Understand automatic changeover regulators

August 12, 2022 By    

Regulators play a key role in a safe and effective propane system. The purpose of the regulator is to control the flow of gas vapor from the container to the burner tip of the appliance.

As part of controlling the flow, the regulator imparts safety by providing overpressure protection, typically through a pressure relief device. This is why we often refer to the regulator as the heart of the propane system.

Although the purpose of all propane regulators is the same, different types of regulators are designed to fit different applications or functions. In this article, I will address the automatic changeover regulator used in residential cylinder exchange and recreational vehicle applications.

What it is

An automatic changeover regulator is similar to an integral two-stage regulator with regard to pressure regulation. But an automatic changeover regulator also has a mechanism that allows it to monitor vapor pressure switching from one container – typically a cylinder – to another in a multi-cylinder installation where two or more cylinders are used.

When the pressure drops in the service cylinder, the regulator automatically switches to the reserve cylinder without causing interruption in service.

The automatic changeover is similar to other regulators, consisting of a body, cover, inlet and outlet ports, orifice, lever, diaphragm, main springs, relief device, vent and vent screen, and a dust cap. In addition, automatic changeover regulators typically have a knob or lever to select the source container and an indicator. The indicator, usually visual, is green when in service and turns red when the regulator automatically switches.

The regulator is a combination of a first-stage and second-stage regulator to connect directly to cylinders with a maximum inlet pressure of 250 psig and an outlet pressure of 11 in. of water column.

Image courtesy of Cavagna Group_ automatic changeover regulator

Image courtesy of Cavagna Group

How it works

Ensure the regulator has appropriate flexible connectors and is mounted correctly above the cylinder valves. Ensure both cylinder valves are open to allow the automatic changeover to maintain continuous service to the gas system (Fig. 1). The automatic changeover cannot switch to the reserve cylinder if the cylinder valve is closed.

With both cylinders full and valves open, the automatic changeover’s visual indicator is green. The arrow on the automatic changeover’s knob shows which one of the two cylinders is supplying gas. In Fig. 1, this is the “service” cylinder.

The other is the “reserve” cylinder. When the pressure in the service cylinder drops to less than 5 psi (Fig. 2), the regulator automatically switches to the reserve cylinder to supply gas flow without interruption. You know this occurred because the visual indicator turns red. When you see the indicator turned red, close the valve on the service cylinder, manually move the selection device to point toward the reserve cylinder, and the indicator will turn green (Fig. 3).

This cylinder is now the service cylinder, and you can safely remove the empty cylinder, ensuring the valve has been closed (Fig. 3). Once the empty cylinder is filled, reinstalled, reconnected to the regulator and checked for leaks, open the service valve. This now makes the replaced cylinder the reserve cylinder.

As the pressure drops in the service cylinder, the regulator senses the drop in pressure and switches to the other cylinder before causing an interruption in service. For this to work, the reserve cylinder valve has to be open. Otherwise, the regulator will not be able to switch because there is no gas source with the service valve closed.

Remember that with automatic changeover regulators, the regulator automatically switches from one cylinder to the other when pressure drops in the service cylinder, but it cannot open and close valves.

Randy Warner is the product safety manager for Cavagna North America. He can be reached at randywarner@us.cavagnagroup.com.

NOTE: The opinions and viewpoints expressed herein are solely the author’s and should in no way be interpreted as those of LP Gas magazine or any of its staff members.

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