As all ce-related directives this is a new-approach directive, which means that only main requirements (essential requirements) are required. The LV-directive shows the way of showing compliance to the main requirements.

Using a list of harmonized standards a manufacturer may assess the safety of it¡¯s product or apparatus.

Manufacturers declaration

• The manufacturers declaration consists mainly of a liability statement from the manufacturer or importing agent in which he accepts the legal consequences (liability) for conformity of it¡¯s equipment  to the LVD-essential requirements. The manufacturer is granted permission to do the testing himself, or let the testing be executed by any test-house. Using this route the manufacturer is strongly suggested to use the so-called Harmonized Standards for type testing, although in absence of these any other safety standard or no standard at all may be applied. 
  Harmonized  standards, especially created for this purpose and modified existing standards are published in the official newspaper of the EC (OJEC), and in the official journals of all EC-members.  

Purchase a model ce declaration of conformity    

Technical Construction File  (TCF).

In order to prove compliance to the essential requirements of the LVD one has to make up a Technical Construction File. This includes all safety related topics, such as precautions, instructions, test reports and everything necessary to identify the apparatus, such as circuit diagrams, mechanical drawings and detailed part lists.

The LVD is not  about electrical safety only. 

Once an apparatus falls into the scope of it, many other aspects of safety like fire hazards, mechanical hazards, radiation and chemical hazards are part of the approval procedure.

Future developments will bring more and more apparatuses within the scope of safety directives.

Basic Safety Concepts

Protection against electrical shock

Electrical safety is implemented using the concept of double safety layers:

1. Isolation + Grounding
2. Insulation + Extra Insulation (double or re-enforced insulation)

Any part at  hazardous voltage should be separated from the operator by 2 layers of safety like specified under 1. or 2.

In addition to this both layers are not to be affected in their efficacy in the CASE OF ANY SINGLE FAULT (loose wire, defective component, loss of earth etc.)

Misuse (foreseeable abuse) of an equipment is considered as a single fault.

The LVD approval procedure is based on the utilization of approved parts in all applicable circuits (most important  in the mains circuit). 

This implies that all parts having a safety function need an examination to their specifications and (if applicable) need a ce-declaration of conformity available, before they are  allowed in the construction of an apparatus.

Component manufacturers in generally are not very cooperative  in producing accurate declarations, as a ce-declaration of conformity involves direct liability of the manufacturer for the safety of it¡¯s components .  A UL, CSA or VDE declaration -although very valuable- is a testimonial declaration and not a manufacturers declaration: less liability for the manufacturer is involved. Most US originated equipment lacks sufficient component safety due to the difference in mains voltage. Although manufacturers may specify a product as being suitable for 250 Vac, this does not imply that the same component is safe at 250 Vac. 

Many more requirements exist considering hazards associated with heat, fire propagation, radiation, mechanical hazards (sharp edges), short circuits, leakage current (touch current) and more.

The electrical safety test procedures are not to be underestimated !

Harmonized standards

This list of standards is an ever increasing subset of world-wide existing standards, that due to their way of defining test-methods, limits and susceptibility criteria, are very well suited for testing by the manufacturer himself, or by any test house using the right equipment

This list of standards is published approximately  once a year.

<list of harmonized standards for the LVD>

Routine testing

The Declaration of Conformity is most often based on a one sample of a "type tested product" that ideally should be identically reproduced in series. In order to maintain safety in real life production, some quality control is imperative. The LVD specifies the requirement of such a scheme.  Therefore each and every  produced apparatus must be numbered and verified for a list of essential parameters -composed by your test house- such as functionality, dielectric strength , the grounding qualities and potential pitfalls created by foreseeable mistakes in production.

This focuses the attention on those faults that are easily made without being detected in functionality tests, and that may create a potential hazard to the operator. Examples are grounding clips, insulation barriers, warning labels, insulation (rubber) rings below ring core transformers etc.

In general, safety measures should be exclusively for the safety purpose, and should not share functionality , unless the safety measure  is very obvious. Safety features must be visible and easy distinguishable .

Routine test must be logged, therefore serial numbering your equipment is required.

Standards exist  for setting up these so-called routine tests::

• House hold appliances    EN 50106
• Hand held motor operated tools    EN 50144-1
• Luminaries    ENEC 303
• ITE equipment    EN 50116

Your test house will be helpful in selecting a routine type test protocol.

Most popular failures....

Insufficient insulation distances in connectors and printed circuit boards.

Although exceptions exist, the insulation between metal parts and hazardous voltages (mains) must be no less of 4 mm and up to 8 mm in medical equipment.

Unknown safety status of safety critical components

Not only equipment but also components must be tested for safety. Most components comply to international IEC or EN standards. Equipment brought to Europe often uses  UL or CSA approved components. 
This is not necessarily sufficient for safe operation at 230 Vac.

In many cases approval by UL is for 115 Volts only instead of 230 Vac for Europe. Often no safety indication  is available but a small sign on the back saying UL or CSA. 

You definitely have to make sure that your components are suitable for European voltages and make sure they are sold to you with written proof of compliance. Just a catalogue page showing the ce mark in the corner won¡¯t do ! If it¡¯s writing "designed for (to) comply with .[standard]..  ¡¯  or "tested for [standard]...." , then you can be sure the part is not compliant.  Look for the phrase: 

"Compliant with [standard] " 

and then don¡¯t forget to check it¡¯s the correct standard  and not an obsolete one.........!

Correct part number and applied standard are best be mentioned on a signed document.

Undefined parts

You must have seen that in your product¡¯s Bill of Materials:  many parts have no specified type or manufacturers name behind them. How can you be sure that this part performs the required function, and how can you declare liability for the safety of those parts ? 
Make sure you know who¡¯s manufacturing the building blocks of your equipment, and on which components the safety of your equipment and reputation of your brand relies.

Did you make a grounding diagram ?

Incomplete manuals

All equipment should ideally be  accompanied by the following documents:

• Compliance declaration
• Statement of origin
• Safety manual
• Installation Manual
• Operators manual
• Service manual