Freezer Power Use Issue

I have an issue with power usage by a built-in chest freezer I want to run buy you all.

My boat has built-in custom DC fridge in the galley with no freezer compartment. In the cockpit, in a somewhat awkward location I have a fairly substantial top-loading chest freezer which is AC powered rated at 1.2A. Both the fridge and freezer are custom from Sea Freeze in Bellingham WA. This freezer is overkill for the weekly trips we typically make but it does a good job of keeping things cold. The downside is, it's very power hungry. Since it's located outsider it gets blasted by the sun at times and the insulation on it is not very good. You can feel the cold on the outside and on humid mornings it condenses moisture on it so I know the heat leak is substantial. On an average day at 80 degrees I would estimate it's running 80-90% of the time. Current draw on the DC side after the inverter loss is 12 amps, so this is a huge drain on the batteries and I have to run the generator for a several hours each day to keep up.
Ideally I don't want to tear out the existing unit and add insultation since it's not in an area where you can easily access the sides. I have put on some reflective bubble wrap which is a little unsightly, but seems to help a bit with insulating.

Here are some options I'm considering but interested to hear from any of you who have ideas on the subject:

1. Replace the AC compressor with a AC/DC Danfoss 50 model (if that has enough power to run the freezer). ND50CB4-QV (ND50OR-VFA-AC-GR) PreCharged Cooling Unit Danfoss Comp. This draws about 5.2 amps @12VDC at full power so would better than half my draw.
2. Abandon the current cooling coils and add an off-the-shelf or slightly custom plate system like the ones from Nova Kool. This should be more efficient and since the coils would be inside the freezer the insulation should be improved.
3. Install a smaller freezer elsewhere which is DC powered. There isn't an obvious place for one so this isn't a great option.
4. Cut out the old freezer and build one with better insulation or find a compatible pre-built unit.
5. Add a couple of solar panels and live with it.
6. Suck it up and just keep running the generator.

I want to improve this situation and hoping to cut running the generator time in half so looking for ideas of things I haven't considered.

Very interested in what others have to say. I'm in the same "boat" with an AC freezer that is a power hog. It kills the batteries requiring lot of generator time. I'm thinking add some insulation on the outside, it's a Home Depot cheap chest freezer on the fly bridge, I won't care what it looks like. Add solar, a good idea in any case.

I'm surprised the SeaFreeze unit is so poorly insulated. He has a reputation for building very efficient units.

It sounds like the primary issue here is poor insulation. The better you can insulate the freezer, the less power any compressor will draw. A less powerful compressor will run at a higher duty cycle, so unless it's actually more efficient I wouldn't expect the total power draw to be any lower.

Unfortunately Sea Freeze closed up shop during COVID. I have a 30 year old Sea Freeze DC freezer that I am Very fond of. I believe that all these freezers are actually DC powered at the Compressor. I would do a little research to see if you could avoid the DC to AC to DC issue.

I wish I had a contact to send you to. Unfortunately, everyone I know has retired.

I used to know everyone in this business, now I just know everyone who has retired from this business.

Watts are watts - whether they are AC or DC. There may be a minor improvement in efficiency, but your big problem is heat and lack of insulation. Insulation issue could be because the current insulation has somehow become water-saturated and no longer works well.

Also, I assume you've made sure the cooling coils (wherever they might be) are clean and dust-free.

If you don't already have one, a seat cushion on top might help. But barring that, either your insulation is fine and it's just hot, or you have an insulation is fine. GIven the looks of the unit, hard to believe you will find something off-the-shelf.

Peter

Two thoughts: 1) I didn't have an outside freezer, but I had a bimini to transom shade made that dramatically reduced heat. It was a screen-type material that you could see though and that let air through but cut the sun. That would affect more than the freezer, but it could help overall if the cockpit is too hot to enjoy when the sun is at "that angle". 2) If you aren't using the entire freezer, loading it up with a block (or blocks) of ice can help keep it cold. I had an interior chest freezer, and I keep it filled with frozen tupperware containers that I could remove if I needed more space.

tiltrider1 said:

Unfortunately Sea Freeze closed up shop during COVID. I have a 30 year old Sea Freeze DC freezer that I am Very fond of. I believe that all these freezers are actually DC powered at the Compressor. I would do a little research to see if you could avoid the DC to AC to DC issue.

