War Of The Refrigerator

So with your new found information that refrigerators take the heat out of your food and push that heat out the backside (underside) of the refrigerator, I have a few questions for you:

What happens to your kitchen temperature after you fill the refrigerator with warm soda and close the refrigerator door?


1. The kitchen will stay the same temperature
2. The kitchen will get cooler
3. The kitchen will get warmer




Remember: the soda is getting colder. . .

Too easy? The answer is number three. The soda started out as warm, and within an hour or so the refrigerator makes it cold. As Newton describes when he stated "Energy can neither be created or destroyed," that heat has to go somewhere. As the refrigerator removes the heat from the warm soda (making it cold for your drinking enjoyment) it releases that heat into the kitchen, making the kitchen warmer.


What happens to the kitchen temperature if you leave the refrigerator door open?

1. The room gets colder
2. The room stays the same temperature
3. The room gets warmer




If you guessed that the room would get colder ask yourself: Where is the heat going? Heat cannot be destroyed so it must be going somewhere.

If the refrigerator was perfectly efficient at removing heat from your soda (the inside) the room would stay the same temperature. It would remove heat from the air closest to the walls of the refrigerator and push it out of the coils on the backside. The air would then mix together and go back to the same temperature as before.

But refrigerators are not perfectly efficient. In the process of moving that heat the refrigerator creates some of its own heat. Another way of saying that: as the compressor runs (the thing you hear kick on from time to time) some electricty is wasted (lost) as heat. Same as running any other kind of motor, there is always some loss (friction etc) that shows up as heat.

So, because the motor in your refrigerator gets warm when it runs (on top of moving heat around), any room exposed to an open refrigerator will actually become warmer, and not colder. Don't tell your parents.

Steve's Question #2

How does a heat pump work?

The basic premis here is to think about heat moving, whether that is you heating your house (bringing heat into your home from the outside) or whether you are cooling your house (heat being forced from inside your house to the outside).

So while it is common to think about a window air conditioner bringing cold air into your home, it is easier to understand the process if you think about heat being removed from the air. That heat is pushed out the back coils.

It may be helpful to think about your refrigerator. I am sure you have noticed that refrigerators tend to be warm on the outside. This heat is two part. One part is the heat created from the compressor (which is what you might hear click on and run from time to time). The other part is the heat that is being pulled out of the food. When you put a warm beverage in the refrigerator and close the door, the compressor pulls the heat out of the liquid and pushes it out the coils on the backside (or the bottom).

With the goal of keeping things short I will stop here for now, and pick it up again later.

Honeywell has a nice flash presentation here

Dear Everyone This Is The "ARTICHOKE"

Dear Artichoke,

This is everyone.

love,

Matt

Artichoke was designed by Poul Henningsen in 1958. It may look familiar since so very many lights have copied it's design since. Just thought you all would like to meet the original.

Steven's Question #1

You keep talking about the electric heat as being 100%, do you really beleive in the 100%? If it really is 100%, why would we do anything but?

I do believe in electric heat being 100% efficient. That does not mean that it is going to be the cheapest heating source ,and it does not mean that it is the best choice for comfort. What it means is that as the electricity is turned into heat, 100% of the electricity is turned into usable heat.

If you want to compare the cost of heating you will need to do some conversions and then compare price of each fuel source. Btus are the most common unit used for this.

For electricity 1 kWh is equavalent to 3,413 Btus. For gas 1 therm is equavalent to 100,000 Btus. If electricity cost $0.08 per kWh and gas costs $1.35 per therm then:

1 million Btus of electricty costs: $23.44

1 million Btu's of gas costs: $13.50.

If this were the whole story the decision is easy. Gas is clearly cheaper. But this is not the whole story.

The average duct system in the US leaks 25-40% of the air outside of the heated space. Since this loss would be the same for gas or electric we can ignore it. But it is a significant cost (and it makes even electric heat less than 100% efficient, since a portion of the heat does not end up in the space you want it).

While we will ignore the small stuff (like fan efficiency, and holes in the house envelope) the other big piece we must consider is the gas furnace efficiency. The gas furnace efficiency tells you how much of your heat leaves the house thru the chimeny (often called a flue). A 60% furnace loses 40% of its heat, along with the poison gases, out the chimeny. So with that furnace for every 10 Btus you create by burning gas, 6 come into the house and 4 go up the chimeny and outside.

Adjusting our cost of 1 million Btus, to account for only the heat ending up in the house we get:

1 million Btus from gas (delivered into the house with a 60% furnace): $22.50

So under those circumstances they are very close (check your local rates to see it this is comparable to what you pay).

