The actuator in this photo is remotely mounted to a butterfly valve

The actuator in this photo is remotely mounted to a butterfly valve.

Does Your VAM Need a Local Disconnect?

Valve actuator motors (VAMs) have the same requirements as regular motors — with a few exceptions.

The most common reference in the industry for valve actuator motors (VAMs) are motor operated valves (MOVs). The reason the term “MOV” wasn’t used in the NEC when they were added to the document several cycles back is because it is also used to indicate a metal oxide varistor. Not only that, but the IEEE had already defined MOVs as VAMs.

The reason VAMs were added to the NEC was based on several factors. First, there was confusion in the industry as to whether or not they were torque motors, which they’re not.  Several major manufacturers, such as Limitorque and Rotork, by virtue of their brand names, misled some users into thinking that the motors were torque motors.

Because VAMs typically have self-contained controllers (i.e., forward/reverse contactors) and no self-contained breaker or fuse disconnecting means, this meant that a local disconnecting means had to be provided within sight of the VAM. Even if the VAM was protected by a remote thermal magnetic breaker or fuses, there still had to be a local disconnecting means within 50 ft of the VAM and within sight.

In some cases, adding this disconnecting means created more of a hazard as a point of failure during a fire than it added for safety. In these cases, it was a common practice to either leave the disconnecting means out within sight of the VAM or cover it up with a fire blanket, which negated the need to have one there in the first place. So, the general rule now is that if there isn’t an additional hazard presented by adding the local disconnecting means, it must be present. However, in cases where it presents additional hazards, such as for a unit block valve or an emergency shutdown valve, then it can be eliminated.

One additional note: VAMs cannot be protected by motor circuit protector (MCP) breakers (known in NEC terms as instantaneous breakers). They must be protected by fuses or thermal magnetic type breakers only.

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