I wish I had a contact to send you to. Unfortunately, everyone I know has retired.

I used to know everyone in this business, now I just know everyone who has retired from this business.

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Sea Freeze still has an active web site. Of course that doesn't mean they're still in business.
Sea Freeze of America - Custom Marine Refrigeration, Deck Freezers, Cold Plates

BroadCove said:

Two thoughts: 1) I didn't have an outside freezer, but I had a bimini to transom shade made that dramatically reduced heat. It was a screen-type material that you could see though and that let air through but cut the sun. That would affect more than the freezer, but it could help overall if the cockpit is too hot to enjoy when the sun is at "that angle". 2) If you aren't using the entire freezer, loading it up with a block (or blocks) of ice can help keep it cold. I had an interior chest freezer, and I keep it filled with frozen tupperware containers that I could remove if I needed more space.

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I have in the past experimented with blocks of dry ice to help out. Mixed success. It's cold, VERY COLD, that can cause problems.

I do use the frozen container concept to keep the freezer full. But when you have to freeze ambient temperature water that requires a fair bit of energy to get there.

I've contacted Sea Freeze, or what's left of them. Apparently they are now part of Northern Lights. One email and a phone message and no reply yet. They transferred me to someone in FL, so who knows if I will hear back.

Peter, I had considered if the insulation had become wet and turned it off for a couple weeks to try and dry it out. Didn't seem to help. From what I can tell there is a maximum of 2" of insulation between the inside and the top and front, so this is less than ideal.

I have the skills to tear it out, redo and potentially increase the insulation, but it would be a lot of work. If this were done the entire cooling coil arrangement would need to be redone so it would be a huge project. At this point I would prefer to find a place to add a separate unit inside.

My thought behind going to the new compressor is that I was under the impression the newer Danfoss were significantly more efficient. This may not be correct and one of the reasons I contacted Sea Freeze.

@BroadCove, agree on shade protection, but the insulated bubble wrap does pretty much the same thing and hasn't appreciably improved power draw.

I found this

You can contact Frostline Marine Refrigeration at frostlinemarine.com or call 360-303-4912

Apparently, the technician wasn’t ready to retire and started up his own service buisness. I would bet he is the best source for any technical help.

I haven’t talked to my NL friends for a while. I am very suspicious of them taking over Sea Freeze. I’ll try to stop by and get a read on what is going on.

I ended up adding an Engel freezer to my boat. It can be run on AC or DC and is adjustable from refrigerator to deep freezer (below 0 Fahrenheit). Used it the last couple of days to bring frozen crabmeat from MD to FL. Plugged it into the cigarette lighter outlet in the back of my car (5.5 amps DC) and took it into the hotel room for the night with the AC plug. It's small enough to be in the boat but large enough to pack frozen meat for my extended cruising.

Ted

Since you state that it is larger than what your needs are, why not add blue board on the inside for added R value, as a cheap experiment. If it is successful, you could then put lexan, cut to fit, over the blue board. We did this on a previous boat with good results. This works if the evaporator is inside the box.

@Stabi wouldn't that insulate the inside from the coolers?

SteveK said:

@Stabi wouldn't that insulate the inside from the coolers?

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I believe Sea Freeze used to put the evaporator plate inside the box, at least they did in ours. If not, it would be cost effective to plumb in a new evaporator plate to the existing Danfoss Compressor.

Where is the condenser for the Seafreeze unit located? I'm assuming it is located in the lazarette and if so, it is effectively trying to dump heat into an under ventilated space. I would try and improve the insulation of the outside freezer and replace the cooling system with a water-cooled unit like the Isotherm. It would increase the maintenance but reduce the power load pretty significantly.

Have you considered replacing the galley refrigerator with a combo unit since you don’t need all the cockpit freezer space? Maybe that would be less of a project and could be hugely more efficient.

I just ordered one of these

Dalema Outdoor Deep Freezer Cover,Heavy Duty 600D 100% Waterproof Chest Freezer Cover,Freezer Covers for Outside 5.0 Cubic Chest Freezer,Top Can Be Opened by Zipper​

Lot's of good suggestions guys, much appreciated.

