Xantrex Inverter Tick Tock noise

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!

PocketAces said:

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)"

Click to expand...

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.

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!

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. :-(