Field Measurements of Heating Efficiency of Electric Forced-Air Furnaces in Six Manufactured Homes. Page: 30 of 62
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BRIEF SUMMARY OF PROTOCOL TESTS
This appendix details several different tests performed to evaluate the heating system efficiency.
and related parameters. These include a thorough house audit, an alternating coheat test, a
furnace steady-state temperature test, tracer gas decay tests, a two-point blower door test, duct
tester measurements, and other miscellaneous measurements. The protocol takes roughly 45
technician-hours over a two day period to complete. The fist day is taken up mostly with setting
up the alternating coheat test (placing thermocouple wires and power meters, etc.). This test runs
overnight under automated control. The next half-day is spent completing testing and removing
the test equipment.
1 House Audit -
We performed a detailed audit of the house and entire heating system prior to running the tests. .
The audit included drawing a floor plan of the house, complete with elevations, from which we-
calculated the house volume. The heating system was described in detail, including furnace and
air handler fan specifications, duct length and make-up air system. Trunk ducts-were checked
with a mirror for crushing and crossover ducts were also inspected. Any peculiarities or flaws in
the furnace or duct system were noted.
2 Coheat Test
This test is the method by which we obtain the overall heating system efficiency. This is defined
as the ratio of the power required to heat the home (as ducted) by electric resistance baseboard
heating to the furnace power used during normal cycling to provide the same average room
temperatures. For the purposes of this test, portable space heaters were placed in every room that
had a supply register, and the house was alternately heated with these heaters and with the
furnace at two hour intervals. Individual rooms were maintained at the same temperature during
space heater operation as during furnace cycling, thus allowing us to separate the furnace and
space heater energy demands. This methodology accounts for all heat delivered to the living
space, including heat recovered from the ducts and crawl space, as well as uneven loading of
buffer zones.
The space heaters and furnace were controlled with Campbell 21X dataloggers, which were
commanded by batch files from a laptop computer. The furnace was controlled to cycle between
six and eight times per hour, and the space heaters maintained room temperatures to 0.250 C of
those produced during the previous furnace period. Furnace and coheat power consumption was
monitored with a pair of clamp-on true power meters attached to the house electrical mains.
Temperatures were measured with copper-constant (Type T) thermocouple wires.
Supply register air temperatures and flows were also measured. The flows were corrected to
standard air density and multiplied by the register temperatures to calculate the total useful heat
delivered to the conditioned space during furnace cycling periods. The heat delivery efficiency
was then calculated by dividing the heat delivered through the registers by the power consumed
by the furnace. This efficiency was calculated for the same furnace cycling period as the heating
system efficiency.23
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Davis, Bob; Palmiter, Larry S. & Siegel, Jeff. Field Measurements of Heating Efficiency of Electric Forced-Air Furnaces in Six Manufactured Homes., report, July 26, 1994; United States. (https://digital.library.unt.edu/ark:/67531/metadc1278222/m1/30/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.