Ted, I like the look of that Engle freezer, but we really don't have a good place to put one.

The evaporator coils are mounted outside of the fiberglass box and then there is insulation on the outside of that between the box and front surface where the ladder mounts, this is the worst area of heat leak along with the lid, both of which are subjected to sunlight. The other surfaces face the engine room, also a bad place for heat...

The condenser is mounted under a bench seat forward of the freezer. I've actually modified that so it has an enclosure around it with only the inlet for the coils facing out. At the top I mounted a 3" duct flange and I routed that to the outside to make the condenser cooling fan also act as the exhaust fan for the bench seat chamber which also has the inverter in it. The outlet for this vent is essentially a dryer vent behind the lid of the freezer shown in the first picture so the hot air is exhausted outside the boat. This mod made a huge improvement to the operation of the inverter and the freezer.

The best way to improve this situation (although not cost effective) would be to cut out the entire freezer and build one with much better insulation and put in a new evaporator coil set and higher efficiency compressor. I just don't think it's worth it though.

@guy with a boat, I've considered changing out the galley fridge with one that has a freezer area, but it's too small already. That and it works very well. I looked around for a drawer unit which could be added, but there isn't much space to put one and the only side that would fit just wouldn't hold much. I will look again this weekend to see if there is a better option to adding a second unit. I like this idea because it would leave the large freezer for other uses down the road if the boat were plugged into shore power for extended periods.

Has anyone tried one of these?

^^^
Looks like a few bad reviews on that model.

Portage_Bay said:

Has anyone tried one of these?

47QT VL45 Portable Fridge Metal Freezer 12V Refrigerator Car Fridge

Adventure Awaits! Save up to 25% OFF.Free Shipping in Domestic US makes your summer road trip even cooler! Shop now for special offers! VL45 car fridge powered by 5-year warranty SECOP compressor, fit for overland, road trips, and outdoor living. LA local after-sale technical support.

icecofreezer.com

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A marina neighbor let us borrow their Bouge RV electric cooler for a trip, plugged it into the 12v power socket and it worked great for us. They also use it alot and are very happy with it.

There’s already a remote condenser, if it’s a danfoss, you should be able to drive it off of 12 volts.
But as has been mentioned, it probably won’t save that much power.
It sounds like the real issue is the way the evaporator is set up. With the coils outside of the compartment they need to be snug to the wall and have great insulation behind them. I wonder what they use for insulation? Is it waterlogged from condensation?
Changing to an interior evaporator would probably be a good route to go, and you’ll probably have to do the condenser at the same time, unless you can actually find a technician to come to the boat, so a switch to 12 volt could happen then if you wanted.
I have an Adler Barbour super cold unit, and it came pre charged and ready to install. You just need to drill holes for the tubing to pass through. The new fitting style even lets you take them apart again without losing refrigerant if repairs are need and the compressor is in the way.

Why not use the old freezer for storage, and purchase a new fridge/freezer combo for the galley? You mention that you don’t require all the freezer space anyway. Just a thought.

There’s already a remote condenser, if it’s a danfoss, you should be able to drive it off of 12 volts.
But as has been mentioned, it probably won’t save that much power.

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I run what I can direct from house bank. If I run my fridge through inverter then I use a portion of the inverter max continuous watt output. Anything run direct saves power, and the power lost in conversion.

If you don’t have them and have the space, add fans in the boxes. At least add a fan in the fridge box. If the coils are external, consider a fan on the coils

I had a chance this weekend to give a good look around at options to add a separate freezer. The options aren't great.
In the galley, there is a spot where the smallest of freezer drawers would fit.




The blue tape area shows the outline. The lower drawer would need to be removed.
Here is a model which would fit.
These run about $1,800, ouch...

The other option is outside behind the door. Some of the boats like mine have an icemaker there so there is some precedence, but it's unsecure and in the weather.



Here we could put one of these units, $1,200


I've come to the conclusion that "the juice isn't worth the squeeze" for this modification.

