27 Jan 2011 - MCB Lockout Comparison

27 January 2011

Introduction:

There are hundreds of different makes and model of Miniature Circuit Breakers (MCB) on the market. Choosing the right lockout device can seem daunting. With the guidance provided in this article, and reference to our selection guide, the choice is made much simpler. With a well fitted MCB lockout, secured in place with a safety padlock, workers are protected against the risk of unexpected start-up or energization of the electrical circuit.

Preamble

This product focus relates only to low voltage breakers; the type that you might find in a domestic or commercial consumer unit which clip on to a standard DIN rail. There are many other breaker types on the market which grow in size as the voltage increases. These large breaker lockouts are not included in this article.

Lockout Types

In this article we make a comparison between the MCB lockouts manufactured by Brady and Master Lock. There are four different versions from each manufacturer each designed to fit the same range of breakers. These are illustrated below.

Given the application similarities of these devices, choice is often made simply on price alone. Indeed there is quite a contrast in price with the Brady versions costing more than twice that of the Master Lock versions. This article aims to provide an objective comparison which highlights the various features and gives the authors opinion of the price variance.

Function

The first three devices in each range work by engaging wire pins into small holes located either side of the MCB switch toggle.

In order to engage the pins into the holes, they have to be exposed further. On the Brady version, this is achieved by pressing the spring loaded plunger with the thumb. On the Master Lock version, the two halves of the lockout device hinge apart. See Figures 3 & 4.

Having exposed the wire pins in this way, they can now be manipulated into the engagement holes on the breaker. This is fiddly task on both versions and requires some dexterity. However, once the task has been successfully completed, one can quickly gain ‘the knack’ making subsequent attempts quite straight forward.

Once fitted, the padlock can be easily added. On the Brady version, the spring loaded plunger retracts exposing the padlock hole. On the Master Lock version, the two halves must be hinged together to align the padlock holes.

The padlock hole diameter on the Brady version is 7.35mm, on the Master Lock version is it 7.9mm. Given that most safety lockout padlocks have a shackle diameter between 5mm and 6.5mm, both are perfectly adequate.

The second versions in each range (Master Lock S2391 and Brady POW) are designed to fit on MCB breaker toggles with a wider engagement hole setting. However on the Master Lock version the width of the wire pins is only marginally wider than their other version S2390; on that note it’s less obvious that these two (S2390 and S2391) are different. To compensate for this, the latter has a red thumb pad, whereas the former is black.

The third versions in each range (Master Lock S2392 and Brady PIS) are designed to fit on MCB’s where the engagement holes are inset from the edge of the breaker.

The fourth versions in each range (Master Lock S2393 and Brady TBLO) offer a degree of universality. Both can be used on multi-pole breakers which are operated with a tie-bar. The Master Lock version can also be used as a substitute for the other versions in the range, giving wider appeal. You could effectively use this version alone for most MCB’s; this capability is not possible with Brady’s TBLO device. The Master Lock version is fixed to the breaker using a small screw driver which drives a pointed grub-screw into the breaker toggle creating a small indentation. Repeated attachment to the same breaker may cause damage, eventually preventing the lockout from attaching.

Build Quality

Overall, the Brady version feels better made. In their literature Brady state that their MCB lockouts are made from glass-filled nylon. Master Lock does not state the material of manufacture in their literature although the plastic does ‘feel’ more fragile.

Fit for purpose

When fitted to the MCB, a small amount of force could be used to tear either device from the breaker. However in doing so, both manufacturers’ products remain undamaged. Damage occurs to the breaker itself with the engagement holes being split open. On this point attention is drawn to Section 8 of The Health & Safety at Work etc. Act 1974 which “Places a duty on everyone not to intentionally or recklessly interfere with or misuse anything provided in the interests of health, safety and welfare”.
Individuals contemplating such action to override a lockout, should be mindful of this and not only the legal consequences but also the personal ones.

Conclusions

In all cases, each lockout from both manufacturers was found to fit to the MCB’s for which they are specified. All perform the function for which they are designed. As previously mentioned, Master Lock’s S2393 offers some universality, potentially negating the need for some of the others in the range. That said, it may not fit quite so well as others which are specifically designed for their host MCB although this aspect has not been fully assessed in this comparison.

The Brady versions are of better quality manufacture and feel more ergonomic. They are marginally easier to fit on the MCB than the equivalent Master Lock equivalent.

Despite all this, at less than half the cost of the Brady range, Master Lock’s MCB lockouts are perfectly fit for purpose. The occasional breakage is tolerable given the cost saving available.