Marine Air Conditioner (Help Please)12v DC

[Rick in Davie]

I am looking for a 12v DC unit for a Lagoon 42. Any suggestions?

 

[FF]

Shop the OTR advertisers ( large truck sites)


They have 5,000 BTU units that can cool the sleeping compartment over night , and recharge a mass of batts in the next 8-10 hour drive... Try Red Dot

 

[Rick in Davie]

Shop the OTR advertisers ( large truck sites)


They have 5,000 BTU units that can cool the sleeping compartment over night , and recharge a mass of batts in the next 8-10 hour drive... Try Red Dot

Thank you for the reply however I don't think that 5000 BTU will cover me. Also where are the OTR advertisers? I am new to this any completely lost.

 

[DavidM]

I suspect that these truck 12V A/C units are like window A/C units. They exhaust heat out the back into the environment. Unless you can mount one to do that, they won't work in your boat.

You probably need a marine specific, raw water cooled 12V A/C unit. These have been debated on this forum, but I think that they are smaller than 5,000 btu/hr, maybe enough for a state room. Do a search.

David

 

[Rick in Davie]

I suspect that these truck 12V A/C units are like window A/C units. They exhaust heat out the back into the environment. Unless you can mount one to do that, they won't work in your boat.

You probably need a marine specific, raw water cooled 12V A/C unit. These have been debated on this forum, but I think that they are smaller than 5,000 btu/hr, maybe enough for a state room. Do a search.

David

Yes sir I am looking for the unit that pulls the water from the ocean and cools it that way. The ones that hang on will not suit my needs. I will research a bit now. Thank you for your help.

 

[mvweebles]

Why are you focused on 12vdc? I looked into same question last year. The Mabru unit advertises around 40A for their 12kBtu A/C. It's over $5000 and proprietary. What's hard is finding actual amp-draw figures for any of the ACs - 12vdc or 120vac. In the end, I could not figure out why the 12vdc would be more efficient as it's essentially the same components in the assembly.

I did not have a good answer to "What problem am I solving?" so I decided to go with an easily sourced/replaced 120vac unit for $1200, 75% less expensive than the 12vdc unit. High end inverters are also pretty affordable these days - I think I paid just over $1k for a hybrid-Magnum 3000w PSW inverter. $5500 - the price of a Mabru 12vdc 12,000Btu A/C - buys a lot of power management and control.

Curious to know your thinking

Peter

 

[Rick in Davie]

Why are you focused on 12vdc? I looked into same question last year. The Mabru unit advertises around 40A for their 12kBtu A/C. It's over $5000 and proprietary. What's hard is finding actual amp-draw figures for any of the ACs - 12vdc or 120vac. In the end, I could not figure out why the 12vdc would be more efficient as it's essentially the same components in the assembly.

In the end, I did not have a good answer to "What problem am I solving?" so I decided to go with an easily sourced 120vac unit. High end inverters are also pretty affordable these days - I think I paid just over $1k for a hybrid-Magnum 3000w PSW inverter.

Curious to know your thinking


Peter

I am new to this, so I really am not thinking as technical as you. I will look into this. Thank you for information! It is all new to me.

 

[DavidM]

I don't believe the 480 watt for 12,000 btu spec of the Mabru for one second. I suspect that they are factoring cycle time into that spec which is basically fraudulent.

David

 

[mvweebles]

I don't believe the 480 watt for 12,000 btu spec of the Mabru for one second. I suspect that they are factoring cycle time into that spec which is basically fraudulent.

David

I danced around it because I have never seen the data, but I agree with you David. The regular Marine A/C OEMs talk about how to size the circuit but there finding actual usage data for sustained operation has been elusive.

These A/Cs are relatively reliable but do not last forever - if you own your boat for 10-years and spend any time in Florida or the Tropics, strong chance you'll replace the unit once, maybe twice. There are several well-respected manufacturers of 120vac reverse cycle A/Cs from which to chose.

Rick/OP - on a 42-foot boat, you either have or should have a decent sized inverter. They are big and heavy which is important to your Cat, but have become very reliable and combine with battery charging nicely.

Finally, the water pump needed for reverse cycle A/C slurps up a fair amount of power - a good 3-4 amps @120vac on its own.

Good luck! I look forward to updates on how you proceed.

Peter

 

[ranger58sb]

I am new to this, so I really am not thinking as technical as you. I will look into this. Thank you for information! It is all new to me.

