near the meter orinside the house near the major gas appliances. From this manifold, independent, parallel lines arerun to each appliance.

Compared to rigid steel pipe, the installation of CSST has several distinct differences. In mostinstallations, there will be no intermediate joints because the tubing is capable of being installed inone continuous run. This significantly reduces not only the total number of joints, but it also minimizesthe number of potential leak sites. Because most gas piping is field run, the flexibility of the corrugatedtubing allows the installer to seek the path of least resistance around existing structural and mechanicalobstacles such as floor beams or air ducts. This flexibility eliminates the repetitive measuring, cutting,threading, and joint assembly that are required with steel pipe systems.

The dual pressure system has become the preferred (although not mandatory) approach to thedesign of the gas distribution network when using CSST. Typically, it is used when the gas loadexceeds 100 CFH (2.8 m3/hr), or there is a significant distance between the gas meter and the gasappliances and the pathways include complex turns and twists. Using Figure 2 as a reference, thesystem can be described as follows:

• Natural gas is delivered to the building at street pressure where a service regulator drops thepressure to 2 psi (13.8 kPa) just upstream of the meter.

• The entire household gas load is then delivered through a single, small diameter line to acentrally located distribution point where a shutoff valve, pressure regulator, and distributionmanifold are located. The maximum pressure drop in this portion of the piping network istypically 1 psi (6.9 kPa).

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• The line pressure is reduced from 1 psi to 0.25 psi (6.9 kPa to 1.7 kPa) through the regulator.The outlet pressure can be varied and is typically set by the supplier between 7 to 10 in. WC(1.7 to 2.5 kPa).

• The gas is then redistributed, at low pressure, through relatively short, independent, parallellines to each appliance. Finally, the tubing is connected to the appliance, according to localpractice. Typically, the pressure drop in this portion of the piping system varies between 0.5and 3 in. WC. (0.12 and 0.73 kPa) depending on the pressure at the outlet of the line regulator.

Experience installing CSST systems identified the need to streamline the assembly and fieldinstallation of the distribution manifold and associated components required in an elevated pressuresystem. Research showed that a prefabricated manifold assembly could significantly reduce theinstallation time and simplify the design and layout of the piping network. In response to this need,the Gas Load Center was conceived, designed and developed. Because an elevated pressure systemcan easily accommodate additional appliances after the home is occupied, it also became clear thata convenient, low cost device for connecting those appliances was required. To make the connectionto the piping network easier for the homeowner, a quick connect device was developed, and is nowsold as the Gas Convenience Outlet.

GAS LOAD CENTER

The Gas Load Center (GLC) is a prefabricated piping assembly and enclosure box shown inFigure 3. The metallic enclosure is designed to be installed either between two standard wall studs

Figure 2. Typical Dual Pressure System Arrangement

Range/oven

R

R

R

Meter2 psi (14 kPa)availabledownstream

Buildingwall

Manifold Water heater

Furnace

<1/2 psi (3.4 kPa)pressuredownstreamof regulator

= Shutoff

= Service pressure regulator

590-ICDV-3240-3

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Figure 3. Gas Load Center

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or on a wall surface. When fully installed, the box includes a service shutoff valve, drip leg, linepressure regulator, piping union (to facilitate regulator replacement) and multiport welded steel orcast manifold with mounting bracket and clamps. The entire manifold assembly can be removedfrom the enclosure to facilitate the mounting of the box between the studs. The enclosure is providedwith knockouts for six tubing runs, and can be oriented for tubing runs entering/existing the GLCfrom above or below.

Although the typical manifold configuration is a four port arrangement, it can be customized interms of the number and size of the ports. For large upscale, single family homes (where many gasappliances are typical) two GLCs can be installed side by side to accommodate the extra load or asecond load center can be installed at another location within the house.

All manifold components can be assembled at the plumbing contractor’s shop prior to fieldinstallation. Once assembled, the entire Gas Load Center can be shop inspected and tested for leakage.After the enclosure is installed in a house, the field operation is reduced to installing the meter andappliance tubing runs, and completing the assembly of the fittings. As an option, shutoff valves canbe installed at each manifold port to facilitate the servicing of the appliances and any future pipingsystem modifications. The GLC also provides the consumer with other safety features. Each portcan be numbered and recorded on a log sheet attached to the unit, so that each appliance connectioncan be easily identified. Safety information, system sizing data and important telephone numberscan also be listed on a notice located inside the GLC.

