Subject to Simultaneous Overload

Where circuits are grouped, there are two availablemethods of calculating the rating factor Cg to be applied:

  • Subject to simultaneousoverload:Assumes that more than one of the grouped circuitsmay be overloaded at any one time –applies grouping using: In/Cg.

[BS7671:2018,Appendix 4,5.1.2:Equation 2]

  • Not subject to simultaneousoverload:Assumes that only one of the grouped circuits will normally be overloaded at any one time (a reasonable assumption for general distribution loads) – uses two calculations to determine Cg from which the highest calculated value is to be used. Usually gives a reduced level of derating compared to ‘Subject to simultaneous overload’.

[BS7671:2018,Appendix 4,5.1.2:Equation 3,4]

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Jarek Wityk

Emergency Lighting in Toilet Cubicles

Summary
1. If the toilet has borrowed light and is less than 8m square:
a. There is no need for emergency lighting, however,
b. If there is a cubicle with full height door – therefore closed without borrowed lighting – then the EM lighting would be required in that cubicle.
2. If the overall toilet has no borrowed light,
a. And the WC cubicles do not have full-size doors; there should be at least one emergency outside row of cubicles.
b. If there is a cubicle with full height door – therefore closed without borrowed lighting – then the EM lighting would be required in that cubicle.

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Jarek Wityk

jet

extinguishing medium, usually water, leaving a nozzle as a continuous

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