Panel Builder US

PBUS Siemens logo 400August 11, 2020

To protect people from injuries caused by electricity, control panels that are used in the U.S. must be designed so that they ensure protection against direct contact. This means that no live parts can be touched under normal operating conditions.

The U.S. standards therefore specify that the enclosure doors must be locked in accordance with specific guidelines, but that they must be accessible for maintenance and service by qualified personnel.

 


Panel Building Tips Part 1:       Door Interlocking Requirements According to US Standards

 

When do I need door interlocking and which conditions must the interlocking meet? PBUS Siemens 1

The following U.S. standards specify in which cases and under which conditions door interlocking must be installed:

-- UL508A (section 66.1.2 and 66.1.3)

-- NFPA79 (section 6.2.4 and 6.2.5) 

When an industrial control panel controls industrial machinery and operates under a voltage more than 50 V AC / 60 V DC, each door of the control panel must be locked with the disconnecting means (e.g. the main switch) so that the door can only be opened when the disconnecting means is switched off.

To do this, the following methods are available:

1. Purely mechanical, e.g. using the main switch
2. Electrical
3. Combination of mechanical and electrical

 PBUS Siemens 2

The door interlocking must also meet the following conditions:

1. Defeat the interlock
It must be possible for a qualified person to defeat the interlock with a tool so that the door can be opened for service and maintenance with the main switch being switched on.

2. Snap lock function
The interlocking must be activated automatically when closing the doors without additional measures (snap lock function).

3. Blocking of disconnecting means
With an open control panel door, activation of the disconnecting means must be blocked by the interlocking.

Exception: It must be possible for a qualified person to override this safety function with a deliberate action.

You can find detailed information in the reference manual "Industrial Control Panels and Electrical Equipment of Industrial Machinery for North America" (section 5.4 Protective measures)

 

Accessories for door interlocking according to UL 508A and NFPA 79

PBUS Siemens 3With more than 500 accessory components, the 3VA molded-case circuit breakers can be configured according to your needs, be expanded to include additional functions and can be adjusted to meet specific requirements.

The manual Max-Flex drive with Bowden cable can be ordered as a convenient kit with switching mechanism, Bowden cable and metal lever.It can also be ordered separately. It offers different Bowden cable lengths and levers for the series 3VA5 and 3VA6. With motor and manual drives with and without Bowden cable, various interlocking options as well as auxiliary and alarm switches, you can easily meet all requirements.

❯ 3VA molded-case circuit breakers with UL approval UL489 (up to 600 A)

❯ 3VL Molded Case Circuit Breakers up to 1600 A acc. to UL 489

 

 When can I forego door interlocking?

A control panel can be designed without door interlocking under the following conditions:

1. Operating voltage < 50 V AC/60 V DC orIt does not control industrial machinery or
2.
It has no door (e.g. only a cover without hinges) or
3.
It does not have its own disconnecting means and
-
it is located at a maximum distance of 15 m and within sight of the control panel with the disconnecting means and
-
is only accessible for qualified persons and
-
it can only be opened with a key or a tool

 

Application example: Electrical door interlocking for any number of control panel doors

For lack of space, the controlling system of a machine or plant must often be distributed over multiple industrial control panels, e.g. side-by-side or decentral panels. As decentral industrial control panels without own disconnecting means, these panels may be supplied by a main control panel with the corresponding main disconnecting means when the following conditions are met:

1. The decentral industrial control panels located directly in sight of the main panel
2. These decentral industrial control panels are located not more than 15 m from the main control panel
3. Like the main control panel, the decentral control panel must be interlocked with the main disconnect inside the main control panel

The advantage of this solution is that only one disconnecting means must be installed with the specified comprehensive identifications. For an individual control panel, it is easiest to design the door interlocking as purely mechanical, for example, by means of a door-coupling rotary operating mechanism of the main switch. The more doors that are coupled to the main switch, however, the higher the demands on construction and design to meet the purely mechanical requirements.

Our recommendation:

An electrical door interlocking with position switch can be easily implemented for any number of doors.

 

Application Example: Main control panel with decentral control panels without own main switch. 

PBUS Siemens 4 The door interlocking in the main control panel is implemented mechanically by using the door-coupling rotary operating mechanism of the 3VA molded-case circuit breaker used as main switch. The decentralized control panels  are equipped with electrical door interlocking.

A position switch is at the center of the application; it is located directly on the door of the decentralized control panels and has two important functions

1. It interlocks the door when the main switch is switched on

2. It signals whether the door is open or closed; this prevents switching on the main switch even though the door of a decentral control panel is still open

 

 

Opening the door with closed main switch (defeating).