Although the primary benefit of the Gas Load Center is to reduce the installation cost of the pipingsystem, it can also be a major factor for increasing the natural gas load. The GLC is a visible andattractive feature (heretofore totally lacking in conventional steel piping systems) that focusesconsumer attention on the enhanced use options available with this new distribution product. Theseuse options include:

• The ability to add more gas appliances (spare ports on the manifold) without any majorreplumbing of the existing piping system.

• The use of individual appliance shutoff valves conveniently located inside the Gas LoadCenter.

• The ability to incorporate home monitoring technology (i.e., smoke and CO detectors) intothe gas distribution network through the use of electrically operated shutoff valves.

GAS CONVENIENCE OUTLETS

The use of 2 psi (13.8 kPa) delivery pressure and flexible tubing to distribute natural gas withinhomes has increased dramatically during this past decade. On average, over 30 million feet(approximately 10 million meters) of CSST have been sold each year. These systems provide thehomeowner with a more extensive and decentralized network of gas piping, and are conducive tothe use of gas convenience outlets. The outlets are intended to be used with both movable and portableappliances. Typical applications include clothes dryers, barbecue grills, space heaters, free-standing

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range/oven units, outdoor lights, and a variety of new lightweight, countertop cooking appliances.These countertop appliances are used extensively in Japan where gas outlets have been available forseveral years. Ultimately, the gas outlets may become as common as electrical outlets, includingthe requirement to preplumb all kitchens and laundry rooms for both gas and electricity.

The GTI developed gas outlet has been commercialized by M.B. Sturgis, Inc. The Model 3/375outlet, shown in Figure 4, has a manual valve with safety interlock integrated with a standard quickconnect device. The appliance plug cannot be inserted unless the manual valve is in the closedposition. The user can then push the locking collar back, insert the connector plug, and capture theplug by releasing the locking collar. The manual valve can then be opened to start the flow of gas.With the valve in the open position, the interlocking safety cam prevents the removal of the connectorplug. The plug can only be removed after the manual valve has been closed, and the locking collarmanually retracted by the user. As an additional safety feature, the Model 3/375 has a built-in thermalfuse that prevents the flow of gas if the outlet is exposed to temperatures in excess of 200°F (93°C).The outlet can be mounted either on a wall surface or within the wall cavity (behind the wallboard)with the use of a special mounting enclosure. For outdoor installations, a plastic cover is providedto protect the unit from the weather and other hazards.

Figure 4. Gas Convenience Outlet

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INSTALLATION CASE STUDIES

Although the natural gas industry has seen an impressive national growth in the residential marketover the past few years, there are local areas in the United States where new construction is slowand/or the opportunity to add new customers is limited. Such is the case in the inner cities and oldersuburban communities. However, load growth even in these mature markets is possible. Sellingmore gas to the existing customer base can significantly increase load. In addition, the ability to easilyand quickly convert (a home or business) from propane or electricity to natural gas can also makea large contribute to load growth. Unfortunately, traditional rigid steel pipe has proven to beincompatible in this potentially large, market growth area. Steel piping systems are difficult andexpensive to modify in retrofit situations. However, based on twenty years of experience, CSSTsystems can make the retrofitting of new gas service or the expansion of existing systems as easy asextending the electrical wiring.

Especially important to the retrofit market is the use of the existing low pressure system andpressure drop. To accommodate the low pressure/pressure drop, the CSST industry has developedand certified CSST sizes greater than 1 in. (25.4 mm) I.D. (which had been the previous maximumtubing size for many years). Based on changes to the ANSI LC-1 Standard, sizes up to 2 in. (50.8 mm)are now commercially available. In addition, the larger sizes can better deal with the flow capacitiesassociated with commercial and industrial applications. As shown in Table 1, there are a number ofsuppliers of CSST product in a wide range of sizes.

