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  • What is 110v & do we need it?

  • 110v Transformer

    What is 110v?

    A question we often get from some of our customers is what is 110v and do we really need it? or at least why is it universally used across larger building sites?

    Well if you want to work on any site other than small residential refurbishments, then yes you probably do need 110v. This may not be the law but is certainly accepted practice. The decision allegedly lies with site agent/ foreman but far more likely with the insurance company that insures the site.

    Do we need 110v?

    The law states that you must take precautions against the risk of death or injury from electricity during construction. So legally there is no reason that you cannot use an RCD (Residual current (trip) device) and 240v. Some would argue that you are just as well protected if not better protected using 240v and an RCD. This device detects faults in the electrical system and rapidly switches off the supply. The problem with an RCD however, is that it can fail and also does not detect every single fault in a system which makes it unreliable.

    If you are allowed to use 240v (really 230v + or – 10v) then not only must you use an RCD but your tools should be tested before being brought onto site. They should then be inspected at the start of every shift and should be further tested every month. This is generally considered to be good practice for all voltage tools.

    110v Cable

    Although it may not be law to use 110v on site, on large sites where there are numerous trailing cables, trades and organizations all working in the same area 110v is considered to be the safest. This is unlikely to change in the foreseeable future because a broken or forgotten RCD could result in injury or even death. No site agent would want to leave themselves open to criminal charges in these circumstances as they would be considered negligent and to have failed in their duty of care.

    The advice from HSE (health and safety executive) is that tools, plugs and cable designed for domestic use are not suitable for site conditions. You should use cordless tools or those that operate from an 110v (CTE) center tapped to an earth supply system so that the maximum voltage to earth does not exceed 55v.

    110v Site transformers are center tapped, this means that they are essentially dual phase, meaning that 110v is actually reduced to 2 x 55v. This lower voltage and current is much safer to use, and it is unlikely to have the punch to cause you problems if you accidently stepped on a live wire in your safety boots. But remember your environment can have a dramatic impact on the behavior of electricity. The presence of water/ moisture or metal will mean that electricity may behave differently then you might otherwise anticipate.

    How do we make sure we’re using 110v?

    Most larger sites will have an onsite generator with 110v sockets attached to it, however if this isn’t available then its pretty imperative that you invest in a transformer. These small but surprisingly robust units seamlessly convert your 240v current into 110v and in most examples then split that current into 2, 4 or 6 plug outlets.

    At ITS we offer a large variety of these 110v transformers, cables and plugs, so if you’re soon to be working on a large site be sure to have a look at our range to make sure that you are as prepared as can be before work starts.

    Top tip

    Have you ever noticed your 110v saws sometimes appear to be underpowered? If so this is likely to be because you are using a long extension cable, the further away you are from a power source (not the transformer but the actual power source) the more likely you are to get a drop in power. To solve this problem you need to use a shorter extension lead.

    For more information on the legal ramifications or specifications please refer to the HSE website here.

    Please comment on and share this article (by clicking below) with colleagues or site managers to ensure that your friends/associates are not putting themselves or others in danger by cutting corners with regards to on site electrical safety.

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    11 comments on “What is 110v & do we need it?
    1. Ron says:

      If I buy a 110v circular saw here in the UK what damage will happen to my saw if I plug it in without a converter and if it does damage the saw it seems pointless for me to buy it cause it seems silly to spend more money to keep from ruining it. I’ll just buy the 240v

      • Richard Hughes says:

        Hi Ron,

        Firstly the 110v models only come with a 110v plug/cable, so you won’t be able to plug them in without a converter/transformer or 110v terminal anyway. That is why they are best for sites.

        If you’re most likely going to be using the tool in a ‘240v’ enviorment like a house or office then getting a 240v tool is your best bet. If you’re going to be using it on a jobsite then 110v would be better.

        You can’t plug in a 110v tool into a 240v socket so it comes down to what sockets you’ll have near you.

        Hope this helps.

    2. Gary says:

      Hi Ron
      I have a generator that kicks out 110 volts on the live wire only . The earth is ok , the third wire is zero volts . My question is would this damage my work tools . Also would I be breaking any uk regulations using it on site ?

    3. Tia says:


      Do we need to plug a transformer in 230V with RCD?

    4. Ove Gram Nipen says:

      110V at job sites and 240V everywhere else? You guys are insane.

      • Job and Knock says:

        Maybe, maybe not. I was working in Germany a few years back when a young lad on the same site was badly injured when accidentally dropped a cracked 230 volt extension cable into a puddle and electrocuted himself. The RCD was found to be non-working so it didn’t cut out. In more than 35 years on sites in the UK I have never seen or heard of such an occurence, and as an SMSTS foreman I do recieve a lot of safety digests and updates from a variety of sources. So maybe not so crazy after all

    5. david lammie says:

      hi i was just wondering i have a 110 transformer would i be able to this for outdoor christmas lights if so would i loss any power in these lights i would be plugging it in from my house supply or would it be dangerous to use

    6. guy lvongstone says:

      How often does my 110v tools need to be Pac tested on a uk building site

    7. Rodders says:

      Main text states “This lower voltage and current is much safer to use.”
      The voltage is lower (approx half) but the current will be higher, not lower (approx double) to supply the same wattage.

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