Air conditioning, single phase, those who have a better grasp of marine electricity than I

[guruboy]

They replaced everything except the wires? Maybe? A 3 conductor wire runs out of the gen, L1, L2, and common. Common goes to the negative of a house battery through a battery equalizer creating a “virtual common” which no one can explain to me. The generator frame ground is to the hull, properly. The negative of the house bank goes to the hull, properly. But if I switch off the battery equalizer, I lose the generator common, improperly, which causes about $8k in damage to sensitive electronics like the air conditioner controllers.

It is probably “virtual” because it is probably not tied directly to ground. When you turn that thing off, you are probably making that common a floating node disconnected from ground.

 

[Wookie]

What model Vanner? The only ones I found in a quick search are 24v to 12v converters and have no connection to the AC system.

Now you know why I'm confused. The neutral from the generator runs from the generator to the 12V side of the Vanner to the negative side of a battery to the hull ground. If the vanner is switched off, the neutral goes away.

 

[Wookie]

Are you sure you have a battery EQUALIZER and not a battery ISOLATOR?

Definitely a battery equalizer which does not equalize anything. It isn't tied into anything 24V. It is only used for this damned virtual neutral.

 

[Wookie]

It is probably “virtual” because it is probably not tied directly to ground. When you turn that thing off, you are probably making that common a floating node disconnected from ground.

And when that happens, you get about $8,000 worth of repairs.

 

[2airishuman]

Now you know why I'm confused. The neutral from the generator runs from the generator to the 12V side of the Vanner to the negative side of a battery to the hull ground. If the vanner is switched off, the neutral goes away.

IMO that's the product of a communication problem when the generator was installed. Some installer was told "run + and ground from the Vanner to the generator" and the nuance that there is more than one ground on the generator (i.e. the DC ground on the engine and the AC neutral) was not understood. So that's why. Hope that story restores peace in the valley and lets you disconnect it and ground it in a reasonable way.

If the Vanner is indeed providing the power to the genset starter, then you should have a +/- 12 volt pair going from the Vanner to the control and engine starting side of the genset, suitably heavy wire depending on distance, with fuses and disconnects to taste.

If you're doing things the ABYC way then you bond white and green together at the generator for the AC side of things. Green should be continuous and be bonded to the vessel's DC system at a single point, probably somewhere besides the generator.

 

[guruboy]

Look at page 6 and page 8.

http://www.vanner.com/wp-content/uploads/2010/07/Battery-Equalizer-Owners-Manual-70-wo-M-8-17-04.pdf

 

[2airishuman]

Are you sure you have a battery EQUALIZER and not a battery ISOLATOR?

Vanner makes battery equalizers.

They are devices that provide an inexpensive, reliable means to "split" a 24v battery bank and draw 12v power from it. On larger yachts, it is common for the house battery to be wired for 24v to support large loads -- usually inverters and bow thrusters -- without unmanagaeably large currents. Most marine electrical equipment can either be ordered in 12v or 24v, or comes in a multi-voltage form that will work on either. However, there are often a few loads that are 12v only. Usually these are the NMEA/CANBUS network, which requires a 12v supply because that's what the standards say, some electronics (the Icom M-802 shortwave transceiver being notable), and the starter for the auxiliary generator. These smaller generators use Yanmar and Kubota diesels, usually, which in turn use nonstandard miniature starters that don't interchange with anything else, and which are only available in 12v.

Anyway, the battery equalizer makes it possible to tap halfway through a 24v bank and get 12 volts, and then "equalizes" the battery string to make up for the current drawn from only half the string, by charging one half of the string from the other half until the voltages are the same. It's much cheaper than a 24v to 12v converter of the same size, although those are used too.

 

[guruboy]

Vanner makes battery equalizers.

They are devices that provide an inexpensive, reliable means to "split" a 24v battery bank and draw 12v power from it. On larger yachts, it is common for the house battery to be wired for 24v to support large loads -- usually inverters and bow thrusters -- without unmanagaeably large currents. Most marine electrical equipment can either be ordered in 12v or 24v, or comes in a multi-voltage form that will work on either. However, there are often a few loads that are 12v only. Usually these are the NMEA/CANBUS network, which requires a 12v supply because that's what the standards say, some electronics (the Icom M-802 shortwave transceiver being notable), and the starter for the auxiliary generator. These smaller generators use Yanmar and Kubota diesels, usually, which in turn use nonstandard miniature starters that don't interchange with anything else, and which are only available in 12v.

Anyway, the battery equalizer makes it possible to tap halfway through a 24v bank and get 12 volts, and then "equalizes" the battery string to make up for the current drawn from only half the string, by charging one half of the string from the other half until the voltages are the same. It's much cheaper than a 24v to 12v converter of the same size, although those are used too.

They also make isolators

Battery Isolators

 

[markmud]

This:

It is probably “virtual” because it is probably not tied directly to ground. When you turn that thing off, you are probably making that common a floating node disconnected from ground.

And this:

IMO that's the product of a communication problem when the generator was installed. Some installer was told "run + and ground from the Vanner to the generator" and the nuance that there is more than one ground on the generator (i.e. the DC ground on the engine and the AC neutral) was not understood. So that's why. Hope that story restores peace in the valley and lets you disconnect it and ground it in a reasonable way.

Plus this:

From 1500 miles away, I think they are onto something. The only AC input, or connection, should be the AC feed for the battery charger (I don't think you have a DC to AC inverter, or do you?).

I'll bet you a dollar!

markm

 

[Wookie]

This:


And this:


Plus this:
View attachment 508467

From 1500 miles away, I think they are onto something. The only AC input, or connection, should be the AC feed for the battery charger (I don't think you have a DC to AC inverter, or do you?).

I'll bet you a dollar!

markm

No bet, I’m sure you’re right. The question wasn’t how is it, the question is why? I found an electrician who knew what a virtual ground is and why. I guess I’m going to have to go be nice.

What 2air said may be exactly correct. Someone hooked it up wrong, and it happens to work unless you turn the battery equalizer off (which isolates it from ground, and therefore the hull). And, it’s an aluminum boat, so maybe they didn’t want the common to go to hull..... which isn’t a problem if all of the conductors are connected to equipment properly.