To document the benefits of using CSST to the gas and plumbing industries, Foster-Miller hasperformed numerous installation time studies. These studies measured the actual cost for the materialsand installation labor for the gas piping system in a wide variety of building types and retrofitapplications. Installation studies in new construction were completed earlier in the research effort.Retrofit installation studies have been completed as well and have also been wide ranging with manyvariations. Installations projects have included the simple addition of one more appliance, theexpansion of an existing steel pipe system to accommodate a large remodeling job and severalappliances, major rehabilitation projects in large multifamily buildings, as well as conversions ofelectric or propane service to natural gas. Although the results from only a few of these studies aredescribed in this paper, CSST systems, in general, are always more cost-effective than steel pipesystems for retrofit applications. In many cases, gas service would not have been provided if steelpipe were the only solution. Retrofitting steel pipe is prohibitively expensive, in general, andfurthermore, it can cause extensive collateral damage to the building interior during the installationprocess.

Single Family Home: Major Expansion of an Existing Gas System (2 Appliances to8 Appliances)

The existing contemporary home was built in 1991 with gas water and space heating systems.The owner, who was undertaking a major remodeling of the home, wished to add six new gasappliances. These included: fireplace log, range/oven unit, clothes dryer, barbecue outlet, and twogarage space heaters. The gas load would be more than double, from 208 to 518 cfh (5.8 to14.5 m3/hr). The existing gas equipment was operated at 7 in. WC (1.7 kPa) and connected with

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Tab

le 1

. A

vaila

ble

CSS

T S

izes

by

Man

ufac

ture

r

EH

D V

alu

e1

315

18

19

23

25

30

31

37

#4

64

86

06

2

No

min

al

Dia

mete

r (

in.)

3/8

3/8

1/2

1/2

3/4

3/4

11

1-1

/41-1

/41

-1/2

1-1

/22

2

CS

ST

Ma

nu

factu

re

r

Ward

XX

XX

XX

X

Ga

stit

eX

XX

XX

XX

Om

ega

flex

XX

XX

XX

X

Park

er

XX

XX

X

Tru

-Fle

xX

XX

X

Meta

l-F

ab

XX

XX

X

# N

o E

HD

valu

e a

ssig

ned

as

of

6/0

1/0

2

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steel pipe. To minimize the disruption to the existing equipment and to be in compliance with theMassachusetts Plumbing Code, a low pressure CSST system was designed. However, to minimizethe cost, the gas pressure was actually raised to 13 in. WC (3.2 kPa) with an allowable pressure dropof 6 in. WC (1.4 kPa) and some portions of the new piping system were plumbed using steel pipe.

A multiport manifold was installed into the steel pipe system in the mechanical equipment roomas shown in Figure 5. Separate parallel CSST lines were installed for the range/oven, the two garageheaters and the clothes dryer/BBQ outlets. The installation of the gas piping system required notonly gas fitters, but also needed carpenters (for restoration of interior spaces) and electricians (wiringof new appliances). The cost of this project as installed was $3800. The cost estimate for doing thesame installation, but only using low pressure steel piping, was $5100. It should be noted that theinstallation contractor would not have installed some of the same runs with steel pipe due to the costand difficulty of the restoration.

High Rise Multifamily Building: Conversion from all Electric Service to Natural Gas

The 14-story Hampden Hall apartment building underwent an eight million dollar renovationthat included conversion of the major appliances from electric to gas. This historic 1920 two tower

Figure 5. Manifold for New CSST Appliance Runs

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building contains 76 housing units. To make the conversion work, Laclede Gas installed a 7 psi(48.3 kPa) welded steel main vertically up the side of the building. The pressure is reduced to 2 psi(13.8 kPa) at each service regulator located on the service balcony on each floor. One service regulatorwas provided for two or three meters, also located on the service balcony. Downstream of the meter,corrugated stainless steel tubing was used for all of the interior gas distribution. The portion of thegas system from the meter to each apartment was operated at 2 psi (13.8 kPa). Once inside theapartment, the pressure was lowered to 8 in. WC at the gas load center. Most apartments had a furnace,water heater, range/oven and a clothes dryer. Each appliance was served with an independent, parallelCSST gas line connected to a multiport manifold.

The biggest driver for the selection of this approach was time. The developer had crucial deadlinesfor occupancy that affected his financing. The CSST system was the only way to meet the two monthtime table. In fact, over 7,600 ft (2300m) of CSST was installed within the stipulated schedule.Laclede Gas estimated that the CSST installation required less than 50 percent of the labor neededto install a comparable low pressure steel piping system. This resulted in savings of 35 percent inthe total installed cost.

