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  1. Richard Burns

    When to issue a danger notification?

    Come on, be realistic! how do you fix it to the busbar!!:sunglasses:
  2. Richard Burns

    When to issue a danger notification?

    I did a danger notification for a ring that was pulling 56A and they were complaining of frequent tripping and the RCBO burning out but did not want to split down the circuit.
  3. Richard Burns

    Lighting connection, socket outlet?

    As an easy solution I would tend to put a local fuse in the conduit box so that you only need to add another terminal and fuse holder to the box, if there is enough room. However a plug and socket arrangement should be OK. The instruction that the lights not be connected to the mains supply is...
  4. Richard Burns

    CCTV cable drop

    Calculate for the actual current draw not the absolute maximum, 30 A sounds a lot for 5 cameras but perhaps they are PTZ. Run the cable as a ring if possible to reduce volt drop.
  5. Richard Burns

    New BS5839 regs out now.

    Thank you, Always nice to know there is some use for all the money piling up!!
  6. 269 pence.jpg

    269 pence.jpg

    • Richard Burns
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  7. Richard Burns

    2365 Design Project - May need some advice.

    Well done on the error, it is vital to be able to spot these (and correct them) The diagram and equations are something I have just written/drawn out to provide a total overview.
  8. Richard Burns

    Disconnection times, some clarification

    Yes 411.3.2.2 ii) includes circuits that supply luminaires. Asking if a regulation about circuit disconnection time applies to light fittings is a bit like asking if the price of eggs includes fluffy bunny rabbits! Correct, a circuit containing luminaries in a domestic premises must comply with...
  9. Richard Burns

    2365 Design Project - May need some advice.

    I think you are missing a key point Look at this calculation you typed Max R1+R2 2.73-0.11/1.2x12 = 181.94Ω And compare it to these that you typed 1.37-0.24/1.2*18* 1000 = 52.31m ohms/metre. Maximum Zs -Ze / I3 factor x length overall x 1000 What is the (small but important) difference? I...
  10. Richard Burns

    Wutos

    That is a sad and unfortunate thing to happen. We have been following the delightful rogue for many years and I am sorry that you have now lost him. A memory of loves lost and times past; the thread of memory holds on but the key player has gone to another stage. I wish you well and hope for the...
  11. Richard Burns

    2365 Design Project - May need some advice.

    Come on, remember what units you are working in at each stage. The calculation you show but do not explain seems to show Zs - Ze (1.37-0.24) Adjust for temperature (1.2) as a divisor goes from 70°C to 20°C Circuit length m (18) as a divisor give a value per m Ω to mΩ (1000) as a multiplier to...
  12. Richard Burns

    2365 Design Project - May need some advice.

    See my responses in red above
  13. Richard Burns

    - Prospective fault current test 2391

    No worries, take it calmly and logically and all will work well. Use the knowledge you have and think, good luck.
  14. Richard Burns

    2365 Design Project - May need some advice.

    The first equation I cannot follow. Surely it should be maximum R1+R2 (not r1+r2) per metre in milliohms. The calculation is working backward to give you the figure to cross reference in table I1. Zs - Ze is the total circuit resistance, Ω, at normal operating temperature, dividing by length...
  15. Richard Burns

    My gravity flappy lid Eureka moment for happy labelling!!

    I have a supply of small neodymium magnets for finding nailed joists in plasterboard and these can hold the lid open as well. I even had to use one fixed permanently on a board mounted sideways to hold the lid closed!
  16. Richard Burns

    - Prospective fault current test 2391

    Prospective fault current at origin is the highest current, further into the installation the current will drop due to circuit resistances. If the protective devices in the next DB are able to withstand the fault current at origin there is no need to measure again at the next DB because you...
  17. Richard Burns

    2365 Design Project - May need some advice.

    2 cm is 100 mm is a workable way of doing it. Westward10 has explained how to use a normal ruler to get your measurements. If you have printed the diagrams at full size on A3 paper then they will be scaled 1:50 so if you measure 9 cm as the width of a room on the page then in reality the room...
  18. Richard Burns

    2365 Design Project - May need some advice.

    It takes a long time to go through multiple questions and it can be hard to identify what numbers you have used and correlating the information that you have used with the results is another difficulty. Note that when using 90°C cables that all the cable terminations and enclosures should be...
  19. Richard Burns

    2365 Design Project - May need some advice.

    Yes that should cover it, I did make a typographical error in that the BS7671 graphs only go to 0.1 not 0.01 seconds however the same effect is there as the time you have is 0.21s.
  20. Richard Burns

    Testing with a CU change

    I had never actually thought of it like that but that is much simpler! I looked at that and thought what is he talking about then actually thought and went, oh yeah! I was thinking volt drop is over the length of circuit for both line and neutral and at 70°C, so twice the length so I can take...

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