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View Full Version : Is there data on how much heat a refrigerator gives off?

09-13-2009, 01:51 PM
I presume, since they are never made such that their coils are outside, like an air conditioner, that it's not enough BTUs to worry about.
But for calculation's sake there should be a number obtainable.

Is it fair to say that all the energy consumed ends up as heat, either from cooling the interior, or directly thrown off by the motor housing?

I have a Kill A Watt meter to tell how much power is consumed in a day.
Can I just say the amount of heat put into the room is equal to the amount removed by the same power on my air conditioner, measured with the same meter?
The result would tell me how many extra minutes I had to run the AC to overcome the fridge.

Has the EPA or some green site done this study?
And should I vent my fridge to the outside on AC days? Perhaps just roll it onto the screened porch?

beowulff
09-13-2009, 02:19 PM
The amount of steady-state heat your refrigerator discharges is exactly equal to the number of Watts that your Kill-a-Watt measures.

the first supraliminal
09-13-2009, 06:42 PM
1 watt for 1 hour = 3.4 BTUs converion calculator (http://www.onlineconversion.com/energy.htm)

Here's a chart of common watts for different appliances. (http://michaelbluejay.com/electricity/howmuch.html)

billfish678
09-13-2009, 06:49 PM
The amount of steady-state heat your refrigerator discharges is exactly equal to the number of Watts that your Kill-a-Watt measures.

Zatcly.

And a rough worst case number is it takes your AC about that many watts to pump THAT heat from inside your house to outside. Its probably more like about 1/4 to 1/2 that.

So, figure out how much it cost to run that fridge, then go from there to decide if its an amount worth worrying about.

the first supraliminal
09-13-2009, 07:00 PM
More randomly selected data points:

typical refrigerator 425 kWh / year = 1,450,000 BTU

According to this chart, (http://michaelbluejay.com/electricity/cooling.html) the fridge competes with the A/C at a rate of 1 to 6. So if you run your fridge indoors in summer for 24 hours you add 4 more hours of A/C to even it out.

So, I'd use that porch.

I wonder why the big boy appliance manufacturers aren't experimenting with outdoor coil options.
In fact I think I should invent an aftermarket retrofit kit to place a diversion coil outside, with a way to divert back inside in the heating season.

PatriotGrrrl
09-13-2009, 07:09 PM
I presume, since they are never made such that their coils are outside, like an air conditioner,

Some of them are, or at least they used to be, and the coils did get pretty warm.

snailboy
09-13-2009, 07:54 PM
The amount of steady-state heat your refrigerator discharges is exactly equal to the number of Watts that your Kill-a-Watt measures.

Not exactly. Once the refrigerator reaches an equilibrium, the heat leaving the condenser is equal to the heat leaking back into the refrigerator. The net heat going into the house is whatever the motor and compressor is putting out.

beowulff
09-13-2009, 08:00 PM
Not exactly. Once the refrigerator reaches an equilibrium, the heat leaving the condenser is equal to the heat leaking back into the refrigerator. The net heat going into the house is whatever the motor and compressor is putting out.

Which, coincidentally, is EXACTLY the amount of power it is consuming.:smack:

Chronos
09-13-2009, 08:17 PM
Sooner or later, all energy ends up as heat. And usually sooner.

Uncertain
09-13-2009, 11:38 PM
I wonder why the big boy appliance manufacturers aren't experimenting with outdoor coil options.
In fact I think I should invent an aftermarket retrofit kit to place a diversion coil outside, with a way to divert back inside in the heating season.

It's not clear to me that that's a win. Pumping the heat from the inside of the refrigerator to the warmer outdoors takes more electricity than pumping it to the cooler indoors. Thermodynamically it doesn't help to put the refrigerator coils outside.

Snnipe 70E
09-14-2009, 12:22 AM
It's not clear to me that that's a win. Pumping the heat from the inside of the refrigerator to the warmer outdoors takes more electricity than pumping it to the cooler indoors. Thermodynamically it doesn't help to put the refrigerator coils outside.

No it would. Because of the energy to remove heat from the frig would be added to the heat load inside the house. And the AC then has to remove that heat from the house to the outside, and the AC units condencer qould be outside.

You can get frigs with the condencing unit out side. The problem is they are more expensive by I would guess double or triple. Also you would not be able to go to the appliance store buy one and bring it home and place it in your kitchen. You could the box and bring it home. Then unless you have a epa card you would need the installer to buy the condensing unit. Then after the condensing unit has been installed, you would need the installing company to conect the lines and adjust to a proper charge.

Uncertain
09-14-2009, 01:16 AM
No it would. Because of the energy to remove heat from the frig would be added to the heat load inside the house. And the AC then has to remove that heat from the house to the outside, and the AC units condencer qould be outside.

I was responding to a post about putting the coils outside.

Brainiac
09-14-2009, 10:42 AM
Sooner or later, all energy ends up as heat. And usually sooner.Nope. Some energy is converted into chemical bonds. This is called "cooking" and in the case of the refrigerator, "aging" of the rubber parts, making them brittle.

Brainiac
09-14-2009, 10:44 AM
It's not clear to me that that's a win. Pumping the heat from the inside of the refrigerator to the warmer outdoors takes more electricity than pumping it to the cooler indoors. Thermodynamically it doesn't help to put the refrigerator coils outside.You don't have to pump things that have thermal gradients. That's why convection currents were invented.

beowulff
09-14-2009, 10:47 AM
Nope. Some energy is converted into chemical bonds. This is called "cooking" and in the case of the refrigerator, "aging" of the rubber parts, making them brittle.