For service and maintenance work with live components, the interlocking of the distributed control cabinets must be defeated with a tool. In this application, the tool is a key for a key-operated pushbutton that starts a time relay. The door interlocking is disabled for a set time period by the time relay, and the control cabinet can be opened with live components.

Three indicator lights are located on the main cabinet which indicate the following:

  • 1st light: All doors are closed
  • 2nd light: Main switch is switched on
  • 3rd light: Defeating is active (door interlocking temporarily suspended)

 

> SIRIUS ACT (switches, pilot devices)

> 3VA molded case circuit breaker

> LOGO! Logic Module

 

Download our free application examples.

Electronic Door Interlocking: In this application, we show you how to comply with the requirements of the US standards for mechanical/electronic door interlocks with a LOGO! controller for distributed control panels with any number of doors, while at the same time saving efforts and costs.

Electric Door Interlocking: In this application example, we show you how to comply with the requirements of the US standards for door interlocks for distributed control panels with any number of doors, while at the same time saving effort and costs.

 

 Check out an explanatory video here!

 

Source 

Editor's Pick: Featured Product News


 

Design and controls engineers can now more easily access, configure and manage HART devices using the new Allen-Bradley FLEX 5000 highly integrated HART I/O modules. The simplified programming experience, available with the Studio 5000 Logix Designer application, can help simplify design, maintenance and operational productivity.

Read More

 

Products for Panel Builders

  • Prev
What if you can achieve better system performance, capacity, productivity, and security to meet the ...
Provides similar user experience of PCAP panels at a lower cost for industrial automation and ...
Insulation type MTW machine tool wire is now available in 22-gauge from AutomationDirect. Existing ...
Trace Software International was recently pleased to announce a cooperation between ...
Connectivity between production and automation systems in process manufacturing and the Internet is ...
Small, compact and now touch-proof: All connectors in WAGO's WINSTA MINI Pluggable ...
Control cabinets are important for the trouble-free operation of machinery, equipment and building ...
TDK Corporation has been granted a United States patent for the GENESYS+ series of programmable ...
Grace Engineered Products has developed a full line of IIoT smart devices for monitoring asset ...

Article Feature - Monthly Industry Focus


 

 

After a lengthy period of connector manufacturers pursuing various approaches with regard to M12 PushPull locks, IEC 61076-2-010 is now finally bringing a system that is consistent across the industry. Or at least that is the opinion held by Dirk-Peter Post, Head of Global Product Management Circular Interface Connectors, Harting Electronics, and Jürgen Sahm, Senior Specialist Product Marketing Circular Connectors, Phoenix Contact, in this interview. 

Read More

News for Panel Builders

News for Panel Builders
  • Prev
A friendly reminder that Tips and tricks for industrial control panels for North America begins ...
Since KEB is a German-based company, they have a long history connecting their PROFIBUS and ...
Launched this May, the HARTING Technology Group is now continuing its successful "HARTING ...
Graybar recently announced the election of Dennis E. DeSousa to its Board of Directors. Dennis ...
Emerson has recently signed a joint commercialization agreement with Integra CMS, a specialty ...
CIP Safety - short for "Common Industrial Protocol" - is designed to provide fail-safe ...
TTI, Inc., a distributor of electronic components, was pleased to recently introduce a suite of ...
nVent Electric plc recenly announced its participation in the 2020 RBC Capital Markets Global ...
Sterling Systems & Controls, Inc. is a dealer in custom engineered and manufactured automatic ...

 

A sudden power outage can be a critical issue for businesses and organizations. If something happens to the power, then it’s important to get things up and running as soon as possible.

For example, a construction company that is working in a remote or isolated location may be at risk for power outages. A back-up generator will minimize the risk of the operation losing power and the project getting significantly delayed.

Read More

 


 



C&K ZMW Series

 

C&K has launched a silent, sealed, subminiature, snap-acting switch series that offers precise actuation in automotive applications. The compact ZMW Series snap-acting switch combines a long stroke with more than 2 mm of over travel for reliable actuation. The ZMW Series is used in rugged environments including automotive, industrial, white good and other applications.

Read More

 

 

FACTS Engineering, the manufacturer of Productivity PLCs for AutomationDirect, has successfully received ABS (American Bureau of Shipping) certification for Productivity2000 and Productivity3000 PLCs.

ABS is a provider of classification and technical advisory services to the marine and offshore industries and is focused on safe and practical application of advanced technologies and digital solutions. For more than 150 years, ABS has been at the forefront of marine and offshore energy innovation, tackling the most pressing technical, operational and regulatory challenges so the marine and offshore industries can operate safely, securely and responsibly.

 Read More