As you're seeing, an AC (voltage) marine A/C (aircon) unit is more common. Essentially a heat pump that uses sea water instead of air.

Is your Lagoon already ducted for heat/AC? That'll be another facet to study... but if so, maybe some of the electrical infrastructure is already there, too.

Or if you're just interested in replacing an existing unit that dies or whatever... you could check out the Dometic DTG units... and then shop on those and others that are similar.

-Chris

 

[OldDan1943]

Why are you focused on 12vdc? I looked into same question last year. The Mabru unit advertises around 40A for their 12kBtu A/C. It's over $5000 and proprietary. What's hard is finding actual amp-draw figures for any of the ACs - 12vdc or 120vac. In the end, I could not figure out why the 12vdc would be more efficient as it's essentially the same components in the assembly.

I did not have a good answer to "What problem am I solving?" so I decided to go with an easily sourced/replaced 120vac unit for $1200, 75% less expensive than the 12vdc unit. High end inverters are also pretty affordable these days - I think I paid just over $1k for a hybrid-Magnum 3000w PSW inverter. $5500 - the price of a Mabru 12vdc 12,000Btu A/C - buys a lot of power management and control.

Curious to know your thinking

Peter

Peter, remember you must have the batteries to support the drain of the inverter.

 

[mvweebles]

Peter, remember you must have the batteries to support the drain of the inverter.

Good clarification OldDan. I did not explain. There really is no practical way to run A/C - 12vdc or 120vac - off solar. You can run it, but you can't recharge the batteries fast enough without a generator. But with a suitably sized and installed alternator, you can run off the batteries with engine providing 12VDC to the batteries. The Mabru would be direct-connect; 120VAC would go via an Inverter.

They are expensive alternators and usually have installation complexities due to serpentine belt; and some controls and bigger cables are needed. But still, guessing you could install a hi-output Balmar (which you'd need regardless of 12v or 120vac A/C) along with inverter and a 120VAC A/C for around the same amount as the $5500 Mabru 12VDC A/C alone.

To the OP - OldDan makes a good point though - mostly, A/C is run off a generator when away from shore power.

Peter

 

[Hand ON Engineering]

I am looking for a 12v DC unit for a Lagoon 42. Any suggestions?

Hi Rick.
I have a 2014 Beneteau Swift Trawler 44 Trawler, with 2 rooms and salon.

For the salon I installed a 12000BTU Self contained Marine air conditioners @12Volts DC. Brand: Mabru Power Systems and cools excellent keeping the air dry and confortable.

For cooling and heating both rooms, I have 1 Mabru 7000 BTU self contained air conditioner @12Volts DC with a split duct ( Y ) to distribute the air for both areas.

I have a Lithium battery bank (3 x 250AH) 750AH total.
These 3 Batteries runs my 2 air conditioners for more than 9 hours at the same time during the day and still remains 15% reserved energy.

I tested the Amps draw for each air conditioner and my results were approximately:

For the smaller: Mabru SC7DC: 29.2 draw Amps including the 350GPH raw water pump. @full sunny day

For the Bigger unit: Mabru SC12DC: 45.6 draw Amps including the 350GPH water pump @full sunny day.

If you are going to install a Small Unit I can recommend you the Mabru 5000BTU @12V marine air conditioner (draw AMPS between the 17-27) , or maybe for a few dollars extra you can go up with the 7KBTU (draw amps between 22 and 28) that works excellent for me.

 

[mvweebles]

For the salon I installed a 12000BTU Self contained Marine air conditioners @12Volts DC. Brand: Mabru Power Systems

For cooling and heating both rooms, I have 1 Mabru 7000 BTU self contained air conditioner @12Volts DC with a split duct ( Y ) to distribute the air for both areas.

I have to ask - those two units combined cost over $10,000 USD. A similar 120VAC pair can be purchased for under $3,000 - and there are a half-dozen reputable builders from which to chose.

What is the value proposition for 12vdc that warrants a 3x price difference? $7k cost difference gets you halfway to a NL6kw generator, for example.

Peter

 

[OldDan1943]

Hi Rick.
I have a 2014 Beneteau Swift Trawler 44 Trawler, with 2 rooms and salon.

For the salon I installed a 12000BTU Self contained Marine air conditioners @12Volts DC. Brand: Mabru Power Systems and cools excellent keeping the air dry and confortable.

For cooling and heating both rooms, I have 1 Mabru 7000 BTU self contained air conditioner @12Volts DC with a split duct ( Y ) to distribute the air for both areas.