Oh, not this again.

Yeah, 1 Bazillionth of the energy going into the refrigerator ends up as potential energy in chemical bonds. And that infinitesimal energy will be released eventually, too.

billfish678
09-14-2009, 10:57 AM
It's not clear to me that that's a win. Pumping the heat from the inside of the refrigerator to the warmer outdoors takes more electricity than pumping it to the cooler indoors. Thermodynamically it doesn't help to put the refrigerator coils outside.

That would only be true if:

The "heat pumper efficiency" of the refrig is significantly/way worse than that of the AC unit.

Having said that, from the OP's data, its only costing a couple bucks a month to run the fridge. Having the AC pump THAT heat out is at best costing a couple more.

Unless its no big deal to put the refrig in the garage or the porch, it aint worth bothering with IMO. And even then I am not sure its worth it.

Anybody wanna do a cost calc for this?

billfish678
09-14-2009, 10:58 AM
Oh, not this again.

Yeah, 1 Bazillionth of the energy going into the refrigerator ends up as potential energy in chemical bonds. And that infinitesimal energy will be released eventually, too.

And there a probably even a few plutonium atoms created ! :)

Brainiac
09-14-2009, 01:22 PM
Oh, not this again.

Yeah, 1 Bazillionth of the energy going into the refrigerator ends up as potential energy in chemical bonds. And that infinitesimal energy will be released eventually, too.If you're going to be picky, I can be too. That energy "released eventually" will not be released in the house but in the landfill a thousand years from now.

beowulff
09-14-2009, 02:35 PM
If you're going to be picky, I can be too. That energy "released eventually" will not be released in the house but in the landfill a thousand years from now.

As an exercise, why don't you calculate how much energy is stored in the embrittlement of the rubber of the average refrigerator and report back?

Dag Otto
09-14-2009, 03:31 PM
Forget calculating. I want him to measure it empirically under actual conditions.

snailboy
09-14-2009, 04:54 PM
Which, coincidentally, is EXACTLY the amount of power it is consuming.:smack:

You got me there. Except for the negligible chemical energy and electromagnetic energy, you're right. My post should've been a response to this instead:

Is it fair to say that all the energy consumed ends up as heat, either from cooling the interior, or directly thrown off by the motor housing?

This suggests to me that the coils, not just the motor, heat the house, when they only release what heat is leaking back into the refrigerator.

Brainiac
09-14-2009, 06:10 PM
As an exercise, why don't you calculate how much energy is stored in the embrittlement of the rubber of the average refrigerator and report back?I have a better idea. I'll wait for you to stop snarking other's posts and then being all crybaby about it.

Uncertain
09-14-2009, 09:42 PM
You don't have to pump things that have thermal gradients. That's why convection currents were invented.

I'm not sure what you mean. Both refrigerators and A/C work as heat engines in reverse, pumping heat against a temperature difference, from colder to hottter. Pumping directly from cold to hot is no easier than pumping from cold to warm and from warm to hot.

Uncertain
09-14-2009, 09:46 PM
That would only be true if:

The "heat pumper efficiency" of the refrig is significantly/way worse than that of the AC unit.

Not so. If both were at the thermodynamically best achievable efficiency, the two would be the same. Depending on which was actually more efficient, one or the other would be the more efficient. So, it's not clear that it's a win.

billfish678
09-14-2009, 09:50 PM
Not so. If both were at the thermodynamically best achievable efficiency, the two would be the same. Depending on which was actually more efficient, one or the other would be the more efficient. So, it's not clear that it's a win.

Your second sentence deals with things not achievable, particularly in household appliances.

Are you Braniacs distant cousin?

Uncertain
09-14-2009, 10:24 PM
Your second sentence deals with things not achievable, particularly in household appliances.

Right, which is clearly the basis of my third sentence. Do you have some reason to believe that the short-comings of real-world heat pumps would favor the configuration with the refrigerator coils outside? It seems that it would depend on such things as which heat pump--A/C or refrigerator--came closer to maximal efficiency. I don't know which one does. Your statement that

The "heat pumper efficiency" of the refrig is significantly/way worse than that of the AC unit.

is not true. What I say would be true if they had equal efficiency.

Are you Braniacs distant cousin?

Sigh. I guess that's supposed to be an insult. That's uncalled for, violates the single rule of this message board ("don't be a jerk"), and exposes your lack of mastery of apostrophe use (not to mention population genetics; we're all distant cousins).

Never Say Dice
09-15-2009, 02:40 PM
Just ignore billfish678. He's always unreliable. That's why he uses personal insults, because he never gets his facts straight and then gets defensive about it.

billfish678
09-15-2009, 03:42 PM
What I say would be true if they had equal efficiency.

So, you are NIT picking, hence the Braniac comment by me . Technically, Braniac is right, but only in the decimal places, the ones that don't matter.

You expect an AC unit and a refrigerator unit, which operate in somewhat different conditions, and are an order of magnitude difference in cost/size to have EXACTLY equal efficiencies for your point to be right. And your point being if they are exactly the same is that there is NO difference. So, your point is, in an ivory tower, it MAY be a wash. Now thats usefull information !

And even THEN I am still not sure you are right, depending on the interpretation of what you've said and what I've said.

billfish678
09-15-2009, 04:21 PM
Uncertain

The ironic thing is I was generally agreeing with you, noting the conditions under which you would be wrong (and nitpicking I guess) and you took the nitpicking to the next level.