Maxitrol 325 Series Gas Pressure Regulators

What is a Gas Pressure Regulator?

Gas pressure regulators maintain the desired system pressure by cutting off the flow of a gas or liquid when it reaches a set pressure. They use a valve system to control natural or propane gas pressure or other gas flow.

How Does a Gas Pressure Regulator Work?

Three primary operating components regulate the pressure within the valve. First, the loading mechanism, typically a spring, determines the delivery pressure. Then the diaphragm senses the force against the spring. Finally, the control element accomplishes the reduction of the inlet pressure through to the outlet pressure.

Operational Diagram of a Typical Gas Pressure Regulator

Gas enters the regulator’s chamber, putting pressure on the diaphragm. The diaphragm then moves upward, as controlled by the set spring, allowing a specific fuel flow from the source to the appliance or device. Adjusting the control knob determines the rate of flow and pressure. Turning clockwise will push the diaphragm down and allow more gas to enter the valve. Turning counterclockwise reduces the amount of fuel and pressure.

Atmospheric pressure (based on the building location’s elevation) will affect gas pressure. The inner parts work by sensing the pressure both upstream and downstream. The air pressure affects the way the regulator senses downstream pressure.

Maxitrol is a leading international manufacturer of electronic gas modulation systems, gas pressure regulators/governors, combination gas control valves, gas safety devices, and gas filters.

Maxitrol 325 Series vs. Maxitrol 325-L Series Gas Pressure Regulators

Maxitrol 325 Series Appliance Regulators Overview

325 Series pounds-to-inches regulators are used in residential, commercial, and industrial applications. The 325 Series features a high-leverage valve linkage assembly to deliver positive dead-end lockup. These regulators can precisely control from full flow down to pilot flow. They are 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).

Maxitrol 325 Series Regulators

325 Series regulators feature:

  • Pipe sizes of 3/8" to 3" with NPT or ISO7-1 threaded connections
  • Aluminum housings
  • Multi-positional mounting (if a vLimiter or vProtector is installed, mount in an upright horizontal position only)
  • Suitable for natural, manufactured, mixed gases, liquefied petroleum gases, LP gas-air mixtures, and gases of DIN EN 437 gas family 1, 2, and 3
  • CSA-certified inlet pressures of 2 to 5 psi
  • Maxitrol-tested inlet pressures of 2 to 10 psi
  • Emergency exposure limit of 65 psi (inlet side only)
  • Maximum individual loads of 100,000 BTU/h to 4,500,000 BTU/h
  • Capacities of 150,000 BTU/h to 4,500,000 BTU/h
  • Ambient temperature range of -40 to 205°F
  • Suitable for pilot flow applications

Maxitrol 325 Series Components

Maxitrol 325 Series Regulators Catalog

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Maxitrol 325-L Series Line Pressure Regulators Overview

Maxitrol 325-L Series regulators are certified as line pressure regulators to supply gas pressure to one or more appliances downstream. 325-L Series regulators are for CSST (corrugated SS), semirigid copper pipe, or steel/black iron pipe. These regulators reduce the pressure to a level within the appliance’s operating supply range. Install the line pressure regulator upstream of devices already fitted with an appliance regulator.

Series 325-L 2 psi Regulators

Maxitrol’s 325‑L Series line pressure regulators are for 2 psi piping systems in residential, commercial, and industrial applications. The 325-L Series’ high-leverage linkage assembly delivers positive dead-end lockup and precisely regulates from full flow down to pilot flow.

Maxitrol 325-L 2 psi Regulators

325-L Series 2 psi regulators feature:

  • Pipe sizes of 3/8" to 3" with NPT or ISO7-1 threaded connections
  • Optional 1/8" NPT outlet pressure taps on certain models
  • Outlet pressures ranging from 7" to 11" WC
  • Aluminum housings
  • Multi-positional mounting (except model 325-11L)
  • Suitable for natural, manufactured, mixed gases, liquefied petroleum gases, and LP gas-air mixtures
  • CSA-certified inlet pressures of 2 psi
  • Maxitrol-tested inlet pressures of 10 psi
  • Emergency exposure limit of 65 psi (inlet side only)
  • Maximum individual loads of 140,000 BTU/h to 4,450,000 BTU/h
  • Capacities of 250,000 BTU/h to 4,500,000 BTU/h
  • Ambient temperature range of -40 to 205°F
  • Suitable for pilot flow applications
  • ImblueTechnology™ available on all models, which increases corrosion resistance and provides extra protection against the elements for regulators used in outdoor applications

