Ready for a new refrigerator

[GoneDiving]

A 7 degree differential BS. It should be pretty simple to run the refrigerator off an inverter and wire the digital thermostat between the refrigerator power cord and outlet....

Ted

There are OEM extension cords with temp controls built in. They are essentially plug and play and designed for home brewers, aquariums etc.

I have no idea in their sensitivity or temp swings

https://www.ebay.com.au/itm/2653580...s4fEo4UTim&var=&widget_ver=artemis&media=COPY

 

[HeadedToTexas]

There are OEM extension cords with temp controls built in.

Very interesting. Guessing I'll find a use for one now that I know about them. That fits into the old If you can think it up, someone is making it already adage.

A 7 degree differential BS. It should be pretty simple to run the refrigerator off an inverter and wire the digital thermostat between the refrigerator power cord and outlet. It would require a small hole to run the temperature sensor cord (discount it from inside the thermostat) through and seal with RTV. Only downside I see is the refrigerator light would only come on when the compressor is running (and the door is open).

That seems like the right answer, Ted. The hole for the temperature sensor already exists. And correct me if I'm wrong, but it doesn't seem like that much rewiring is necessary. I get what you're saying about putting the new digital thermostat between the power cord and the compressor, but I should be able to preserve the AC/DC features by simply replacing the thermostat and sensor with the new digital one. All of the same inputs, outputs, and load ratings exist. Remove the components outlined in red on the attached schematic and wire in the digital thermostat to the existing connections. What am I missing?

 

[rslifkin]

Ran across this today. Norcold laying off just about everybody in Ohio:

https://www.dailyadvocate.com/2020/03/24/norcold-lays-off-345-employees/

Old article from March 2020

 

[GoneFarrell]

Doh! Missed the date stamp on that!

 

[HeadedToTexas]

I love it when the physical layout lines up well with the schematic. Replacing the thermostat (with integral power switch) and temperature sensor as outlined in red on the schematic with a digital version as described in posts on previous pages seems pretty simple. What am I missing?

 

[Propnut]

I've owned all of the top brands of marine refrigerators and none lived up to my expectations . Soft ice cream, warm beer and constant defrosting seem to be the norm during the hot summer months.
I finally purchased a Summit Refrigerator . Self defrosting , built in ice maker and very energy efficient .
I now have hard ice cream and cold beer. I'll never own anything else.
Just my two cents worth.

 

[GoneDiving]

I've owned all of the top brands of marine refrigerators and none lived up to my expectations . Soft ice cream, warm beer and constant defrosting seem to be the norm during the hot summer months.
I finally purchased a Summit Refrigerator . Self defrosting , built in ice maker and very energy efficient .
I now have hard ice cream and cold beer. I'll never own anything else.
Just my two cents worth.View attachment 133563

Residential style refrigerators are designed to swallow bags full of room temperature shopping and cool them down quickly to the designed storage temp. This gives them a lot of headroom over simply maintaining temperature.

Camping/4WD/Marine low voltage units seem to be designed to maintain temp, have little excess cooling capacity so struggle to cope with anything that reduces their efficiency or effectiveness. This leads to the problems you mentioned.

 

[HeadedToTexas]

I finally purchased a Summit Refrigerator . Self defrosting , built in ice maker and very energy efficient .
I now have hard ice cream and cold beer. I'll never own anything else.

That is compelling. Not exactly sure why, but I continue to struggle to understand the power issues surrounding AC and DC. The following is pretty clear.

1. In a marina slip with virtually unlimited shore power, it is pretty clear that an AC only fridge is fine.
2. Underway with plenty of power from the main engine, I believe we have enough amps to both charge batteries fast enough and run an AC only fridge with our big Xantrex 3000 watt inverter.
3. At anchor or anywhere overnight without shore power, I think our 600 amp-hour AGM house batteries probably have enough amps to run an AC only fridge with our big Xantrex 3000 watt.

