Degree days & Fuel Use

Mike20

I am from the old school.

To the best of my Knowledge, the only accurate way to compare fuel use from one day to the next or one year to the next is to add up the gallons of oil used for a period of time and divide by the number of degree days for that same period.

This should give a figure Gallons or BTU per degree day which should be fairly consistent throughout the year and unique to the building.

Does anyone know of another way to accurately analyze fuel use from one day to the next?

Thanks in advance.
MG




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Al Letellier_9

degree days

That system will give you an average fuel use. The only way to be more accurate would be to use a chart recorded to record on/off time or a clock attached to the burner circuit. Someone would have to reset the clock each 24 hr period and take accurate readings of various conditions to be more accurate...there is no simple way that I know of.

Constantin

Dataloggers may be of help here...

... some models allow you to take samples every couple of seconds and store the results for months at a time before you download them to your computer. Capture the exterior temperature, the "on time" of the burner (if single-stage) or the fuel consumption (if modulating/kWh) and you should have a pretty good handle on when the house is calling for heat and the resultant fuel consumption. Adding a wind sensor might be extra icing on the cake.

gasfolk

We agree

The Heating-Degree-Day (HDD) method gives an average heat loss, but consider the following example:

Indoor setpoint 70, outdoor temp 20 = Heating Degrees 50

If passive solar heating provides any significant fraction of the heat loss, then the fuel use at noon will differ from the fuel use at midnight. Without a solar correction, one could be left short in the middle of the night.

Some of the following thread may be interesting to you.

http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=184222&_#Message184222

gf

gasfolk

But, For Comparing Average Fuel Use...

We reread your original post and realize that as long as one doesn't compare fuel use on sunny days to fuel use on cloudy days, the systematic error in the HDD method should [still] give a number that allows a simple comparison from one structure to another, particularly if the average solar exposure over the period of observation is comparable.

gf