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Current Heater Testing at Lopez Labs

February 17, 1997

(9:30 a.m)

Today, we did run 8 of a 10 run series with a controlled wood load. All pieces in a given run have the same moisture content, and are split from hardwood boles between 8" and 14" in diameter. Today's wood load consists of 9 pieces and 2 lb kindling. The pieces are stacked in a 3-3-3 log cabin configuration. The two top rows are stacked tight, with the bark down (see fuel load photo).

For today's run, the wood had several percentage points less moisture than Friday. Pieces were a little larger, and the load was 17 lbs more. Efficiency was a couple of percentage points higher at 70%.

It is a little early yet to start drawing conclusions, but our basic thesis is that wood sizing and stacking has as large an influence on heater performance as any other factor, including heater brand.

The stacking of the bottom row was changed from 2 pieces to 3. This resulted in a faster fire, with less excess air (lower stack oxygen). Compare today's photos and graph with Friday, and the day before.

RUN No. HK-f27
Number of Pieces
Total Weight, lb
Wood Moisture %
Fuel Surfac/Vol


Average Stack Temp, F

+/- 0.1

Average O2 %

+/- 0.2

Stack Dilution Factor
g/kg CO
Combustion Efficiency %
Heat Transfer Efficiency %
Overall Efficiency %

+/- 1.5

Average Output, 24 hrs, Kw




Click on thumbnails below for larger image.
Click HERE for a continuous set of large images

2 minutes
Kindling has different arrangement,
some pieces in front of pile, left to right
5 minutes
10 minutes
The top right piece has just rolled
over to the right.
15 minutes
1" air slot at bottom
of glass was closed after
this photograph
20 minutes 
25 minutes
30 minutes
40 minutes
50 minutes
Wood stack collapsed
See next photo
53 minutes
70 minutes
82 minutes
90 minutes
Fire was poked
after reading
100 minutes
Fire poked
after reading
110 minutes
120 minutes 
Compare with previous test
0 minutes

This page last updated on April 9, 2003