But I struggle to understand what may be a fine line between sacrificing the energy overhead required to run the Xantrex Freedom SW 3012 to power an AC only fridge. The day will come when the 3 year old AGMs are replaced by the technology of the day and we install solar on the pilothouse roof, but until then I expect we will be close come morning after a night of running a bigger fridge.

It is also not clear whether our current Norcold DE0061 inverts and transforms DC to AC to run the Danfoss compressor, or whether it (when on shore power) converts AC to DC to run the compressor. Or whether all that energy nerdism even rises to the level of mattering?

 

[Circumnavigator]

That is compelling. Not exactly sure why, but I continue to struggle to understand the power issues surrounding AC and DC. The following is pretty clear.

1. In a marina slip with virtually unlimited shore power, it is pretty clear that an AC only fridge is fine.
2. Underway with plenty of power from the main engine, I believe we have enough amps to both charge batteries fast enough and run an AC only fridge with our big Xantrex 3000 watt inverter.
3. At anchor or anywhere overnight without shore power, I think our 600 amp-hour AGM house batteries probably have enough amps to run an AC only fridge with our big Xantrex 3000 watt.

But I struggle to understand what may be a fine line between sacrificing the energy overhead required to run the Xantrex Freedom SW 3012 to power an AC only fridge. The day will come when the 3 year old AGMs are replaced by the technology of the day and we install solar on the pilothouse roof, but until then I expect we will be close come morning after a night of running a bigger fridge.

It is also not clear whether our current Norcold DE0061 inverts and transforms DC to AC to run the Danfoss compressor, or whether it (when on shore power) converts AC to DC to run the compressor. Or whether all that energy nerdism even rises to the level of mattering?

The DE0061 transforms and rectifies the 120VAC down to 12VDC -- the Danfoss is a DC compressor.


As for your new setup, a modern refrigerator the size of the Norcold will draw around six amps when running, maybe less. At 120VAC, that's 720 Watts. Estimates of the duty cycle vary, but I would guess that at night, with no one opening the door, it would run a third of the time. In a nine hour night, that would be 2160 Watt-hours.



I assume your house batteries are 12VDC and not 24VDC, so your batteries have a nominal 7200 Watt-hours stored if fully charged and in good condition. You never want to discharge lead acid batteries to more than 50% of their nominal capacity, but that still gives you 3600 Watt-hours.


So, you have 3600 Watt-hours available and a refrigerator load of 2160. If there's nothing else significant running on 120VAC, that should be plenty of leeway to deal with inefficiencies in the inverter.


Jim

 

[Helmsman]

I think the choice could be stated this way. If you value food being refrigerated at a consistent temperature, and can accomplish that with your current battery bank through the inverter, then a 120 volt fridge would fit the bill. However, if your battery supply overnight is not sufficient to supply the fridge and other requirements, then a marine fridge with a 12 volt Danfoss compressor makes sense. You can simply turn the AC breaker off when underway.

 

[GoneDiving]

The DE0061 transforms and rectifies the 120VAC down to 12VDC -- the Danfoss is a DC compressor.


As for your new setup, a modern refrigerator the size of the Norcold will draw around six amps when running, maybe less. At 120VAC, that's 720 Watts. Estimates of the duty cycle vary, but I would guess that at night, with no one opening the door, it would run a third of the time. In a nine hour night, that would be 2160 Watt-hours.



I assume your house batteries are 12VDC and not 24VDC, so your batteries have a nominal 7200 Watt-hours stored if fully charged and in good condition. You never want to discharge lead acid batteries to more than 50% of their nominal capacity, but that still gives you 3600 Watt-hours.


So, you have 3600 Watt-hours available and a refrigerator load of 2160. If there's nothing else significant running on 120VAC, that should be plenty of leeway to deal with inefficiencies in the inverter.


Jim

I'm not sure on how optimistic the marketing is for the 7cuft DE0061 is. However, the manual shows 48w on AC and 38w on 12vdc. That's a tiny compressor, approximately half the size of my cold water dispenser. 48w running at 100% for 9hrs is 432wh. Obviously, this can be derated based upon real world duty cycle but I'd expect such a small compressor to be working hard when under any sort of load.

