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  1. S

    240VAC power relay coil diodes

    by the way the relay's sole function is to jumper the trafo in some simple way that I didnt bother to follow for the cranking amps function
  2. S

    240VAC power relay coil diodes

    I wondered that too but on close inspection, the relay's coil inside was tape-wrapped and on the tape was stamped 240VAC.
  3. S

    240VAC power relay coil diodes

    yeah I wondered if they were zeners. 2 diodes checked out OK 0.5V forward & open cct revers. the other 2 were dead short. replaced them with 1N3094's tried it. relay chattered away like it didnt have enough pull. coil meters at 5K. think the coil must have gone o/c. replaced it with a contactor...
  4. S

    240VAC power relay coil diodes

    trying to fix a dysfunctional booster-starter-charger. there is a large chinese relay (part nr WJQX-38F-2H) which has a funny little set of diodes which seem to ahve been connected across the coil terminals. I would have expected a diode in this position on a DC coil but Im not sure what the...
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    what do you call the "armour" in SY cable

    thanks all. indeed this stuff is regularly used on decks of workboats so loads of oxygen, salt & sunlight. the braid seems to have a very short life as the rot gets in rapidly and you can see its rusty through the transparent jacket. I think it is transparent so that punters in a shop are...
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    what do you call the "armour" in SY cable

    very interesting. case in point at the moment are the deck power cables for containerised diving air-compressors and containerised hyperbaric chamber. (in use with 5-pin 32A 400V 3-phase plus neutral site-type connectors) would this be an appropriate cable for use in this context?
  7. S

    what do you call the "armour" in SY cable

    does SY cable have a practical place within any interpretation of a British Standard? what is it actually for? why does it *always* have a transparent outer jacket? in my own provincial orbit, the popular view is that it is Armoured Cable. I believe that it is strictly not armoured. I...
  8. S

    Worcester green star heat slave ll reset

    A friend has a Worcester green star heat slave ll, he diagnosed problem - weather had got into control PCB and caused a mains short on the PCB which destroyed part of the track. he took the PCB to me and I cleaned it up, repaired the tracks, meggered the mains input line which was OK at 250V...
  9. S

    three phase immersion heater

    this thought crossed my mind too but that will lose precious watts won't it? plus wanted to keep it as s i m p l e as poss.
  10. S

    three phase immersion heater

    I have an idea but I'm sure I am missing something possibly to do with efficient power transfer, hopefully some of the erudite contributors to this forum can comment: Consider a cheap "chinese" wind turbine. nominally 24V 400W, price about £140 ex ebay. They are what they are. Ive got experience...
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    earthing conductor sizes

    well quite, I was going to say that it begs the question, how did you size the working conductors....
  12. S

    earthing conductor sizes

    Thanks. more questions though! what are I, t and k? (I'm guessing basically I is some nominal current value, and k is some resistive coefficient of the conductor... t is ... a time period?) but in broad practical terms, the idea of these ready-reckoner tables are that you choose the earth CSA...
  13. S

    earthing conductor sizes

    please can I get a bit of help in reading table 4.4(i) in the OSG. Is the idea that you simply size the earthing conductor relative to the line/neutral conductors? I dont know how else you would do it but wanted to make sure my interpretation of the table is correct.
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    BS7671 543.3.2

    please can someone give me a steer on what 543.3.2 is? I cannot find it in my OSG. Context is "Condition and accessibility of main protective bonding conductor connections (543.3.2; 544.1.2) requires further investigation without delay." thanks
  15. S

    uk 13A 3-pin plugs

    when did the familiar 13A plug get half-insulated pins on L & N?
  16. S

    time switching with Economy 7

    please can wiser people comment on the below: if I ask for an Economy 7 tarriff, will the energy supplier arrange for a new meter to be installed? Does an economy 7 meter come pre-preogrammed with the low rate periods? can I get an aux output signal from the meter to enable me to...
  17. S

    3 phase residential /teleswitch heating

    I guess that there might be a period available (when no other switching is taking place) where individual teleswitches could be "stunned" by the LW signal
  18. S

    3 phase residential /teleswitch heating

    supply at the property in question is arranged as follows: L1, L2 & L3 are connected into a 3-phase mechanical meter, out of which only L1 and L2 are utilised. L1 energises storage heating via a radio-teleswitch/contactor arrangement. L2 supplies the "24 hour low rate" fusebox which is feeding...
  19. S

    3 phase residential /teleswitch heating

    there were (are!) 2 meters - 1 for normal rate, and 1 for low rate. the main low rate load (heating) would energise using the long-wave controlled teleswitch (sometimes via a separate contactor) the 24-hour low rate fuse box would be permanently energised, and metered via the low rate meter...
  20. S

    3 phase residential /teleswitch heating

    The supply arrangement in question is certainly full 3 phase & neutral. 400V between the line of all 3 fuseboxes. 400V exists within the single dwelling house. each phase has a 100A cutout. I have done work on the property and measured it myself. and Yes - regarding the "24 hour low rate"...
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