Interesting Mac magazine article

[Russ]

Wattage is wattage whether you raise or lower the voltage . A 30 watt unit would be substantially weaker than a 150 watt unit , no matter the voltage. 30 watts won't provide the same cooling as a 150 watt model.

Well, wattage is a relative term of electricity flow. 7w 110AC is a nightlight. 7w@12VDC is almost an amp or the amperage equivalent of a 75 watt 110VAC bulb. So wattage is only comparative if you are using equal voltages.

A 150 watt 110 vac is the same same as 150 watt 12vdc except the amperage is higher on the DC side .

Yes. the amperage is 10 times higher at least. Amperage is the flow rate. 150WAC to 12VDC is 12.5amps on the DC side.
If your boat had a hole in it, would you rather a 1" hole or a 10" hole? Bigger hole, more flow rate. Which would flood your boat faster? What's gonna drain your batteries faster, a 1 amp of running lights or 12.5 amps of fridge running?

On our Bayliner we have ran 110 vac fans that total up to about 150 watts . We run these thru a 700 watt inverter We run the fans all night and have battery the neaxt day , in fact we have stayed at anchor for two nights and not ran the motor in between , and the fans , and the one house battery do fine.

You can get away with pulling that kind of amperage (10 amps) out of 12v for a while. But eventually you will need to charge it back up and the Bayliner probably has a 65amp alternator.

Give it a try. I suggest before you hardwire stuff in, you try it in the garage. Plug that inverter into a battery and then the fridge into the inverter and run it for 12 hours. Then take a digital voltmeter to your battery and see what the drop is. Also, you need to make sure the fridge will "start" when the battery drops to 11.8 volts and the inverter capacity drops.

Good luck and let us know your results.
Many of us are envious of your journey.


--Russ

[Sumner]

............. The fridge we have is a 3.5 cu ft .
Judging from the pictures , ours appears bigger than the one in the posted pictures . We looked at some smaller ones. To do what we need , we needed more cubic feet , than what we could afford in DC ....

If I did the math right........

http://www.edgestar.com/products/fridgefreeze/fp630.asp

........, our EdgeStars are 1.77 cu. ft., so you are right yous is about twice the size.

Do you have any pictures of how and where it is mounted? I'd like to see the install.

Thanks,

Sum

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[Gypsy]

We bought the fridge , but haven't mounted it yet .
The plan is for it to go in the stern , on the port side , straight back from the battery compartment . It should stand up nicely in the high part of the stern area .

I will try what Russ suggested and do a test run , here at home , rig up inverter , battery , and fridge and see how it goes.
My son and I sat at the table , one night for hours , trying to come up with some calculations to determine if it would work or not . By our estimates / calculations it will not only work , but fully charge the battery , on an average day.

But I am aware that there is a BIG difference between a kitchen table calculation and reality .

It may be we might have to shut off the fridge at night , and turn it back on in the morning.
We have done this in the past ,here at home , when we would lose power from a hurricane . I would run fridge and freezer thru an inverter and run them one at a time.

[DaveB]

Sum, the spec's on that page is not correct.
I have the 63 quart refig/freezer and the plate on it says it is a 66 quart and draws DC 4.5 amps at start up and 2.5 amps running at 12 volts.
The plate has to be correct and don't go by advertisement specs.
I would think they would advertise with correct specs so they sell more Units as theirs are very high for draw.
For me in 95 degree heat and water temps at 86-90 degrees I draw on avarage 1 amp hr at most from my unit set at 38 degrees. Most efficiant unit by far in my experances includeing All the builtins. Water cooling on a Adler Barber still will draw 2-2.25 amps per hr. in a well built Box but they can cool 5 cubic ft. for that unit.
Dave

............. The fridge we have is a 3.5 cu ft .
Judging from the pictures , ours appears bigger than the one in the posted pictures . We looked at some smaller ones. To do what we need , we needed more cubic feet , than what we could afford in DC ....

If I did the math right........

http://www.edgestar.com/products/fridgefreeze/fp630.asp

........, our EdgeStars are 1.77 cu. ft., so you are right yous is about twice the size.

Do you have any pictures of how and where it is mounted? I'd like to see the install.

Thanks,

Sum

Our Trips to....