Maxitrol 325-L 2 psi Series Regulators Catalog

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Series 325-L 5 psi Regulators

325‑L Series line pressure regulators with overpressure protection devices (OPDs) are for use in 5 psi piping systems. These regulators reduce pounds pressure to a level within the appliance or equipment’s operating supply range. Line regulators are located upstream of equipment already fitted with an appliance regulator. 325-L Series regulators with separate OPDs are factory preassembled and supplied to the field as a unit. At supply pressures above 2 PSI, the ANSI Z21.80/CSA 6.22 standard requires an OPD 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. In a 5 psi system, a second appliance regulator (RV Series or 210 with vLimiter) is needed.

Maxitrol 325-L 5 psi Regulators

325-L Series 5 psi regulators feature:

  • Pipe sizes of 3/8" to 2" with NPT or ISO7-1 threaded connections
  • Optional 1/8" NPT outlet pressure taps on certain models
  • Outlet pressures ranging from 7" to 11" WC
  • Aluminum housings
  • Suitable for natural, manufactured, mixed gases, liquefied petroleum gases, and LP gas-air mixtures
  • CSA-certified inlet pressures of 5 psi
  • Maxitrol-tested inlet pressures of 2 to 10 psi
  • Emergency exposure limit of 65 psi (inlet side only)
  • Maximum individual loads and capacities of 125,000 BTU/h to 4,550,000 BTU/h
  • Ambient temperature range of -40 to 205°F
  • Suitable for pilot flow applications
  • ImblueTechnology™ available on certain models, which increases corrosion resistance and provides extra protection against the elements for regulators used in outdoor applications

Maxitrol 325-L 5 psi Regulators Diagram

Maxitrol 325-L 5 psi Series Regulators Catalog

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Gas Regulator FAQs

How Do You Size a Maxitrol Regulator?

When sizing a regulator, gather the following information:

  • Gas type
  • Available inlet pressure
  • Desired outlet pressure
  • Zero governor application (indicated by a model number ending in “Z”)
  • Will the regulator control the main burner and pilot load or the main burner only?
  • Required minimum and maximum flow rate in CFH or m3/h or BTU/h
  • Pipe size

The manifold pipe size has typically already been selected, and the regulator pipe size should conform to this size. The capacity of any regulator is not an absolute value but will vary with the application depending on the prevailing differential pressure.

Use the Maxitrol 325 Regulator Sizing Program to properly size your regulator.

    What is Capacity?

    Capacities are used to determine the maximum multiple appliance load. The
    largest single appliance served by the regulator should not exceed the maximum individual load specified above.

    What Does a Vent Limiting Device Do?

    Maxitrol vent limiting devices eliminate the need to run vent piping to the outside and are designed for indoor use and in spaces where limiting the amount of gas escapement due to diaphragm failure is critical. They should not be used outdoors if they are exposed to the environment. When installed outdoors, a certified Maxitrol vent protector is recommended.

    What is the Spring That Comes With a Maxitrol Regulator Used For?

    The spring within a Maxitrol regulator determines the allowable range of gas pressure. Different springs have lower or higher tension, raising or lowering the gas pressure range. The color of a spring is a visual indicator of its outlet pressure range. The red spring included with 325 Series regulators has an outlet pressure of 10" to 22" WC.

    Consult the Maxitrol Spring Selection Chart to see which springs are available for which regulator.

    How Do You Calculate Pressure Drop at Various Flow Rates From a Capacity Chart?

    When using a natural gas pressure drop chart to determine the LP pressure drop in terms of BTU/h, multiply NAT BTU/h by 1.61; in terms of CFH, multiply NAT CFH by 0.645.

    Formula: P2 = P1 x (Q2/Q1)2

    P2 = Pressure drop at desired flow rate

    Q2 = Desired flow rate

    P1 = Known pressure drop

    Q1 = Known flow rate

    Check the Capacity Chart to ensure the regulator has an ample range of regulation and individual load capacities (for use with pilot). You must know the minimum encountered inlet pressure. Minimum inlet pressure minus “P2” must be greater than the desired outlet pressure. Solve for “P2” using the formula above.

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