Solar Upgrade verse Running the Generator

[a64pilot]

Not to bust too many manufacturers of "marine" fridge systems, but there is no boost in efficiency when you go from 120 V to 12 V. In fact the 12 VDC compressors are actually AC driven, the controller changes the DC to AC, three phase.
Any efficiency difference will be due to not having to run an inverter, and a good one of those is close to 95% efficient?

In short, if you have a big system it will require a lot of current to run it, flavor of power will not significantly increase efficiency.

[Exile]

Originally Posted by a64pilot

Not to bust too many manufacturers of "marine" fridge systems, but there is no boost in efficiency when you go from 120 V to 12 V. In fact the 12 VDC compressors are actually AC driven, the controller changes the DC to AC, three phase.
Any efficiency difference will be due to not having to run an inverter, and a good one of those is close to 95% efficient?

In short, if you have a big system it will require a lot of current to run it, flavor of power will not significantly increase efficiency.

I figured, if anything, AC would be more efficient but thanks for the explanation.

Fwiw, I've looked into running my AC fridge off an inverter but was advised against. It's spec'd to run at 5.5 amps plus the r/w pump and any inversion loss. So say 6 amps @120v = 66 amps @12v. Not sure about add'l start-up amperage. Even with a huge battery bank it may not be feasible or worthwhile. Esp. when compared to running the genset 2hrs/day @0.5 gals/hr. If I expend 30% of my fuel reserves on passage to running the genset vs. the propulsion engine, that's at least a month of keeping the beer cold. The remaining 70% of engine time would also keep it cold thanks to the engine drive compressor.

Either way you look at it, and for better or worse, there's no beating the efficiency contained in a small quantity of fossil fuel. But it sure would be nice not to have to rely on it so much!

[a64pilot]

To pull 6 amps, you must have a LARGE compressor, my 6K BTU air conditioner with the water pump">raw water pump only pulls about that.
There may not be a DC compressor that large.

[AboFares]

Solar is the best way for you, I have 27ft boat and I have different type of installation, my method is ONE solar panel 100w small controller with MPPT technology victron 3 house battery 105AH each Trojan and 2500w inverter pure sine wave, in addition I have battery charger, this system works great for my AC and all the devices inside my boat, 3780W of house battery it's ok for my boat I keep in my mind I should take only the half of battery house bank and I keep the rest for my engine [emoji28], If I faced any critical situation in my battery by going below, I have my 2000w Honda generator, to charge my battery by battery charger.

[Exile]

Originally Posted by a64pilot

To pull 6 amps, you must have a LARGE compressor, my 6K BTU air conditioner with the raw water pump only pulls about that.
There may not be a DC compressor that large.

Just going off the specs on the Seafrost website which says 5.5 amps (running). Main (reverse cycle) aircon pulls closer to 10. These are old appliances at this point so maybe not so efficient. Still running fine though. I'm guesstimating the fridge is around 8 cu.ft. with one large holding plate, and the freezer about 5 cf with two large plates. I'm not on the boat now so measurements could be off.

[skipgundlach]

Originally Posted by a64pilot

To pull 6 amps, you must have a LARGE compressor, my 6K BTU air conditioner with the raw water pump only pulls about that.
There may not be a DC compressor that large.

Mine is a BD80, and with nothing other than ghost loads (panic button on VHF) and two Hotwire Port Fans (about 0.2 Total Amps) if there is no wind, I average 12A consumption overnight (e.g. a 10 hour period with no sun or wind, and no other in or out amperage, will use 120AH), most of which is my water and air cooled unit running full time.

I have not seen my freezer cycle once in the last 3 months. It's making cold - lots of it, including past the exit; I may have to twiddle the valve to keep the cold inside the box, only, and unless there has been some catastrophic failure of my molded block (2" and 4" cut from 4x8 sheets) extruded polystyrene insulation, which I highly doubt, that's merely what it costs in amps to run my freezer, despite my having moved up my previously OK set point twice, to what is now 7.5F, and makes me a bit nervous, as the box gets too warm that way...

