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Old 01-03-2021, 10:08 PM   #21
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Also, that 1v between neutral and ground is a lot. You may want to trace that to see where it is leaking, e.g. start at your power pedestal, and the the other end of your power cord, and the shore power inlet, then the main breaker, then the inverter input, then the inverter output, then the loads, and see where it first appears with everything upstream disconnected.

If the boat is leaking it, it could, for example, be enough to pop shore GFCI/RCD if you plug in at a modern marina.
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Old 01-04-2021, 10:37 PM   #22
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gkesden: The process of divide and conquer suggests that the fault must be inside the inverter. If it were on the connection into the inverter, then we would see similar behavior when the unit is on or off (which we do not). I cannot get back to the boat for a while to do any more tests, but don't think there is much more I can do anyway.

The manual for the Xantrex unit also describes various thermal protections to prevent overheating situations. Plus, now seeing that there is a problem running the microwave when the Inverter is off, it is a simple matter to ensure that it is on (which is pretty much what I have been doing for the last 10 years).

I do understand about the potential hazard of unplanned voltage drops under load so overall, so will do some more testing at a later stage.

Thanks again for your help!

PS there are three 30A circuit breakers leading up to the Inverter AC input, so I do believe this is well covered.
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Old 01-04-2021, 11:43 PM   #23
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gkesden: The process of divide and conquer suggests that the fault must be inside the inverter. If it were on the connection into the inverter, then we would see similar behavior when the unit is on or off (which we do not). I cannot get back to the boat for a while to do any more tests, but don't think there is much more I can do anyway.
I don't want to suggest that the following scenario is probable. Just possible...

Let's assume the inverter is seeing low voltage. When the inverter is enabled, it's "brown out" mode supplies good voltage to the device from the batteries by inversion instead of shore power. The energy is replaced by the battery charger. With the inverter off, it can't bridge a brown out, so it supplies the low voltage via the transfer switch ad it has no other option other than supplying nothing at all.

Normally, inverters kick in at ~90VAC. For some inverters a lower voltage won't be passed by the transfer switch when the inverter is off, but for others it will. So, although possibly unlikely, a low input voltage could still explain the symptom.

I don't know your battery or charger capacity, but how long it can support the load and the behavior of the charger might also be tells.

I'm not trying to discouraged you from buying a new inverter. The new ones are much nicer, e.g. true sine wave vs modified sine wave, most integrate chargers, and often times play nicer with RCD on shore. I just don't want you to miss another problem or buy something you don't really want or before you want.
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Old 01-04-2021, 11:51 PM   #24
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Hey PocketAces,

Also, out of curiosity, what type of charger do you have? What is its capacity? What about batteries serving the inverter?

My thinking is that, whether the problem is inside or outside of the inverter, since the voltage is only right when the inverter is on, you are likely to be supplying that load by inversion from 12V. So, beyond your chargers capacity, it is likely to be coming from the batteries, which then might be recharged later.

...you may want to check the water on those batteries more often if they are flooded and they get loaded and charged a lot.
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Old 01-04-2021, 11:59 PM   #25
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Going from my memory which is bad my inverter same brand as yours used to make a tick sound about every two seconds and the ac voltage gauge would show a ac current kicking in but for only a second and then the ac voltage gauge would go back to zero. It was some kind of power saving mode to save power. The voltage gauge kept bouncing up and down. I changed out of this power saving mode somehow, I don’t remember how and the tick and voltage meter stoped bouncing up and down.
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Old 01-05-2021, 12:06 AM   #26
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Going from my memory which is bad my inverter same brand as yours used to make a tick sound about every two seconds and the ac voltage gauge would show a ac current kicking in but for only a second and then the ac voltage gauge would go back to zero. It was some kind of power saving mode to save power. The voltage gauge kept bouncing up and down. I changed out of this power saving mode somehow, I donít remember how and the tick and voltage meter stopped bouncing up and down.
They do have a battery power saver mode, a search feature to see if anything wants power and then sleep to draw less during no demand times.
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Old 01-06-2021, 01:41 PM   #27
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gkesden: Thanks for the ongoing feedback. I will do a few more tests on the 1V between Neutral and Ground. Do you know what a more reasonable value would be? (0.1 or 0.5?) I will also do a few checks for the source as you suggest.

I have 4 newish GolfCart batteries which are in good shape and relatively new and topped with water only a few weeks ago. I simple check would be to turn off the switch between batteries and inverter, then turn on the inverter and try the microwave. I will do that next time at the boat.

From memory, the charger is a Promariner 1230 (12VX30A). That is not great but has worked well enough for me. Supplementing that with an additional 40A or so from an Inverter Charger would make sense if I do replace the inverter.

Regarding the other comments re Battery Power saver mode: I believe that if the inverter is off (as is almost always the case), then the inverter should not be drawing anything from the battery?
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Old 01-06-2021, 07:49 PM   #28
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Even with the inverter off, like most modern electronics it probably draws a little. This is a type of "parasitic load".

