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  1. P

    Isolation of TN supplies.

    I have seen a few occasions when a switch that had not been used for donkey's years was operated and failed as the contacts were poor/overheated due to dirt or tarnishing. I guess that might be a common risk for items that are hardly ever operated except for very rare jobs, like an isolator...
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    Isolation of TN supplies.

    There is not quite the same thing as "reverse polarity" as you can have: L-L swap leading to wrong rotation. This is not obvious without specific test (closer to SP reversal) but will likely trouble machines using 3P motors as fan direction reversed, etc, or N-L swap and then almost certainly...
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    Isolation of TN supplies.

    My own experience is very limited compared to many folks on here, so I can only really say why I used 4P DB isolators and that is largely as we have up-front RCD for fire risk reasons on a TN-S supply (so similar to TT in that respect) and it allows me to work on a sub-DB without risking a N-E...
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    Isolation of TN supplies.

    Another practical aspect to using a 4P isolator is it simplified any IR testing (part of original thread I think...) as you are not likely to energise the load at all when doing a global IR check, or if you are testing the load on its own you can do so without needing to disconnecting a terminal...
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    Isolation of TN supplies.

    Isolation and switching are different aspects. One example where you need 4P switching is a generator transfer switch where the two supplies are on differently earthed neutrals, so you need to break one while running off the other. I'm not sure of why the UK regs differ in terms of mandating DP...
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    Non type-tested parts

    I see your financial pain here: https://www.kempstoncontrols.co.uk/category/34/circuit-protection/circuit-protection/rcbos?manufacturer=mem-classic At that sort of price a garage CU style of DIN box for an RCD added to a single RFC's MCB would be my solution, not pretty but if a stop-gap prior...
  7. P

    Incoming size cable ??

    Some of the DNO offer advice on property "After Diversity Maximum Demand" calculations, for example: https://www.spenergynetworks.co.uk/pages/admd_calculator.aspx
  8. P

    CK T3678 Heavy Duty Ratchet Cable Cutters - how good?

    We have one of these Klein cutters which is good enough but still hard work when you get to 25mm+ cable sizes: https://www.cef.co.uk/catalogue/products/4226166-high-leverage-cable-cutter
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    CK T3678 Heavy Duty Ratchet Cable Cutters - how good?

    I ended up ordering one to try it out so can tell folks later. A few cutters say no hard-drawn copper, most say no steel. I don't plan on using it for cutting SWA but it could be handy, but I don't work with ACSR wire: https://en.wikipedia.org/wiki/Aluminium-conductor_steel-reinforced_cable...
  10. P

    Help with Low insulation resistance reading

    Did you try at 250V and 500V? If they differ by a lot then you still have a SPD to E somewhere. It could be a permanently wired bit of equipment like a boiler, etc, where you don't have (or did not find) an all-pole isolator for it. Switching off the SP/TP MCBs might isolate some circuits and...
  11. P

    Maintenance replacements and Type AC RCDs

    Just test the RCD and if working then do the usual like-for-like swap. The use of type AC where type A should be used now is normally a C3 code on EICR (page 19 of Best Practice Guide #4 issue 7)
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    Incoming size cable ??

    60A, 50m and 35mm^2 is not quite adding up to me! Start by putting down each circuit in a table, what the loads are, and for domestic stuff use the OSG diversity values in Appendix A to get an idea of max demand. Electric heating, and to some extent instant showers, are where you will really...
  13. P

    CK T3678 Heavy Duty Ratchet Cable Cutters - how good?

    As the title say, is the CK T3678 worth getting for a modest amount of work cutting stuff like 50mm hard-drawn copper, and maybe up to 120mm soft drawn copper cables?
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    Need help about Surge Protective Device

    It is not a brand that I know, but on the appearance it would look like a good enough choice for most situations where you do not expect a direct strike. Type 2 SPD are for induced surges, i.e. nearby strike, whereas Type 1 or Type 1+2 are able to cope with higher energy surges from a hit to...
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    CCTV colour at night alternatives.

    It is kind of inevitable that if you split the light in to 3 parts for colour, and have a sensor of a given sensitivity, then you need 3x the exposure time to get a given S/N ratio and so 3 times less frame rate is possible. More so if you chase high pixel numbers (so each pixel has less...
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    hand tools when your old and falling apart

    Not used if tor real yet but it has quite a nice fine ratchet action. The forwards/backwards toggle is a bit fiddly to operate and it lacks a middle locked position (handy for adjustment use), but otherwise does what it says. The hex bit holder has a good positive retention of bits and the...
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    UK Change in current capacity along run

    In the current book (18th, amendment 2) it is under regs 433.2 and 434.2 In most domestic situations the usual approach is the whole circuit is designed for a given load, and that is the supply MCB/RCBO rating. In some cases you can rely on a load not being able to cause overload, for example a...
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    Need help about Surge Protective Device

    This might also be worth considering: https://in.rsdelivers.com/product/mersen/83020116/stpt2-40k275v-2pg/mersen-stpt2-40-surge-protection-device-275-v-ac-2/1793059
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    Need help about Surge Protective Device

    These are not the cheapest of brands, but they have a good reputation and appear to have an office in India: https://www.dehn.in/store/f/41912671/Artikelnummer_PDF/941110.pdf
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    Need help about Surge Protective Device

    This document (about 18MB PDF download) has a lot of useful guidance on lightning protection: https://www.nvent.com/sites/default/files/acquiadam/assets/E907W-WWEN.pdf

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