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

[rhwestfall]

@ajtoady

 

[tekkydiver]

How did the electrical issues get by the survey?

 

[Wookie]

How did the electrical issues get by the survey?

Marine electricity. No one gets it. Ever.

 

[2airishuman]

After paying hundreds of dollars to ABYC, I find that the generator common should go to the hull with the battery negative, but my wife is hesitant because “they did it this way for a reason”. Yes, because the electrician has a severe learning disability, and knows nothing about marine AC systems.

Do you have shore power? Do you have an isolation transformer?

If you don't have shore power, you can ground the generator neutral, and should.

If you do have shore power, and you have an isolation transformer, you can ground the generator neutral, and should. (It is also permissible to bond the vessel side of the isolation transformer, instead, and use a 2-pole transfer switch)

If you have shore power, and no isolation transformer, then you can only ground the generator neutral when the transfer switch is in the "generator" position so that the shore power inlet, including the neutral in it, is disconnected. This was probably the original idea behind whatever broken circuit you have involving the battery equalizer.

 

[2airishuman]

How did the electrical issues get by the survey?

Because it's a subspecialty. There are very, very, few people who really understand yacht wiring. It's not the same as any other kind of wiring. A good surveyor will catch wiring problems that can be identified by visual inspection without any disassembly. That's part of their job. It is not part of their job to figure out whether, for example, ground lifts are working the way they should.

 

[2airishuman]

The boat has a 5 ton chill water system, single chiller, sized for an 85 footer, with only 57000 btu of air handler. In short, the chiller short cycles. Like 50 seconds on, 2 minutes off. I’m tearing up starters and capacitors. Did I mention that I have a half-assed electrical system?

... inventive suggestions are welcome.

5 tons = 60,000 BTU/h so you're not that far off. Might want to check filters and air handler airflow also.

I would put in a buffer tank and leave the electrical system alone. Size it to run 3 minutes on, 7 minutes off.

24 gallons should work if your setpoint differential is 10 degrees F.

60,000 BTH / 60 min/h * 2 minutes / 8.333 lbs/gal / 10 degrees = 24

 

[Wookie]

Do you have shore power? Do you have an isolation transformer?

If you don't have shore power, you can ground the generator neutral, and should.

If you do have shore power, and you have an isolation transformer, you can ground the generator neutral, and should.

If you have shore power, and no isolation transformer, then you can only ground the generator neutral when the transfer switch is in the "generator" position so that the shore power inlet, including the neutral in it, is disconnected. This was probably the original idea behind whatever broken circuit you have involving the battery equalizer.

Yes, shore power with a very expensive isolation boost (no buck that I can find in the manual) that corrects for low voltage without me having to re-tap the transformer.

The ABYC chapter E11-16 very carefully tells me that I should ground the generator neutral to the ground bus, and off to the engine bed. That, I understand. I am used to a floating neutral on a 3 phase wye, it's what I grew up with and trained in the Navy for. Also what this boat had on it before someone "upgraded" it. Now, it has this virtual neutral made with a Vanner battery equalizer. I don't understand the battery equalizer or why I have one. None of the house bank is 24 volt. None of the engine bank is 12 volt. The engine banks are separate from the house bank except they all go to ground on the engine bed, same place the single phase 240V generator neutral should go.

But I have a wife who wants to understand things. It's actually caused a massive fight. She wants to know why we have a virtual neutral instead of a regular neutral. "It must have been done for a reason". Since I don't have a reason, I'm not welcome to change it.

The only guy who ever said "Oh, someone used a Vanner battery equalizer to create a virtual neutral" is mad at me and won't talk to me any more.

 

[2airishuman]

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.

 

[2airishuman]

I would guess that the only reason you have a Vanner is to start the generator from the engine bank, since generators that size usually aren't available with 24v starters. The fact that it is bonding your AC system is just because it is miswired. On the generator side it should be connected to engine ground, not to the common in the output.

Just for an abundance of clarity, I have no idea what I'm talking about, so don't do anything dumb just because I said it was a good idea. But you knew that

 

[guruboy]

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.

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