Page 1 of 2 12 LastLast
Results 1 to 15 of 25
  1. #1
    Join Date
    Nov 2012
    Location
    Blue Mtns
    Posts
    115

    Default RCDs and old machines

    Slowly setting up the workshop . Most of the machines will be wired through a vass busbar. I couple of the machines like the 3phase bandsaw are quite old. The mill, lathe and drill don’t have a neutral . The sparky who I’ll get to set up the sub mains has suggested We use a 4 pole RCD over everything then individual breakers (there is hrc fuses on each busbar take off.

    I like the Saftey of an RCD on all its just am a little dubious with some of the old welders and machines that they’ll trip the earth leakage !

  2. #2
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,541

    Default

    Earth leakage devices look at the current in and the current out, and if there is more than a pre-defined difference, trip. I'm not sure that they will be the problem. I think the bigger issue will be the breakers that you install, as there are various types, depending on the device that they are connected to. I know there is a type that is better for using on circuits with welders on for example.

    Michael

  3. #3
    Join Date
    Jul 2006
    Location
    Athelstone, SA 5076
    Posts
    4,255

    Default

    yep...rcd's and older equipment could be a pain..but usually only where old electronics are concerned, where they wire in caps etc to earth to do filtering...
    but until you start having problems you wont know...they can always be taken off the RCD circuit later...just make sure the rcd is fitted at the sub-board in the shed...and not the main board.

  4. #4
    Join Date
    Jun 2008
    Location
    The Whitsundays
    Posts
    229

    Default

    Hi achjimmy,

    AS3000 has very recently changed and now stipulates all sub-circuits to be protected by RCDs in residential situations. I'm not sure if each sub-circuit has to have it's own RCD or whether one RCD/MCB combination can be used as a main switch and thus cover the sub-circuits.

    Given that RCDs are a primary protection from active to earth shocks (also fires!) I'd be more inclined to find out why a particular machine causes nuisance RCD trips and see if it can be fixed.

    Cheers

    The Beryl Bloke
    Equipment er.... Projects I own

    Lathes - Sherline 4410 CNC
    Mills - Deckel FP2LB, Hardinge TM-UM, Sherline 2000 CNC.

  5. #5
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

    Default

    Quote Originally Posted by Michael G View Post
    Earth leakage devices look at the current in and the current out, and if there is more than a pre-defined difference, trip. I'm not sure that they will be the problem. I think the bigger issue will be the breakers that you install, as there are various types, depending on the device that they are connected to. I know there is a type that is better for using on circuits with welders on for example.

    Michael

    That can't be right. The electricity gets consumed remember. A kettle says is "uses" 1000W.

    So less must come back then goes in.

    What I wrote above is probably a common misconception.



    If I have learned correctly then it is more the wattage is the amount of force needed to push electrons in a circuit.
    Gold, the colour of choice for the discerning person.

  6. #6
    Join Date
    Oct 2015
    Location
    melbourne
    Posts
    473

    Default

    The electron flow 'in' and 'out' must be the same. If less 'comes back' (via neutral by convention) than goes out, some is 'leaking' to earth, hence the 'earth leakage' device, or 'residual current detector' trips.

    But capacitive coupling, either parasitic or via noise filters mean that a small amount of leakage is unavoidable so the limit is typically 30mA.

    But as far as I know, there are others available designed for particular purposes which have different limits, and also different time sensitivity.

    The power used is measured by the voltage drop across the device (240v) times the current.

    Russ

  7. #7
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,779

    Default

    Hi there,

    I have 2 machines that are over 60 years old, still with original 3 phase motors. These have never triped the RCD. Realistically, if there is any current leakage to earth then it's best to find out because an RCD has tripped rather than from you or someone else receiving a lethal electrical shock.

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  8. #8
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    Quote Originally Posted by russ57 View Post
    The electron flow 'in' and 'out' must be the same. If less 'comes back' (via neutral by convention) than goes out, some is 'leaking' to earth, hence the 'earth leakage' device, or 'residual current detector' trips.
    Just to add to the confusion there's no actual electron movement in one direction in AC circuits. The electrons in the wires move back and forth less than a mm during the 1/50s that a standard AC cycle takes to complete. Despite this, AC currents (in AC its the back and forth movement of electrons) can be easily measured by measuring the small V drops across a very low value resistors in the circuit

  9. #9
    Join Date
    Aug 2010
    Location
    Near Bendigo, Victoria, AUS
    Age
    72
    Posts
    3,102

    Default

    Quote Originally Posted by .RC. View Post
    That can't be right. The electricity gets consumed remember. A kettle says is "uses" 1000W.

