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  1. Lucien Nunes

    Wiring new hot tub using old hot tub wiring

    This is not safe. I believe it is a violation of article 250.6 as neutral current will be flowing via an equipment grounding conductor. The presence of the GFCI doesn't unfortunately overcome the inherent danger in using an EGC as a surrogate neutral. If a high-resistance or loose connection...
  2. Lucien Nunes

    DPDT switch burnt while off

    Sounds like moisture ingress or an internally damaged / shorted switch, as it seems there was current flowing when it was supposed to be off. What was the rating of the switch and the motor load currrent?
  3. Lucien Nunes

    Im really struggling with this Q expecially at transposing the formula

    I'm not saying it's not a powerful tool when used appropriately. Merely that it can produce utter train wrecks if relied upon to answer questions by itself in the absence of constructive input and collaboration from its human handler.
  4. Lucien Nunes

    Im really struggling with this Q expecially at transposing the formula

    As soon as I started reading the post I had a hunch about the source, before reading that comment. A cheat's dream come true, perhaps. Or perhaps not. I have been experimenting with it, testing its knowledge and problem-solving abilities on technical topics that are not well documented on the...
  5. Lucien Nunes

    Machine Safety Circuit: Fuse Integration Query

    In what way are these devices failing? What is the source of power that is thought to be 'dirty' and in what way? I find it hard to imagine that a fuse will prevent damage, other than perhaps preventing failure due to VDRs that are breaking over on transients and then destroying the module.
  6. Lucien Nunes

    Metal ceiling grid voltage

    I would like to understand better what the problem is, before choosing a solution. * Is the leakage to the drivers' secondary output within spec or are they faulty? E.g. if they are designed for a maximum of 0.25mA leakage and they are all measuring at 0.2mA the drivers themselves are in the...
  7. Lucien Nunes

    question for the experienced or recently qualified sparky

    Maths is a box of tools that we can use to help understand and predict how things behave in the real world. Electricity is particularly well suited to being understood mathematically, because it faithfully follows the laws of physics. If you can do the maths to apply those laws, you can gain...
  8. Lucien Nunes

    Metal ceiling grid voltage

    Clearly the thing that is supposed to have good insulation and not leak excessively is the driver, as that has an SELV output that should be safe to touch. So there are two parts to this - are the drivers leaking excessively from primary to secondary, and why is the secondary circuit apparently...
  9. Lucien Nunes

    Metal ceiling grid voltage

    Devices leak current, not voltage. The exact voltage present on the casing isn't terribly important or significant in and of itself, unless the leakage current is excessive. If the ceiling grid happens to be well insulated from earth and you are testing with a meter with a high input resistance...
  10. Lucien Nunes

    Vintage BrookHirst DC motor starters.

    I always wanted to use a starter of this type around the house to operate some inconspicuous piece of equipment such as an extractor fan. Even when operating in its normal industrial habitat, the sense of ceremony operating the ratchet handle is exciting and satisfying. I agree that the survival...
  11. Lucien Nunes

    Can anyone explain type A RCD's

    We can discover how the DC propagates through the upstream / parallel-connected system by comparing impedances. In the case you mention, we are interested in the impedance of the supply (that feeds both the main and additional RV boards) versus the IR of the circuits connected to the main board...
  12. Lucien Nunes

    Soft Starters for Single Phase Submersible Pump

    Capacitor life varies widely with temperature, working voltage and voltage spikes that can cause progressive damage. Premature failures of motor-run caps are quite common and they are often the first component to fail in a machine. A good insurance policy to increase the useful life of a cap is...
  13. Lucien Nunes

    Can anyone explain type A RCD's

    DC only matters to an RCD if it is differential i.e. an imbalance. DC leakage (and indeed DC components of distorted AC load waveforms, which are likely to be much larger in magnitude) causes DC to flow in the mains. Most of it passes through the supply transformer as that offers the lowest...
  14. Lucien Nunes

    Earthing question - TNC in Bulgaria - DIY

    The more of the neutrals and earths you can separate and the nearer the origin you can do so, the better. There's no harm doing that alongside existing combined neutral/earths so long as it is clear what's what. Adding a rod makes sense, it's not going to have a low enough Ra to prevent all...
  15. Lucien Nunes

    Soft Starters for Single Phase Submersible Pump

    The ideal run capacitor for a given motor depends on a number of compromises. You can make a good estimate from the requirement in VArs but the manufacturer is likely to have selected the value after testing for various parameters including operation over a range of load torques, line voltages...
  16. Lucien Nunes

    110 V Motor Question

    Result! So you had line continuity from the NVR to the motor feed and a return to hold the coil on, but no neutral reaching the motor itself. At least it's a much easier / cheaper repair than something deep inside the motor. Hopefully the washing machine will yield to similar investigation...
  17. Lucien Nunes

    Soft Starters for Single Phase Submersible Pump

    Presumably the pump is intended to start direct-on-line. Is there an actual problem with doing so, that you want to overcome by using a soft start? What size pump is it? I am not sure I have seen an incorrect size capacitor fitted to a motor (I have on some PSU modules) but low capacitance is a...
  18. Lucien Nunes

    Use of Wago boxes for spur

    The point about the aggregate current is that each connection under load dissipates some heat, so the total amount of heat within the box depends both on the circuit current and the number of times the conductors pass through. If you loop the same 20A through the box, round the ring and then...
  19. Lucien Nunes

    110 V Motor Question

    Could there even be a break in the 4-core cable?
  20. Lucien Nunes

    110 V Motor Question

    Well then something should be happening. There is solid zero-ohm continuity from 1-3 through the thermal protector so the NVR coil circuit is complete and should hold on (does it?) There is continuity of a fraction of an ohm through at least the main winding from 1-2 so the motor should hum...

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