Test trip RCD - Page 1
Forum section: electronics / general

author: @rt
author_rank: Super Contributor
timestamp: March 19, 2019, 03:05:01 am
content: Hello,Does the RCD test trip actually connect active to ground, causing the device to do it’s job,or does it just check some springs inside it are working?Thanks.

author: ataradov
author_rank: Super Contributor
timestamp: March 19, 2019, 03:37:16 am
content: Typically they do connect a resistor across the wires, introducing an actual fault.

author: Ian.M
author_rank: Super Contributor
timestamp: March 19, 2019, 03:43:17 am
content: Usually the built in ones are a resistor or capacitor (to limit the current to slightly more than the 'must trip' threshold) in series with a momentary switch diagonally across the RCD from Line to Neutral, input side to output side (or visa-versa) so it introduces an imbalance. Therefore any upstream RCD wont 'see' the imbalance from the one being tested and wont trip.Plug-in testers have to pass current from Line to Ground, as they don't have access to the feed to the RCD being tested, so, as they unbalance the whole circuit, tend to trip all upstream RCDs with the same trip time.

author: @rt
author_rank: Super Contributor
timestamp: March 19, 2019, 04:20:23 am
content: Ive got a guy in the US, where I assume MENS system (I’m in Australia), and it looks like a home-brew sparky has bypassed the RCD connecting Neutral to Earth inside the house or something.I’ll try to send him here.We have Neutral & Earth tied together somewhere, but there would be some difference between the two.He claims things are powered between Active & Earth in the house he’s in, which I think would bypass the RCD.

author: Sedit
author_rank: Newbie
timestamp: March 19, 2019, 04:46:45 am
content: Hello everyone, I am the US guy that spoke with him and he suggested I register here as he said the members are knowledgeable and might be able to help me out.I have some experience with wiring but not a whole lot and my terminology might be a bit messed up I am not really sure to be honest.The reason I had asked for help is because I am working on a job for someone and noticed my tools started to smoke, mainly drills. I did not give them time to fully burn out however one was brand new never used before so I knew something was wrong. I decided to test the voltages across various prongs because I knew the original owner of the house has everything screwed up and I feared he had 240 hooked up to the plug or some weird stuff.I have three openings on the receptacle , the left, right and bottom middle round, normal 3 prong 120 plug. If my memory is correct I am looking at the Left/Right is Common and Hot with the bottom prong being the ground. Across the Common and Hot I get 120, on plugs I tested that are known good at a few different houses I also got 120 across the Hot and ground but nothing across Common and ground. On the plug that was burning up my drills I get nothing across Hot and ground and am concerned this is causing my problems.The original owners brother made mention a long time ago that the house in that area was wired so that the 120 was pulled off of a 240 leg and run to the receptacle there.I am basically trying to get an idea exactly what might be going on any why my tools are burning up as well as a rough idea what might be done to remedy the situation.In the meantime I have just brought a generator over as to not risk my equipment on shoddy electrical work as the entire house needs gone over before I will trust anything.

author: ataradov
author_rank: Super Contributor
timestamp: March 19, 2019, 05:54:27 am
content: It looks like there is no ground connection at all. But I'm not sure why that would cause problems for tools apart from usual safety concerns.What happens if you plug a regular incandescent light bulb? It possible that something strange happens under load.

author: Sedit
author_rank: Newbie
timestamp: March 19, 2019, 06:02:31 am
content: Im not really sure, the plug is setup, and connected to wires he has going to vanity lights. In the wall a thick wire comes in and breaks into a 4way box, he has the outlet (plugged in?? Maybe hardwired, I will have to let you know in the morning because my memory is poor) but the Vanity lights are two strips of 4 likely large bulbs and to power them its into a single plug that is split off into two parts right there at the plug going to the set of 4 lights on either side.If I can find a bulb for it I will try it tomorrow and see what results I get.The lack of ground is what concerned me because if what the original owners brother is telling us is true he made the 120 line from a single left of a 240 line and I am thinking maybe he went no further than that and I am not truly grounded at all, only sitting here plugged into a single leg of a 240 line with the rest of the wires going god knows where.Once I get there tomorrow and can get a better idea of what is in front of me I will update this thread and let you know ok.Thanks for the help, looking at the wiring this place feels like a death trap to be honest. LOL, He has Powerstrips cut off and hardwired into boxes and just dangling there in some places.