But be assured, by looking at the specs at SeaFrost, that is an entirely possible draw.

I wish it weren't -but there you are...

[a64pilot]

Mine is also a BD80, but it's a 14 cu ft spillover and keeps the freezer at single digits and the fridge in the low 30's F of course.
I think mine runs at lower RPM at times, cause right now with the 32' TV on and the KVH Sat on, and a few lights, total DC consumption is 12 amps. TV etc are all DC powered.

On edit.
Skip, his 6 amps is 6 amps at 120 VAC, which of course is pretty close to 55 amps or so at 13 VDC.
That is a lot of draw for a fridge.

[foggysail]

Originally Posted by a64pilot

Not to bust too many manufacturers of "marine" fridge systems, but there is no boost in efficiency when you go from 120 V to 12 V. In fact the 12 VDC compressors are actually AC driven, the controller changes the DC to AC, three phase.
Any efficiency difference will be due to not having to run an inverter, and a good one of those is close to 95% efficient?

In short, if you have a big system it will require a lot of current to run it, flavor of power will not significantly increase efficiency.

Forget about efficiency, think MONEY! The pedigreed papered so called marine 12V fridge cost 3 times as much as an apartment size unit with the same cuft. On top of that the 120vac apartment unit will not only have an interior light but also self defrost. My Summit fridge keeps ice cream so solid that it becomes difficult to scoop.

Some people, self included don't give a poop about efficiency especially with 1180 watts of solar.

[Kenomac]

Originally Posted by Exile

It's actually pretty impressive what you [U]can[U] run just off your batts., particularly the induction cooktop. And when you're motoring I think you said you have a heat exchanger for the h/w? Does your boat have aircon?

Originally Posted by Kenomac

We have a/c which we haven't used in five years and yes we have a heat exchanger in the waterheater.

Can I offer up a bit of good advice that will probably save you a boatload of money and trouble?

Originally Posted by Exile

Yes, of course/always! Lemme guess . . . if it's all been working fine all these years then add some solar to supplement and move along to the next system that needs attention. That's been my approach on the electrical & refrig the past 10 yrs., except w/o the solar. But then again just about everything else has broken so I've been busy.

Watchu got?

You're over-thinking this cruising thing and on the path to spend way more than necessary. I've been doing the 6 on/6 off thing for six years now and some of the systems we paid plenty of money for, have gone unused most of the time.

Air conditioning: Never use it since none of our quality time is spent in marinas. It's much cooler in anchorages where we can also wear less clothing. Weathermax transparent tent-type shades are the answer, they cool the boat by ten degrees, allow the breeze to blow through and we can still see out.

Bimini: Day sailing and week-long sailing trips are much different than living on a boat for extended times. Get a bimini, install some solar and leave it up. Being able to "see" your sails becomes much less important, jeez.... the vast majority of the people we know out cruising rarely if ever actually sail their boats anywhere. We're the exception. Basically, we're generally under no time constraints so it doesn't matter if it takes a little longer to get someplace if the sails aren't trimmed just right, besides... neither of us cares to tinker with them constantly.

Fuel conservation and energy: Since we're in no hurry, we motor along (if under 7 knots of wind) at a fuel sipping pace of 4.5-5 knots at 1500-1800rpms, we can sail much faster when the wind picks up.

Marinas suck: if you wanna just sit and bake in your boat, jammed in with other boats, no privacy, slapping halyards, air con running while watching TV... then marinas are what you'll like. We enjoy just the opposite.

Batteries: Wait until you're out cruising before making any changes. If it ain't broke... don't fix it. 1000w of solar is ridiculous over-kill IMHO, 500w seems to be the sweet spot with a generator. 300w plan on running the generator almost daily. We enjoy peace and quiet, so it's nice not needing the generator. Solar for us isn't a money thing.... it's a quality of life issue.

