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Volt drop % - Private Supply Def

Peter Hartley

Good day everyone 

Public supply Volt drop 3% Lighting 5% Power.

Private supply Volt drop 5% Lighting 8% Power.

Define private supply?

Option 1 - HV public grid supply to privately owned transformer. Is LV supply private?

Option 2 - Main source of supply is from Privately owned source of generation such as PV, diesel/gas/nuclear generator?

Why is this not defined in BS7671?

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  • 0

    May I also point out that the core requirement to achieve regards volt-drop are Regs 525.1 and 525.201

    525.202 says that, if you do meed the guidance in Appendix 4, Section 6.4, you're deemed to comply with 525.1 and 525.201. But at the end of the day, do you comply with 525.1 and 525.201?

  • 0 in reply to gkenyon

    The main aim is to ensure that the voltage drop in any circuit and in the whole installation does not exceed 4% of the nominal voltage, as required by Regulation 525.1 and 525.201. Appendix 4, Section 6.4 provides some recommended values for the voltage drop in each circuit, but they are not mandatory. They are only a way to achieve compliance with Regulation 525.1 and 525.201, but not the only way.

  • 0 in reply to AMK
    AMK said:
    The main aim is to ensure that the voltage drop in any circuit and in the whole installation does not exceed 4% of the nominal voltage, as required by Regulation 525.1 and 525.201.

    That's not what those Regulations say! The "main aim" is to make sure that the voltage drop is not so excessive that equipment becomes unsafe, or does not exceed the minimum voltage specified by the product standard.

    The 4 % only comes in the guidance in Appendix 4, Section 6.4 (which is referenced in 525.202).

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  • 0 in reply to AMK
    AMK said:
    The main aim is to ensure that the voltage drop in any circuit and in the whole installation does not exceed 4% of the nominal voltage, as required by Regulation 525.1 and 525.201.

    That's not what those Regulations say! The "main aim" is to make sure that the voltage drop is not so excessive that equipment becomes unsafe, or does not exceed the minimum voltage specified by the product standard.

    The 4 % only comes in the guidance in Appendix 4, Section 6.4 (which is referenced in 525.202).

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  • 0 in reply to gkenyon

    I agree with you that the 4% limit for the voltage drop in the installation is not a regulation, but a guidance that is given in Appendix 4, Section 6.4 of BS 7671. I also understand that other methods or calculations may be used to ensure compliance with Regulation 525.1 and 525.201, which are the core requirements for limiting the voltage drop in any circuit and in the installation.

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