    So less must come back then goes in.
    An easy way to think about it is the analogy to water: imagine a waterwheel or turbine. THe amount of water going over/under or through it doesn't change. THe energy extracted is from the potential or force of the water, not the water itself. Same with electricity. The amount going in and out stays the same, no matter where it goes - back in Neutral or leaking to Earth.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  10. #10
    Join Date
    Nov 2016
    Location
    Gulfview Heights, Adelaide
    Posts
    83

    Default

    Quote Originally Posted by simonl View Post
    Hi there,

    I have 2 machines that are over 60 years old, still with original 3 phase motors. These have never triped the RCD. Realistically, if there is any current leakage to earth then it's best to find out because an RCD has tripped rather than from you or someone else receiving a lethal electrical shock.

    Simon
    I have an old 3 phase milling machine, lathe and welder, none of these machines have ever tripped the RCD. Recently I had trouble with my air compressor tripping the RCD. This was a relatively new machine, single phase. The fault
    was the motor run capacitor shorting to earth.

  11. #11
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

    Default

    Speaking of RCD's I m not sure how widespread this story got around the country, but a week ago in north Queensland, a woman and her daughter were electrocuted to death through some odd occurance.

    The media report was there was a battery charger connected to a truck battery and somehow they got electrocuted, the report also mentioned an electric fence was involved.

    https://www.news.com.au/national/que...044bb84da813ba

    Police said a family member had attached a cable from an electric fence to the bull bar of a semi-trailer to keep some horses from escaping.
    It is believed the truck later became electrified when a battery charger was attached to the vehicle.
    Gold, the colour of choice for the discerning person.

  12. #12
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    Quote Originally Posted by .RC. View Post
    Speaking of RCD's I m not sure how widespread this story got around the country, but a week ago in north Queensland, a woman and her daughter were electrocuted to death through some odd occurance.

    The media report was there was a battery charger connected to a truck battery and somehow they got electrocuted, the report also mentioned an electric fence was involved.
    Unless the pulses from the electrical fence fried something inside the charger the electric fence connection could be a red herring. Most probably something inside the charger shorted allowing mains V onto the truck frame.

  13. #13
    Join Date
    Nov 2016
    Location
    Gulfview Heights, Adelaide
    Posts
    83

    Default

    This news story was reported in South Australia. There was a photo of the wire connected from the fence to the bull bar. In the news story, it was not explained very well how the connection was made from the vehicle.

  14. #14
    Join Date
    Nov 2010
    Location
    Frankston south
    Posts
    102

    Default

    [QUOTE=Theberylbloke;1944890]Hi achjimmy,

    AS3000 has very recently changed and now stipulates all sub-circuits to be protected by RCDs in residential situations. I'm not sure if each sub-circuit has to have it's own RCD or whether one RCD/MCB combination can be used as a main switch and thus cover the sub-circuits.

    Given that RCDs are a primary protection from active to earth shocks (also fires!) I'd be more inclined to find out why a particular machine causes nuisance RCD trips and see if it can be fixed.

    Cheers

    The "stipulation" as I understand it is that it's up to the Electricians disgression. I recently had my shed rewired with three non RCD protected circuits that are hardwired to machines fitted with VFD's. No more nuisance tripping.

  15. #15
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    Quote Originally Posted by waxen View Post
    The "stipulation" as I understand it is that it's up to the Electricians disgression. I recently had my shed rewired with three non RCD protected circuits that are hardwired to machines fitted with VFD's. No more nuisance tripping.
    I've had 8 VFDs for up to 8 years in my shed and the whole shed supply is on an RCD and have never had a nuisance RCD trip.

Page 1 of 2 12 LastLast

Similar Threads

  1. Smart machines
    By neksmerj in forum METALWORK GENERAL
    Replies: 1
    Last Post: 3rd Jun 2016, 01:02 AM
  2. Levelling machines
    By Mike4 in forum METALWORK GENERAL
    Replies: 8
    Last Post: 5th Nov 2015, 09:26 AM
  3. Little Machines
    By kwijibo99 in forum METALWORK GENERAL
    Replies: 2
    Last Post: 23rd Jan 2015, 08:08 PM
  4. For Lovers of Old Machines
    By wheelinround in forum METALWORK GENERAL
    Replies: 3
    Last Post: 24th Dec 2012, 10:37 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •