Some thoughts on multiple socket extension board checks and tests.
I would appreciate any feedback comments.
Bill
Recent Safety Notices highlight electrical hazards associated with the widespread use of mains extension blocks (Multiple Portable Socket-Outlets) in clinical environments.
MDA SN 2002(26) – Use of mains extension leads
SHS SAN(SC)02/34 - Electrical extension leads: electrical hazards (Scottish)
MDA/2003/015 – All medical electrical equipment
Risks can arise when medical electrical equipment is connected to other medical or non-medical electrical equipment, or when it is connected to the supply mains by a shared extension lead. Commonly found examples include (but are not restricted to): a patient monitor connected to a computer, an endoscope connected to a domestic video recorder, several items of medical equipment on a trolley sharing a common extension lead.
Such combinations are often referred to as "medical electrical systems" and may be assembled temporarily or more-or-less permanently. Medical electrical systems pose risks that may not have been taken into account in the design of individual items of equipment, even where the equipment involved is fully compliant with its relevant safety standards or is CE marked.
A British Standard (BS EN 60601-1-1:2001) exists to address these additional risks; all healthcare providers should be aware of and endeavour to implement it. All multiple socket outlets on medical equipment systems should conform to BS EN 60601-1-1 :2001 “Connection of equipment used in medical practice to a Multiple Portable Socket-Outlet shall only be possible by using a tool, or the Multiple Portable Socket-Outlet shall be supplied via a separating transformer”
The use of ANY mains extension lead (Plug Ramps) should be subject to a risk assessment.
 The use of Multiple Portable Socket-Outlet should be avoided as far as possible.
 The Multiple Portable Socket-Outlets shall be of Class 1 and comply with IEC 60884-1
 Multiple Portable Socket-Outlets shall not be placed on the floor and should be mounted in such a way as to prevent ingress of liquids and to avoid mechanical damage during normal use.
 The party assembling or modifying a Medical Electrical System should calculate the power consumption making sure it's consumption is consistent with the power that the Multiple Portable Socket-Outlet can support.
 All mains extension leads should be regularly tested by suitably qualified persons with regard to their safe condition and suitability for the intended purpose prior to use in clinical environments.
There appears to be no specific Multiple Portable Socket-Outlet inspection and testing requirements or advice. Adopting the philosophy that a Multiple Portable Socket-Outlet block is a flexible (spur) extension of the electrical mains installation, tests and checks to demonstrate compliance to BS7671 may be appropriate.
The Following test protocol was derived from various references e.g. The Electricians Guide to the 16th Edition IEE Regulations by J Whitfield ;
www.pat-testing. by
www.plugtest.co.uk: EN 60601-1-1:2001; EN 60601-1 : 1990.
All test equipment used should conform to the appropriate British Standard safety specification (BS EN 61010 for electronic types, and BS 5458 for electrical instruments).
Draft suggested multiple socket board checks/tests
Visual Inspection :- Mains Plug; Flexible cable; Distribution block
Identify signs of:- damage, overheating, burning odours, fluid ingress, where appropriate indicator neon and switch functions.
Internal inspection; cord security, polarity, connections, correct size fuses (appropriate to rating for cable and equipment power consumption), BS, IEC 60884-1 marked, security of covers, anchorage at the equipment/trolley.
Protective conductor continuity
 All protective and bonding conductors must be tested to ensure that they are electrically safe and correctly connected. The test resistance is measured between the mains plug earth pin and each of the distribution socket earth terminals.
 Any accessible metal parts which could become live in the case of failure in basic insulation should be checked.
The Pass readings should normally be less than 0.1 Ohms
A standard low resistance ohmmeter Instrument conforming to BS EN 61557-4 will comply.
Basic instrument accuracy required is +/- 5%
Test voltage ac or dc, between 4 V and 24 V
Test current not less than 200 mA
Able to measure to within 0.01 Ohms (resolution of 0.01)
Testing insulation resistance
A low resistance between phase and neutral conductors, or from live conductors to earth, will result in leakage currents, the resistance between poles or to earth must never be less than 20 M Ohms.
Mains fuses must be housed and intact, and any distribution block switches in the On position.
Where Neon indicators are in circuit erroneous readings may de observed.
Insulation resistance tester
Test voltage 500 Vdc
Capable of delivering a current of 1 mA
Basic instrument accuracy required is +/-5%
The insulation resistance between all three conductors, LINE to NEUTRAL and LINE/NEUTRAL to EARTH should be measured using a 500 V dc test supply, the measured resistance should normally be greater than 20M Ohms, lower readings require further investigation.
Separating transformer
Separating transformers shall be of class 1 construction and comply with the requirements of IEC60989. They require to be tested as a class 1 item of medical equipment.