Our Mac Pages

Mac-Venture Links

[DaveB]

Gypsy,
You can lead a Horse to water.. but you can't make it drink.
Belive me you need a top loading DC Refig. Take a good look at the Edgestar and other portable 12 volt Refig/freezers units for very low current drain. A 110 AC frig. unit does not belong on Mac. unless you run a genarator or motoring all day long, every day or hook up to Marina and have a builting DC charger and AC outlets with elect. Panel.
Inverters draw so much power to convert AC to DC and only worth it on small items useing less than 50 watts fora 60-75 watts Inverter.(these don't require fans) Any Inverter above that uses fans and large cooling plates and are always on even if you don't use it. Rule of thumb is a Inverter that is rated 60 watts will use between 3-6 % converting DC to AC. Much more as the size of inverter increaces.
Most people who have large Inverters turn off the inverter after use.
Dave

/freuote="Gypsy"]We bought the fridge , but haven't mounted it yet .
The plan is for it to go in the stern , on the port side , straight back from the battery compartment . It should stand up nicely in the high part of the stern area .

I will try what Russ suggested and do a test run , here at home , rig up inverter , battery , and fridge and see how it goes.
My son and I sat at the table , one night for hours , trying to come up with some calculations to determine if it would work or not . By our estimates / calculations it will not only work , but fully charge the battery , on an average day.

But I am aware that there is a BIG difference between a kitchen table calculation and reality .

It may be we might have to shut off the fridge at night , and turn it back on in the morning.
We have done this in the past ,here at home , when we would lose power from a hurricane . I would run fridge and freezer thru an inverter and run them one at a time. [/quote]

[nedmiller]

I was also thinking about the Engel 35 but the admiral liked using the space under the aft dinette seat as a pantry and stores food, coffee, and galley supplies there. That meant we could go on up to the Engel 45 since we were not so space limited. I couldn't be happier with the efficiency at 12V or the usefulness. It switches off the DC and onto AC if you plug into house current. Right now it is in the back of the pickup and thermostat is set at 19 degrees and plugged into house current. We are about to leave on a week-long trip and have decided for this one, we'll use the Engel as a freezer in tow vehicle and the then the first half of the boat trip. We will put a cooler in the Mac for things that just need to be refrigerated.
This afternoon, we'll plug the Engel into the truck 12V and drive over and buy all the meat for the trip frozen and add any other frozen food (ice cream?) we will need to the Engel. If there is any space, it will be filled with frozen water bottles.
As the trip progresses, we will pull out meat and other frozen food that needs to be thawed and throw them in the cooler where they will keep drinks, etc. cool as they thaw. At some point late in the trip. we will just switch the Engel to refrigerate and the Engel will kick on when things thaw.
SILK has 2 house batteries and an isolated marine starter battery. It has a 65 watt solar panel to keep the batteries in good shape. The Engel is so efficient that I don't think we will have to worry all week about battery power. I think if I tried to use an inverter and 110 V. cooler, we might last 3 days and our batteries would be shot.
The Engel is wow expensive. We tried all kinds of alternatives and if we just used it for the boat, it might not have made sense. But, on any road trip, it can be put in the car and plugged into DC. Cold Soda is always available and you can save stopping at fast food. You can pack lunch meat and have sandwiches. It even holds the cold overnight if you unplug it.

SILK

[Catigale]

I just came back from a week long trip with 6 crew. Two coolers with ice are a lot cheaper than a fridge and generators/batteries to manage, imho.

[technicalman]

I have to agree with you. Also, with fridge and generators/batteries, there's a significant amount of weight added to the boat. So there might have to be a significant amount of floatation added to the boat to make up for it. It might be better going with Freeze Dried foods on long trips. But that's also a change in lifestyle that many won't want to do.

I just came back from a week long trip with 6 crew. Two coolers with ice are a lot cheaper than a fridge and generators/batteries to manage, imho.

[Catigale]

You do begin to figure out how to get stuff out of the fridge as you get better at this cruising gig, Ive found.

I used to carry 2 gallons of milk - now I use Parmalat for cereal and mashed potatoes and suddenly all that cooling load is just dry food storage!!!

Likewise on our SAT-FRi cruises we have frozen meat SAT-WED, the last dinner out on Thursday we do local fish, FRI is pasta night.....by the end of day Friday the freezer locker is empty of perishables but we have eaten well.

[Russ]

I just came back from a week long trip with 6 crew. Two coolers with ice are a lot cheaper than a fridge and generators/batteries to manage, imho.

6 crew on a 26' Mac. Wow! That's impressive.

Just make sure you buy two GOOD coolers with a minimum of 5 day rating. We made the mistake of buying based on size/wheels and not by "days" it will last. So now we have a cooler farm of mistake purchases in our garage. Even with the 5 day coolers, we never managed the ice properly and had to add more. Done properly this might not have been the case.

Our 12v Edgestar and 80w solar panel works great. No more wet sloshy food. We leave it turned on all week powered by the sun and when we go down it's already loaded with cold drinks. We have no A/C power at our marina.


--Russ