Ammeter replacement questions

[jonelli]

I have the original ammeter on my panel and have confirmed there is no shunt. It’s wired directly through everything. It’s now sketchy if you touch the wires on it.

I bought this new meter, it’s cheap and I plan on using RTV to seal it up once I install it, but it uses a shunt instead.
Mare there any concerns about doing this or using this type of meter? It’s rated 100V/50A

 

[RoyS]

I have no idea how your present ammeter works. Discard all of it and install your new meter. The shunt should be installed on the negative cable coming from the house battery. Your new meter will measure all current in the battery circuit, whether charging or discharging.

 

[jviss]

The shunt should be installed on the negative cable coming from the house battery.

Depends on what current you're trying to measure, of course!

 

[jviss]

It’s rated 100V/50A

50A is not enough, in my experience, if you have a windlass or inverter.

 

[Davidasailor26]

50A will also not be enough to measure current going into the house bank if you have an alternator larger than 50A. Ideally the shunt would be connected directly to the negative battery terminal to measure all of those inflow and outflow currents. In your case if you want to stick with the 50A shunt you’ll need to make sure you put any of the larger loads and charging sources on the battery side of the shunt. If you’re only looking to use the shunt to see instantaneous draw of house loads that’s not a big problem. If the shunt were being used to measure battery state of charge it would be a bigger issue.

Our boat came with a 100A shunt, but all of the charging sources and bigger loads (like the windlass) were connected on the battery side of the shunt. I’ve since added a 500A Victron Smart Shunt (the smallest they make) in the proper place to measure all inflow and outflow.

 

[jviss]

50A will also not be enough to measure current going into the house bank if you have an alternator larger than 50A.

Maybe he just wants to monitor the current of the house loads, not the charging current, etc. I think that's the original intent of that Ammeter.

 

[kloudie1]

To make it work like the old one, connect the ends of the shunt to the old ammeter leads. (bigger screws?) then hook up the new meter per the instructions. The shunt will have to be insulated and secured to prevent a fire.

 

[jonelli]

Maybe he just wants to monitor the current of the house loads, not the charging current, etc. I think that's the original intent of that Ammeter.

I believe you are correct that is how the original setup of the Ammeter is wired. My charging systems are not wired through the battery switch anyway. The alternator and charging systems go directly to the House Bank 1 with a battery combiner.
I don't know if the windlass is run through the existing Ammeter, I'm guessing it's not since the original Ammeter tops out at 15A.
But, the original Ammeter does appear to be on the Positive out feed to the terminal blocks.

 

[LeslieTroyer]

The shunt is typically installed on the ground side of things which is opposite from the amp meter. While the shunt can measure current on either positive or negative - if on the positive side the red and yellow go to the shunt with the red on the battery end and black to ground. This assumes the meter is 100% isolated from the power leads if it’s not the magic smoke will be released. Be sure and fuse both reds and the yellow with 1/2 amp fuses.

While silicone may ( stress the may part) prevent you from getting shocked, it will also trap heat inside the shunt which is open so it can dissipate heat. You don’t really need to worry to much about 12V circuits it isnt

Additionally, remember unlike the amp meter this device is always on consuming power,

If you want to measure the high side your much better choice of meter would use a hall sensor or a CT rather than a shunt. These have a doughnut shaped device that your positive runs through and measures the magnetic flux created when current is flowing thru the wire.

You might want to connect either type to a switch (circuit breaker)

 

[jviss]

Additionally, remember unlike the amp meter this device is always on consuming power,

?

 

[LeslieTroyer]

The analogue meter uses power (very small) when current is flowing. The digital meter uses power to run the integrated circuits and power the led display 100% of the time.

 

[Stu Jackson]

Ammeters & Shunts 101 Ammeters & Shunts 101

The "gauge" ammeters that only measured house currents usually had the shunts built in. Those of you talking about using the negative are discussing a completely different tool.

 

[jviss]

The analogue meter uses power (very small) when current is flowing. The digital meter uses power to run the integrated circuits and power the led display 100% of the time.

Ah, yes, gotcha!

 

[jonelli]

I'm not familiar with DC circuits that can measure current via the wires through the "donut". Thought that was AC Voltage only. At least that's what I was taught. I'm trying to measure my house load usage. 12V.
Everything I've seen shows these meters used on the negative side. That's fine with me. There are lots of other exposed Negative terminals inside the electrical panel. Not sure how it's any more or less dangerous. It looks like the shunt itself is coated, so the only thing exposed are the connection screws and their pads. That should be coverable with liquid tape.
Here are the instructions/wiring for the unit I bought:

 

[Davidasailor26]

Makes sense to me. You’ll want to fuse the positive wires into the meter with a fuse appropriately sized for the gauge of those wires. And rather than having the negative wire going into the shunt start at the “controller” it will start at your house panel negative, but it looks ok otherwise.

