The bare bones of protection, the Skeleton Units and their more modern replacements

The following is a full quote of the article Electrical Wholesaler News posted not long ago via, The bare bones of protection, in which someone at MK Electric talks about the difficulties and hardships of using and working with an old-style Skeleton unit. Of course, these days you can use the 17th Edition Consumer units(see the Complete guide to the 17th Edition Consumer Unit and the Wiring Regulations), but many of the homes and buildings today still use the old-style Skeleton Units.

Joanne Reynolds, Senior Marketing Communications Manager of MK Electric looks at the proliferation of Skeleton Units in older public sector housing and how modern replacements take the pain out of dealing with these awkward systems.

As many will hopefully be aware, many local authorities historically (and almost notoriously) favoured Skeleton Units as the main framework for consumer protection within dwellings. They were never much liked by contractors as they can be awkward to work with and can result in some eccentric arrangements – these were particularly popular in the 1960s through to the 1980s. Indeed, it may now seem controversial that an RCD was favoured as the mains rather than circuit isolator.

Reduce hazards

Sometimes referred to as skeleton boards, these are spine backplate assemblies designed to fit within a Mantel or Clifton type enclosure which is essentially a kind of metal utilities cupboard which may also contain the meter. The Institute of Engineering & Technology (IET) who is responsible for the Wiring Regulations never really liked them either, and the 16th Edition of the regulations implicitly concerned itself with their use and paved the way for the introduction of split load boards. This helped obviate hazards arising in fault conditions, such as the RCD tripping as a result of a downstairs lamp blowing and plunging an entire household into darkness.

As an aside, power supply companies, especially in more rural areas, still manage this; and some argue that there’s little point in protecting against an internal fault when the same external one can still arise.  Of course, installers working with older social housing still encounter these and experience difficulties in bringing a property up to current electrical safety standards.

Consequently, while the concept of Skeleton Units is effectively obsolete for new installations, most manufacturers still offer them for replacement purposes. This is because the applications and/or locations can make it extremely difficult to substitute them with a current consumer unit – either for reasons of space, or the ability/inability to provide sufficient circuits. Happily, the modern equivalents take much of the fuss out of dealing with them away, and provide a far faster, cleaner and easier installation than would previously have been the case.

Make improvements

Needless to say, 17th Edition regulations apply as one might expect; and this pressure has combined with the Government’s Decent Homes Initiative targets to make the replacement of these old-style installations imperative. So a great opportunity exists to improve the electrical safety of such properties through up-to-the-minute units; but also to improve the overall quality of housing stock which is conceivably one of the country’s greatest built assets.

Necessarily, high quality proprietorial products are available to make this possible, all of which might be explained by the phrase ‘get the right busbar and you can make any combination of split load’. From the stockist’s perspective, you will never shift millions of these, but they definitely have their market opportunity and the cost and space implications of having a few to hand are negligible. So when an installer needs, and has to have one, because there’s nothing really else that will do, you will have the right product on your
shelves to satisfy his requirement.

Features

As mentioned above, there are a number or proprietorial equivalents out there but when seeking to satisfy the particular needs of the installer and end-user alike, there are a number of features that really ought to be incorporated. Look for a DIN rail that is easily removable, as this improves first fix (although remember that if any unused ways are required, a DIN rail mounted blanking plate must be used to complete the installation). Backed out and captive combi-head screws also make for a quicker and easier installation; while modern versions should, against the cramped styles of old, offer far better wiring space to, among other things, allow provision for RCBOs.

Flexibility

Importantly, flexible neutral bar configurations and a floating busbar system (one that can be cut according to the number of devices fitted) are very useful to enable a wide combination of protected and unprotected circuits as well as offer configuration flexibility depending on local authority requirements (be it single/dual RCD/all RCBOs).

If truth be told, no-one really liked dealing with the older-style Skeleton Units if they can help it and it may be thought annoying that they got such a grip in the public sector when they did. That said, they are a frequently encountered reality, and when a Skeleton Unit is all that can replace a Skeleton Unit then at least up-to-date versions now exist that can take much of the pain (and swearing) out of their installation.

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