Home refrigerator in catamaran?

[44'cruisingcat]

Originally Posted by Palarran

It's hard to believe that a regular home refrigerator only draws 60 watts when running. At 120v that's .5 amps. But I totally agree with the rest of your post.

Of all the electricity-powered household appliances, your refrigerator uses the second largest amount of energy, after the air conditioner. According to the U.S. Department of Energy, the average refrigerator uses approximately 725 watts of electricity and 15 to 20 amps, which can equal 10 percent or more of your home's total energy usage.

Well these are a bit smaller than a regular home fridge. 100 litres. A bar fridge. The power usage of the compressor is on a label on the back. I've also tested with a power consumption monitor, to see what the peak start up load was. They both actually use just a little less than 60 Watts when running.

Newer fridges are better.

[Palarran]

It still surprises me.

As for not knowing what the difference between power and energy, maybe you can explain it to me. I received a college degree in Heating, Cooling, and Refrigeration Technology, have worded and owned one of the largest HVAC companies in my state with about 120 employees for 35 years, and just must not get it. No matter how much insulation you put on the units and how well sealed the door is, and how efficient the compressor is, you still have to cool down the product you put in it and the air that escapes when you open the door.

www.belaire.com

[nebster]

Originally Posted by Palarran

As for not knowing what the difference between power and energy, maybe you can explain it to me. I received a college degree in Heating, Cooling, and Refrigeration Technology, have worded and owned one of the largest HVAC companies in my state with about 120 employees for 35 years, and just must not get it.

I'm sorry you felt like I was attacking your ego, when in truth I was trying to show how far off the writer of that little blurb was.

To be clear, though: the physics don't really care what you, or I, or anyone else have accomplished in this world.

According to the U.S. Department of Energy, the average refrigerator uses approximately 725 watts of electricity and 15 to 20 amps, which can equal 10 percent or more of your home's total energy usage.

I simply don't know what to make of this sentence.

1) I guess maybe this writer is confusing nameplate (peak) wattage with average demand.

2) It's unusual to write about "watts of electricity," since "electricity" is colloquially synonymous with energy, not power.

3) It's awkward to list a wattage and a current with an "and" in between. They are redundant, nor do they add to each other.

Number two and three suggest a writer that doesn't understand the basic concepts needed to discuss the subject at hand. Palarran, I wasn't suggesting that you don't understand those concepts.

4) But, if the writer is going to be redundant, he or she should at least do the math. That he comes up with "15 to 20 amps" is weird, since that doesn't match their other (wrong) number. 725W would be 6A.

5) The average home last year used 867kWh per month. As discussed, modern fridges use about 30kWh per month, or 3% of the average home's energy demand. Where the 10% came from, I have no idea.

So I don't know what this writer was smoking, or how much they got paid to assemble that disaster of a sentence, but it's basically confusing or wrong from head to toe.

No matter how much insulation you put on the units and how well sealed the door is, and how efficient the compressor is, you still have to cool down the product you put in it and the air that escapes when you open the door.

The energy data we've been discussing factors people loading in food and opening the doors.

There have been huge gains in a lot of dimensions. Certainly, better insulation and better seals and better compressors help. But, anti-sweat and defrost mechanisms have been improved substantially, and those use a ton of energy when they're heating. And circ fans just dump all of their energy directly back into the fridge, so efficiency gains in those motors yield big savings around the clock.

It's very hard today to beat a residential style fridge on efficiency, especially once capacity and cost are factored in. These things have simply been engineered quite close to the limits.

[CatNewBee]

Originally Posted by nebster

I'm sorry you felt like I was attacking your ego, when in truth I was trying to show how far off the writer of that little blurb was.

To be clear, though: the physics don't really care what you, or I, or anyone else have accomplished in this world.



I simply don't know what to make of this sentence.

1) I guess maybe this writer is confusing nameplate (peak) wattage with average demand.

2) It's unusual to write about "watts of electricity," since "electricity" is colloquially synonymous with energy, not power.

3) It's awkward to list a wattage and a current with an "and" in between. They are redundant, nor do they add to each other.

Number two and three suggest a writer that doesn't understand the basic concepts needed to discuss the subject at hand. Palarran, I wasn't suggesting that you don't understand those concepts.

4) But, if the writer is going to be redundant, he or she should at least do the math. That he comes up with "15 to 20 amps" is weird, since that doesn't match their other (wrong) number. 725W would be 6A.

5) The average home last year used 867kWh per month. As discussed, modern fridges use about 30kWh per month, or 3% of the average home's energy demand. Where the 10% came from, I have no idea.

So I don't know what this writer was smoking, or how much they got paid to assemble that disaster of a sentence, but it's basically confusing or wrong from head to toe.



The energy data we've been discussing factors people loading in food and opening the doors.

There have been huge gains in a lot of dimensions. Certainly, better insulation and better seals and better compressors help. But, anti-sweat and defrost mechanisms have been improved substantially, and those use a ton of energy when they're heating. And circ fans just dump all of their energy directly back into the fridge, so efficiency gains in those motors yield big savings around the clock.

It's very hard today to beat a residential style fridge on efficiency, especially once capacity and cost are factored in. These things have simply been engineered quite close to the limits.

I do not know what you are referring to, but IF it was my statement, the math are correct.

I have calculated the Watts to 220V and Amps on the high voltage secondary side -> to 12V and required Amps on the primary side resulting by the conversion using an inverter. 20A on 12V produce 240W of power, that transforms with 10% loss to approximately 220W at 220V and 1A.

