Circuit Breaker Lockout Design – an R&D Journey

Mitsubishi CP30BA LockoutThere seems to be an infinite number of miniature circuit breakers, RCD’s, MCCB’s and Circuit Protectors on the market and their shape and size are constantly evolving as manufacturers seek out improvements and refinements in their design.

This creates an additional challenge for manufacturers of locking devices.

It’s widely acknowledged that a circuit breaker is a primary isolation point as a means to de-energize and lock off when maintenance work is required.

  • This is stipulated in the OSHA standard for The Control of Hazardous Energy (Lockout/Tagout) (29 CFR 1910.147) for general industry. So, the need for some form of lockout device is essential for all variants.
  • For more complex breaker designs, often the manufacturer will produce their own OEM Accessory locking device. For all the rest, users rely on after-market solutions from manufacturers such as Brady, Master Lock, Abus and a growing group of manufacturers from Asia.

But there are always some circuit breakers that fall through the gaps and no viable locking device can be found.

At Total Lockout, we identified this issue and devised a way to overcome it by designing and producing new circuit breaker locking devices on an ad-hoc basis.

The latest 3D Printing equipment can produce robust and durable finished products which are wholly viable for extended use.

Our latest project is for a Mitsubishi CP30-BA Circuit Protector. As lockout equipment designers we view any new project without any regard for the electrical specification and function, but more in consideration of its mechanical function. How can we effectively and safely block the movement of the toggle? In this case, the device has a wide toggle (on/off rocker), is very slim in cross-section, and has little movement from the on to off positions.

To begin, we mapped out the cross-sectional profile of the breaker. It was necessary to disassemble the breaker to allow for accurate measurement of the toggle. With these dimensions to hand, we printed and cut out a paper profile. Once we were satisfied the profile was accurate, we moved to produce a laser-cut model from 3mm thick acrylic. This allowed us to prove that the device would move into and out of position unhindered and without snagging.

The next stage of the process is to move to a pre-production 3D print. This will give us further validation of the profile, but also enable us to add finishing features like the threaded hole for the socket grub screw, ensuring the device will stay in place.

So there you have it, just one example of the R&D journey to produce a new product in a short timescale at an affordable price that Total Lockout has undertaken. A great demonstration of our experience, expertise and engineering background that allow us to create bespoke solutions for customers to fit their exact specifications.


In this instance, our customer ordered 100 pieces. From start to finish the project took 4 weeks.

Mitsubishi CP30BA Lockout