Heat pumps are a different story. Air source heat pumps provide heat at 2 to 4 times the efficiency of an electric furnace.

Skipping over the details, at the same rates as before here is a 92% gas furnace compared to an 18 SEER heat pump (this is heat delivered into the home assuming perfectly sealed ducting):

1 million Btus from 18 SEER heat pump: $7.56

1 million Btus from 92% gas furnace: $14.67

Sorry for all the numbers and so few pictures with this post. Maybe next time I will just post pictures, then the time after that we can start to calculate duct losses. . .

Do we get electricity from natural gas here in Oregon?

Yes, let me see if I can find a picture of the NW energy portfolio. . . Looks like NG is around 9% of the Northwest Electrical Resources. This suggests that he regiong currently gets more electrical power from conservation than from NG. But NG is still a significant portion since it can be called up at any time. Resources like wind and solar (currently too small to show up here) are only available when the wind is blowing or the sun is shining. I have heard a rumor that last year the wind did not blow for 15 days straight. So for that time period the wind farms did not produce a single watt of electricity.

Field Picture: Moldy Attic Hatch

Anyone out there curious what happens when none of the exhaust fans work in a house, and some of the ceiling has insulation and some does not?

Wonder no more:

This attic was insulated last year, along with the floor. The contractor did not put any insulation on the access to the attic. Therefore that access hatch was the coldest surface in the whole house.

Moisture always knows where the cold spots are and it will find them. It will condense on the surface. And days, if not hours later, mold will begin to show up.

Two lessons here:

1. Make sure your exhaust fans work. Hold up a piece of tissue paper to the vent to see if it will hold it up. If it falls you are not getting any airflow out of that fan. Check the vent path and think about replacing the fan.

2. When you go to insulate a portion of the home be consistent. By leaving small portions undone you will get surface temperature variations that will encourage condensation.

P.S. Answers to previous questions are still coming. . .

A Pilot Flame About Gas Furnaces

A long time ago in a land far far away I wrote about electric heaters, and how (if you ignore ducts) they are essentially 100% efficient. This is because all the heat produced from the coils ends up in the heated space.

To repeat, 100% of the heat that is created is brought into the space you are intending to heat. This is also true when considering the waste heat created by the fan motor, since that heat also ends up in the heated space.

Gas furnaces are a different beast altogether.
Since this is going on:

We cannot treat it like an electric furnace unless you want to wear one of these stylish head pieces around your house 24/7:

Your average natural gas exhaust contains: Benzo-a-Pyrene, benzene, toluene, carbon monoxide, soot, formaldehyde, radon gas, radon daughters, PCBs, DIOXINS, FURANS, dust, rust, olefins, waxes, tars, oxides, sulfuric acid, mercaptans, marticulates, oils, and lots of water vapor.

A rather intimidating list, but still shorter and relatively safer than the list you will find from burning coal. Which wasn't all that long ago.

Lots of these chemicals in your home will cause death, especially the carbon monoxide. Relatively small amounts of these in your home may cause flue-like symptoms. So if you have an old gas furnace and often feel sick in the winters you may want to have your unit serviced. Even if it costs you money to fix it. (Check with your local CAP if you absolutely cannot afford to service your unit.)

Without getting into too much detail your furnace is designed to exhaust these poisonous fumes out of your flue. Like the blue arrow in this picture:

Your furnace is designed to keep those gases separate from the air being circulated in your home. Much like putting your hands in the smoke of an open fire, the exhaust gas can be very hot still. For you all using gas furnaces to heat your homes, that is lost heat. The heat leaving your flue with the poisonous gasses is lost efficiency, because it does not end up in the space you are intending to heat. Furnaces are rated based on what % of the heat ends up in your home.

Older furnaces generally range between 50% and 70% efficient, meaning some furnaces push half the heat out the chimney.

Newer, high efficiency furnaces, can perform above 90% efficiency. These furnaces actually pull the heat out of the water vapor before they exhaust the air. Then they pump the water out separately from the air. At that efficiency the exhaust air is cool enough to vent thru PVC pipe like in this example:

At the price of natural gas these days furnace upgrades are getting shorter and shorter paybacks. I do not know enough about different models and manufacturers to recommend one over another, but I can tell you that upgrading your 70% furnace to a 90%+ is likely to have a much shorter financial payback than any of the new fangled solar electrical panels.

But they sure do look nice, don't they?

Wait. How did this picture of Jackie end up with the solar ones? Hmmmm, too late to take it out now I already posted.