Low Rise Multifamily Building: Rehabilitation of Abandoned Building with Entirely New GasPiping System

The abandoned, three story structure was formerly an apartment building with retail shops onthe ground level. Although the existing masonry walls were left unchanged, the entire interior spacewas gutted and repartitioned into 20 small living units. The original building had the traditional lowpressure steel piping gas service with all the meters located in a small room in the basement level.The old gas piping network had been removed during the interior rebuilding, and was replaced witha new 2 psi (13.8 kPa) CSST system, starting from the same meter room. Each apartment was providedwith a combination space and water heating unit and a range/oven unit. The typical gas load centerfor these apartments was quite simple. Given the small size of each apartment and the use of onlytwo appliances, there was close similarity between the CSST system and the comparable steel pipesystem. However, the complex routing of the piping within the existing and new walls and floorsof the building proved the value of the flexible tubing approach.

The results from the time and materials study were quite dramatic. As shown in Figure 6, theaverage time to install the CSST system was 1.90 hr per apartment. Compared to the average timefor the steel pipe system (8.5 hr), the CSST was installed in 78 percent less time. The total installedcost savings of the CSST system over the steel pipe approach was 25 percent.

Low Rise Multifamily Building: Conversion from Centrally Heated Oil to Decentralized Gas

Many of the multifamily buildings in Brooklyn, NY are centrally heated with fuel oil. Manyprevious research studies have proven that individual renter responsibility and control of the energyusage will result in lower energy use compared to centralized services without cost constraints.However, the cost of these conversions is made more difficult to justify when faced with the highcost of installing individual apartment piping for natural gas service. Each floor has four apartmentsbuilt around a central corridor and staircase. The central system was removed as part of a general

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reconstruction of the interior space. In it place, individual gas fired hydronic boiler units were installedin the basement. Each boiler is served by its own gas meter. A tee fitting was installed at the meterto permit separate CSST lines to be installed to each boiler and to each apartment for the range/ovenunit.

The entire installation of the gas piping system was accomplished by two plumbers and a parttime helper. Because of the extreme low pressure conditions in the streets of Brooklyn, only a lowpressure piping system was possible. According to New York City Plumbing Code, the total headloss allowed from the meter to the range/oven is 0.5 in. WC (0.12 kPa). This necessitated the use oflarger sized CSST than would have been needed for a 2 psi (13.8 kPa) system. The time required toinstall the CSST system was measured at 66 hr. The total time needed to install a comparable steelpipe system was calculated to be 128 hr. The total installed cost savings were much smaller due tothe higher cost of materials for the CSST system. Although the savings were calculated to be only3 percent, the actual savings are understated. The time study does not include any time for locatingand repairing leaks in the piping system. For steel pipe systems, 10 percent additional cost is typicallyadded to the price to accommodate this highly probable occurrence.

Commercial Building: Installation of New Gas Piping Network for a Laboratory TestingFacility

The decision by CSA to move its operations to an existing 15,000 ft2 commercial building insouthern California brought with it the need to completely re-pipe the facility. CSA provides appliancetesting services to the gas industry, and has the need for eleven test stations. Each station is supplied

Figure 6. Average Installation Time per Apartment

8.53 SMH

Steel PipeSystem

1.89 SMH

Corrugated TubingSystem

2.17 SMH

Copper TubingSystem

Ave

rage Inst

alla

tion T

ime for

One U

nit

Sta

ndard

Man H

ours

(S

MH

)

0

1

2

3

4

5

6

7

8

9

450-OH-2111-3

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with four different gases: natural gas, LP gas, butane and a butane/air mixture. The natural gas andbutane/air are supplied at 14 in. WC (3.4 kPa) and the propane and butane are supplied at 21 in. WC(5.1 kPa). Using steel pipe for this experimental setup would be extremely expensive for two reasons.The close quarters around each test station would create a “rats nest” of pipe and pipe supports. Giventhe need for seismic restraints on these pipes, the cost and complexity would be further exacerbated.