I have a Lithium battery bank (3 x 250AH) 750AH total.
These 3 Batteries runs my 2 air conditioners for more than 9 hours at the same time during the day and still remains 15% reserved energy.

I tested the Amps draw for each air conditioner and my results were approximately:

For the smaller: Mabru SC7DC: 29.2 draw Amps including the 350GPH raw water pump. @full sunny day

For the Bigger unit: Mabru SC12DC: 45.6 draw Amps including the 350GPH water pump @full sunny day.

If you are going to install a Small Unit I can recommend you the Mabru 5000BTU @12V marine air conditioner (draw AMPS between the 17-27) , or maybe for a few dollars extra you can go up with the 7KBTU (draw amps between 22 and 28) that works excellent for me.

************
You forgot to mention sea water temp. That has a great deal to do with the efficiency of the units.

 

[Hand ON Engineering]

Yes. The sea water temperature right now is around 86 F.

 

[OldDan1943]

Yes. The sea water temperature right now is around 86 F.

Not sure what to say. Difficult to efficiently add heat to hot sea water temp and difficult to efficiently get heat from cold sea water. I am guessing the sea water temp in this maria (FL) is in the mid 80sF so. Winter time sea water temps, cant remember. I do know, it is not in the 80sF

 

[Hand ON Engineering]

I have to ask - those two units combined cost over $10,000 USD. A similar 120VAC pair can be purchased for under $3,000 - and there are a half-dozen reputable builders from which to chose.

What is the value proposition for 12vdc that warrants a 3x price difference? $7k cost difference gets you halfway to a NL6kw generator, for example.

Peter

The benefits of batteries instead generator:

Less weight
Less Noise
No maintenance every 250 hours
Less contamination (oil)
don't have to carry diesel fuel on a big tank

If you want to change to clean energy is a good way by losing weight and saving space at the same time. You can fully charge the Battery bank from shore power during the night (lithium batteries charge very fast) and when you go out you can enjoy the sea without noise.

 

[mvweebles]

The benefits of batteries instead generator:

Less weight
Less Noise
No maintenance every 250 hours
Less contamination (oil)
don't have to carry diesel fuel on a big tank

If you want to change to clean energy is a good way by losing weight and saving space at the same time. You can fully charge the Battery bank from shore power during the night (lithium batteries charge very fast) and when you go out you can enjoy the sea without noise.

You've made the case for lithium. No argument there - I have 800AH of lithium.

But for A/C? Sorry, simply not happening on batteries. A few hours...sure.

But how does this equate to spending $10k on 12VDC A/C vs $3k on 120VAC A/C? Let's say for sake of discussion, the 12VDC is 30% more efficient. How does that convert to running on batteries? I spent $7k on my Lithium bank - I could increase it 30% and spend just $2100. I'd still be over $5k ahead.

What am I missing? What is so special about 12vdc that warrants the 3x pricing?

Peter

PS - huge fan of solar. In addition to 800w solar on my boat, I have a net-zero home, and I've installed an off-grid system for a friend's cabin.

 

[Hand ON Engineering]

I danced around it because I have never seen the data, but I agree with you David. The regular Marine A/C OEMs talk about how to size the circuit but there finding actual usage data for sustained operation has been elusive.

These A/Cs are relatively reliable but do not last forever - if you own your boat for 10-years and spend any time in Florida or the Tropics, strong chance you'll replace the unit once, maybe twice. There are several well-respected manufacturers of 120vac reverse cycle A/Cs from which to chose.

Rick/OP - on a 42-foot boat, you either have or should have a decent sized inverter. They are big and heavy which is important to your Cat, but have become very reliable and combine with battery charging nicely.

Finally, the water pump needed for reverse cycle A/C slurps up a fair amount of power - a good 3-4 amps @120vac on its own.

Good luck! I look forward to updates on how you proceed.

Peter

I have tested my Mabru self contained unit 12V dc 12KBTU with the tester at Florida's seas yesterday and I am surprised that the Draw amps are accuraced with the specifications catalog. It says between 33 and 44 amp max at maximum speed.
I am attaching some pics.

 

[DavidM]

Well OK, I accept your current measurements as being accurate. But how do you know the unit was putting out 12,000 btu/hr when you took those measurements? That is the other side of the coin and is just as important as the first side.

David

 

[OldDan1943]

Well OK, I accept your current measurements as being accurate. But how do you know the unit was putting out 12,000 btu/hr when you took those measurements? That is the other side of the coin and is just as important as the first side.

