February 20, 2000
Paul Tiegs
paultiegs@omni-test.com
http://omni-test.com
Phone:
Fax:
Hello Paul:
Thanks for forwarding your proposed protocol for comment. It
looks good, in terms of obtaining a U.L. equivalent clearance.
As you know, some manufacturers would like to get away from U.L.
labelling, and instead extend the building code to specify
clearances for appliances that now fall outside of the wall
thickness specifications for masonry fireplaces. This is an issue
with masonry heater manufacturers, in particular.
One view is that the existing U.L. protocol was designed for low
mass metal stoves, and is inappropriate for testing high mass
appliances, since the temperature stabilization requirement
imposes an unfair penalty on certain appliances, and certain
materials by requiring unrealistic quantities of wood to be
consumed. There are anecdotal stories of laboratory personnel
having to approach the heater in fireproof suits in order to be
able to get near enough to the loading doors to add another
charge of brands. Everyone would probably agree that this would
never be a real world scenario of fireplace operation.
On the other hand, two years ago during the Great Ice Storm here
in the Northeast, several fires and deaths resulted from people
using their masonry fireplaces as a sole source of emergency heat
for extended periods (days). So, one could also question the burn
rate assumptions of the UL test. In the Ice Storm scenario,
temperature stabilization data would be useful, but at realistic
burn rates, and with realistic fuel.
MHA has discussed this recently, also with HPA, and there is a
consensus that it would be useful to have a new fueling protocol
for safety testing of masonry appliances, perhaps as an ASTM
standard, in order to determine prescribed clearances for a wider
range of masonry appliances and wall sections.
I have put forward one proposal for masonry heaters, as follows:
- define a fuel load, in kg., based on firebox floor area or
volume
- define an overfiring percentage, say 500%
- using 20% moisture cordwood, have the specified number of
back-to-back burns
- using an infrared thermometer, record surface temperatures on
the heater, using a standardized grid, to be defined
- define a methodology for doing the surface temperature scan,
including calibration and quality control issues, and administer
it, for example, through the MHA
Certified Heater Mason program. It could be taught as a
continuing education module, for instance. This could provide a
large and robust data pool on which to base code requirements.
- obtain laboratory data to correlate masonry surface
temperatures with adjacent combustibles surface temperatures
- evaluate existing thermal simulation software to define a
software model for the above process, using laboratory data to
calibrate the software model.
Since heat transfer physics is simpler than combustion chemistry,
it makes sense to use a low cost method where appropriate, as in
safety testing. This would allow us to affordably build a
database of heater types and wall sections, and confidently
extend the clearance language in the code to more types of
construction.
Laboratory data from an accredited lab would, of course, still be
needed. It would be necessary to calibrate the proposed field
method, and to define some reference cases. In addition, one
could perhaps devise a conversion factor to the UL protocol. The
use of cordwood instead of brands would lower the cost of testing
significantly.
Having said that, the following data would be very useful from
your upcoming tests:
- calibration data for Jerry Frisch's infrared thermometer. For
example, obtain a temperature reading every 30 minutes for a
heating-cooling cycle on a surface point of the masonry for which
there is also calibrated thermocouple data. Ditto for a point on
the plywood surround. For an open fireplace, the hottest point,
depending on wall thickness, is probably about 8 - 12" from
the floor, at the centre of the fireback. Jerry or Jim Buckley
could advise on this. It may be necessary to take this into
account when designing the surround. For example, one may need to
access the plywood from the back and remove a plug in order to
get an IR reading off the back of the firebox.
- characterization of the wall section at this point. A sample of
the actual face brick and firebrick should be labelled and
retained. The density of both materials should be known. This
could be obtained with a ruler and a weight scale. These data are
needed to calibrate potential software models. We have done some
preliminary testing, and show an example of simulation software,
at
http://mha-net.org/msb/html/lopezd.htm
- complete fueling description. For brands, it would probably be
most useful to have photographs showing exact fuel location, and
appearance of the firebox and coal bed at different stages of the
test.
I'll post your testing protocol, along with these and any other
comments, in the MHA Members' Lounge.
Best Regards ................. Norbert
----------------------------------------
Norbert Senf---------- mheat@mha-net.org-nospam
Masonry Stove Builders
RR 5, Shawville------- www.mha-net.org/msb/
Quebec J0X 2Y0-----fax:-----819.647.6082
---------------------- voice:---819.647.509
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February 18, 2000
Dear Mr. Senf,
Attached please find a description of the test protocol we propose to use on the BIA standardized fireplace. Testing is scheduled to begin Wednesday March 1, 2000. It is anticipated that Jerry Frisch and Jim Buckley will be here to observe test progress. Please let us know if you have additional suggestions on procedures or specifications or even other data that can be collected.
The attached file is MS Word. If anyone needs something else, let me know.
Paul Tiegs
paultiegs@omni-test.com
http://omni-test.com
Phone: 503-643-3788
Fax: 503-643-3799
Attachment Converted: "D:\PROGRAMS\EUDORA\ATTACH\BrickIndustryAssoc01.doc"