As a comparison, my 14cuft Samsung domestic inverter fridge in my kitchen draws 600w at full load but only a fraction of that to maintain temperature. Loaded with a week's new shopping, it will draw about 1300wh in 24hrs. Once at temperature, that falls to less than 1000wh.

https://norcold.com/product/norcold-de-0061-ev-0061-ac-dc-ev-refrigerator/

 

[Simi 60]

Batteries and solar are cheap
DC refrigeration of any size is not.

 

[catalinajack]

I'm not sure on how optimistic the marketing is for the 7cuft DE0061 is. However, the manual shows 48w on AC and 38w on 12vdc. That's a tiny compressor, approximately half the size of my cold water dispenser. 48w running at 100% for 9hrs is 432wh. Obviously, this can be derated based upon real world duty cycle but I'd expect such a small compressor to be working hard when under any sort of load.



As a comparison, my 14cuft Samsung domestic inverter fridge in my kitchen draws 600w at full load but only a fraction of that to maintain temperature. Loaded with a week's new shopping, it will draw about 1300wh in 24hrs. Once at temperature, that falls to less than 1000wh.



https://norcold.com/product/norcold-de-0061-ev-0061-ac-dc-ev-refrigerator/

At the end of the day, the only fact that counts is how many electrons are required to keep a given volume cold. If a particular household fridge is more efficient, then that might be the way to go. It's really s simple exercise in arithmetic. Compare the inverted DC draw of an AC-powered domestic fridge to the DC draw of a Danfoss unit. All I know is our experience with 8.4 cubic feet of Vitrifrigo DC-only (two 4.2 cf units). Overnight, defined as 12 hours, they generally consume about 200 amp-hours but ours are well-ventilated including two exhaust muffin fans. As for cooling, even in warmer conditions, these fridges keep beer plenty cold without ever having had to turn the thermostat to max cold. If we do, delicate items such as veggies freeze. The household fridges that the Vitrifrigos replaced could not keep up. But, household fridges are, indeed, less expensive.

 

[GoneDiving]

The household fridges that the Vitrifrigos replaced could not keep up. But, household fridges are, indeed, less expensive.

No reflection on your old fridges but I'd certainly agree that my previous comments only apply to residential fridges that are a decent manufacturer and size. Inverter control is a game changer. The $100 small dorm/bar fridges are hopelessly inefficient both in terms of compressor draw and thermal insulation.

 

[sbman]

That is compelling. Not exactly sure why, but I continue to struggle to understand the power issues surrounding AC and DC. The following is pretty clear.

1. In a marina slip with virtually unlimited shore power, it is pretty clear that an AC only fridge is fine.
2. Underway with plenty of power from the main engine, I believe we have enough amps to both charge batteries fast enough and run an AC only fridge with our big Xantrex 3000 watt inverter.
3. At anchor or anywhere overnight without shore power, I think our 600 amp-hour AGM house batteries probably have enough amps to run an AC only fridge with our big Xantrex 3000 watt.

But I struggle to understand what may be a fine line between sacrificing the energy overhead required to run the Xantrex Freedom SW 3012 to power an AC only fridge. The day will come when the 3 year old AGMs are replaced by the technology of the day and we install solar on the pilothouse roof, but until then I expect we will be close come morning after a night of running a bigger fridge.

It is also not clear whether our current Norcold DE0061 inverts and transforms DC to AC to run the Danfoss compressor, or whether it (when on shore power) converts AC to DC to run the compressor. Or whether all that energy nerdism even rises to the level of mattering?

I run a standard household fridge 24x7 on a dedicated inverter. It's a basic unit, a Magic Chef 9.9 cu/ft and it runs on a dedicated Victron 1200W pure sine inverter that only costs about $300. The idle current of the small inverter is only 1.5A (18W). Your larger 3000W inverter is going to have a much larger idle current. I have 800 Ah of flooded lead acid batteries that run it at night and plenty of solar to both charge up and run it during the day.