Electronic gadgets, computers and chartplotters: Get an iPad, it'll replace everything and they're easier to use. Weather info, charts/chartplotting, music, photos, internet, news, answers to questions. Just insert a Sim card and you're good to go.

Dive equipment: Spend some money on scuba equipment and learn to use it. Life under your boat shouldn't be a mystery.

Watermakers are wonderful: Watermakers are wonderful... nuff said.

Washing machines are wonderful: Washing machines are wonderful... nuff said.

Tools and spares: Have lots of tools and spare parts for everything onboard.

Deep freezer: You'll rarely use it unless you catch a big fish.

Dinghy: Buy a good hard bottom dinghy with at least a 15hp outboard, it's your car and tow truck.

Folding bikes: Get some.

[StuM]

Originally Posted by a64pilot

To pull 6 amps, you must have a LARGE compressor, my 6K BTU air conditioner with the raw water pump only pulls about that.
There may not be a DC compressor that large.

I suspect we have the common problem of talking about Amps and confusing voltages. That's why I like to work in Watts.

6 Amps sounds about right to me for a fridge or freezer. but only if he is talking about 12V DC

My quite common Coolmatic/Waeco CU-95 compressor condensors (one for fridge, one for freezer) are listed at 60-100 Watts each.

[Exile]

Originally Posted by StuM

I suspect we have the common problem of talking about Amps and confusing voltages. That's why I like to work in Watts.

6 Amps sounds about right to me for a fridge or freezer. but only if he is talking about 12V DC

My quite common Coolmatic/Waeco CU-95 compressor condensors (one for fridge, one for freezer) are listed at 60-100 Watts each.

110v x 5.5 amps = 605 watts AC according to the specs from Seafrost, plus whatever the r/w pump draws. Seems about right from what my meter shows. It's called the "Shore Power Assist 3" model which should give you a hint of how the boat was used by the PO. But it has worked very well off the genset all these years so I haven't messed with it, even though it's the biggest obstacle to cutting down on genset use.

[john61ct]

Yes, just insane IMO to run that off batteries.

Convert to Danfoss style ASAP if you do a lot of liveaboard away from shore power.

Technautics Cool Blue would be a good bet for a top-notch customized conversion

Rich Boren, 619-609-3432, info@technauticsInc.com

SV THIRD DAY here on CF

[Exile]

Originally Posted by Kenomac

You're over-thinking this cruising thing and on the path to spend way more than necessary. I've been doing the 6 on/6 off thing for six years now and some of the systems we paid plenty of money for, have gone unused most of the time.

Good point. For many of these decisions it's probably best to wait until you're actually doing the type of cruising you've long been planning for.

Air conditioning: Never use it since none of our quality time is spent in marinas. It's much cooler in anchorages where we can also wear less clothing. Weathermax transparent tent-type shades are the answer, they cool the boat by ten degrees, allow the breeze to blow through and we can still see out.

That's been my experience as well with aircon. Occasionally nice to run for an hour at anchor after a long hot day sailing in the tropics to cool & dry the boat but tends to get used mainly at the dock.

Bimini: Day sailing and week-long sailing trips are much different than living on a boat for extended times. Get a bimini, install some solar and leave it up. Being able to "see" your sails becomes much less important, jeez.... the vast majority of the people we know out cruising rarely if ever actually sail their boats anywhere. We're the exception. Basically, we're generally under no time constraints so it doesn't matter if it takes a little longer to get someplace if the sails aren't trimmed just right, besides... neither of us cares to tinker with them constantly.

I'm more of a tinkerer when it comes to sail trim & tend to not rely on the motor as much as some. Used the bimini a lot more when the boat was in Fla. and we were sailing the Bahamas. Lately a wide-brimmed straw hat has taken its place but the bimini is easy enough to deploy if needed. Things could always change once out cruising full-time as you suggest.

Fuel conservation and energy: Since we're in no hurry, we motor along (if under 7 knots of wind) at a fuel sipping pace of 4.5-5 knots at 1500-1800rpms, we can sail much faster when the wind picks up.