As for that 1v N-G, I'd 1st want to understand it better. Is it present at the power pedestal? End of shore power cable? Back of shire power inlet? Main panel? Inverter input? Inverter output? Receptacle?

How concerned I am depends on how long the run is and what is attached to it. If it is a really long run with a lot of cumulative resistance or had many devices that could be capacitive coming, 1-3V wouldn't bother me. But, most runs in boats are relatively short with a relatively light load.

So, what is more concerning to me is something like a high-resistance corroded connection, or water or corrosion where the shire power cable meets the pedestal or boat or a soggy or worn out shore power cable or other wiring or extension cord or a runnwith a lot of splines, etc.

So, if the problem is the marina has old wiring and it is coming to you like that -- not your worry. If the problem is that you are buying up either end of your shore powerncord or receptacle because salt water got in there, or yourbshore power cord is old and soggy, etc, you want to fix that.

If Un plugging devices lowers it, a lot, probably not a problem.

So, I'm more concerned about the possibility of it occurring at a single point (bad connection) or few, than if it is just the result of along run or a bunch of leaky loads.

In a residential setting ~2-3% of 120v is probably where people would start getting concerned.

But in a boat with /no/ load on the circuit, I'd look for an explanation even at 1v. The reason is just that there is often a point problem at a bad connection rather than just acumulative effect.

On my boat, if it isn't just old marina wiring, it is always a blackening, overheating or wet shore power connection.

Also, that Premarin 1230 is a workhorse, reliable charger, at least among those I know with it. It may not have the capacity or features you want, but Ibsusoect ut'll do what it does for a long time.
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Old 01-07-2021, 10:42 PM   #29
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Update: I check the 1V between neutral and ground and it originates in the shore power outlet. My boat has isolation transformers, so one question is which components are isolated? Live, Neutral and/or ground? It looks like the 1V is being passed through the isolation transformer into the boat AC.

I tried disconnecting the battery to see if the AC would be passed through the inverter, but with no DC, the Inverter does nothing and passes nothing through. With Inverter on, if I use the microwave, the green light denoting Shore power remains on, so it is unlikely that it is switching to DC supply due to voltage drop.

I have sent an email to Xantrex technical support asking their input, but am not optimistic of any reply. I will wait a while and take it from there.
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Old 01-07-2021, 11:53 PM   #30
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An isolation transformer is normally wired so that no current path from shore continues to the boat's wiring.

Normally the shore hot (black) runs through the primary coil of the transformer and returns via the neutral (white) completing the circuit.

The shore grounding conductor (green) is tied to neutral back at the main and is basically a parallel safety neutral to keep a metal chassis from becoming hot if wiring goes bad. I'll come back to this in a minute.

The boat power is electromagnetically (inductively) coupled to the shore power via another coil, called the secondary coil, placed next to the primary coil in the transformer box. Just like the primary, it has a black connected to one end, which, in this case, will serve as the boat's hot. And, just like the primary, it has a white connected to the other end, which, in this case, will serve as the boat's neutral. As loads are connected between the black and the white on the boat side, they complete the circuit.

As alternating current from shore power passes through the primary coil, like an electromagnet, the current generates a perpendicular magnetic force. It is this magnetic force that, because it is changing, produces the flux that can drive current flow in the 2ndary circuit.in this way there are two different circuits, one including the primary qinding and one including the secondary winding. These circuits each have electrical current flow, and the primary is driving the secondary -- but through a magnetic (inductive) coupling vs an electrical coupling.

Since the transformer is the source of current for the boat, the grounding conductor on the boat is tied to the white wire on the boat. In this way if a hot wire chaffes and touches exposed metal, it'll shirt and pop an on-board breaker or fuse rather than being a shock hazard for a human.

The transformer, itself, us in a metal case. Thus case could become energized by a chuffed shore hot wire or by a chaffed boat hot wire. Bht, UT can only be protected from one or the other by connecting UT to either the shore grounding conductor or the boat grounding conductor. Since the greater risk is from the boat's wiring as it is more prevelant on the boat, that is the one it is tied to.

What then happens with the shore grounding conductor? It is either not connected to anything or, more commonly is connects to an electrostatic shield (not to be confused with the chassis, which is the outside metal tied to the boat's grounding conductor and neutral). This shield is just a piece of foil between the two coils that prevents a certain type of capacitive electrical noise that can result from having two energized blobs of metal nearby.

The upshot is that I'm not seeing how the 1v measured between neutral and ground on the boat can be related to the 1v between neutral and ground on the shore side.

....but this email is full of assumptions.

One question might be, if you unplug shore power and let your inverter supply the boat...is the 1v still present? If so, you know it isn't coming from shore!

The control bits of most inverters are powered off of the 12v circuit. As a result, I am unsurlrised that it seems off, disabled, and shutdown without 12v.

