There i disagree. The corrosion would have been way worse on a multi-strand cable with moisture getting in between the strands and corroding there. They may be meant for multi-strand but the main cause is of course moisture causing corrosion.
Those leakage breakers detect anything over 40mA between either phase or the neutral line to the earth wire not to actual earth which as one might expect is rather resistant and has huge capacitance anyway. Normally speaking an earth wire would be connected to a metal enclosure of some kind and to all copper plumbing in a house, protecting humans from electrified metal. The plumbing usually ends up in the earth, which is also the most common way to create an 'earth-wire' but the leakage breaker only detects current between the wires and not actual leakage into the earth.
I disagree, at least for the UK. One way or another, at least in the UK, the earth (the muddy stuff outside), the earth wire and neutral are connected somewhere. Leakage to earth or the earth wire, or to any metal bonded to earth will (should) trip the earth leakage protection. Live to neutral leakage won't trip the breaker because the neutral is on the load (not earthed) side of the breaker, so live to neutral doesn't unbalance the supply current, it just looks like additional load.
I accept that practice in other countries might be different so what you say could be true in a different part of the world.
Yes they are, well the earth-wire and the earth are, The neutral should go all the way back to the power plant.
Leakage to the earth technically speaking should, but won't. As i stated, that the earth-wire is connected to earth does not mean current will flow from the live-wire through the earth back to earth-wire, or at least not enough to trip the circuit breaker.
This is true, that is what the fuse is for, many amps can flow between the two before that pops.
Mind you, Neutral to earth-wire should also trip the earth-circuit breaker, probably less quickly, and if the Neutral is actually fully isolated to the plant, then maybe not, but chances are some current will flow and it takes 40mA to trip the thing. (at least according to EU standards, and the UK may have left the EU, but they did not change all of that stuff thereafter.)
But look, i am willing to accept that what you say is true if you can prove this with an experiment. You see the circuit breaker detects the current between the Earth-wire and the Phase(Live) and/or Neutral. (in the EU it's both and i am pretty sure the UK is no different) and if this current exceeds 40mA, trips the breaker. If the live wire connect to the actual earth, even if it's moist, the current will flow between the Live-wire and something else. The Earthwire, although connected to Earth, is just a side branch. Do i need to draw a schematic ?
I would build a separate UL/CE rated metal enclosure for the high voltage switching..
Would use plug in base relays, a step down transformer for the coils, probably 24vac..
This box would also have an external breaker box to switch off the incoming before opening cover..
Then lose the wood enclosure..
another non-metal enclosure for the guts..
Liquid electrical tape is quite handy..
But now we're only switching 24vac..
The neutral wire goes back to the star point of the local distribution transformer, which is connected to earth at the transformer. It might be connected to earth at other points, although I am not clear on that. The neutral conductor doesn't go back to the power plant. The HV distribution is 3 wire delta connected, no neutral conductor. The local transformer is delta connected on the HV side and star connected on the low voltage side.
I maintain that leakage from live to the muddy stuff will flow back to the neutral conductor on the distribution side, either where is is earthed at the transformer or anywhere else. I shall check with my electrician colleague what value of resistance he'd expect when measuring the earth loop impedance when the earth at the consumer is provided by an earth spike. From memory, which is likely to be wrong, a recent installation I helped him with measured about 200Ohms, giving a prospective earth current live to earth would be 230/200 = 1.15A, well in excess of what is needed to trip earth leakage protection.
I shall return with actual figures.
Edit: I have been advised that 200Ohms is the maximum permitted.
Oh yes. Well outside of the house, and before the meter, let's agree on this.
The circuit-breaker actually measures current flowing through the earth-wire, (to the earth or from the earth i mean it's AC) not differences in current between Live & Neutral & Earth.
I remember vaguely when I was a boy helping my dad to rewire the house that earth leakage protection was the latest thing and worked as you describe. Modern earth leakage protection measures the difference between the live and neutral current and if they differ by more than the rated trip current of the breaker the breaker trips.
I am concerned that we are well off topic and that I should split this discussion to a separate topic.
@pointy , is our discussion helpful to you or would you prefer I spilt this off to a new topic?
We are well of topic, this topic has started a discussion on SSR's blaming relays at fault for what is clearly a moisture issue, but
I would be rather surprised about that, just the way a lot of appliances work, it seems rather unlikely. Not to mention that 1 circuit-breaker can serve 3 phases and work for 3 phase power as well, But if you can show what you claim through experiment, i will be convinced. I live in an apartment building, so i am sure this is a little hard to prove, particularly since i don't even have earth-leak circuit breakers in here.
