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

[Wookie]

So I have a lovely crewboat that someone slapped lipstick on a pig and called it a yacht, and put all kinds of yacht club crap on it, and never took it offshore. It has a million dollar interior (literally, they spent 1.3 million at Palmer Johnson finishing it out) and it’s mostly worthless as an offshore vessel, what with all of the horsepower in the world and a stupid half-assed electrical distribution system.

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?

Someone took out the 3 phase and installed a single phase, 21kW 240v genset. So I can’t put the chiller on a VFD, as it’s only single phase. I could air condition the engineroom, and the engineer in me would be happy, but I couldn’t afford the power bill.

I’m looking for an alternative solution to buying a $14,000 4 or 3 ton chiller. Can I VFD single phase? Get a phase converter and new compressor? I can put in a smaller compressor, the heat exchanger wouldn’t care about that, any inventive suggestions are welcome.

 

[Bryan@Vintage Double Hose]

I worked in a facility that had single phase VFDs on return lines to their small water features. Motors were 1/2 hp if I remember correctly. Not sure if that helps or not.

 

[Wookie]

Y

I worked in a facility that had single phase VFDs on return lines to their small water features. Motors were 1/2 hp if I remember correctly. Not sure if that helps or not.

Yup, found a YouTube video describing exactly what I want. Now, to make it work with the fancy controller I already have...

 

[Bryan@Vintage Double Hose]

The ones I'm describing had to use a special single phase motor to work with the VFD. Motor was made by Grundfos and the VFD was Mitsubishi with the controls directly on the drive

 

[markmud]

Someone took out the 3 phase and installed a single phase, 21kW 240v genset.

How do you do that without creating an abortion?

Did I mention that I have a half-assed electrical system?

I would love to see this "system".

Something needs to be ripped out by the roots and made ship-shape. Either the electrical system or the gen set needs to be replaced with a 3 phase system But, you know that.

Why would someone throw in a single phase gen set into a three phase system? dunno.

As for the AC problem, well I can't help you. I can fix some of that but I sure as hell can't build a Frankenstein system.

Good luck!

mm

 

[kelemvor]

Single Phase VFD. Available for purchase Single Phase VFD, control speed for single phase motors | ATO.com

$170-$570 depending on your output requirements. Some output three phase from single phase input. Some output controlled single phase.

 

[tbone1004]

single phase in and out vfd's are available. May want to look at doing single phase in, 3p out vfd *usually 3hp max if looking at "official" ones. You can just double the size of the VFD if you need anything bigger. I.e. 5hp motor would need a 10hp vfd to handle the amps*. You get an extra perk of a more efficient motor. Shouldn't have to swap the compressor, just the motor.

 

[Wookie]

single phase in and out vfd's are available. May want to look at doing single phase in, 3p out vfd *usually 3hp max if looking at "official" ones. You can just double the size of the VFD if you need anything bigger. I.e. 5hp motor would need a 10hp vfd to handle the amps*. You get an extra perk of a more efficient motor. Shouldn't have to swap the compressor, just the motor.

Well, the a/c compressor and motor are intergral. I saw some literature that cap start motors aren’t compatible with VFD’s, but then I saw a guy doing it with an immersion chiller for a bubbler. I’m told a 5 ton chiller is a 5 hp motor. I dunno.

I understand 3 phase.

 

[Wookie]

How do you do that without creating an abortion?



I would love to see this "system".

Something needs to be ripped out by the roots and made ship-shape. Either the electrical system or the gen set needs to be replaced with a 3 phase system But, you know that.

Why would someone throw in a single phase gen set into a three phase system? dunno.

As for the AC problem, well I can't help you. I can fix some of that but I sure as hell can't build a Frankenstein system.

Good luck!

mm

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.

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.

 

[markmud]

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.

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.

Hi Wookie,

It has been years since I worked on marine electrical systems with a steel hull. As I recall, we always kept the different system separated. They may share the hull for equipment grounding, but never the same path. AC common mixed with a DC ground? Sounds like an electrolytic problem in the making if the equalizer malfunctions.

Kluster foxtrot.

Good luck!