One thing you can do is to look at your Premarin charger. Shut down all of the loads except Keith's and the inverter (just briefly) and look at the current it is supplying to the battery. Microwave a cup of qater and see if it jumps up a lot. Stop the microwave and see if it settles back down in a few minutes after replenishing the batteries. When it does repeat the experiment. If you see the current jump, do it 2, 3, or 4 times to convince yourself.

If the current goes up a lot tgen the microwave comes on, even though correlation isn't necessarily causation, it'll be a good bet it is supplying the microwave. If you can run the microwave for a few minutes and the charger doesn't start working hard, good bet the inverter isn't inverting 12vdc into 120vac
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Old 01-08-2021, 05:28 PM   #31
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gkesden: Thanks again. That is a good explanation of how a transformer works and reminds my of my old physics classes many years ago

Presumably if I turn off everything and disconnect from shore power and then check the resistance from the shore power cable (where disconnected from shore power) to any of the earthings of any plug in the boat, I will get a high resistance if there is no direct connection and a low resistance if there is a physical connection for the earth line.

re the 1V passing through the isolation transformer, I would have thought that if the transformer windings can pass 120V via the Neutral and Hot, they might be able to pass 1V between Neutral and Earth. But thinking more on this there are no windings for the earth so no inductance.

I will measure for Neutral/Earth voltage when powered from DC as you suggest and also watch the voltage on the house bank while using AC to heat some water. If the Inverter uses some DC power, then I would see some drop of the House bank voltage.

What I cannot figure is if the Earth on the boat is physically connected to the Neutral on the boat (as you allude above), then how could you build up 1V without a short circuit and sparks etc? (Quote: "the grounding conductor on the boat is tied to the white wire on the boat)"

I'll let you know the next set of measurements!
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Old 01-08-2021, 11:17 PM   #32
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What I cannot figure is if the Earth on the boat is physically connected to the Neutral on the boat (as you allude above), then how could you build up 1V without a short circuit and sparks etc? (Quote: "the grounding conductor on the boat is tied to the white wire on the boat)"
This is a tricky one. When we look at wires on a schematic, or think of them that way in our heads, we often tend to assume that they are "ideal conductors", in other words that they have 0 Ohms of resistance.

When we do that, no matter what the wiring might be, we find that since the neutral and grounding conductors are tied together, there should always be 0v of potential and 0 Ohms of resistance between them.

But, in a real world model, we need to add a lot of detail to that picture. Ignoring other phenomena such as inductance and capacitance for right now, each wire, for example, should really be modelled as a resistor. And, the thinner the wire and the longer it runs, the greater the resistance. Additionally, each connection should also be modelled as a resistor. And, some connections, such as those that are corroded, might be higher resistance.

Once we do this we find that we aren't really measuring at two equivalent points. Instead, we are measuring voltage or resistance at two points in a network of resistors. Measuring resistance without the circuit energized will show a non-0 resistance. And, once energized, depending upon the voltage(s) introduced and where, we'll be measuring the voltage difference across two different points in this network, rather than effectively at a single point as we would with ideal wires and connectors.

When wire is chosen to be thick enough for the current and distance, and the connections are good, we can often ignore the voltage drops along the wire and at the connections. But, if we start to draw more current through circuits than they were designed to support, or connections corrode, age, loosen, or suffer other damage, then we can start to see these things come up.

We might see less voltage at the windlass or charger than the battery, etc. And, this is often okay.

I'm not super concerned if there is 1v of difference between neutral and ground is accumulated over a bunch of wire and connections. I'm more concerned if it is all or mostly appearing in one place, e.g. at a weathered shore power inlet. In that case, it is often a sign that the connection needs cleaned up.
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Old 01-11-2021, 01:47 PM   #33
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gkesden: Some more feedback - but not exactly as per your email...
I measured lots of voltages and resistances yesterday. The isolation transformer is doing its job by decoupling the shore supply from the boat. (Open circuit for each of N, L, E between shore cable and plug sockets on boat.)
Checked wiring for AC in and out at Inverter. All connections are solid.
Checked DC voltage at house bank while using Inverter to power microwave. No change in DC voltage showing that all power to microwave is coming from AC. (V was 13.5 vs 12.0 when running microwave off of DC supply).
Earth on boat is connected to Live on boat as you suggested previously.

But... This time I saw different behaviour from Inverter when Inverter is OFF and trying to run AC using the AC bypass. The breaker lights for Microwave and TV were flashing on and off (likely in time with the Tick Tock). In any case, if the Inverter is giving inconsistent behaviour, then that really suggests that all is not well inside it. If the breaker switch lights are flashing on and off, it suggests that the voltage is turning on and off (as there are not fancy electronics in these lights to make them flash otherwise).

So my conclusion from all these observations and measurements is that the external wiring for the boat is sound and the inverter is faulty. So I will consider a replacement before boating season this summer. Thanks again for your help!
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Old 01-11-2021, 02:38 PM   #34
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I don't think that model is super configurable. For example, I don't think it has an energy saving mode that can be turned on or off or threshold set or anything.

So, if everything else is good -- sadly, you might be at new inverter time. :-(
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