Saturday, May 06, 2017

heat 3

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It has been interesting to record how hard my furnace works as the outside temperature changes. The points are observations of the running time of the furnace and how often it comes on taken first thing in the morning from my smart meter compared to the outside temperature. The process takes about the same time as a morning cup of coffee to record one point. The graph fills in as I add more points but I can already clearly see the trend (the line).

I divide the run time by the time between cycles to get a fraction (and then a percentage) which I've called the Duty Cycle. This is how much of the time the furnace runs. The colder it gets outside, the more the furnace runs, using electricity and oil in my case to generate heat for the house.

As an example, here is the smart meter graph from this morning with some measurements I have made from the graph.

Being overnight, the only things going on in the house electrically (other than the base load) are the furnace (the peaks that I have put dimensions on), the refrigerator and the freezer. The fridge and freezer are the "choppiness" in the graph. They use much less electricity than the furnace.

I can pick them out with difficulty but I don't need to since I am only interested in when the furnace is running. The water heater is also "running" but it does not appear in this section of chart because it cycles over a much longer time (six to twelve hours) so it does not show up in this time period from about 1:30am to 6am. So the furnace is relatively easy to measure.

The dimension lines I add to a screen capture with a drafting tool (CorelDraw). The dimensions are cm which I convert to time by noting the length of an hour on the graph bottom scale. The top set of numbers is the furnace run time, the middle set is the time between runs (the cycle time) and the bottom number I use to convert centimeters to time.

Here is the calculation for this morning's data point at 4 degrees C. The spreadsheet is here.

Since I don't have smart meter data from last year I can't compare historically like I could with degree days. Next year I should be able to see the effect of improvements to insulation for example. When I get a new, more efficient furnace I should be able to see a difference in this chart.

"You can't manage what you don't measure" - Peter Drucker

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

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Sunday, April 30, 2017

heating degree days 2

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This graph shows my progress at using less electricity for heat.

The blue line is the 2016-2017 heating season. The blue line is lower than the others and slopes less. The graph tells me that I used less electricity per heating degree day last year than the previous three years.

Although I heat with an oil burning furnace, a fair amount of electricity gets used to power the two motors in the furnace, about 600 watts while it runs. If it runs less often, it uses less kWh.

The graph was simple to make and only requires two numbers for each month. One number, the total kWh used, is from my electricity bill. The second number is the heating degree days for that same month that the electricity was used from a government site like the one I showed in the previous article. A copy of my spreadsheet (.xls) is here.

I made a number of improvements in the house to reduce heat loss but particularly last summer (new insulation, leaks plugged, air circulation cut from the sun room and a new door) so it is good to be able to show the improvement in spite of changing weather.

I am ignoring price here and focusing only on the kWh used and the outside temperature as expressed in the heating degree days for my location.

Last winter was not as cold as the previous three but that does not matter when the data is compared as kWh per heating degree day.

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

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Saturday, April 29, 2017

heating degree days

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In order to compare my energy costs for different periods I am looking at the "heating degree days" for the nearest weather station Tobermory.

The graph confirms my memory of the last few winters. Certainly this past winter was NOT AS COLD as the previous three. I need to keep this in mind before I go patting myself on the back for energy reduction this past year as I have worked on this project.

I am midway between Tobermory and Wiarton. The data for other locations in Canada are available at weatherstats.ca. I thought Tobermory might be slightly more pessimistic data since it is further north and indeed as I compare month by month for last year, Tobermory is usually, but not always colder than Wiarton (higher degree days for the month).

The data is available monthly as well as quarterly.



Heating Degree Days are similar but different from Growing Degree Days (for agriculture) or Cooling Degree Days (for air conditioning).

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

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