On Feb 16, 5:57�pm, "Donna Ohl, Grady Volunteer Coordinator"
wrote:
On Wed, 13 Feb 2008 11:53:00 -0800 (PST), wrote:
On Wed, 13 Feb 2008 11:53:00 -0800 (PST), wrote:
But it still doesn't say where the "magic" 41,045 BTU comes from.

Whatever magic it is, googling for 41045 BTU gets *lots* of related PDFs!

Residential ACM Manual: Water Heating Calculation Method, page 8http://www..energy.ca.gov/title24/2005standards/residential_acm/2005_R...
The standard energy in the hot water delivered, 41,045 Btu/day.

Comments on Energy Star Ratings of Home Water Heaters, Page 5http://www.energystar.gov/ia/partners/prod_development/new_specs/down...
Using the formula: 41,045 Btu/EF($/Btu)*365

ENERGY STAR Residential Water Heaters: Analysis, page 10http://www.energystar.gov/ia/partners/prod_development/new_specs/down...
Energy consumption estimated using the DOE test procedure.
Based on the following formula: (41,045 BTU/EF x 365)/100,000

LIFE CYCLE COSTS AND SAVINGS FOR WATER HEATING SYSTEMS, page 3http://www1.eere.energy.gov/solar/ush2o/pdfs/life_cycle_costs_info_sh...
The annual delivered energy is 14.98 MMBtu (41045 Btu/day).

OPERATING GUIDELINES AND STANDARDS FOR WATER HEATING SYSTEMS, page 32http://www.solar-rating.org/standards/ogdocuments/OG300SEP02.pdf
Total Energy Draw 43.302 MJ (41,045 Btu)

Consumers Directory of Home Water Heater Ratings, pagehttp://www.gamanet.org/gama/inforesources.nsf/vAttachmentLaunch/BA8B7...
Using the formula: 41045 Btu/EF($/Btu)*365

Calculating water heater costs for meaningful comparisonshttp://www.daviddarling.info/encyclopedia/W/AE_water_heater_cost.html
You need to know the unit cost of fuel
365 � 41045/EF � fuel cost (BTU) = estimated annual cost of operation
365 � 0.4105/EF � fuel cost (therm) = estimated annual cost of operation

Review of hot water heatershttp://www.consumersearch.com/www/house_and_home/water-heaters/review...
365 X 41045/EF X Fuel Cost (BTU) = estimated annual cost of operation
365 X 0.4105/EF X Fuel Cost (therm) = estimated annual cost of operation

On-demand water heaters, page 8http://www.naffainc.com/PDF-Files/on%20demand%20water%20heater.pdf
.41045 x cost per therm of gas x 365 / EF = yearly cost to operate

etc.

I would guess any engineer should be able to tell us what this 41,045 magic
number really is.

maybe its a test standard somehow.

i have seen tanks under 30,000 BTU