Do I need a Voltmeter on my AC panel?

[captmikem]

Originally Posted by sully75

Sorry Michael, no pictures seem to have come through.

try again.... think I hit the wrong upload button

[Lake-Effect]

Originally Posted by Dave Lochner

Low voltage may be come an issue if you are running high load devices, on a boat that would be an electric heater, air conditioning, etc. If the voltage starts to drop under 110 the motors in these devices don't run as efficiently and will may over heat or get damaged.

The other condition is if the voltage has dropped is it a marina issue, that is somewhere between the power pedestal and the nearest generating station or is the problem on your boat? Corrosion and bad connections can overheat and become a fire hazard.

Dedicated voltage meters are handy because it is easy to monitor and see the voltage. Handheld digital voltmeters are more useful, but you have to get it out and actually test the voltage in an outlet. Voltmeters of reasonable quality are fairly inexpensive, and then there are Flukes...

For situations like the above, a dedicated AC meter is handy. In particular, if you connect up shorepower, meter shows proper AC voltage, then as soon as you switch on a big load (eg the water heater, the microwave, the airconditioner) and the AC voltage drops noticably - there may be a connection problem between the pedestel and your AC panel... or even further back along the dock. That voltage change under load indicates that a significant amount of power (eg a 10% drop means that 10% of 120v times whatever current you're pulling) might be heat at a bad contact and this could burn up or melt in short order. The fix might be as simple as just giving the connectors a firm turn... but if you don't notice the problem right off, you will soon notice the smell, and the dimming lights ;-)

Sure, sticking some probes in a socket is simple, but if you don't have a AC socket close to the panel, and the multimeter's buried ...somewhere, then it isn't very handy, and you won't get the immediate feedback of the panel meter every time you switch something on.

Also depends on budgets, how much you're going to cruise and where, how big the boat, how many AC loads you'll use, etc. of course.

[Terra Nova]

The AC panel should show AC amps and volts. This isn't mainly to check the voltage of your shore power source; it is to monitor and troubleshoot your own electrical system.

[Colin A]

As I recall ABYC technically requires a voltmeter for AC when the system will include a AC motor load.

[sully75]

Originally Posted by Dave Lochner

Yes. Do you have any underwater metals? Through hulls?

All boats in the marina connected to shore power are connected through the ground wire. That effectively makes the marina a great big low voltage battery and any metal underwater will begin to sacrifice itself.

The GI allows AC voltage to pass through in the case of a short, but does not allow low voltage DC to pass through the ground connector.

I do have 2 bronze through hulls and stainless steel rudder hardware. Otherwise nothing. I'm confused...if I'm not grounding the AC through the engine or below the waterline, why do I need to use an isolator...what would it do?

[Dave Lochner]

Originally Posted by sully75

I do have 2 bronze through hulls and stainless steel rudder hardware. Otherwise nothing. I'm confused...if I'm not grounding the AC through the engine or below the waterline, why do I need to use an isolator...what would it do?

Here's a link to a good article on the issue. BoatUS: Seaworthy

If your outboard is an electric start, then the outboard is connected to the DC - which, if you add a battery charger, will connect to the AC ground which will connect to the rest of the boats in the marina.

So, if your outboard has a little bit of aluminum sitting in the water, that aluminum will waste away and you'll need a new lower unit or outboard.

[svinshallah]

Adequate AC meters aren't expensive. MPJA in Florida has a digital AC amp/voltmeter for about $20.


Sent from my iPad using Cruisers Sailing Forum

[sully75]

Would this work?

http://www.amazon.com/DROK-Multimete...amp+volt+meter

[sully75]

Originally Posted by Dave Lochner

Here's a link to a good article on the issue. BoatUS: Seaworthy

If your outboard is an electric start, then the outboard is connected to the DC - which, if you add a battery charger, will connect to the AC ground which will connect to the rest of the boats in the marina.

So, if your outboard has a little bit of aluminum sitting in the water, that aluminum will waste away and you'll need a new lower unit or outboard.

It's a pull start. There is an alternator which I will attach. But the outboard is totally out of the water at the dock. It's in a well. I could put a switch on the alternator to isolate it maybe, just in case? Doesn't look like these isolators are particularly cheap.

[Hoodsail]

Considering your budget, would go a season on shore power and see how your sacrificial zincs have fared... can use their end of season condition as an indication of the errant voltage in your respective marina...in the end you may not need a galvanic isolator and save a few hundred $. Dave

[mitiempo]

Originally Posted by Colin A

As I recall ABYC technically requires a voltmeter for AC when the system will include a AC motor load.

ABYC only requires an AC voltmeter when there is an inverter in the system.

ABYC does not require a galvanic isolator but as posted it is a very good idea due to possible corrosion issues. But with an outboard tipped out of the water and especially if you have Marelon seacocks it isn't necessary.

I find the most useful meter is an AC ammeter. It shows my total AC load and by monitoring it I can prevent popping the breaker on the dock.

[adlib2]

Originally Posted by boatpoker

You cannot rely on dock power being 120VAC. Many marinas have crappy wiring and when everyone turns on their a/c voltage can drop. Running your a/c on 90 volts will shorten it's life dramatically. This is not uncommon.

Add a Galvanic Isolator while you are at it. When you plug into shore power you are connecting yourself to every other boats electrical problems (very common) a GI will protect you from them.

For a given wattage usage when volts drop amps rise which causes burnouts of receptacles and equipment. You should always be aware of the voltage you are using; although, the only recourse you have is to switch off power until voltage resumes to full level.

[valhalla360]

For $20 at home depot they have a meter that just plugs into a socket and constantly reads out the voltage (or amperage/watts/kwh). We got this separate form a test meter (with leads).


The problem with using a test meter is you plug in late afternoon after a lot of the air/con have cycled off, so the voltage looks fine. The next day as it heats up and all the air/con units kick on, the voltage starts dropping...will you constantly be pulling out your test meter? We have it plugged in where it's easy to see and I just glance at it when going by it.


If you are outboard powered with no other metal, don't worry about an isolator. With no metal contacts connected to your electrical system in the water, you can't create a battery.

[Terra Nova]

It is a boat's water heater that can benefit most from a galvanic isolator.

[adlib2]

Originally Posted by sully75

Would this work?

http://www.amazon.com/DROK-Multimete...amp+volt+meter

I was about to say the 20amp rating would be better if higher to at least cover 30 amp shore power; however, the details say 100 amp, so what is correct?
This itemROK® Digital Current Voltage Multimeter AC 100-300V 100A Voltage Amperage Meter, AC Volt Amp… $14.98