The fridge and inverter combined including efficiency losses and idle current draws 500W in 12 hours (41 Ah). Double that of course for a 24 hour usage. Overnight only uses 5% of my battery bank, 10% per day. I can run for several days with no solar input and the fridge and batteries are fine. If I plug into shore power, the fridge still runs on the inverter no fancy switching equipment needed, the shore power battery charger keeps up just fine.

A $400 fridge plugged into a $300 inverter. Very reliable, simple and efficient, the numbers just don't add up to me on the fancy marine brands and DC based fridges. Only the specialty 'off-grid' fridges seem to be an upgrade, and that's all because of the extra insulation. If you have the space to put a normal household fridge I'd go for it but add a very good quality, small dedicated inverter for it. With my AC powered fridge if I need to replace the fridge, the only question I need to ask is: Will fit through the companionway?

If you decide to buy an AC powered fridge, look at the energy star energy use ratings. Divide the power used in a year on the label by 365 and you get daily use. Energy star numbers aren't guesses or estimates, but actual testing done by a third party and are very, very close to what you will see in real life. Add 10% for inverter losses and another 10% for inverter idle (assuming you use a small, efficient inverter).

As an example, my magic chef was energy star rated at 297KWhr/yr, 800 watts/day. In actual use it's right at 1000W per day but that includes inverter losses and inverter idle current, so the label is within 40 watts of what I see in the real world. My Victron system has measured the usage for over a year so the numbers are solid. I've had zero issues with refrigeration and if I start to have issues I just head to Home Depot and get another one.

 

[HeadedToTexas]

Compelling stuff, SB. I like the idea of a dedicated inverter. Attractively priced as well.

 

[sbman]

Compelling stuff, SB. I like the idea of a dedicated inverter. Attractively priced as well.

My boat is on a Mooring so I run on solar 24x7 as well and keep close tabs on my energy usage in all aspects. I have 1200W of solar, I also cook with induction, use full size PC computer onboard, etc...

 

[rslifkin]

Interesting that your inverter draws so much at idle relative to its size. Idle draw on my 2000VA Victron Multiplus is right about 10 watts (usually shows about 0.8 amps). At least for the older generation of them, the 3000VA Multiplus draws double what mine does at idle.

 

[HeadedToTexas]

Xantrex specs indicate that the Freedom SW 3012 has a no load power draw of 3 amps or 36 watts. If the compressor on my Norcold runs 33% of a typical summer day, then the big Xantrex consumes an extra 24 amp hours each day. If a dedicated inverter for the fridge load has a no load power draw of 18 watts like SBman's, and if the fridge compressor runs 33% of the time, then the difference is 143 watt hours or 12 amp hours per day (if my math is right).

If the trade off between a boat fridge like my Norcold is warm beer and soft ice cream or an extra 24 amp hours to run an AC fridge, then it's a pretty clear choice.

That said, I believe my beer is warm and ice cream soft because of the ridiculously wide swing of the Norcold thermostat, and fixing that feels like the right direction at the moment. If that doesn't do it, the Norcold is headed for the dumpster anyway.

 

[O C Diver]

An interesting bit of information for using 120 VAC refrigerators. As a result of hurricane Ian, my winter dock won't have shore power till mid 2023. While I don't have the Summit refrigerator on, I would like to keep a portable dehumidifier running to maintain low humidity within the boat. My compressor driven dehumidifier draws 125 watts intermittently (built in humidistat). Unfortunately the Magnum Energy inverter has too much of a standby energy draw and requires more energy per day than the dehumidifier.

Not interested in a Chinese Junk inverter. Victron makes a 500 watt pure sine wave inverter for around $160. What caught my eye was the standby power consumption of 6 watts and 90+% efficiency. There is an economy mode that only draws 1 watt, but won't likely work with an electronic thermostat or humidistat. Will likely add one of these to the boat for a dedicated refrigerator inverter and use it this winter as a power source for the dehumidifier.

https://www.victronenergy.com/inverters/phoenix-inverter-vedirect-250va-800va

Ted

 

[Simi 60]

Xantrex specs indicate that the Freedom SW 3012 has a no load power draw of 3 amps or 36 watts. If the compressor on my Norcold runs 33% of a typical summer day, then the big Xantrex consumes an extra 24 amp hours each day. If a dedicated inverter for the fridge load has a no load power draw of 18 watts like SBman's, and if the fridge compressor runs 33% of the time, then the difference is 143 watt hours or 12 amp hours per day (if my math is right).

