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Old 08-12-2019, 23:33   #1
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AC panel ammeter - necessary?

What is the purpose of the 0-50 ammeter on AC main distribution panel and would it be better as a digital versus analog meter? How about a 0-150 voltmeter? Are they necessary? I see main panels sold with and without them. Not sure if there's an ABYC code requirement
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Old 08-12-2019, 23:39   #2
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Re: AC panel ammeter - necessary?

It's not a requirement but it's nice to be able to keep an eye on your electrical system.

I would consider voltage more critical. It's not unusual in a marina on a hot summer weekend to see low voltage as a large percentage of the boats have the air/con running full bore. If it gets too low, you risk damage to the compressor motor.

Amp meters are less critical but nice to see if you are pushing the limits of shore/generator power. They can also be nice to track usage if you want to set up an inverter to run AC loads off battery power.
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Old 09-12-2019, 00:43   #3
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Re: AC panel ammeter - necessary?

I think voltage is an abyc requirement

Current is very usefull. People blow dock breakers all the time and no idea how much they are using.

I would always have both. Digital is better.
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Old 09-12-2019, 00:50   #4
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Re: AC panel ammeter - necessary?

The only real need for an AC ammeter is if you have a genset and have high loads and want to keep an eye on them to not overload it. Or if you are plugged into a downsized shorepower service and don't want to trip the pedestal breaker. If you were on a metered service it is also nice to have a better feel for how much juice you are using before the bill comes. Of course an ammeter is not a watt-hour meter, but you can see at a glance how hard your system is drinking juice at any given moment and adjust your usage accordingly.

As for a voltmeter in the panel a far more economical alternative if you dont already have obe is to juat buy a simple plug-in LED voltmeter and leave it in a receptacle that is in plain view. I have one I leave in at the nav station outlet when on shore power. You can buy them at any big box home building supply store or Amazon for under $10.

Ours once saved us at a marina when the dockhand plugged us into pedistal that was wired wrong and the 30A 120v connection was actually 240v. The meter in the receptacle told the tale instantly and they fixed it right away.

Be careful with these plug-in LED meters if you have an inverter that isn't a true sine wave unit. They will read very low on modified sine wave or square wave AC inverter and could actually burn out or maybe even cause a fire in rare cases.

Eversame Flat US Plug AC 80-300V LCD Digital Voltmeter: https://www.amazon.com/dp/B015H0A3FO..._1XF7Db6KP8NEV
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Old 09-12-2019, 00:53   #5
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Re: AC panel ammeter - necessary?

A panel volt meter is wired before the main breaker. So you can check it before the boat power is turned on. If it’s already at the plugs. You ‘ve already fried every thing.
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Old 09-12-2019, 01:23   #6
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Re: AC panel ammeter - necessary?

Not if you don't have anything plugged in. And not everything will be fried on overvoltage anyhow. Its not necessarily a doomsday scenario. Many modern electronics are rated for 90-250v and 50-60hz primary. Most chargers for phones & computers, and many battery chargers are made this way. This makes it much easier to market products to different countries, and only the feed cords or plug attachments need be swapped. Apple is but one example.

We have a very simple AC panel. 2 circuits and an ELCI main. 1 circuit is the receptacles and nothing is ever left plugged in, and the other feeds the dual-bank marine battery charger which doesn't care about input voltage or frequency.

It is a boat, not a palace. Almost everything is on DC anyhow. We are only ever on shore power a few days a year and went 11 months last year without ever taking the shore power cord out of the lazarette. Full-time cruisers. Almost every night on the hook with the occasional free wall.

My background is as a commercial electrician. I may know a thing or two. Don't try and teach grandma how to suck eggs.
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Old 09-12-2019, 04:27   #7
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Re: AC panel ammeter - necessary?

No meter is necessary but either a volt meter or ammeter is nice to have.

My boat has a volt meter. It's an old analog type that gives you a reading between E and F like a gas gauge.

I usually get my more precise voltage reading off my old PWM Controller which at present does not have a solar panel hooked to it.

The solar panels for now are going through the Victron Controller which only has a light display which will tell you when you reach about 13.8 volts which is Float when the amber light stops blinking. The Victron will also tell you when you are above 14 volts because it will have a slow blinking amber light notifying you that it is in absorption mode.

When sailing, at least one panel will be attached to the PWM Controller

If you need an immediate voltage check though, it's always good to have a volt meter onboard. They are especially important when troubleshooting electrical or electronic problems
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Old 09-12-2019, 05:24   #8
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Re: AC panel ammeter - necessary?

You can also take current measurements with a VOM on the exact area you want to check not necessarily the total current draw
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Old 09-12-2019, 10:36   #9
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Re: AC panel ammeter - necessary?

I find an AC ammeter handy to have when running off a small generator (and soon, the new inverter). It helps budget your available power, and can be a real eye-opener about the different loads. (I usually have to run the farm off generators for a few weeks each year too.) After a while, you learn what the loads the system can handle together, as long as the equipment remains constant. But it's still handy to check the meter before flipping on the microwave or a drill (oops, need to wait until the pump finishes cycling.)
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Old 09-12-2019, 16:31   #10
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Re: AC panel ammeter - necessary?

I use an inexpensive digital power meter that displays ac volts, Watts, amps, and several other things. At $12 itís a real bargain. Nice when youíre on generators power to see what the load is before you power on the microwave. Iíve used it for about a year now with no problems. It uses a small coil pickup around the primary ac wire to measure the current before the main breaker. And...the blue display makes a nice nightlight
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Old 09-12-2019, 18:36   #11
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Re: AC panel ammeter - necessary?

Quote:
Originally Posted by Cyrus Safdari View Post
What is the purpose of the 0-50 ammeter on AC main distribution panel and would it be better as a digital versus analog meter? How about a 0-150 voltmeter? Are they necessary? I see main panels sold with and without them. Not sure if there's an ABYC code requirement
You need an AC voltmeter on your AC panel if you have a motor or generator connected. It is nice to have an AC voltmeter and ammeter, so you can see what is coming into the boat and if it is within limits. An analog meter full scale is not supposed to be more than 150% of the nominal voltage measured, but a digital meter should be more precise. A high quality meter including AC Volts, Amps, Watts and freq. (Blue seas) is about US$250, down to about $35 from China on Amazon.
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Old 10-12-2019, 16:50   #12
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Re: AC panel ammeter - necessary?

We have an older panel with an analog AC ammeter which comes in pretty handy when we are plugged in at the dock. My inverter/charger will not pass 30 A continuous so I can monitor how much current is flowing at a given time when I plug in an appliance and adjust what is running so I don't continually blow the reset button on the inv/chg.
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Old 10-12-2019, 18:03   #13
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Re: AC panel ammeter - necessary?

ABYC E-11.9.3.2 Requires a voltmeter if the panelboard is connected to a motor or a genset or an inverter.
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Old 16-12-2019, 19:27   #14
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Re: AC panel ammeter - necessary?

Would there be much of a point if you have an isolation transformer?
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