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 19, 2019, 11:47:18 am
content: All I can think of right now is on a split phase not having an actually wired common or common/ground got swapped at some point (supposing there is also some mess on the RCD side making things really dangerous).You could have a "virtual" common that shifts around depending on other power consumption, try repeating your voltage checks on the faulty socket while switching other equipment on that you may use when you drill. (Powerful lighting?)Don't expect to read 240V but look out for anything too far off 120V.

author: Gregg
author_rank: Super Contributor
timestamp: March 19, 2019, 04:15:19 pm
content: Somebody may have connected two or more 120V outlets in series without connecting the neutral (what you referred to as common) back to the main entrance.Or they might have connected the neutral to a poor ground connection that has a fairly high resistance to actual ground (for a power circuit, it may be only a few ohms).You are correct about the 3 hole outlet wiring: the larger slot should be the neutral, the shorter slot should be the line and the larger round hole should be the ground.In any case, if the neutral is not connected all the way back to the utility power transformer, one leg of the 120V that has the most load will have the voltage sag while the other leg will have a high voltage. I have seen cases that showed similar symptoms where the utility neutral had no connection to the house and the imbalance was attempting to return via the ground.If you want to investigate a little further and are confident in opening the main breaker panel; check that the neutral and ground are connected together there. The only place in a house where the neutral and ground should be connected together is at the main panel. However, some people who know just enough about electricity to be dangerous seem to think that the ground and neutral are interchangeable (with a lot of weird results). If you have a meter and feel confident in using it on mains voltage, let us know; we can figure this out.

author: Sedit
author_rank: Newbie
timestamp: March 19, 2019, 07:51:47 pm
content: I am generally one of those people that know enough to be dangerousHowever I know enough to not do that. I am back at the house and this specific receptacle is a mess to say the least.What we have is one large thick wire, the type I would honestly expect to see in 220 line running to a 4 way receptacle box(I have yet to try it to see if it is 220, it very well might be). From there they have plugged into the receptacle a plug that immediately splits into two wires...One of those wires runs to another receptacle on the wall here. That was the one my drills were plugged into.The other one runs to the light strips for the vanity. It goes into the vanity light strip on one side then Jumps across and hooks to the other light strip on the vanity lights. There is three bulbs in each. It is dark in the wall and my phone on the Camera sucks but was going to try to get a picture of this clusterfuck and let you see this mess I am looking at.Shakalnokturn, I am kind of leaning towards the same thing that they never properly grounded any of this and just stole a leg off a 240 line and hooked it up like no one would be any of the wiser. Perhaps just grounding to some arbitrary system in the house like the pipes or something IDK.I will go check the main box and see if I can get pictures of that and this mess I have on front of me. I just got here on the job so give me a minute and I will post an update.

author: Sedit
author_rank: Newbie
timestamp: March 19, 2019, 08:02:14 pm
content: [ihere are picture. Goes in to box then left and right go to diff boxes one to receptacle other to lights sorry for quality its hard to use this small phone

author: Sedit
author_rank: Newbie
timestamp: March 19, 2019, 08:04:35 pm
content: Lasst Picture is the receptacle. Ima try to open it and see whats going on inside. Also try to get pictures of the Breakerbox as I think that is likely more important then this. I would like to know where this Fat wire that powers all of this is coming from because that is likely the problem

author: Gregg
author_rank: Super Contributor
timestamp: March 19, 2019, 10:13:37 pm
content: It is hard to see the large wire going into the two gang (4 outlet) box but it may not be the problem. Try carefully unplugging the two plugs and see if your problem goes away. It looks like there are two Romex wires connected at the one plug and that may be your immediate problem. Not to say that you don’t have a lot more problems yet unrealized.Then it looks like a bungie cord holding the plastic junction box into the wall. Some of this stuff you cannot make up.Edit: Hardware stores and big box stores sell a nifty little outlet tester for about $6https://www.homedepot.com/p/Power-Gear-3-Wire-Receptacle-Tester-50542/206212329and for a couple $ more they have them with a ground fault test button.