MEGR-1122H-AAJ Propane LP First-Stage Regulator — Adjustable 8–12 PSI, 1/4 in x 1/2 in NPT, 1,000,000 BTU Capacity

The Marshall MEGR-1122H-AAJ is a first-stage propane/LPG regulator that reduces high cylinder pressure to a stable low pressure (adjustable 8–12 PSI) with a 1/4" female NPT inlet and 1/2" female NPT outlet.

This compact first-stage regulator is engineered to bring cylinder or bulk-tank pressures down to a controlled low-pressure feed for downstream appliances or a second-stage regulator. It accepts up to 250 PSI on the inlet and is rated to supply up to 1,000,000 BTU, so it’s suitable for commercial and heavy-duty residential setups that require a reliable primary pressure reduction. The unit is adjustable across a narrow low-pressure band, and it’s designed to pair with a dedicated second-stage low-pressure regulator for final appliance delivery.

How does this regulator fit into a two-stage propane system?

The MEGR-1122H-AAJ serves as the initial pressure reducer between a high-pressure source and the downstream low-pressure controls. It lowers tank pressure to a safe, adjustable range (8–12 PSI) so the second-stage regulator can fine-tune delivery to appliances. Using two stages improves stability and reduces wear on the downstream regulator.

• First-stage input rating: 250 PSI maximum.
• Adjustable output window: 8–12 PSI for consistent downstream supply.
• Designed to be followed by a second-stage low-pressure regulator.

What connections and pressure ratings should I expect?

This unit provides a 1/4" female NPT inlet and a 1/2" female NPT outlet for easy plumbing to common LPG systems. The maximum inlet pressure is 250 PSI, and the regulator is built to handle a large heat output capacity up to 1,000,000 BTU when sized and installed correctly. Thread sizes and pressure limits make it compatible with many commercial and industrial installations.

• Inlet: 1/4" female NPT; Outlet: 1/2" female NPT.
• Max inlet pressure: 250 PSI.
• Maximum output capacity: 1,000,000 BTU when installed per specifications.

Is the MEGR-1122H-AAJ compatible with my existing regulator model?

This Marshall regulator is offered as a direct replacement for several common models, so it often fits applications where equivalent parts were used. Check physical connections and pressure range to confirm interchangeability. Replacing matched first-stage parts with a unit of the same specs simplifies maintenance and system restoration.

• Common cross-references: Rego LV3403TR, Fisher R122H-AAJ, Cavagna 984HP-04.
• Confirm thread types and pressure ratings before swapping parts.
• Compatible when system requires 8–12 PSI adjustable first-stage output.

How do I adjust and maintain this regulator for reliable performance?

Adjustment is done within the specified 8–12 PSI range; small turns of the adjustment mechanism alter outlet pressure. Routine inspection for leaks, corrosion, and proper mounting will extend service life. Always follow safe isolation procedures and local codes when adjusting or servicing regulators.

• Adjust output carefully to remain within 8–12 PSI recommended band.
• Inspect seals, fittings, and body for wear or leaks regularly.
• Service only when fuel supply is isolated and per applicable codes.

Who this is for: Technicians, contractors, and fleet maintenance teams who install or service commercial propane systems will find the Marshall MEGR-1122H-AAJ useful as a heavy-duty first-stage regulator. It’s well suited to facilities that require a robust primary pressure reducer with sizeable BTU capacity, and for anyone replacing the listed cross-reference models. If your setup needs a reliable, adjustable 10 PSI nominal first-stage regulator with standard NPT connections and high BTU throughput, this unit is designed for that role.