Electrical design for older installations

Older installations may easily be non-compliant with the design requirements of BS 7671, especially if modifications have been made to the installation without a check of the design as a whole.

Join us for this look at the problems arising when modifying older installations and how they can be properly managed within an effective electrical design process.  Choose from our cartoon PDF or Slideshare Presentation.


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Electrical design for older installations

Achieving and maintaining compliance using ProDesign

1980: The construction of Cranford Fabrication’s new Plant
The electrical installation at the newly built Cranford’s Plant has been designed by an electrical designer in compliance with the regulations of theday and then installed and inspected before handover to the client at Cranford’s. As was the case with installations of this age it was designed with anominal supply voltage of 240V.

1990: Alterations and additions are made to accommodate new equipment
The newly installed circuits appear to be in compliance with the current standards but the overall integrity of the installation has been compromised.

The additional boards DB 1/1/1 and DB 1/1/2 have adversely affected the supply to DB/2/1 possibly resulting in equipment failure and increased disconnection times etc.

The client is unaware that parts of the original untouched installation have been compromised and may now be in breach of the statutory Electricity at Work Regulations.

2000: More alterations and additions are made without input from a designer
More additions have been made without considering the affect they have on the design of the installation in general. More than 50% of the boards onthe site are no longer compliant with design regulations. Installations are now designed with a nominal supply voltage of 230V as per BS 7671 whichmay compound any non-compliances with regards to voltage drop.

The installer and the clients of Cranford’s are still unaware that the design of the installation is non-compliant - they think everything is OK asit passes electrical inspection.

2015: Yet more modifications are made and the installation is overloaded causing equipment failure
Yet another addition has been made without considering the affect it will have on the installation as a whole - the lack of design input over the years hasled to an almost wholly non-compliant installation. The latest change has adversely affected the voltage drops within the installation and has causedequipment failure that is directly attributable to the non-compliant design of the installation. The client is responsible for the system and is afraid hecould face severe consequences if he doesn’t address the design issues.

2015: Achieving compliance using ProDesign
The installation engineer carries out a site survey.

The electrical designer uses the results of the survey entering them into electrical software, such as ProDesign, to verify the design ofthe existing system against the current regulations.

He identifies areas of non-compliance and uses ProDesign to establish the required design changes.

The changes are made to the installation and it is inspected and verified. The owner of Cranford’s is now secure in the knowledge that the design of hisinstallation complies with current regulations. 

The Future: All changes to the installation must be designed using ProDesign
The owner of Cranford’s requires that all changes to the installation must be designed using ProDesign before he will issue a permit to work. This meanshe can always be sure that all installations are designed to comply with the requirements of BS7671.

The data in this document is subject to change without notice and should not be construed as the acceptance of any obligation by AmtechGroup Limited. The data in this document is believed to be accurate at the time of publication but is provided “as is”. Amtech accepts no liabilityfor any errors that may appear on this document save to the extent that such liability cannot be excluded or limited at law. In no event shallAmtech be liable for indirect or consequential loss in connection with, or arising from, the use of the information in this document.


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