But this is not important because energy used matters, and this is power x time. If this runs for 10 hours per day, it would be 2200Wh and you would draw 2400Wh on the battery. Because in the 12V world people tend to represent the energy used as battery capacity you can also calculate this by dividing the Energy 2400Wh by the battery voltage 12V resulting in a necessary capacity or used capacity of 200Ah per day.

Btw, this is the energy a camping absorber fridge/freezer from Thedford takes on 12V / 220V used in European RV. It has a 220V - 220W heater, a 180W 12V heater and a propane heater. It runs approx 10h in a 24h period to compensate the insulation losses and the losses by opening the doors eventually to get stuff out and in. And I know this, because I have one and run it on solar/battery during the summer time. So this are validated values, not just manufacturer data and estimations.

I hope you understand the math.

[rom]

Originally Posted by nebster

A modern residential refrigerator consumes about 1kWh per day with typical usage. The best ones come in at around 0.8kWh per day.

They are very efficient for their volume.

As a side note, the person you quoted doesn't understand the difference between power and energy. That's something that it seems might be important when writing on this topic.

Yes but your assertion that a "residential refrigerator consumes about 1kWh per day with typical usage" is meaningless just the same if you don't say whether it's 50l or a 300l, A+ or A+++

Dsanduril took some time to describe the consumption of his residential fridges in post #42. That would average about 0.4kWh per day for a 110l fridge, which is somewhat confirmed by 44'C.

[CatNewBee]

Originally Posted by rom

Yes but your assertion that a "residential refrigerator consumes about 1kWh per day with typical usage" is meaningless just the same if you don't say whether it's 50l or a 300l, A+ or A+++

Dsanduril took some time to describe the consumption of his residential fridges in post #42. That would average about 0.4kWh per day for a 110l fridge, which is somewhat confirmed by 44'C.

Attachment 179958

Energy label of the Samsung SBS fridge, they claim 1kWh per day, in reality it draws almost double that amount of energy when used. You can reach this value only using all the power saving settings, and not taking stuff out and in frequently.

[44'cruisingcat]

Originally Posted by Palarran

No matter how much insulation you put on the units and how well sealed the door is, and how efficient the compressor is, you still have to cool down the product you put in it and the air that escapes when you open the door.

www.belaire.com

Does this not apply equally to 12 volt fridges?

[rom]

Originally Posted by CatNewBee

Energy label of the Samsung SBS fridge, they claim 1kWh per day, in reality it draws almost double that amount of energy when used. You can reach this value only using all the power saving settings, and not taking stuff out and in frequently.

I am not sure how a 543L fridge is relevant to this conversation. You are not using one on your boat and you will have a hard time finding someone who does and can provide actual electricity consumption figures. Let's be honest, the vast majority of us are interested in "table top" or smaller units.


Why are you trying negate what's been said here by cruisers with actual experience using residential fridges, that they draw about what the label says ?

[44'cruisingcat]

I wondered how big that fridge was. 543 litres. Yep, totally relevant.

So I guess it would be equally reasonable to say diesel engines are thirsty, based on the fuel consumption of a ship motor....

[Mr B]

I dont have a residential fridge freezer,

But I do have two ammonia fridges that run on gas, One in my boat and one in my RV,
Both are Dometic fridge freezers, and yes, I can pull an Icy cold beer out of them both at any time, The freezers always keeps the food frozen solid,

The only time they stop working is when the gas bottle runs out,
I sail with the fridge working, Three small bottles, Lasts about 4 weeks,
I drive the 36 foot RV with the fridge working, I have 5 bottles in that, It just dont run out,
Neither have ever shut down from being thrown around on sea or roads,
My drive is 1 in 3, So if my fridge was going to shut down from not being level, It would have done,

As for being unsafe, They both have a couple of gas detectors under them, or very close to them,
The gas storage has gas detectors in them as well, Plus a hole under them to let any gas escape,
Both my stoves are also propane gas,

Cheers, Brian,

[valhalla360]

Originally Posted by Chotu

However, I'm contemplating going solar/domestic when this one breaks only because you absolutely never have to get propane.

But you do have to replace the batteries every so many years. (less often but it's a big bill when it comes due).

[CatNewBee]

Originally Posted by rom

I am not sure how a 543L fridge is relevant to this conversation. You are not using one on your boat and you will have a hard time finding someone who does and can provide actual electricity consumption figures. Let's be honest, the vast majority of us are interested in "table top" or smaller units.


Why are you trying negate what's been said here by cruisers with actual experience using residential fridges, that they draw about what the label says ?

It was for referrence, because a similar model is factory installed in the Nautitec Open 46 catamarans.

[nebster]

Originally Posted by CatNewBee

I do not know what you are referring to, but IF it was my statement, the math are correct.

I was responding to someone else.

[nebster]

Originally Posted by rom

Yes but your assertion that a "residential refrigerator consumes about 1kWh per day with typical usage" is meaningless just the same if you don't say whether it's 50l or a 300l, A+ or A+++

My reference was to USA residential refrigerators, most of which are similar in size and all of which include a freezer section. There is a standard for usage based on a typical family and a government agency that measures consumption using that standard. USA residential fridges are the largest, so a smaller unit with similar design should use even less energy.

I should have clarified that I was talking about these larger units, since this is an international audience, but the information is still accurate.

[nebster]

Originally Posted by CatNewBee

Energy label of the Samsung SBS fridge, they claim 1kWh per day, in reality it draws almost double that amount of energy when used. You can reach this value only using all the power saving settings, and not taking stuff out and in frequently.Attachment 179959

I have had two residential fridges on two of my RVs that I have lived in full time. Both were about that size, and both actually used about 1kWh per day.