 

[LeslieTroyer]

current transformers are AC - Hall effect are DC
If you look on Amazon with “Hall effect volt amps” you’ll see a bunch of DC meters.
If you have a central grounding terminal strip for your grounds (on wire running back to the battery) that would be perfect.

Looking at your wire photo I notice a few ABYC wiring issues
1) too many lugs on the battery switch common 3 max
2) black wire connected to bat (1 or 2) battery switch
3) yellow wire on battery switch common
4) 12 (10?) ga wires on battery switch with no fuse
5) wire to amp meter and man panel way undersized ( 30A continuous for 3’ is 8ga)

1) ignore unless survey brings it up
2&3 are easily fixed with 6” of appropriately colored tape.
4) should have inline fuses
5) figure out load and duration and size wire with a marine wire calculator.

These are all very common on “older” boats.
Les

 

[jonelli]

FWIW, here's my main re-wired battery setup:

That yellow wire is the stereo's memory wire. They're always yellow.
That black wire on Batt1 is the original bilge pump feed. it was already there and black. I agree though, I should change that to red.
The two other red wires on the common positive are 1 - to the main house panel (originally run through the ammeter), and 2 - to the autopilot.
I think the autopilot system was wired in that way by the PO after the fact. It has it's own toggle switch not part of the breaker panel that switches the autopilot/pedestal power.
To fix some of that stuff, I'll need to add another terminal block, as I'm just out of available terminal screws.
Pretty sure the yellow wire has a fuse at the other end by the radio, The other two red wires, one goes to the house breakers and the other to the autopilot which I believe has its own fuse, so I don't think I'm missing any fuses.
I agree, after going through all this, I should pull a bigger wire to main feeds there. The negative on the entire panel feed is the same as those positive ones, 12ga. That's how i got the boat. I was originally focused on fixing the wiring to the batteries and starter, so that I replaced with 1/0 size wire long ago. I never bothered with all the little 12V wiring.

 

[Stu Jackson]

If what you are trying to measure is the power (amps) being used in your distribution panel, i.e., the main electrical panel with all of your subcircuit's switches or breakers, then you need to find the positive wire coming in from the 1-2-B switch common terminal TO the distribution panel. Insert the new ammeter into this wire.

Your old ammeter had a shunt built into it. This was discussed in the link I provided in reply #12. Your new ammeter has a separate shunt. This was also discussed in the link I provided in reply #12.

The ammeter I have on my boat does just this. Common post of 1-2--B switch to ammeter to distribution panel. Your new ammeter will be: common post of 1-2-B switch to shunt, other end of shunt to distribution panel, plus the power wire to the display.

As noted in that link, ammeters measure FLOW of electrons, i.e., amps, which means all the power to whatever you are measureing has to GO THROUGH the ammeter, i.e., in series. This is just the opposite of measuring voltage, i.e., in parallel.

Finally: Why the positive wire (instead of the negative, as too many have proposed)? The REASON is that there are usually many negative wires coming from the distribution panel, BUT ONLY ONE positive from the 1-2-B switch common post. The ammeter doesn't care whether it is positive or negative, it is measuring flow. So, you measure it at the one wire that you know for certain contains all the flow for the distribution panel.

 

[LeslieTroyer]

The purpose of the colors is to prevent confusion. Red = DC Positive. Black = AC Neutral or DC ground. Yellow= DC ground , white = AC hot, Green = AC ground. yellow is preferred for DC ground over black to avoid confusion between AC & DC.
I understand you know why those wires are that way but some mechanic might not. Tape is cheep insurance that it won’t cause confusion in the future.

As far as fuses on consumer electronics - they are put on devices near the device primarily for liability purposes. It leaves the wire from the fuse to the power source unprotected. Always fuse where wire size is reduced and upstream fuse is too big to protect the device.

1/0 is a great way to upgrade your boat. Might I suggest MRBF fuses at the battery also. A 200A fuse can still start your boat and still prevent that wire from turning into an arc welder burning a hole in the boat. (Yes I’m evangelistic about fuses)

I really do applaud you for asking for help and trying to make your boat safer!!

Les

 

[jviss]

power current (aAmps)

fixed it for you

As noted in that link, ammeters measure FLOW of electrons, i.e., amps, which means all the power to whatever you are measureing has to GO THROUGH the ammeter, i.e., in series. This is just the opposite of measuring voltage, i.e., in parallel.

This is correct, in a sense, but a confusing way to express it. It might confuse people, especially to say that voltage is measured in parallel, and that it's opposite of current. But, I get it.

Most EEs capitalize units that are named after people, in honor of those people: George Ohm, André-Marie Ampère, Alessandro Volta, James Watt, and so on.