The choice of CSST eliminated all these concerns. The lightweight and flexible nature of thetubing allowed the use of simple unistruts for support and organizing the numerous tubing runs. Theunistrut, while providing effective support, is also relatively inexpensive. Figures 7 and 8 give someappreciation for the complexity of the piping network and some of the installation issues associatedwith the design of the piping within the open space configuration of the building. Results from theinstallation study were dramatic. The CSST system was installed in 40 percent less time and withmore than $8,000 in total savings compared to the steel pipe approach.

HOME AUTOMATION SYSTEMS

Office and home automation are evolving with similar goals to serve different building markets.They both offer facilities for the interoperation of systems that were formerly independent, includinglife safety, heating and cooling, lighting, and the distribution and utilization of energy, includingnatural gas. The technology that implements these automation features is typically electronic andmicroprocessorbased, with a strong bias towards all-electric homes and offices. Therefore, the gasindustry faces three immediate challenges in attempting to remain competitive with electricity in theseemerging markets:

• An adaptable interior gas energy distribution network is needed that can be integrated withthe electrical network, and make gas service available throughout any given building in a cost-effective manner. It is essential to provide the consumer with enhanced use and safety optionsfor gas applications.

• Natural gas appliances must be designed for compatibility with an automation environment.This requires capabilities for transmitting, receiving and processing data and control signalsusing one of the emerging standards specifying the formal rules for communications.

• The integration of gas with home and office automation must be available both to new andexisting structures. There are more than 50 million homes in the United States currently usingnatural gas, while the number of new gas-fueled houses constructed each year is only about600,000.

The impending widespread use of automation technology clearly indicates that the blindacceptance of “business as usual” including the use of low pressure steel pipe technology for thedistribution of natural gas must be rethought. The gas piping must be viewed as an energy distributionnetwork, and not just a plumbing subsystem. With flexible tubing arranged in a parallel fashion froma distribution center, operated at elevated pressures, and connected to appliances through quickconnect outlets, many analogies can be made between this approach and the way electrical energyis distributed.

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Figure 7. Manifold and Regulator Station for Four Test Fuels

Figure 8. Overview of Gas Piping Installation

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There are many communications protocols appropriate for home and office automation. At thistime, CEBus is one of the strongest candidate protocols. CEBus and other communication systemsprovides a digital data communications network that links appliances and monitoring systemcomponents, such as switches, sensors and control panels, allowing the exchange of commands,operating data and equipment status. These communication protocols have been designed toaccommodate a variety of communication media, including: the power line; twisted pair wires; coaxialcable; infrared signaling; radio frequency signaling; and fiber optics.

Foster-Miller has proposed a framework for the integrated of the interior gas piping system withthe home and/or office automation system called Gas-Wise. Key components of the Gas-Wise systeminclude the service entry, the intelligent load center, and smart gas appliance outlets. The integrationof the gas piping system with home and office automation enhances the basic functions of aconventional gas piping system, including energy metering, interior gas distribution, system controland monitoring, and consumer safety.

Energy Metering: The Gas-Wise system is designed to accommodate either a single or multiplemetering devices. Multiple flow sensors/metering devices will allow individual analysis of appliancegas consumption, as well as the measurement of the total gas load for billing purposes. The use ofa remote read meter with electronic interfaces would be standard in the Gas-Wise system. The mainmeter is part of the Service Entry that serves as the utility gateway between the Gas-Wisecommunications network and the utility’s distribution automation system.

Gas Distribution: All gas piping system components of the Gas-Wise system are interconnectedwith semi-rigid tubing, and appliances connected through smart convenience gas outlets. Theseoutlets permit quick plug-in appliance connectors, and also contain interfaces for the electroniccontrols and sensors within each appliance. The smart outlets determine gas load requirements, andallow gas to flow only when a valid request (by the appliance) for service is made. The decentralizeddistribution network allows gas usage anywhere inside the structure.

Control and Monitoring: The principal function of the control and monitoring subsystems is safety.The overall system is broken down into zones, and each zone is monitored separately, but the controlcan be applied either by zone or for the entire network. The brains of the control and monitoringsystem is the Gas Load Center which contains the microprocessors, sensors and hardware necessaryto supervise the gas flow throughout the system. The GLC checks the status of components withinthe Gas-Wise network, such as regulators, valves, piping, and appliances, and also receives signalsfrom sensors outside the system, such as a smoke detector, thermostat or security system. The systemdetermines if an unsafe condition exists, and engages the necessary safety devices (such as a shutoffvalve) isolating a particular zone or shutting down the gas flow to the entire house.