David

Check the temp of the A/C exit at the outlet. That will give you a hint.

 

[FF]

The problem with DC is it requires batterys , and batts are expensive and usually heavy.

To cool a volume the size of a cat would require far more power and weight than this boat style is built to operate with.

The std boat air cond system with a small noisemaker would make more sense , cost less and be easier to maintain.
Talk to the cat dealer about what they normally install.

 

[DavidM]

Check the temp of the A/C exit at the outlet. That will give you a hint.

But you also need to know the air flow rate to figure btu/hr.

David

 

[Baker]

The benefits of batteries instead generator:

You can fully charge the Battery bank from shore power during the night (lithium batteries charge very fast) and when you go out you can enjoy the sea without noise.

And there is your answer folks. Hands on, what if you are cruising and don't have that option?

 

[OldDan1943]

But you also need to know the air flow rate to figure btu/hr.

David

of course.

 

[OldDan1943]

I dont consider the noise made of the generator a burden. It's inside a sound box.
In fact, while underway, the main engine makes more noise than the gen. SMILE
Yes, I can sleep all night with the gen running.

 

[silentfaith]

ocean breeze a/c . they build whatever you want, all different shapes and sizes. located in stuart fla.

 

[B28_Majic]

You've made the case for lithium. No argument there - I have 800AH of lithium.

But for A/C? Sorry, simply not happening on batteries. A few hours...sure.

But how does this equate to spending $10k on 12VDC A/C vs $3k on 120VAC A/C? Let's say for sake of discussion, the 12VDC is 30% more efficient. How does that convert to running on batteries? I spent $7k on my Lithium bank - I could increase it 30% and spend just $2100. I'd still be over $5k ahead.

What am I missing? What is so special about 12vdc that warrants the 3x pricing?

Peter

PS - huge fan of solar. In addition to 800w solar on my boat, I have a net-zero home, and I've installed an off-grid system for a friend's cabin.

I just came across this post and wanted to divulge a bit of relevant information regarding the 12v air conditioning debate. I have tried running a 12,000BTU 115v unit off of a 2,800W inverter and measured starting amps past 300A DC and running amps over 100A.

Looking at those numbers alone and comparing to the readings taken by Hand on Engineering @ 42.6A, the Mabru 12,000BTU 12v is more than twice as efficient, not 30%. This is also not taking in to account the difference in starting amps that you see with the 115v unit.

I have been going back and forth on options for my little 28' boat but do not want to lose valuable engine room real estate with a generator so have decided to go the DC route. I increased the alternator output of my inboards to 120A Powerline alternators and am seeing about 30A per motor @ 800RPM.

I have seen 10 hrs of runtime for the Mabru 12,000BTU DC on a 500AH lithium bank without running the engines. I have also seen a 12,000BTU DC running off of a Honda 1000. The generator was powering a battery charger and the vessel's battery monitor was showing a positive charge rather than a drain on the batteries.

 

[mvweebles]

I just came across this post and wanted to divulge a bit of relevant information regarding the 12v air conditioning debate. I have tried running a 12,000BTU 115v unit off of a 2,800W inverter and measured starting amps past 300A DC and running amps over 100A.

Looking at those numbers alone and comparing to the readings taken by Hand on Engineering @ 42.6A, the Mabru 12,000BTU 12v is more than twice as efficient, not 30%. This is also not taking in to account the difference in starting amps that you see with the 115v unit.

I have been going back and forth on options for my little 28' boat but do not want to lose valuable engine room real estate with a generator so have decided to go the DC route. I increased the alternator output of my inboards to 120A Powerline alternators and am seeing about 30A per motor @ 800RPM.

I have seen 10 hrs of runtime for the Mabru 12,000BTU DC on a 500AH lithium bank without running the engines. I have also seen a 12,000BTU DC running off of a Honda 1000. The generator was powering a battery charger and the vessel's battery monitor was showing a positive charge rather than a drain on the batteries.

Something just doesn't seem right about these numbers. I can't quite put my finger on it, but the Mabru numbers seem overly optimistic. I have 12k Btu 23-SEER mini-split that runs about 500-600 watts, which would be in the 50A range at 12V. The Mabru unit plus a water pump is consuming less electricity than my 23-SEER home-based A/C. For energy monitoring, I have a SMAPPEE system that monitors both solar and usage.

Just doesn't make sense to me.

Peter