If the trade off between a boat fridge like my Norcold is warm beer and soft ice cream or an extra 24 amp hours to run an AC fridge, then it's a pretty clear choice.

That said, I believe my beer is warm and ice cream soft because of the ridiculously wide swing of the Norcold thermostat, and fixing that feels like the right direction at the moment. If that doesn't do it, the Norcold is headed for the dumpster anyway.

Just put in extra battery
It's cheap
Then things like wattage used by inverter become statistical noise.

 

[HeadedToTexas]

In boat bucks, perhaps they are cheap. Adding a fourth AGM to my bank would cost $400 or so plus the cost of wiring, configuring, and containing.

At the moment, our house bank is in the lazarette and virtually inaccessible for normal sized humans. My plan is to relocate the bank to the engine room where they are easier to service and inspect, disconnect when needed, and reach the panel with less cable. The timing of that plan hinges on when the three AGMs need replacing. They were new in 2019 and I am hoping they last for the rest of our marina era, so another 4 years or so. Might be optimistic, but that’s my plan.

I still think the cheap option is a $50 digital thermostat to replace the crappy one Norcold supplies. The DE0061 has no problem getting the fridge cold. The warm beer and soft ice cream problem is caused by the wide swings the crappy thermostat allows, not a failure of the compressor or coil or fan to remove heat.

 

[HeadedToTexas]

Finally back in the water and the digital thermostat upgrade of my Norcold DE0061 was a success. Still hoping to find a way to calibrate the display, but the new $12 thermostat holds a very tight temperature. Far cry from the original Norcold thermostat that let the temperature swing from 33° to 41°.

 

[Choices]

No, it converts 120v AC to 12v DC. The Danfoss compressors package is DC.

So, just run it on DC.

 

[OldDan1943]

Headed to Texas, the battery location is for weight distribution and ballasting the boat.
Please think this through. You might get away with it, as I did. I added a 3rd 4D with no ill effect.
Also, I have been told putting the batteries in the ER will/may shorten the life of the batteries. I sort of doubt that but, I have no first hand experience other the 8Ds in my N46, properly place for ballasting.

 

[HeadedToTexas]

I get the weight distribution. Our boat has a permanent list to starboard and my math indicates that reducing the weight of the house bank will help level the boat. We also have a slight bow high attitude at rest and moving the bank forward should help that as well. That said, I am certainly no marine architect, so input is always welcome.

 

[Helmsman]

HtT, in the 38e’s the house batteries are right behind the transmission in front of the shaft seal. I can get a picture to you when I am back at the boat, if that would help.

 

[OldDan1943]

I get the weight distribution. Our boat has a permanent list to starboard and my math indicates that reducing the weight of the house bank will help level the boat. We also have a slight bow high attitude at rest and moving the bank forward should help that as well. That said, I am certainly no marine architect, so input is always welcome.

The batteries are no doubt mounted low in the boat so the effects on the list will be minimal. You may have to move fuel to take the list off or run on the Stbd tank and then either return to the port tank if possible or move fuel to the Stbd tank as necessary to maintain the trim. I suspect you knew that. SMILE
I wonder what your battery shifting program will do for the ‘bow up’ situation.
Please keep us all informed.

 

[HeadedToTexas]

I have seen a picture of the battery location in the 38s models. The salon hatch must have been moved aft because locating them there on my 37 would really intrude into the hatch entry. Thanks guys.

 

[OldDan1943]

I have seen a picture of the battery location in the 38s models. The salon hatch must have been moved aft because locating them there on my 37 would really intrude into the hatch entry. Thanks guys.

So much for Plan A. Now what?