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Maxitrol Regulator - Line Pressure vs. Appliance Regulators

by | on | in Measurement and Control of Natural Gas | 0 Comments

Confused by line pressure regulator and appliance regulator standards? Can an appliance regulator serve as a line pressure regulator? Alternatively, can a line pressure regulator serve as an appliance regulator? Get Maxitrol regulator answers.

Recently, it became clear that a customer was using an appliance regulator as a line pressure regulator and they were not conforming to standards. Here is the reader's digest version of the rules and how they apply to Maxitrol regulators.

Maxitrol Madness Cheat Sheet

Regulatory Standards

The current standards for appliance regulators are ANSI Z21.18/CSA 6.3 while line pressure regulator standards are ANSI Z21.80/CSA 6.22. Historically, appliance regulators were used as line pressure regulators before ANSI Z21.80/CSA 6.22 was developed. With the implementation of the newer and revised standards, appliance regulators should no longer be used as line pressure regulators. This rule has been confusing given that many longtime favorite appliance regulators were used as line pressure regulators.

The standards apply to natural gas, manufactured and mixed gases, liquefied petroleum gases, and LP gas-air mixture systems.

maxitrol regulator 325-L SeriesMaxitrol Line Pressure Regulators 325-L SeriesMaxitrol Appliance Regulators

The Maxitrol RV Poppet Series, RV Straight-Thru-Flow Series, and RS Balanced Valve Series are certified ANSI Z21.18 as appliance regulators and rated for a maximum inlet pressure of ½ PSI with outlet pressures being 2.8" or 3" to 12" WC.

Maxitrol's 325 Series regulators (325-3, 325-5, 325-7A and 325-9) are also certified ANSI Z21.18/CSA 6.3 as appliance regulators for main burner or pilot applications with a maximum inlet pressure of 5 PSI (CSA certified).

The same Maxitrol 325 Series has an "L" line, denoting that the "L" regulators are certified as line pressure regulators able to supply gas pressure to one or more appliances downstream.

Maxitrol Line Pressure Regulators

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We use line pressure regulators in a building's gas distribution system and install them between the service regulator and the gas appliance's pressure regulator.

Maxitrol's 325-L Series line pressure regulators are certified ANSI Z21.80/CSA 6.22 in 2 PSI and 5 PSI systems [when installed with an overpressure protection device (OPD)]. The L-Series regs are used in CSST (corrugated SS), semirigid copper pipe, or steel/black iron pipe. The regulators reduce the pressure to a level within the appliances operating supply range. Install the line pressure regulator upstream of devices already fitted with an appliance regulator.


The Maxitrol 325 L-Series line pressure regulators are certified for 2 PSI inlet pressure, with outlet pressures ranging 7 to 11 inches WC. The 325-L Series regulators in 2 PSI systems deliver positive dead-end lockup capable of precise control from full flow down to pilot flow; suggesting that one 325-L would suffice as both a line pressure and appliance regulator.


At supply pressures above 2 PSI, the ANSI Z21.80/CSA 6.22 standard requires an overpressure protection device that is factory assembled, approved and tested for use with the regulator, to limit the downstream pressure to 2 PSI maximum, in the event of line regulator failure.

The Maxitrol 325 L-Series regulator with an overpressure protection device (OPDs) is certified for up to 5 PSI inlet pressure and outlet pressures ranging 7 to 11 inches WC.

In a 5 PSI system, a second appliance regulator (RV Series or 210 with vLimiter) in series with the 325-L regulator (with OPD) would be needed. The following factory-assembled 325-L line regulator with OPD will work:

Line Size  Maxitrol 325-L  Description
½" 325-3L48 Line Regulator with OPD
¾" or 1" 325-5L600 Line Regulator with OPD
1-1/4" or 1-1/2" 325-7AL210D Line Regulator with OPD
1-1/2" or 2" 325-9L210E Line Regulator with OPD






Options for Maxitrol Line Pressure Regulators

Vent Limiting Device

The vLimiter is a vent limiting device that eliminates the need to vent to an exterior wall. When using the vLimiter, the regulator must be installed in a horizontal upright position, and if there is a diaphragm rupture, the gas escapement is within ANSI standard requirements.

Vent Protectors

The vProtector is for outdoor applications of Maxitrol regulators. Install the vent protector on the vent opening to protect the breather hole from the elements and debris.

If you are interested in Maxitrol regulators, submit your inquiry to the request for information or call us at (303) 697-6701.

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Blog posted from 12450 W Cedar Dr, Lakewood, CO 80228, USA View larger map
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About The Author

Tom is a former engineer for Xcel Energy, where he designed gas meter and regulator applications. He has also worked for mechanical contractors and engineering firms approving gas meters and regulators in various applications. He currently manages the Linc Energy Meter and Regular Department and is working on flare gas measurement.


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Guest Monday, 22 April 2019
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