Also, I looked at taking out the existing freezer, making a new tub and adding 2" of insulation. This would be a big project and I just don't think it's worth it. I could add cooling plates and a new condenser to the inside of the existing, but without adding insulation around it or making it smaller I don't think the improvement would be great.

Sometimes the answer is: there is no good answer.
I figure running the generator a couple extra hours a day only costs $4-5 a day at current fuel costs so that's a lot of hours to make up the difference of adding these units or modifying the existing unit.

Maybe another option. I'm assuming the couple of extra generator hours per day may reflect battery charger DC amperage output. You might consider evaluating your battery bank size and chemistry to see if you can add an additional battery charger, atleast for the bulk phase of charging. In most cases, battery charging uses a small percentage of the generator's output capacity. If you can add additional charger capacity, the additional generator time might become less significant.

Ted

I've been using this one on the fly bridge for 2 years now, works good. Much less expensive too.

O C Diver said:

Maybe another option. I'm assuming the couple of extra generator hours per day may reflect battery charger DC amperage output. You might consider evaluating your battery bank size and chemistry to see if you can add an additional battery charger, atleast for the bulk phase of charging. In most cases, battery charging uses a small percentage of the generator's output capacity. If you can add additional charger capacity, the additional generator time might become less significant.

Ted

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Thanks Ted, this is a good suggestion. I have three 8D AGM batteries as my house bank. The charger, a Xantrex Freedom 25 can in theory put in 130A during the bulk charge phase. I've seen around 100A via the control panel, but I think it drops off faster than I would expect and the charger spends a fair bit of time in the Accept phase. I know the Freedom is an old unit, but can't justify ripping it out and redoing it at this point. I was close to pulling the trigger on a Victron Multi-plus system, but then I would have to make a lot of other changes and in the end it doesn't supply much more charging current. On our next trip I will monitor the charging current to see what's going on over the charge time. I usually bring let the SOC drop to ~350 amp/hours and it usually takes 3 hours to get it back up to 100 which is where I usually turn it off so that seems to be proving the charger is putting in 100A give or take which is probably within reason.

I'm not sure if there is a better way to get some juice into those batteries but the generator has additional capacity for sure. Shortening the charge cycle would be a good solution, I just don't know enough about how to improve this without going to lithium and a new more powerful charger.

@Delta Riverat , do you find the size of that drawer to be reasonable? My wife thought it was so small it wouldn't be worth it.

lwarden said:

Thanks Ted, this is a good suggestion. I have three 8D AGM batteries as my house bank. The charger, a Xantrex Freedom 25 can in theory put in 130A during the bulk charge phase. I've seen around 100A via the control panel, but I think it drops off faster than I would expect and the charger spends a fair bit of time in the Accept phase. I know the Freedom is an old unit, but can't justify ripping it out and redoing it at this point. I was close to pulling the trigger on a Victron Multi-plus system, but then I would have to make a lot of other changes and in the end it doesn't supply much more charging current. On our next trip I will monitor the charging current to see what's going on over the charge time. I usually bring let the SOC drop to ~350 amp/hours and it usually takes 3 hours to get it back up to 100 which is where I usually turn it off so that seems to be proving the charger is putting in 100A give or take which is probably within reason.

I'm not sure if there is a better way to get some juice into those batteries but the generator has additional capacity for sure. Shortening the charge cycle would be a good solution, I just don't know enough about how to improve this without going to lithium and a new more powerful charger.

@Delta Riverat , do you find the size of that drawer to be reasonable? My wife thought it was so small it wouldn't be worth it.

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Couple points to consider:

First would be to check the battery charger programming. In bulk phase, the charger should be putting out rated amperage. This is adjustable based on the size (amp hours) of the bank. If the previous owner had smaller batteries or open lead acid, he may have reduced the amperage to prevent cooking the batteries.

Second, it would be helpful to understand your use profile. While it's always a good idea to completely recharge the bank, in most cases, doing it every 3 or four days should be sufficient. You definitely want to complete the bulk and absorption phases, but completing the float charge phases doesn't need to be done every day. If you sit for 2 or 3 days and then motor where the bank is getting completely recharged on the fourth day, you can probably skip the float phase on days one through three.

Ted