Fridge Power Usage

[Freddmc]

I'm looking at a fridge that draws 700 watts per day which converts into 30 watts per hour. I have a 1500w inverter but am wondering if I could use a dedicated 100 w cheap inverter to reduce the parasitic draw of the inverter? How can I determine the parasitic draw of the inverter?

Thanks

Fred

 

[efficientPV]

Depending n inverter, even 1500W may not be enough. My fridge draws 1200W at startup for a couple seconds. My inverter is only powered on when the temp switch closes. If your fridge doesn't have anything fancy like defrost it is not hard to rewire.

 

[Ped]

No fridge draws 700w per day. It does not work that way. Its draw is dependant on a half dozen factors that change average compressor run time drastically.

You look at amp draw of the compressor.

A 100w will not start a compressor. Often a 600w will not start a small compressor. You can get away with a very small inverter, say 400w, with an easy start unit for $300.

My 1500w PSW inverter draws .88a and my 400w MSW draws about .33a measured. The inverter draw issue is a bit overblown IMO.

 

[Freddmc]

"No fridge draws 700w per day. It does not work that way. Its draw is dependant on a half dozen factors that change average compressor run time drastically.
Actually, according to this guy it does. (http://www.beginningfromthismorning.com/securing-the-refrigerator/)
Its rated at 1kwh per day but according to his kill-a-watt- it only uses about .7 KWH per day.

 

[Ped]

Does he open it up more than you? Is he in very hot or cold weather? Will you be? My 1.7cu ft fridge uses from 150w-950w depending on the season.

 

[JeepHammer]

What we did when first living off grid 20 years ago...

A chest freezer turned up above freezing.
Freezers have better insulation, chest type keeps the cold in when the lid is opened, built in thermostat,
Even used an external PID to switch inverter On/Off to save power, inverter powers up when temp rises.

Adding thermal insulation and venting compressor heat helps any fridge/freezer.

 

[Supervstech]

"No fridge draws 700w per day. It does not work that way. Its draw is dependant on a half dozen factors that change average compressor run time drastically.
Actually, according to this guy it does. (http://www.beginningfromthismorning.com/securing-the-refrigerator/)
Its rated at 1kwh per day but according to his kill-a-watt- it only uses about .7 KWH per day.

I would like to know the startup watts needed to use the fridge...
700wh is not the same as 700watts.
Fridges are a duty cycle item.
Full, with the door closed, they cycle less.
Empty with doors open a lot, they cycle more... it could easily pull over 1000 watts for a few seconds, run a few minutes at 300 or so watts, then shut off for a few hours, and still use less than 700Wh per day...

 

[Rider]

I've posted those kinds of number more than once in different threads, for a 3.5cf freezer as a fridge, and a 21cf full kitchen fridge. Search for 'fridge', user Rider and you'll find it all.

 

[Maggie Flinn]

I'm looking at a fridge that draws 700 watts per day which converts into 30 watts per hour. I have a 1500w inverter but am wondering if I could use a dedicated 100 w cheap inverter to reduce the parasitic draw of the inverter? How can I determine the parasitic draw of the inverter?

Thanks

Fred

I believe if you use a clamp meter to the power cord it may show how much is going through it.

 

[Supervstech]

I found this at homedepot...

 

[Supervstech]

So, 180watts normally, and likely 3 times that startup. FYI...

 

[Steve_S]

As an off-gridder relying on solar, I went down the Fridge Rabbit Hole and I can tell you, it's one heck of a warren ! I looked at a LOT of options an considered many factors as I hate to waste my pennies. I found that Energy Star Rated refrigerators are the first step (and boy what a mixed bag) to locating power efficient models, whittling that down was a chore too. I ended up buying a Danby "Apartment Sized" 10 cubic foot fridge which uses only 530 Kwh per year. It's not hard on the Inverter at all (a Samlex shows watts, amps etc as used, Real Time). Danby also owns eh Magic Chef label and a few others (I forget which, quite a few). Best part is, I got it on sale at Costco for $425 CAD / $318 USD (roughly). They have since updated the model BUT there has been a change at Energy Star as the Trump Gov't dropped it's support for it... So pay attention to the labels & markings, some lost efficiency ratings.

This is the latest version of the one I purchased & use which I am very happy with BTW:

Danby 10 cu. ft. Apartment Size Refrigerator - DFF100C1BSLDB | Danby USA

This apartment-sized refrigerator by Danby is second to none when it

www.danby.com

 

[bulrush]

I'm looking at a fridge that draws 700 watts per day which converts into 30 watts per hour.

That's the average watts per hour over a 24 hour period but compressors don't work that way. They draw a BUNCH of power when the compressor first starts, then will draw less while it runs, then it will stop running for maybe 20 minutes, then repeat the process.

It's like a fluorescent light. The F light uses so much power when it first starts that you don't save any money until the F light has been on for 15 minutes. Just because it's "fast start" does not mean it uses less power in the startup phase. Many people don't understand this, install F lights in bathrooms where a typical bathroom trip turns on the light for 3 minutes, and they end up using more power with the F lights because they turn it off and on so often.

And this is why I changed to LED lights. They don't use that burst of power when they turn on, and they still use about half the power than an F light while it's on (excluding the F light's startup phase).

 

[bulrush]

"No fridge draws 700w per day. It does not work that way. Its draw is dependant on a half dozen factors that change average compressor run time drastically."
Actually, according to this guy it does. (http://www.beginningfromthismorning.com/securing-the-refrigerator/)
Its rated at 1kwh per day but according to his kill-a-watt- it only uses about .7 KWH per day.

The web page doesn't say if he measured the power of the fridge when the compressor was running or not, a very important detail which was missed. The page also doesn't say how he calculated that number. Did he measure power usage over 30 days and divide by 30? Or some other method? The devil is in the details.

The page says:

It is the exact height we need, but the best part is that it uses less than 1kwh per day. In fact, when we tested it with our Kilowatt meter, it was consistently using about 0.7kwh per day.