A Complete Guide to Site Transformers

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Also sometimes called junction box transformers, site transformers are usually utilized on construction or industrial sites to safely supply power for tools, equipment and lighting. Voltage transformers are particularly important if multiple devices are being used simultaneously since it prevents overloading.  

What is 110V? 

Beneficial in areas with a high workload and large building sites, 110V voltage tools are often used in professional situations for safety reasons. Site transformers, in turn, are used to convert the standard power supply of 240V to 110V. Usually yellow in colour, site transformers produce the power output in lines — 2 x 55V. Since the lower voltage is less likely to lead to serious injury or even fatality in case a wire is accidentally cut or damaged, 110V is the accepted general standard for work sites today.  

Do You Need 110V? 

While a 110V power supply is not usually a regulatory requirement in the UK and other countries, it is required by many insurance companies. After all, 110V is very important when it comes to minimising the risk of death and injury caused by electrical problems on construction and industrial sites.  

How to Ensure 110V Power? 

While many large worksites are connected to power generators with 110V sockets, those that do not need to invest in a quality junction box transformer. Ranging in size, site transformers come with a different number of sockets. They are also much more reliable than residual current devices (RCDs), which may fail to find every fault in a 240V system. 

How Do 110V and 240V Equipment and Tools Differ? 

There is a simple difference between 110V and 240V equipment. While 240V tools are compatible with standard power points found in homes, 110V tools are specifically designed for use on construction and industrial sites. As such, 240V tools are best for use on DIY projects around the home and small workshops while 110V tools are suitable for use in large workshops and on construction sites. A junction box transformer is required to operate 110V tools in a 240V environment and vice versa. There is absolutely no difference in the power output of 110V and 240V tools. 

What Do 240V to 110V Site Transformers Do? 

A great alternative to circuit breakers, site transformers reduce the power voltage from 240V to a much safer 110V. They usually feature 2 x 55V lines, which means that the voltage is halved if an accident does happen to take place. Many workplaces view site transformers as an essential component of their internal occupational health and safety regulations.  

Site transformers are ultra-versatile and can also be used in domestic settings. If a power tool is only available in 110V (many hire tools only come in 110V), you can use a junction box transformer to convert it from 110V into 240V for use on DIY projects at home. 

Industrial Lighting 

Lighting can be an important component of workshops and construction sites. And just like power tools, it also sometimes requires voltage conversion from 240V into 110V to prevent any electrical overloads. As an aside, lighting transformers are also sometimes used in household situations to make light brighter or dimmer. With this in mind, here are some common light types for industrial situations.  

Work Lights

Designed for both indoor and outdoor use, most work lights are sturdy enough to stand up to all kinds of weather as well as the occasional knocks and bumps. Work lights are mountable or freestanding and can be either main powered or rechargeable to suit any worksite or workshop. 


Site Lighting 

110v site lighting is often used on large worksites that require a great deal of light. They are typically used in large indoor workshops and on construction sites that require tradespeople to work at night. 

Inspection Lamps 

Highly portable, inspection lamps are a great tool to keep in your car or even bag in case you need a powerful source of light. Mains powered or rechargeable, inspection lamps are impact-resistant and great for dealing with emergencies. Many inspection lamps even come with magnets and hooks so you know exactly where to find them. 

Industrial Extension Leads 

Whether for tools or lighting, industrial extension leads are essential if you are working away from power points. Most industrial extension leads are sturdy enough for both indoor and outdoor use. Plus, they can be as long as 40 metres. 110V extension leads are usually used on industrial and construction sites.  

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DC (or direct current) is only used in electronic equipment powered by a battery. AC (or alternating current), on the other hand, is used to power all other electrical devices. Site transformers also operate only on AC electricity. In fact, they are used to increase or decrease the level of AC current or voltage. 

Plugging a 110V appliance into a 220V power point may cause the power to quadruple when the device is switched on. If this happens the device will become overvoltaged and may start emitting smoke and sparks. The fuse could also melt, damaging the appliance. This is why you should never plug a 110V tool or appliance into a 220V power point without a site transformer.  


Converting a 110V power point into a 220V power point is not an easy job. As such, this job is best left to the professionals. Rather than changing the power source, a much easier option is using a site transformer to step up 110V power source into a 220V power point. 

Step down site transformers convert, or step down, electricity from 220V to 110V. Step up site transformers, on the other hand, convert, or step up, electricity from 110V to 220V. All site transformers are grounded and have in-built fuses to minimise any risks of electric shocks. 

It is possible to use several tools on the same site transformer simultaneously provided that its wattage capacity is not exceeded.  To minimise the risk of power fluctuations and damage to your tools, set up your site to run at 80% of its maximum recommended wattage. 


While you may find different people referring to 110V, 115V and 120V when it comes to the voltage of power tools, essentially this means the same thing. This is because 120V is likely to drop to 115V when it reaches the power tool. And if you are using an industrial extension lead, it could even drop to 110V by the time the voltage reaches the equipment it is supposed to power. The 110V rating means that a tool will still operate at this lower voltage. The same situation goes for 220V, 230V and 240V — they are all essentially referring to the same voltage set up.  

The lifespan of a site transformer is between 25 and 40 years. Site transformers usually only fail in cases where another part in the electrical system short-circuits. If this happens to take place, it is essential to find out the exact nature of the problem that caused the short-circuit. If this is not done and the site transformer is replaced, the same issue is likely to happen again.