Consumer Safety: In addition to the safety aspects of the control and monitoring system, the Gas-Wise system addresses other safety issues. Each connected appliance is integrated into the networkand allows for constant monitoring of the gas consumption, combustion by-products and the operationof mechanical components. Deviations from established operational norms could be charted andcorrective action taken automatically if the condition persists beyond a predetermined time. Othersafety features of the network include:

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• Thermal fuses to prevent gas escape from individual gas lines during fires.• Tunable excess flow devices to protect against major and minor line breaks.• Tamper sensors to monitor unauthorized changes to the system.

The introduction of home and building automation may significantly influence the expansion ofthe natural gas market. An integrated automation and gas piping system offers many advantagesboth to consumers and to local gas companies. Consumers will have more access options withenhanced safety, and thereby, more opportunities for using gas appliances. As a result, gas companieswill increase sales while decreasing operating costs by linking distribution automation with homeand office automation. These benefits should help convince local utilities to make the necessaryinvestments in automation and encourage the housing and building industries to do the same to forman integrated network.

CONCLUSIONS

In highly competitive environments, innovative methods for gas delivery have proven to be asales advantage to local gas companies. In the upscale single family market, the combined use ofthe CSST system, elevated operating pressure, gas load centers and outlets has been very successfulin maximizing gas load per house for new installation. In many cases, 8 to 12 appliances are routinelyinstalled in these types of homes. Future tie-ins with home automation/monitoring systems; the abilityto easily retrofit the piping network for new load additions; and the significant cost advantage of CSSTfor major rehabilitation projects and fuel conversion opportunities have more than justified anyincrease in material costs for the CSST, GLC and outlets.

The availability of corrugated stainless steel tubing systems has changed the rules for evaluatingoptions in the residential and commercial markets for new construction, retrofit, remodeling andrehabilitation. In the retrofit markets, it is particularly difficult to cost-effectively install and/or extendsteel piping systems. The complexity of the building geometry and the need to minimize the damageto the existing interior space are factors that make rigid steel pipe difficult to use and expensive tospecify. Lost market growth can be recaptured through the use of flexible gas piping that makes gasas easy to install as electric wiring. CSST essentially allows the plumber to “wire” the building forgas.

Results from numerous field installation studies in a wide variety of building types and retrofitapplications confirm this claim. Typically, CSST can be installed in less than half the time neededfor steel pipe. For many applications, the total installed cost for CSST will be 50 to 75 percent lowerthan for steel pipe. It has been noted on several occasions, that installers would not even attempt touse steel pipe for many of the installations that were included in this paper. In general, steel pipebecomes cost prohibitive when the complexity of the building geometry is too great, and the potentialexists to damage the existing interior walls and floors.

What has been lacking in the past, and what these new innovative products bring, is a marketingfocus on infrastructure benefits rather than the conventional wisdom of selling gas based on comfort/energy savings. Flexible gas piping operating at 2 psi (34.5 kPa) pressure, distributed throughoutthe home through a GLC, and supplying appliances through quick connect outlets is a system concept

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and represents enabling technology. Like natural gas itself, enabling technology is a fundamentalbackbone that allows other benefits to be realized. A homeowner who appreciates how electricityis distributed throughout the house will also realize that the gas can be similarly distributed. Oncethe consumer realizes that gas can be easily made available anywhere in the home, then a demandfor more gas service is sure to follow.

ACKNOWLEDGMENTS

Mr. Paul Belkus of Foster-Miller, Inc. was the Principal Investigator for all of the field installationstudies and was the Project Manger for much of the research that is reported in this paper.Unfortunately, Paul was killed in a tragic motorcycle accident in April 2001. This paper is dedicatedto his long-standing dedication to gas industry research, in general, and to the gas piping program,in particular.

The author also wishes to acknowledge the Gas Research Institute/Gas Technology Institute (theprincipal project sponsor for many years) for its support of this research and to Mr. Marlon McClintonfor his staunch and long-standing commitment to and support of gas piping research.