Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 15 of 25
Thread: RCDs and old machines
-
22nd Dec 2018, 10:40 AM #1Senior Member
- Join Date
- Nov 2012
- Location
- Blue Mtns
- Posts
- 115
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 !
-
22nd Dec 2018, 11:30 AM #2Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,561
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
-
27th Dec 2018, 11:11 AM #3Most Valued Member
- Join Date
- Jul 2006
- Location
- Athelstone, SA 5076
- Posts
- 4,258
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.
-
28th Dec 2018, 08:23 PM #4
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 BlokeEquipmenter.... Projects I own
Lathes - Sherline 4410 CNC
Mills - Deckel FP2LB, Hardinge TM-UM, Sherline 2000 CNC.
-
28th Dec 2018, 09:56 PM #5Pink 10EE owner
- Join Date
- Aug 2008
- Location
- near Rockhampton
- Posts
- 6,218
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.
-
29th Dec 2018, 04:34 PM #6Senior Member
- Join Date
- Oct 2015
- Location
- melbourne
- Posts
- 473
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
-
4th Jan 2019, 09:55 PM #7Most Valued Member
- Join Date
- Aug 2011
- Location
- Melbourne
- Posts
- 4,779
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.
SimonGirl, 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.
-
6th Jan 2019, 12:00 PM #8Member: Blue and white apron brigade
- Join Date
- Feb 2006
- Location
- Perth
- Posts
- 7,189
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
-
6th Jan 2019, 12:48 PM #9
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....
-
7th Jan 2019, 11:16 AM #10Member
- Join Date
- Nov 2016
- Location
- Gulfview Heights, Adelaide
- Posts
- 83
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.
-
7th Jan 2019, 01:26 PM #11Pink 10EE owner
- Join Date
- Aug 2008
- Location
- near Rockhampton
- Posts
- 6,218
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.
-
7th Jan 2019, 02:00 PM #12Member: Blue and white apron brigade
- Join Date
- Feb 2006
- Location
- Perth
- Posts
- 7,189
-
7th Jan 2019, 02:07 PM #13Member
- Join Date
- Nov 2016
- Location
- Gulfview Heights, Adelaide
- Posts
- 83
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.
-
8th Jan 2019, 06:07 PM #14Senior Member
- Join Date
- Nov 2010
- Location
- Frankston south
- Posts
- 102
[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.
-
10th Jan 2019, 09:09 AM #15Member: Blue and white apron brigade
- Join Date
- Feb 2006
- Location
- Perth
- Posts
- 7,189
Similar Threads
-
Smart machines
By neksmerj in forum METALWORK GENERALReplies: 1Last Post: 3rd Jun 2016, 01:02 AM -
Levelling machines
By Mike4 in forum METALWORK GENERALReplies: 8Last Post: 5th Nov 2015, 09:26 AM -
Little Machines
By kwijibo99 in forum METALWORK GENERALReplies: 2Last Post: 23rd Jan 2015, 08:08 PM -
For Lovers of Old Machines
By wheelinround in forum METALWORK GENERALReplies: 3Last Post: 24th Dec 2012, 10:37 PM