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UL 6200: An Overview

What is UL 6200?

Since the publication of UL 508A in 2001, many of the components and mechanisms used in control panels have changed significantly. Though the standard is constantly updated, new technologies leave room for creating entirely new standards that go into greater detail on specific components and functions.

One such standard is UL 6200, introduced in 2019, which outlines the standards governing the utilization and construction of control units (related to power generation and utility synchronization) and the various control and safety circuits used in power generation controllers and within related control panels. Function of these devices include:

  • Synchronization Controls

  • Starting Controls

  • Fuel System Controls

  • Generator Paralleling Controls

  • Engine Speed Controls

  • Safety Circuits

The publication of UL 6200 can be attributed to the use of automatic controls set to certain conditions, and remotely activated mechanisms relating to power generation and utility synchronization. The standard builds on UL 508A for control panels, including its hardware testing procedures, enclosure construction, spacing, wire ampacity, Class 1 power/ Class 2 control circuits, and functional safety for use in both the US and Canada. Additional guidelines as outlined in Article 725 of the NEC for the classification of remote-control signaling circuits, some construction requirements rely on additional standards related to Generators such as UL2200, Low Voltage circuit breakers UL489 in addition to UL508A for industrial control panels.

Here we’ll take a closer look at some of the essential specifications of UL 6200 and how it affects compliance for power generation and parallels with utility control systems.

ComAp Neo 6000 controller

UL 6200: Important Specifications for Compliance

First, we’ll take a non-exhaustive look at the various components that constitute control mechanisms. While many of these components align with existing safety and usage standards, particularly for electrical components, certain distinctions exist. Following that, we’ll provide insight into the specific components which necessitated UL 6200 and its unique specifications.

Electrical Components

Solid Insulating Materials

Solid insulating materials must comply with UL 746C (US) or CSA 22.2 No. 17 (Canada). There is, however, a list of materials and recommended thicknesses that are eligible for exemption.

Disconnection and Overcurrent Protection Devices

These devices must meet one of the following specifications as covered in either UL 2200, UL 508A (US) or CSA 22.2 No. 14 (Canada). In class 1 power circuits of 30V to1000V, the overcurrent protection must not surpass 167% of the volt-ampere rating over the nominal system voltage.

Switching Devices

A key-operated reset (or another means for locking an “OFF” state) should be utilized with any emergency stop switch that controls a prime mover or excitation circuit. The mechanism should be connected in a manner that prevents it from being bypassed by another local or remote control. Manufacturers and safety officers should also consult standards such as UL 508A and the Standard for Low-Voltage Switchgear and Controlgear – Part 5-1 for panel-mounted start, run, stop, on, off or test switches. Similar standards apply to the evaluation of relays.

Overload Testing

Mandatory overload testing establishes that relays or semiconductor switches can carry designated load levels and sustain an OFF-state without circuit damage or failure. The test entails 50 repetitions at 100-110% of the manufacturer-specified maximum load capacity. Following the test, it is to be confirmed that there was no loss of commutating capability, blocking capability or functionality, and no visual evidence of damage.

Specific UL 6200 Requirements

Generator Paralleling Control Equipment

The standard provides comprehensive guidelines for running paralleling controls between gensets or other power supply sources. These guidelines include ensuring that, at the moment of closure of the paralleling device, its frequency, voltage, and phase angle are within manufacturer-rated ranges. If they are not, the paralleling device should not close. Moreover, the incoming device is required to parallel with the online generator, adhering to the following tolerances:

  1. Frequency: ±0.1%

  2. Voltage: ±5%

  3. Phase angle: ± 10 degree

The exception to these criteria applies to paralleling controls that rely on indirect voltage, frequency, or phase angle methods, which should adhere to the standards for synchronization controls (Section 33).

Safety Circuits

In application, safety circuits mitigate the risk of fire, electric shock, and other personal injury hazards. UL 6200 contains several recommendations about their testing, installation, and performance. These directives encompass a range of applications, including safety circuits responsible for sustaining line pressure in engine-driven fire pump systems, governing detection timeframes, regulating parameters, and ensuring the safeguarding of devices, engines, generators, and pumps. Additionally, they address the imperative task of limiting the consequences of abnormal voltage and overcurrent conditions.


UL6200 adds new testing requirements for Generator paralleling controllers firmware, which is the software that the controller uses to define operating parameters, timing and synchronization functions that affect the system's ability to safely parallel with other power generation or sources of power in a system of sources that the controller is connected to. A manufacturer will submit controllers with a firmware reflecting a control number for certification testing. In the near future, subsequent changes to the firmware will need to be re-evaluated by UL for compliance of the controllers firmware to maintain its UL6200 paralleling certification.

Engine Start Controls

This necessitates including a manual start control and an automatic start control, with the manual having override priority. Automatic start controls must also be configured to prevent the activation of a prime mover while an emergency stop circuit is engaged. The standard also outlines specifications for starting cycles, emergency applications, and the seamless operation of automatic start controls in case of a loss of mains power.

Fuel System Control Circuits

Among the distinctive mandates within UL 6200, these standards are specifically designed to facilitate the operation of automatic fuel stop valves in coordination with fire detection and alarm systems. Their purpose extends to shutting off pumps or valves to prevent the escape of liquid or gaseous fuel. Additionally, when integrated into an electronic protection system, these components must conform to the stipulations outlined in UL 6200 Section 37 (Safety Circuits).

The specifications include risk assessments that consider design faults, environmental impacts, hardware failures, and human error and detail relevant standards, functions, and exceptions that apply to safety circuits in industrial control panels.

What UL 6200 Means

As evident from the selected inclusions from UL 6200, the standard heavily focuses on the increased usage of automatic controls within control panels, specifically those associated with power generation. While UL 508A is still the predominant standard for control panel fabrication. The potential risk associated with high energy power generation and paralleling with utility necessitated a discrete UL standard to ensure complex controllers and paralleling systems remained in compliance and safe to operate.

The present article is intended as a non-exhaustive insight into the various specification categories within UL 6200. The complete standard is accessible through Underwriters Laboratories.


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