If you're in the trade you're probably aware of the requirement for installing devices (MCBs, RCDs etc.) using manufacturers' torque settings.
My own certification partner, Elecsa, informs me that although having a calibrated torque screwdriver isn't a certification requirement per se, it is the case that should a fire occur in a board I have installed, questions will be asked, and if I can not demonstrate that I have installed the board using the manufacturer's published torque settings, I may be regarded as liable.
At a recent trade show, a manufacturer asked electricians to turn a handheld screwdriver in a calibration unit with a torque of 2.5Nm, working blind. Not one professional electrician I saw even got close. It was a good demonstration that you can't reliably or accurately apply correct torques by hand.
Several manufacturers offer torque screwdrivers. I opted for the WIHA Vario-S.
Various kits are available from WIHA with different torque ranges, blade sets and cases / holder options. My preference was for the basic electrician's kit (torque range 1.0-5.0Nm and two blades, sold as model 2872, option 26626), which I purchased along with their LiftUp VDE Magazine Bit Holder which gave me an additional handle and a range of bits.
The Vario-S 2872 is supplied in a small reusable plastic box as a torque handle, along with:
The Vario-S requires an additional tool to adjust the torque setting. Some other manufacturers' systems do not require this; it is an additional tool to lose and without it, the screwdriver is pretty valueless.
However, setting is easy: you simply insert the adjustment tool and turn it until the required torque appears in the window below the handle. Then remove the adjustment tool, insert the blade adapter, which pushes positively into place, and then insert your blade of choice.
You will of course need to know the required torque setting for the item you are installing. Where instructions are provided, torque settings are sometimes (not always) listed. However, not every manufacturer provides a data sheet with all products. In practice I found manufacturers' websites listed appropriate torque settings for all the brands I commonly encounter, and I pulled these together into a single list for ease of reference. Most manufacturers list different torque settings for terminal bars, main switches, RCDs and MCBs / RCBOs, and they vary somewhat between manufacturer and between ranges from the same manufacturer, so it's pointless trying to guess.
As with all torque tools, the screwdriver should be set to zero prior to storage. Note that it will also need annual calibration.
Once set up, you simply use the Vario-S to tighten the screw until it clicks once. If you continue turning, it continues clicking and will not tighten the screw any further. It really is that simple.
Although the torque function appears to still be active when unscrewing, in practice I found that screws torqued up to the correct settings could still be removed without having to change drivers; this saves time and extra tools.
Changing blades is also easy; the blade holder has a collar which releases the blade when slid towards the tip, and locks the blade in place when pulled towards the handle. The blade holder is compatible with a large range of VDE blades supplied by WIHA. In practice, most electricians will use the Xeno terminal blades the vast majority of the time.
When installing a board, for example, the Vario-S is fast and easy to use. There's something satisfying about hearing the click and knowing you've just set the torque exactly right; the satisfaction of a job well done, perhaps.
I have found some MCBs difficult to set to the correct torque simply because the cable clamp twists and distorts when you tighten them up, but this is purely a fault with the MCBs, not the torque screwdriver.
My local wholesaler estimates that only 10% of electricians in this area use a torque screwdriver. Some of us have been scared into buying one by our certification partners; in my case I opted for one for peace of mind.
The answer depends on your definition of "need". No, you don't legally have to shell out £100 or so on a torque screwdriver. However, having used this one for a while, I'm very glad I did; it's a precise, professional tool which speeds up my workflow and also creates a good impression on customers.
Maybe having it will one day save a board from catching fire, and if this is the case, I know that I can look the investigator in the eye and tell him the board was installed entirely according to the manufacturer's specification.
If you are looking for a torque screwdriver, the WIHA Vario-S offers a high-quality tool with a range of blades and accessories. It's fast and efficient to use, and will give you peace of mind that you're always working safely and within the regulations.
The need for an adjustment tool may sway some users towards other brands but I'm happy to trade this minor inconvenience for the quality and performance of the tool.
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Malborough, Devon TQ7 3SU
Tel: 01548 561561
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