If the OP plans to have earth-circuit-break protection on a metal enclosure and is thinking that connecting it to earth, will trip the circuit-breaker inside the house in case of an earth-leak, then this discussion is relevant.
On an extra note,
So you were saying that these circuit breakers measure differences between 20.04A & 20.00A I was under the impression that measuring high current is a little tricky, particularly at that accuracy.
You don't need to measure the current absolutely, only the difference. I don't know how modern residual current devices work but I remember an early version that had a large toroidal transformer with 3 windings: 2 identical high current windings for live and neutral, connected so that if the live and neutral currents are the same then the net magnetic field is zero. The 3rd winding senses any difference resulting from inbalance between the live and neutral windings. I don't have an old breaker to dismantle to see how they work but I assume the principle is the same.
Which is why it is consigned to the next bonfire. As I said the whole project is getting a makeover. The new improved (hopefully) version will either use one of these or an IP66 rated box which I want to mount on the outside wall of the filter house.
I did originally buy something like this but when I pressed the test button it tripped the RCD in the house, so I figured it was pointless.
Thanks, that's an older version, the new one shows rough water levels based on the float switch inputs. You can also view log files and set the timers from it too.
Ok, so the feed is protected against earth leakage. My opinion, which I accept others will disagree with, is that damp is unlikely to be the cause of your problems.
@pointy You cannot have ground fault circuit interrupters… in “series” with another. Probably why, when you tested the one at the pond it tripped the RCD in the house. 1 is sufficient wether it protects the entire circuit or only at the point of use.
30-40mA is scary!!! Here in Canada, 5mA is a class A ground fault circuit interrupter and the only acceptable install in a residential setting. Class B -30-40mA is allowed in industrial settings when equipment needing ground fault protection cannot start up.
Way off topic but if circumstances are right…
10mA is muscle paralysis or freezing
30mA is respiratory paralysis
30-50mA ventricular fibrillation
Glad you have something to protect you @pointy !!! Wear your rubber boots, gloves and hip weighers when in the pond . Or turn the power off, LOL
This is absolutely correct, the slightest amount of moisture would trip a RCD, some would consider it an inconvenience but it is definitely a life saver.
The way they work is by measuring the current through the live and the neutral which obviously should be equal. If the live or the neutral have a path to ground, such as through the human body, then the two become unequal, it does not matter if it is live or neutral that has the path to ground. I forget the trip point and I think that can differ depending on the RCD or local codes but it is usually less than 100mA.
Are you sure that the neutral goes all the way back to the power plant? I have always heard that it starts at the power transformer that steps down the transmission line voltage to voltages correct to feed into the power meter and main power panel.
Here in Canada Neutral goes to the center tap of a transformer.
Neutral connects to earth grounding rod.
Outside transformer lead is 120VAC L1, other outside transformer lead is 120VAC L2, between L1 and L2 we have 240VAC.
In house breaker panel, Neutral goes to water service (earth ground).
A 240 outlet has L1, L2, Neutral, Earth ground.
A 120 outlet has L1 (or L2), Neutral, Earth ground.
Look closely at the photo with the wiring through the enclosure after you took the relay board off (the one with the Rasp Pi depicted in it as well). There is one wire that sort of loops further, let's call it east, than the other wires, a little more than halfway down, closest to the plastic mounting clip.
Was that exposed wire near the top of the loop caused by the relay board failure, or was that exposed wire the cause of the relay board failure? If it was touching the back of the relay board, that wouldn't be good.
Or am I just seeing something that only LOOKS like bare copper where it ought not be?
On both relay boards the main pump connector looks good. Is this because it hardly ever gets switched or because it is running all the time, it has some small amount of heat that keeps the moisture away?
I have a new 8 way module that you can see in the 2nd post, I bought a few of them to experiment with.
What is the best type of screw terminal for solid wire? Is a rising clamp better?
Something else that has not been mentioned is the chocolate blocks on the back of the wooden box, they all look very clean and corrosion free.
Another thing, the lights relay has pretty much never been used as they stopped working, probably within the 1st year or 2. They looked nice when they worked though, and colors/patterns were configurable through a web interface.
The fact that the contacts are corroded for them, suggests moisture to me. I suspect that the screw contacts are just plated steel on these cheap connectors, whereas something like CamdenBoss are plated brass.
Particularly on the older board it looks like drops of water have been dripping 'down'
Whereas on the second board it appears water has accumulated with a drip near the center. I may have my orientation wrong.
And dry. also those blocks are not near any solder. Solder will make corrosion happen sooner.
Whatever you do, make sure it is all hermitically sealed and dry.
. Or turn the power off, LOL