Ditto, unless trying to get in somewhere before dark. Looking forward to not having to get in anywhere before dark.

Marinas suck: if you wanna just sit and bake in your boat, jammed in with other boats, no privacy, slapping halyards, air con running while watching TV... then marinas are what you'll like. We enjoy just the opposite.

Ditto.

Batteries: Wait until you're out cruising before making any changes. If it ain't broke... don't fix it. 1000w of solar is ridiculous over-kill IMHO, 500w seems to be the sweet spot with a generator. 300w plan on running the generator almost daily. We enjoy peace and quiet, so it's nice not needing the generator. Solar for us isn't a money thing.... it's a quality of life issue.

300w of solar could easily relieve daily generator runs if you had a larger battery bank, but it sounds like you've reached a very workable balance given what you have.

Electronic gadgets, computers and chartplotters: Get an iPad, it'll replace everything and they're easier to use. Weather info, charts/chartplotting, music, photos, internet, news, answers to questions. Just insert a Sim card and you're good to go.

I like all the gadgets, incl. the iPad!

Dive equipment: Spend some money on scuba equipment and learn to use it. Life under your boat shouldn't be a mystery.

Got the hookah but no scuba tanks.

Watermakers are wonderful: Watermakers are wonderful... nuff said.

Definitely worth waiting until you're out there.

Washing machines are wonderful: Washing machines are wonderful... nuff said.

No doubt I'm sure, but don't think I'd wanna devote the space to it.

Tools and spares: Have lots of tools and spare parts for everything onboard.

Have all that, except for the spare I need for when I'm out at sea I'm sure.

Deep freezer: You'll rarely use it unless you catch a big fish.

That's what I thought at first but it's come in handy for storing frozen meat, and a bag of ice for cocktails lasts indefinitely!

Dinghy: Buy a good hard bottom dinghy with at least a 15hp outboard, it's your car and tow truck.

Maybe one day, but then you're stuck with it in either davits or taking up the entire foredeck. So far the inflatable with a 4hp I don't need a crane to lift is working out OK.

Folding bikes: Get some.

Nice to have some wheels to get around I'm sure.

[Exile]

Originally Posted by john61ct

Yes, just insane IMO to run that off batteries.

Convert to Danfoss style ASAP if you do a lot of liveaboard away from shore power.

Technautics Cool Blue would be a good bet for a top-notch customized conversion

Rich Boren, 619-609-3432, info@technauticsInc.com

SV THIRD DAY here on CF

Good suggestion, although I thought Cool Blue was air-cooled only. Might be OK but given the size of my system it may be worth keeping the water cooling in place for efficiency. I plan on checking with Cleave at Seafrost to see if just my compressor can be swapped out and lines & plates kept in place.

[a64pilot]

Originally Posted by Exile

Good suggestion, although I thought Cool Blue was air-cooled only. Might be OK but given the size of my system it may be worth keeping the water cooling in place for efficiency. I plan on checking with Cleave at Seafrost to see if just my compressor can be swapped out and lines & plates kept in place.

Cool Blue is air cooled.
There is no real difference in efficiency between air cooled and water cooled. Water cooling is only required if the air cooling isn't done right.
Water cooling brings with it a host of potential problems that air cooling doesn't.
Think about how many big commercial fridges and freezers that you have seen that are water cooled?
My BD80 system is dual cold plate and is a Cool Blue. It's a 14 cu ft spill over and it takes all of the BD80 too. However it's the original 30 yr old ice box, so it's insulation is questionable at best, and insulation is likely the biggest thing that eats power, that you can control.
I turned off everything last night except the fridge and it pulls about 5 amps at 13 V, so 65watts maybe? Then I turned everything off and still had 1.4 amps going into the bank, so maybe my fridge draw when cold is really 5 minus 1.4, or 3.6 amps at 13 v or a little less than 50 watts?
Now this thing is variable speed so I feel sure that is at low speed cause I have seen it draw 12+ when it had been off for a week and I first turn it on with room temp plates.